Author name code: vourlidas ADS astronomy entries on 2022-09-14 author:"Vourlidas, Angelos" ------------------------------------------------------------------------ Title: Extracting the Heliographic Coordinates of Coronal Rays using Images from WISPR/Parker Solar Probe Authors: Liewer, P. C.; Qiu, J.; Ark, F.; Penteado, P.; Stenborg, G.; Vourlidas, A.; Hall, J. R.; Riley, P. Bibcode: 2022arXiv220902779L Altcode: The Wide-field Imager for Solar Probe (WISPR) onboard Parker Solar Probe (PSP), observing in white light, has a fixed angular field of view, extending from 13.5 degree to 108 degree from the Sun and approximately 50 degree in the transverse direction. In January 2021, on its seventh orbit, PSP crossed the heliospheric current sheet (HCS) near perihelion at a distance of 20 solar radii. At this time, WISPR observed a broad band of highly variable solar wind and multiple coronal rays. For six days around perihelion, PSP was moving with an angular velocity exceeding that of the Sun. During this period, WISPR was able to image coronal rays as PSP approached and then passed under or over them. We have developed a technique for using the multiple viewpoints of the coronal rays to determine their location (longitude and latitude) in a heliocentric coordinate system and used the technique to determine the coordinates of three coronal rays. The technique was validated by comparing the results to observations of the coronal rays from Solar and Heliophysics Observatory (SOHO) / Large Angle and Spectrometric COronagraph (LASCO)/C3 and Solar Terrestrial Relations Observatory (STEREO)-A/COR2. Comparison of the rays' locations were also made with the HCS predicted by a 3D MHD model. In the future, results from this technique can be used to validate dynamic models of the corona. Title: Overview of the Remote Sensing Observations from PSP Solar Encounter 10 with Perihelion at 13.3 R ⊙ Authors: Howard, Russell A.; Stenborg, Guillermo; Vourlidas, Angelos; Gallagher, Brendan M.; Linton, Mark G.; Hess, Phillip; Rich, Nathan B.; Liewer, Paulett C. Bibcode: 2022ApJ...936...43H Altcode: 2022arXiv220712175H The closest perihelion pass of Parker Solar Probe (PSP), so far, occurred between 2021 November 16 and 26 and reached ~13.29 R ☉ from Sun center. This pass resulted in very unique observations of the solar corona by the Wide-field Instrument for Solar PRobe (WISPR). WISPR observed at least 10 coronal mass ejections (CMEs), some of which were so close that the structures appear distorted. All of the CMEs appeared to have a magnetic flux rope (MFR) structure, and most were oriented such that the view was along the axis orientation, revealing very complex interiors. Two CMEs had a small MFR develop in the interior, with a bright circular boundary surrounding a very dark interior. Trailing the larger CMEs were substantial outflows of small blobs and flux-rope-like structures within striated ribbons, lasting for many hours. When the heliospheric plasma sheet was inclined, as it was during the days around perihelion on 2021 November 21, the outflow was over a very wide latitude range. One CME was overtaken by a faster one, with a resultant compression of the rear of the leading CME and an unusual expansion in the trailing CME. The small Thomson surface creates brightness variations of structures as they pass through the field of view. In addition to this dynamic activity, a brightness band from excess dust along the orbit of asteroid/comet 3200 Phaethon is also seen for several days. Title: Defining the Middle Corona Authors: West, Matthew J.; Seaton, Daniel B.; Wexler, David B.; Raymond, John C.; Del Zanna, Giulio; Rivera, Yeimy J.; Kobelski, Adam R.; DeForest, Craig; Golub, Leon; Caspi, Amir; Gilly, Chris R.; Kooi, Jason E.; Alterman, Benjamin L.; Alzate, Nathalia; Banerjee, Dipankar; Berghmans, David; Chen, Bin; Chitta, Lakshmi Pradeep; Downs, Cooper; Giordano, Silvio; Higginson, Aleida; Howard, Russel A.; Mason, Emily; Mason, James P.; Meyer, Karen A.; Nykyri, Katariina; Rachmeler, Laurel; Reardon, Kevin P.; Reeves, Katharine K.; Savage, Sabrina; Thompson, Barbara J.; Van Kooten, Samuel J.; Viall, Nicholeen M.; Vourlidas, Angelos Bibcode: 2022arXiv220804485W Altcode: The middle corona, the region roughly spanning heliocentric altitudes from $1.5$ to $6\,R_\odot$, encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere. Eruptions that could disrupt the near-Earth environment propagate through it. Importantly, it modulates inflow from above that can drive dynamic changes at lower heights in the inner corona. Consequently, this region is essential for comprehensively connecting the corona to the heliosphere and for developing corresponding global models. Nonetheless, because it is challenging to observe, the middle corona has been poorly studied by major solar remote sensing missions and instruments, extending back to the Solar and Heliospheric Observatory (SoHO) era. Thanks to recent advances in instrumentation, observational processing techniques, and a realization of the importance of the region, interest in the middle corona has increased. Although the region cannot be intrinsically separated from other regions of the solar atmosphere, there has emerged a need to define the region in terms of its location and extension in the solar atmosphere, its composition, the physical transitions it covers, and the underlying physics believed to be encapsulated by the region. This paper aims to define the middle corona and give an overview of the processes that occur there. Title: The Low-Corona Evolution of Coronal Mass Ejections: Solar Truth and Implications for Stellar Coronal Mass Ejections Authors: Patsourakos, Spiros; Vourlidas, Angelos; Balmaceda, Laura Bibcode: 2022cosp...44.1407P Altcode: Once a Coronal Mass Ejection (CME) is underway, it sparks a variety of phenomena in the low corona including dimmings, waves and shocks. An important finding of multi-viewpoint and high-cadence imaging observations of the initial stages of CMEs from STEREO and SDO is that they evolve differently in the lateral compared to the radial direction. The CME lateral expansion in the low corona is of particular interest to solar-stellar studies because it occurs in the region that dominates the emission in stellar observations, and triggers wave and shock phenomena. With this presentation we will discuss: i) basic observational aspects of the lateral expansion of CMEs in the solar corona, and ii) how these may contribute to the hunt for stellar CMEs. We will show how our understanding of the low lateral expansion of CMEs in the solar corona may help into deciphering and eventually modeling of the light-curves of dimmings presumably associated with stellar CMEs. Title: 4π Heliospheric Observing System - 4π-HeliOS: Exploring the Heliosphere from the Solar Interior to the Solar Wind Authors: Raouafi, Nour E.; Gibson, Sarah; Ho, George; Laming, J. Martin; Georgoulis, Manolis K.; Szabo, Adam; Vourlidas, Angelos; Mason, Glenn M.; Hoeksema, J. Todd; Velli, Marco; Berger, Thomas; Hassler, Donald M.; Kinnison, James; Viall, Nicholeen; Case, Anthony; Newmark, Jeffrey; Lepri, Susan; Krishna Jagarlamudi, Vamsee; Raouafi, Nour; Bourouaine, Sofiane; Vievering, Juliana T.; Englander, Jacob A.; Shannon, Jackson L.; Perez, Rafael M.; Chattopadhyay, Debarati; Mason, James P.; Leary, Meagan L.; Santo, Andy; Casti, Marta; Upton, Lisa A. Bibcode: 2022cosp...44.1530R Altcode: The 4$\pi$ Heliospheric Observing System (4$\pi$-HeliOS) is an innovative mission concept study for the next Solar and Space Physics Decadal Survey to fill long-standing knowledge gaps in Heliophysics. A constellation of spacecraft will provide both remote sensing and in situ observations of the Sun and heliosphere from a full 4$\pi$-steradian field of view. The concept implements a holistic observational philosophy that extends from the Sun's interior, to the photosphere, through the corona, and into the solar wind simultaneously with multiple spacecraft at multiple vantage points optimized for continual global coverage over much of a solar cycle. The mission constellation includes two spacecraft in the ecliptic and two flying as high as $\sim$70$^\circ$ solar latitude. 4$\pi$-HeliOS will provide new insights into the fundamental processes that shape the whole heliosphere. The overarching goals of the 4$\pi$-HeliOS concept are to understand the global structure and dynamics of the Sun's interior, the generation of solar magnetic fields, the origin of the solar cycle, the causes of solar activity, and the structure and dynamics of the corona as it creates the heliosphere. The mission design study is underway at the Johns Hopkins Applied Physics Laboratory Concurrent Engineering Laboratory (ACE Lab), a premier mission design center, fostering rapid and collaborative mission design evolutions. Title: Parker Solar Probe Observations of Near-Sun 3He-rich Solar Energetic Particle Events Authors: Leske, Richard; Roelof, Edmond; Davis, Andrew; Mitchell, Donald; Cohen, Christina; Labrador, Allan; Cummings, A. C.; McNutt, Ralph; Stone, E. C.; Hill, Matthew; De Nolfo, Georgia; Matthaeus, William; Christian, Eric; Macdowall, Robert; Schwadron, Nathan; Giacalone, Joe; Bale, Stuart; Desai, Mihir; Mewaldt, Richard; Vourlidas, Angelos; Wiedenbeck, Mark; Szalay, Jamey; McComas, David; Pulupa, Marc; Mitchell, John Grant; Joyce, Colin; Rankin, Jamie Bibcode: 2022cosp...44.1443L Altcode: On 21 January 2021, just after Parker Solar Probe's 7th solar perihelion while at $\sim$0.18 AU, the EPI-Hi instrument in the Integrated Science Investigation of the Sun (IS$\Theta$IS) instrument suite observed two tiny, very anisotropic solar energetic particle (SEP) events that were highly enriched in $^{3}$He. In both events at $\sim$1 MeV/nucleon, the $^{3}$He intensity exceeded the proton intensity. The $^{3}$He/$^{4}$He ratio exceeded 10, but dropped rapidly at higher energies and also was below 1 in EPI-Lo between $\sim$0.1 and 0.4 MeV/nucleon. The spectra of both $^{3}$He and $^{4}$He were power laws in EPI-Hi, with $^{3}$He softer than $^{4}$He, so if this had continued down to lower energies $^{3}$He should have greatly exceeded $^{4}$He in EPI-Lo. Instead, the lack of a detected $^{3}$He/$^{4}$He enhancement in EPI-Lo indicates that either the $^{3}$He spectrum or the $^{4}$He spectrum or both changed at lower energies, perhaps suggesting that the $^{3}$He spectrum was curved as has been reported in other $^{3}$He-rich events at 1 AU. Type III radio emission was observed by the PSP/FIELDS instrument in association with both of these events. Since PSP was $\sim$120$^\circ$ west of the Earth-Sun line and directly behind the Sun from STEREO, the solar source region was unseen. We present PSP observations of the H and He time profiles, spectra, composition, and anisotropies of these events and compare them with earlier $^{3}$He-rich events observed near 1 AU. Title: Deciphering the Genesis of Coronal Mass Ejections and Shock Waves in the Low Corona Authors: Balmaceda, Laura; Vourlidas, Angelos; Kwon, Ryun Young; Stenborg, Guillermo Bibcode: 2022cosp...44.2428B Altcode: We study the formation and 3D evolution of fast Coronal Mass Ejections (CMEs) and their associated waves in the low corona via a detailed multi-viewpoint analysis of extreme ultraviolet observations. We carefully separate the erupting magnetic structure from the surrounding wave and analyze the kinematics in the radial and lateral directions. Our analysis reveals three stages in the early evolution of the CME: (1) the hyper-inflation stage, when the CME laterally expands at speeds of ~1000 km/s, (2) followed by a shorter and slower expansion stage of a few minutes and (3) ending with a self-similar phase that carries the CME into the middle corona. The first two stages coincide with the impulsive phase of the accompanying X-ray flare, the formation and separation of an EUV wave from the CME and the start of the metric type-II radio burst. Although detected in previous analyses, the hyper-inflation phase has received relatively little attention. Our 3D analysis suggests that it may be a crucial stage in the CME formation with wide-ranging implications for solar eruption research. The hyper-inflation phase likely represents the formation stage of the magnetic structure that is eventually ejected into the corona, as the white light CME. It appears to be driven by the injection of poloidal flux into the ejecting magnetic structure, which leads to the lateral (primarily) growth of the magnetic flux rope (MFR). The rapid growth results in the creation of EUV waves and eventually shocks at the CME flanks. The coronal shocks are detected as metric type-II radio bursts. In other words, the hyper-inflation stage in the early CME evolution may be the 'missing' link between CMEs, flares, and coronal shocks. Title: COSPAR Roadmap update from the ISWAT clusters H1 and 2 Authors: Temmer, Manuela; Richardson, Ian G.; Vourlidas, Angelos; Bisi, Mario M.; Scolini, Camilla; Heinemann, Stephan; Paouris, Evangelos Bibcode: 2022cosp...44.3523T Altcode: We present the COSPAR Roadmap update paper from the ISWAT clusters H1 and 2. These two clusters are focused on interplanetary space and its dynamic features such as stream interaction regions and coronal mass ejections, the major drivers of space weather. The interplay between these phenomena changes the structure of interplanetary space on various temporal and spatial scales and effects the propagation behavior of individual events. The limitations of observational data and current models lead to large uncertainties in our understanding of solar wind structures, making reliablespace weather forecasts difficult. The solar wind also becomes more complex as solar activity increases. We discuss the current understanding of dynamic changes in interplanetary space, indicate the caveats related to data and models, and provide recommendations for future studies. Title: High-sensitivity ultra-compact Lyman-alpha Spectrometer Authors: Hosseini, Sona; Vourlidas, Angelos; Vievering, Juliana T. Bibcode: 2022cosp...44.1178H Altcode: We present the results of developing the Compact Lyman-alpha Spatial heterodyne Spectrometer (CLASS) based on an interferometric technology called Spatial Heterodyne Spectrometer (SHS) to obtain ultra-high sensitivity data from angularly extended and diffused targets such as the solar corona. The measurement approach aims to detect deviations of the line profile wings from its nominal Gaussian profile, as evidence of a suprathermal proton population in the extended solar corona. The science objectives that can be addressed by the development of this measurement capability are Q.1) Do proton seed particles exist in the inner corona, where CME shocks may form? Q.2) How does the seed particle abundance vary with time? Q.3) How does the presence of seed particles relate to SEP production? Current investigations to study these questions are accomplished by large instruments with considerable demands on spacecraft resources (mass, power, volume). The low-mass, compact configuration of CLASS enables sensitive, high-resolution spectroscopy for SmallSat missions. CLASS is configured to target the H I Lyα line at 1216Å but in the future CLASS is configurable for a variety of spectral lines with a very narrow bandpass anywhere from the FUV to the visible region. For that reason, our concept is applicable to more than one mission and is capable of meeting multiple science objectives onboard SmallSats or larger spacecraft. Title: The impact of virtual mass and magnetic erosion on the propagation of fast ICMEs Authors: Stamkos, Sotiris; Patsourakos, Spiros; Daglis, Ioannis A.; Vourlidas, Angelos Bibcode: 2022cosp...44.1406S Altcode: In order to enhance our understanding of the dynamic interactions of Interplanetary Coronal Mass Ejections (ICMEs) with the solar wind and interplanetary magnetic field, we investigate the effect of magnetic erosion on the well-known aerodynamic drag force acting on ICMEs. In particular, we generate empirical equations for the basic parameters of an ICME assuming a cylindrical morphology. Furthermore, we examine the impact of the virtual mass on the equation of motion by essentially studying a variable mass system. We quantify the effect of the reconnection process, which erodes part of the ICME's magnetic flux and outer-shell mass, on the drag acting on ICMEs and, eventually, we determine its impact on the time and speed of arrival of those transients at 1 AU. Title: The Solar 'Yardstick': What Can the Sun Teaches us About Stellar Eruptions Authors: Vourlidas, Angelos Bibcode: 2022cosp...44.1403V Altcode: The Sun-Earth system holds a special place in astrophysics. As the only known inhabited planetary system where stellar-planetary interactions cab be studied in detail, it forms the foundation for understanding exoplanetary environments, and by extension, assessing their habitability. Explosive energy release in the form of solar flares and coronal mass ejections (CMEs) comprise the two major drivers of space weather for the inner planets. In the last 50 years, we have learned a great deal about the nature of solar eruptions. Can we use this knowledge to understand stellar activity or assess the habitability of exoplanet environments? 
 In this review, I summarize our current knowledge of the properties of flares and CMEs and how it is used to estimate the eruptive activity of there stars. I look into the obvious question on whether the solar observation can be used as a reliable yardstick, discuss the constraints and offer some ideas for discussion on how to move forward. Title: On the Structure of the Zodiacal Cloud in the Inner Heliosphere Authors: Howard, Russell; Vourlidas, Angelos; Stenborg, Guillermo Bibcode: 2022cosp...44.1018H Altcode: Images from the STEREO/SECCHI/HI-1 heliospheric imager (launched in 2006) and the PSP/WISPR (launched in 2018) have been used to update and extend the historical observations of the zodiacal light (ZL), (e.g., Leinert et al 1981). We will discuss the findings from a series of recent papers giving the following results from the SECCHI and WISPR observations: (1) Constancy of the intensity of the symmetry axis of the ZL; (2) Extension of the exponent of the radial profile from -2.3 to -2.31 down to ~0.1 AU; (3) Confirmation of a slight increase in the slope approaching the Sun; (4) Observation of the dependence of the inclination and ascending node on heliocentric distance; (5) Center of the Zodiacal Cloud offset toward the barycenter; (6) Determination of the shape of the ZL as a function of heliocentric distance; (7) Discovery of dust in or near the orbit of Mercury; (8) Discovery of dust in or near the entire orbit of Venus; (9) Determination of a dust depletion zone beginning at 19 Rsun; (10) Determination of the dust free zone beginning at about 5 Rsun. Title: On modeling ICME cross sections as static MHD columns Authors: Bhattacharjee, Debesh; Nieves-Chinchilla, Teresa; Bothmer, Volker; Subramanian, Prasad; Vourlidas, Angelos Bibcode: 2022cosp...44.1376B Altcode: Solar coronal mass ejections (CMEs) are observed to expand during their propagation through the solar wind. However, their cross-sections are usually modeled as static plasma columns within the framework of magnetohydrodynamics (MHD). In this study, we test the validity of this approach using in-situ plasma data from 151 magnetic clouds (MCs) observed by the WIND spacecraft and 45 observed by the Helios spacecrafts. We find that the most probable cross-section expansion speeds for the WIND events are only $\approx 0.06$ times the Alfvén speed inside the MCs while the most probable cross-section expansion speeds for the Helios MCs is $\approx 0.03$. Hence, the MC cross-sections can be considered approximately static over an Alfvén crossing timescale. Using estimates of electrical conductivity arising from Coulomb collisions, we find that the Lundquist number inside MCs is high ( $\approx 10^{13}$), suggesting that the MHD description is well justified. The Joule heating rates using our conductivity estimates are several orders of magnitude lower than the requirement for plasma heating inside MCs at 1 AU. The low heating rates are consistent with the MHD description which assumes no dissipation. However, the discrepancy with the heating requirement suggests possible departures from MHD and the need for a better understanding of plasma heating inside MCs. Title: State-of-the-art modelling of CMEs kinematics utilizing heliospheric imagers: Challenges and Perspectives Authors: Paouris, Evangelos; Vourlidas, Angelos; Papaioannou, Athanasios; Anastasiadis, Anastasios Bibcode: 2022cosp...44.1375P Altcode: The interplanetary coronal mass ejections (ICMEs) are the main drivers of the most intense geomagnetic storms. These events could also produce space radiation storms as they can accelerate energetic particles which are dangerous especially for astronauts in orbit. Nowadays, where the planned manned missions to Moon are a reality, the early and accurate forecast of the arrival and impact of ICMEs in a specific place in the heliosphere is a necessity for the success of such missions. We present the state-of-the-art modelling of CME kinematics utilizing heliospheric imagers. Our approach is simple and at the same time reasonable: (1) all the fast (slow) CMEs are decelerating (accelerating) from the Sun up to some distance and (2) they move with a constant speed past that distance. The core of our algorithm is based on this "two-phase kinematics" behavior. We transform the elongation angle of CME's front into radial distance utilizing basic stereoscopic techniques (i.e. fixed-phi, harmonic mean, and self-similar expansion). Then we use our algorithm to create kinematic profiles for each case to provide two basic results: the Time-of-Arrival (ToA) and the Speed-on-Arrival (SoA) of ICMEs. We test our methodology in a sample of 50 Earth-directed CMEs/ICMEs with promising results as the predictions for the ToA for almost 60% of our sample has an error ($\Delta$t) for ToA of the order of $\pm$5 hours and for SoA of $\pm$100 km/s. In particular, 80% of these cases has an absolute error less than 55 minutes. We further discuss the challenges and the limitations of our methodology and the perspectives of our work such as: a) the development of a near real-time space weather forecasting tool for CME propagation as soon as L5 data will be available and b) the first attempt for forecasts at the orbit of Mars. Title: The Characteristics of Magnetic Flux Ropes in the Low and Middle Corona Authors: Vourlidas, Angelos Bibcode: 2022cosp...44.2430V Altcode: The magnetic structure of Coronal Mass Ejections (CMEs) holds vital information for understanding explosive energy release from the Sun. Theory and simulations predict that a magnetic flux rope structure (MFR) should be the core structure of all CMEs. Visible light coronagraph observations have been offering tantalizing hints that such structure exists within CMEs for decades. More recently, MFR-like structures have been detected in EUV observations of the low corona. Yet, such signatures are not as ubiquitous as theory seems to suggest. Is this (apparent) discrepancy an observational effect or does it imply a gap in our physical understanding of explosive energy release? In this talk, I will explore this questions by reviewing the current state of observations of MFRs in the low and middle corona and discuss the implications for understanding CME images and how we can now create a common picture among CMEs, flux ropes, interplanetary CMEs and magnetic clouds. Title: Extracting characteristics of interplanetary CMEs from database of synthetic white-light images based on ensemble MHD simulations Authors: Provornikova, Elena; Gibson, Sarah; Wiltberger, Michael; Dalmasse, Kévin; Merkin, Viacheslav; Malanushenko, Anna; Vourlidas, Angelos; Arge, Charles Bibcode: 2022cosp...44.2433P Altcode: In this work, we investigate to what extent properties of CMEs determined from synthetic white light images represent properties of simulated interplanetary CMEs. The propagation of an interplanetary CME with an internal flux rope is modeled with the GAMERA global model of the inner heliosphere (0.1- 1 AU) coupled with the Gibson-Low (G&L) model of a self-similarly expanding CME with an internal magnetic field. The solar wind background in the inner heliosphere is driven by the Wang-Sheeley-Arge (WSA)-ADAPT corona solution. An ensemble of CME simulations is created by setting different input parameters of a CME flux rope in the G&L model (e.g., magnetic field topology and magnetic field strength, angular width, speed, orientation, latitude, and longitude). A set of values for each of the defining G&L parameters are taken from statistical distributions obtained from an analysis of white light CME imagery near the Sun. To set the CME magnetic structure we choose four topologies allowed by the G&L model: spheromak, tethered spheromak, flux rope, and magnetic arcade. We run an ensemble of a few hundred MHD simulations of interplanetary CMEs with internal flux rope. The ensemble is used to produce a database of synthetic CME images in white-light total brightness. We use the CACTUS package to autonomously detect CMEs in synthetic white light images and determine CME angular width and variations of CME velocity, mass, and trajectory during the interplanetary CME propagation. We then compare results from CACTUS with the ground truth data extracted directly from MHD simulation output. We analyze cases showing a disagreement between the true and inferred properties in more detail. Title: The view of the corona from within the Alfven surface Authors: Howard, Russell; Liewer, Paulett; Linton, Mark; Vourlidas, Angelos; Hess, Phillip; Stenborg, Guillermo; Rich, Nathan; Gallagher, Brendan Bibcode: 2022cosp...44.1446H Altcode: Since its launch in August, 2018, the Parker Solar Probe (PSP) has used five close fly-bys of Venus to gradually reduce its perihelion distance from the initial perihelion of 35 Rsun on 5 November, 2018 to the lowest perihelion of 13.3 Rsun achieved on 21 November 2021 in Orbit 10. This perihelion will be the same for the next seven orbits. The Orbit 10 perihelion pass occurred from 16 to 25 November 2021 and has enabled very unique observations of the solar corona by the Widefield Imager for Solar PRobe (WISPR). At the perihelion of 13.3 Rsun, the WISPR field of view is 3.1 - 25 Rsun. The detailed views of the CMEs and outflows are revealing new features including the details of the CME flux rope, the collision and resulting interactions between a fast CME overtaking a slower one. In addition to this dynamic activity, enhanced scattering from dust in the orbit of asteroid/comet Phaethon is seen for several days. Title: The dust environment near the Sun: Remote observations from 0.062-0.25 AU Authors: Stenborg, Guillermo; Vourlidas, Angelos; Howard, Russell Bibcode: 2022cosp...44.1445S Altcode: Visible light observations obtained by the Wide-field Imager for Solar PRobe (WISPR) on board the Parker Solar Probe (PSP) mission provide a unique opportunity to shed light on the dust environment near the Sun. Our analysis of WISPR images, obtained from PSP heliocentric distances between 13.3 - 53.7 Rsun (0.062 - 0.25 AU) over multiple PSP orbits, shows a gradually decreasing brightness gradient along the symmetry axis of the F-corona in coronal heights from 19 to 9 Rsun. (The field of view of WISPR inner telescope covers coronal heights as low as 3.5 Rsun from this observer's location range). Below 9 Rsun, the brightness gradient reverses the trend, its slope asymptotically approaching a constant value that matches the value found for heights beyond 19 Rsun (which agrees with the gradients' slope obtained from observer's distances between 0.3 and 1 AU). In addition, the brightness of the F-corona is found to be dependent on the observer's location for coronal heights below 15 Rsun. After considering the effects of 1) the diffuse component of the K-corona background, and 2) the presence of discrete dust density enhancements over the background Zodiacal dust cloud, the aggregated brightness measurements can be explained by forward-modeling simulations of the F-corona expected brightness from a dust cloud assuming 1) a circumsolar region of depleted dust density between 19 and 5 Rsun and, 2) a region free of dust below 5 Rsun (i.e., a dust free zone or DFZ). The DFZ, a direct consequence of the DDZ, has been postulated for almost a century. Despite numerous attempts to detect it from as close as 0.3 AU, the DFZ has remained elusive until now. Here, we present the observations and analysis that led to these groundbreaking findings. Title: Learning about Flares and Coronal Mass Ejections from Some of the Largest Stellar Flaring Events Authors: Osten, Rachel; Vourlidas, Angelos; Salander, Samuel; Norman, Colin Bibcode: 2022cosp...44.2447O Altcode: We report on a coherent analysis of a set of large stellar flaring events in the nearby universe, captured as part of the Neil Gehrels' Swift Observatory rapid response and multi-wavelength follow-up. The characteristics of these stellar flares (rapid increase in signal at hard X-ray energies, multi-wavelength signatures) make the automated response for probing gamma-ray bursts and their afterglows complementary to understanding energy release in these extreme magnetic reconnection events. I will present an initial study of time-resolved spectroscopy which has two main goals: to characterize the properties of these large flaring events in comparison and contrast with lower intensity flaring events, and to search in the time-spectral signal for any signature of associated transient mass loss. Title: When do solar erupting hot magnetic flux ropes form? Authors: Nindos, Alexander; Zhang, Jie; Patsourakos, Spiros; Cheng, Xin; Vourlidas, Angelos Bibcode: 2022cosp...44.2419N Altcode: We investigate the formation times of eruptive magnetic flux ropes relative to the onset of solar eruptions, which is important for constraining models of coronal mass ejection (CME) initiation. We inspected uninterrupted sequences of 131 A images that spanned more than eight hours and were obtained by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to identify the formation times of hot flux ropes that erupted in CMEs from locations close to the limb. The appearance of the flux ropes as well as their evolution toward eruptions were determined using morphological criteria. Two-thirds (20/30) of the flux ropes were formed well before the onset of the eruption (from 51 min to more than eight hours), and their formation was associated with the occurrence of a confined flare. We also found four events with preexisting hot flux ropes whose formations occurred a matter of minutes (from three to 39) prior to the eruptions without any association with distinct confined flare activity. Six flux ropes were formed once the eruptions were underway. However, in three of them, prominence material could be seen in 131 Å images, which may indicate the presence of preexisting flux ropes that were not hot. The formation patterns of the last three groups of hot flux ropes did not show significant differences. For the whole population of events, the mean and median values of the time difference between the onset of the eruptive flare and the appearance of the hot flux rope were 151 and 98 min, respectively. Our results provide, on average, indirect support for CME models that involve preexisting flux ropes; on the other hand, for a third of the events, models in which the ejected flux rope is formed during the eruption appear more appropriate. Title: Evidence of a complex structure within the 2013 August 19 coronal mass ejection. Radial and longitudinal evolution in the inner heliosphere Authors: Rodríguez-García, L.; Nieves-Chinchilla, T.; Gómez-Herrero, R.; Zouganelis, I.; Vourlidas, A.; Balmaceda, L. A.; Dumbović, M.; Jian, L. K.; Mays, L.; Carcaboso, F.; dos Santos, L. F. G.; Rodríguez-Pacheco, J. Bibcode: 2022A&A...662A..45R Altcode: 2022arXiv220302713R Context. Late on 2013 August 19, a coronal mass ejection (CME) erupted from an active region located near the far-side central meridian from Earth's perspective. The event and its accompanying shock were remotely observed by the STEREO-A, STEREO-B, and SOHO spacecraft. The interplanetary counterpart (ICME) was intercepted by MESSENGER near 0.3 au and by both STEREO-A and STEREO-B near 1 au, which were separated from each other by 78° in heliolongitude.
Aims: The main objective of this study is to follow the radial and longitudinal evolution of the ICME throughout the inner heliosphere and to examine possible scenarios for the different magnetic flux-rope configuration observed on the solar disk and measured in situ at the locations of MESSENGER and STEREO-A, separated by 15° in heliolongitude, and at STEREO-B, which detected the ICME flank.
Methods: Solar disk observations are used to estimate the "magnetic flux-rope type", namely, the magnetic helicity, axis orientation, and axial magnetic field direction of the flux rope. The graduated cylindrical shell model is used to reconstruct the CME in the corona. The analysis of in situ data, specifically the plasma and magnetic field, is used to estimate the global interplanetary shock geometry and to derive the magnetic flux-rope type at different in situ locations, which is compared to the type estimated from solar disk observations. The elliptical cylindrical analytical model is used for the in situ magnetic flux-rope reconstruction.
Results: Based on the CME geometry and on the spacecraft configuration, we find that the magnetic flux-rope structure detected at STEREO-B belongs to the same ICME detected at MESSENGER and STEREO-A. The opposite helicity deduced at STEREO-B might be due to that fact that it intercepted one of the legs of the structure far from the flux-rope axis, in contrast to STEREO-A and MESSENGER, which were crossing through the core of the magnetic flux rope. The different flux-rope orientations measured at MESSENGER and STEREO-A probably arise because the two spacecraft measure a curved, highly distorted, and rather complex magnetic flux-rope topology. The ICME may have suffered additional distortion in its evolution in the inner heliosphere, such as the west flank propagating faster than the east flank when arriving near 1 au.
Conclusions: This work illustrates how a wide, curved, highly distorted, and rather complex CME showed different orientations as observed on the solar disk and measured in situ at 0.3 au and near 1 au. Furthermore, the work shows how the ambient conditions can significantly affect the expansion and propagation of the CME and ICME, introducing additional irregularities to the already asymmetric eruption. The study also manifests how these complex structures cannot be directly reconstructed with the currently available models and that multi-point analysis is of the utmost importance in such complex events.

Movies are available at https://www.aanda.org Title: PSP/WISPR Observations of Dust Density Depletion near the Sun. II. New Insights from within the Depletion Zone Authors: Stenborg, Guillermo; Howard, Russell A.; Vourlidas, Angelos; Gallagher, Brendan Bibcode: 2022ApJ...932...75S Altcode: Visible light observations from the Wide-field Imager for Solar PRobe (WISPR) aboard the Parker Solar Probe (PSP) mission offer a unique opportunity to study the dust environment near the Sun. The existence of a dust-free zone (DFZ) around stars was postulated almost a century ago. Despite numerous attempts to detect it from as close as 0.3 au, observational evidence of a circumsolar DFZ has remained elusive. Analysis of WISPR images obtained from heliocentric distances between 13.3-53.7 R ⊙ over multiple PSP orbits shows a gradually decreasing brightness gradient along the symmetry axis of the F-corona for coronal heights between 19 and 9 R ⊙. Below 9 R ⊙, the gradient reverses its trend, approaching the radial dependence exhibited at heights above 19 R ⊙. After taking into account the effects of both the electron corona background and the nonresolved starlight, the WISPR observations down to 4 R ⊙ are consistent with forward-modeling simulations of the F-corona brightness within [-6, 5]% if a circumsolar region of depleted dust density between 19 and 5 R ⊙ enclosing a DFZ is considered. In addition, we show, for the first time, that the F-corona brightness inward of about 15 R ⊙ depends on the observer's location for observing distances below 35 R ⊙. Title: VizieR Online Data Catalog: 421 Forbush Decreases with 1995/2015 EPHIN/SOHO (Belov+, 2021) Authors: Belov, A.; Papaioannou, A.; Abunina, M.; Dumbovic, M.; Richardson, I. G.; Heber, B.; Kuhl, P.; Herbst, K.; Anastasiadis, A.; Vourlidas, A.; Eroshenko, E.; Abunin, A. Bibcode: 2022yCat..19080005B Altcode: The rigidity dependence of all Forbush Decreases (FDs) recorded from 1995 to 2015 has been determined using neutron monitor (NM) and Solar and Heliospheric Observatory (SOHO) (EPHIN) spacecraft data, covering the energy (rigidity) range from ~433MeV (1GV) to 9.10GeV (10GV). We analyzed a total of 421 events and determined the spectrum in rigidity with an inverse power-law fit. As a result, the mean spectral index was identified to be <γF>=0.46{+/-}0.02. The majority (~66%) of the FDs have γF within the range 0.3-0.7. The remaining one-third of the events (~33%) have either (very) soft or hard FD spectra, with the latter being more common than the former. Significant variations of γF occur within almost every FD event. During the initial FD decay phase the spectrum becomes gradually harder, in contrast to the recovery phase, when it becomes softer. Additionally, low energies (rigidities) seem to be better suited for studying the fine structure of interplanetary disturbances (primarily interplanetary coronal mass ejections) that lead to FDs. In particular, FDs recorded by the EPHIN instrument on SOHO better capture a two-step structure than FDs observed by NMs. Finally, the ejecta of an ICME, especially when identified as a magnetic cloud, often leads to abrupt changes in the slope of γF.

(1 data file). Title: The Hyper-inflation Stage in the Coronal Mass Ejection Formation: A Missing Link That Connects Flares, Coronal Mass Ejections, and Shocks in the Low Corona Authors: Balmaceda, Laura A.; Vourlidas, Angelos; Stenborg, Guillermo; Kwon, Ryun-Young Bibcode: 2022ApJ...931..141B Altcode: We analyze the formation and three-dimensional (3D) evolution of two coronal mass ejections (CMEs) and their associated waves in the low corona via a detailed multi-viewpoint analysis of extreme-ultraviolet observations. We analyze the kinematics in the radial and lateral directions and identify three stages in the early evolution of the CME: (1) a hyper-inflation stage, when the CME laterally expands at speeds of ~1000 km s-1, followed by (2) a shorter and slower expansion stage of a few minutes and ending with (3) a self-similar phase that carries the CME into the middle corona. The first two stages coincide with the impulsive phase of the accompanying flare, the formation and separation of an EUV wave from the CME, and the start of the metric type II radio burst. Our 3D analysis suggests that the hyper-inflation phase may be a crucial stage in the CME formation with wide-ranging implications for solar eruption research. It likely represents the formation stage of the magnetic structure that is eventually ejected into the corona, as the white-light CME. It appears to be driven by the injection of poloidal flux into the ejecting magnetic structure, which leads to the lateral (primarily) growth of the magnetic flux rope. The rapid growth results in the creation of EUV waves and eventually shocks at the CME flanks that are detected as metric type II radio bursts. In other words, the hyper-inflation stage in the early CME evolution may be the "missing" link between CMEs, flares, and coronal shocks. Title: On Modeling ICME Cross-Sections as Static MHD Columns Authors: Bhattacharjee, Debesh; Subramanian, Prasad; Bothmer, Volker; Nieves-Chinchilla, Teresa; Vourlidas, Angelos Bibcode: 2022SoPh..297...45B Altcode: 2022arXiv220306996B Solar coronal mass ejections are well-known to expand as they propagate through the heliosphere. Despite this, their cross-sections are usually modeled as static plasma columns within the magnetohydrodynamics (MHD) framework. We test the validity of this approach using in-situ plasma data from 151 magnetic clouds (MCs) observed by the WIND spacecraft and 45 observed by the Helios spacecraft. We find that the most probable cross-section expansion speeds for the WIND events are only ≈0.06 times the Alfvén speed inside the MCs, while the most probable cross-section expansion speeds for the Helios events is ≈0.03 . MC cross-sections can thus be considered to be nearly static over an Alfvén crossing timescale. Using estimates of electrical conductivity arising from Coulomb collisions, we find that the Lundquist number inside MCs is high (≈1013), suggesting that the MHD description is well justified. The Joule heating rates using our conductivity estimates are several orders of magnitude lower than the requirement for plasma heating inside MCs near the Earth. While the (low) heating rates we compute are consistent with the MHD description, the discrepancy with the heating requirement points to possible departures from MHD and the need for a better understanding of plasma heating in MCs. Title: Parker Solar Probe's Measurements of the 29 November 2020 Solar Energetic Particle Event Authors: Cohen, C.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; Desai, M. I.; Nolfo, G. A. de.; Giacalone, J.; Hill, M. E.; Joyce, C. J.; Labrador, A. W.; Leske, R. A.; Matthaeus, W. H.; McComas, D. J.; Mewaldt, R. A.; Mitchell, D. G.; Mitchell, J. G.; Rankin, J. S.; Roelof, E. C.; Schwadron, N. A.; Stone, E. C.; Szalay, J. R.; Wiedenbeck, M. E.; Vourlidas, A.; Bale, S. D.; Pulupa, M.; MacDowall, R. J.; McNutt, R. L., Jr. Bibcode: 2022icrc.confE1292C Altcode: 2022PoS...395E1292C No abstract at ADS Title: Parker Solar Probe Imaging of the Night Side of Venus Authors: Wood, Brian E.; Hess, Phillip; Lustig-Yaeger, Jacob; Gallagher, Brendan; Korwan, Daniel; Rich, Nathan; Stenborg, Guillermo; Thernisien, Arnaud; Qadri, Syed N.; Santiago, Freddie; Peralta, Javier; Arney, Giada N.; Izenberg, Noam R.; Vourlidas, Angelos; Linton, Mark G.; Howard, Russell A.; Raouafi, Nour E. Bibcode: 2022GeoRL..4996302W Altcode: We present images of Venus from the Wide-Field Imager for Parker Solar Probe (WISPR) telescope on board the Parker Solar Probe (PSP) spacecraft, obtained during PSP's third and fourth flybys of Venus on 2020 July 11 and 2021 February 20, respectively. Thermal emission from the surface is observed on the night side, representing the shortest wavelength observations of this emission ever, the first detection of the Venusian surface by an optical telescope observing below 0.8 μm. Consistent with previous observations at 1 μm, the cooler highland areas are fainter than the surrounding lowlands. The irradiances measured by WISPR are consistent with model predictions assuming a surface temperature of T = 735 K. In addition to the thermal emission, the WISPR images also show bright nightglow emission at the limb, and we compare the WISPR intensities with previous spectroscopic measurements of the molecular oxygen nightglow lines from Venus Express. Title: Small Satellite Mission Concepts for Space Weather Research and as Pathfinders for Operations Authors: Caspi, Amir; Barthelemy, M.; Bussy-Virat, C. D.; Cohen, I. J.; DeForest, C. E.; Jackson, D. R.; Vourlidas, A.; Nieves-Chinchilla, T. Bibcode: 2022SpWea..2002554C Altcode: 2022arXiv220107426C Recent advances in miniaturization and commercial availability of critical satellite subsystems and detector technology have made small satellites (SmallSats, including CubeSats) an attractive, low-cost potential solution for space weather research and operational needs. Motivated by the first International Workshop on SmallSats for Space Weather Research and Forecasting, held in Washington, DC on 1-4 August 2017, we discuss the need for advanced space weather measurement capabilities, driven by analyses from the World Meteorological Organization (WMO), and how SmallSats can efficiently fill these measurement gaps. We present some current, recent missions and proposed/upcoming mission concepts using SmallSats that enhance space weather research and provide prototyping pathways for future operational applications; how they relate to the WMO requirements; and what challenges remain to be overcome to meet the WMO goals and operational needs in the future. With additional investment from cognizant funding agencies worldwide, SmallSats—including standalone missions and constellations—could significantly enhance space weather research and, eventually, operations, by reducing costs and enabling new measurements not feasible from traditional, large, monolithic missions. Title: Parker Solar Probe Observations of the January 2021 3He-Rich Solar Energetic Particle Events Authors: Leske, Richard; Christian, Eric; Cohen, Christina; Cummings, Alan; Davis, Andrew; Desai, Mihir; de Nolfo, Georgia; Giacalone, Joe; Hill, Matthew; Joyce, Colin; Labrador, Allan; Matthaeus, William; McComas, David; McNutt, Ralph; Mewaldt, Richard; Mitchell, Donald; Mitchell, J. Grant; Rankin, Jamie; Roelof, Edmond; Schwadron, Nathan; Stone, Edward; Szalay, Jamey; Wiedenbeck, Mark; Vourlidas, Angelos; Bale, Stuart; Pulupa, Marc; MacDowall, Robert Bibcode: 2021AGUFMSH15A2029L Altcode: On 21 January 2021, while at ~0.18 AU after its seventh solar perihelion pass, Parker Solar Probe's Integrated Science Investigation of the Sun (ISIS) detected a pair of small, highly anisotropic solar energetic particle (SEP) events. In terms of their composition, these events were distinguished by a very high helium abundance, with the elemental He and H intensities essentially equal at 1 MeV/nucleon. These events were by far the most 3He-rich detected by PSP to date, with a 3He/4He ratio of ~4 at 1 MeV/nucleon, but less at both lower and higher energies, as has sometimes been seen in earlier SEP events at 1 AU. Both events were accompanied by clear type III radio emission observed by the PSP FIELDS instrument, but the source region was unobserved since PSP was ~120 degrees west of Earth and directly opposite the Sun from STEREO. We present ISIS observations of the composition, spectra, time profiles, and anisotropies of these events and compare them with other 3He-rich events observed much farther from the Sun. Title: Investigating Energy Release during Solar Eruptive Events with RHESSI, STEREO, and SDO Authors: Vievering, Juliana; Vourlidas, Angelos; Zhu, Chunming; Qiu, Jiong; Glesener, Lindsay Bibcode: 2021AGUFMSH22B..05V Altcode: Hard X-rays (HXRs) provide a key diagnostic for energy release during a solar flare, as HXRs are emitted from flare-accelerated electrons and strongly heated flare plasma. In the case of a solar eruptive event, a flare is associated with the eruption of a coronal mass ejection (CME); though it is largely understood that reconnection is important for the eventual release of the CME, the triggering mechanism for the eruption and its relationship to flare energy release remains under debate. In this study, we leverage the optimal viewing geometry of the Solar TErrestrial RElations Observatory (STEREO) relative to the Solar Dynamics Observatory (SDO) and the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) during 2010-2013 to provide simultaneous measurements of CME evolution, magnetic reconnection, and flare energy release for 12 solar eruptive events. We analyze the relative timing of these phenomena, focusing on event onset and fast-varying features, or bursts, in the time profiles to improve our understanding of particle acceleration mechanisms and the connections between flare and CME energization. Notably, this study has identified two events with rarely-studied RHESSI HXR flares occurring outside of active regions, which can provide additional insight on how the magnetic configuration affects the evolution of eruptive events. Title: Variations in the He/H Abundance Ratio Measured in Solar Energetic Particle Events by Parker Solar Probe Authors: Cohen, Christina; Christian, Eric; Cummings, Alan; Davis, Andrew; Desai, Mihir; de Nolfo, Georgia; Giacalone, Joe; Hill, Matthew; Joyce, Colin; Labrador, Allan; Leske, Richard; Matthaeus, William; McComas, David; McNutt, Ralph; Mewaldt, Richard; Mitchell, Donald; Mitchell, J. Grant; Rankin, Jamie; Roelof, Edmond; Schwadron, Nathan; Stone, Edward; Szalay, Jamey; Wiedenbeck, Mark; Vourlidas, Angelos; Bale, Stuart; Pulupa, Marc; MacDowall, Robert Bibcode: 2021AGUFMSH51B..06C Altcode: In late May, 2020 the Integrated Science Investigation of the Sun (ISIS) on Parker Solar Probe observed a triad of solar energetic particle (SEP) events originating from the same active region on the Sun. Although these events were each separated in time by less than 24 hours, their He/H abundance ratios varied by over a factor of 50, with one event exhibiting an extremely low value of 0.33% (as compared to the typical value of 3.5%). During the following year, ISIS detected many additional SEP events, some similar in size to the May 2020 events, some significantly larger (e.g., the circumsolar November 2020 event). Among these events the He/H continued to be quite variable, including events with He/H ratios a factor of two lower than the lowest of the May 2020 events. Here we summarize these variations and investigate the solar and interplanetary conditions in which they occur in an effort to understand the process(es) that dictate the observed SEP He/H abundance ratios. Title: Coronal Mass Ejection Distortion at 0.1 au Observed by WISPR Authors: Braga, Carlos; Vourlidas, Angelos; Liewer, Paulett; Hess, Phillip; Stenborg, Guillermo Bibcode: 2021AGUFMSH42A..09B Altcode: Although many coronal mass ejections (CMEs) are modeled using geometric models expanding self-similarly, various numerical MHD simulations, imaging, and in situ observations suggest that CMEs become distorted. Common distortions descriptions are "pancaking", front flattering, and rotational skew. Many distortions are associated with spatial and temporal changes in CME background solar wind conditions. Other studies suggest that distortion happens because CMEs lose coherence over their full angular extend once portions of plasma separate exceeding the Alfven speed, which can occur between 0.1 and 0.2 au. We present evidence of one CME becoming distorted while WISPR observed it and explore possible explanations. The inner and outer cameras observe the CME on January 20-22, 2021, while it propagates almost through the entire field-of-view, extending 95 degrees radially. We derive the CME kinematics using multiple techniques, and reconstruct it using WISPR and coronagraph observations. We find that up to ~0.08 au, the CME follows the graduated cylindrical shell (GCS) model well and expands approximately self-similarly. After this period in which WISPR observes a circular-like front profile, it becomes concave. By projecting the GCS model over WISPR images, we are unable to reproduce the profile change observed. As projection effects cannot explain the concave profile, our interpretation is that the CME becomes distorted by ~0.1 au. The CME seems to expand more at higher latitudes, where the solar wind speed is likely higher. We also discuss CME plasma conditions necessary for loss of coherence at ~0.1 au, which occurs when the relative separation speed between CME plasma parcels becomes higher than the Alfven speed. Title: PSP/IS⊙IS observations of the 29 November 2020 solar energetic particle event Authors: Cohen, C. M. S.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; Desai, M. I.; de Nolfo, G. A.; Giacalone, J.; Hill, M. E.; Joyce, C. J.; Labrador, A. W.; Leske, R. A.; Matthaeus, W. H.; McComas, D. J.; McNutt, R. L.; Mewaldt, R. A.; Mitchell, D. G.; Mitchell, J. G.; Rankin, J. S.; Roelof, E. C.; Schwadron, N. A.; Stone, E. C.; Szalay, J. R.; Wiedenbeck, M. E.; Vourlidas, A.; Bale, S. D.; Pulupa, M.; MacDowall, R. J. Bibcode: 2021A&A...656A..29C Altcode:
Aims: On 29 November 2020, at 12:34 UT, active region 12790 erupted with an M4.4 class flare and a 1700 km s−1 coronal mass ejection. Parker Solar Probe (PSP) was completing its seventh orbit around the Sun and was located at 0.8 au when the Integrated Science Investigation of the Sun (IS⊙IS) measured the ensuing mid-sized solar energetic particle (SEP) event. Not only was this the first SEP event with heavy ions above 10 MeV nuc−1 to be measured by IS⊙IS, it was also measured by several spacecraft positioned around the Sun, making it the first circumsolar event of solar cycle 25. Here we describe an overview of the SEP event characteristics at PSP.
Methods: Fluence spectra for electrons, H, He, O, and Fe were calculated for the decay portion of the event. For the entire time period of the event, it was possible to calculate fluence spectra for electrons, O, and Fe only due to instrumental mode changes in one of the IS⊙IS telescopes, affecting H and He during the period of peak intensities. Using higher time resolution data, we also studied the onset of the event and temporal variations in the particle intensities at the shock and during the magnetic cloud passage.
Results: During the decay, the ion spectra are consistent with power laws at low energies with an exponential rollover at a few MeV nuc−1, while the electron spectrum is consistent with a power law of index −5.3. Based on fits to the spectra, Fe/O and He/H abundance ratios as a function of energy are calculated and found to be nominal for large SEP events at hundreds of keV/nuc, but decrease strongly with increasing energy. The full-event spectra for O and Fe have similar shapes to those of the decay, but with higher roll-over energies. The electron spectrum for the full event is harder with an index of −3.4 and there is some evidence of higher energy components near ∼2 MeV and above ∼4 MeV. Despite the spacecraft being tilted 45° with respect to the nominal orientation of the spacecraft's long axis pointed towards the Sun, there is some anisotropy apparent in MeV protons during the onset of the event. Velocity dispersion is also evident, consistent with a solar release time of 13:15 UT and pathlength of 1.3 au. The arrival of the related magnetic cloud resulted in the suppression of SEP intensities, although a brief increase in particle intensities suggests PSP moved out of the cloud for ∼30 min. This appears to be the first medium-sized event in the rise of cycle 25 activity, with additional large events likely to occur. Additional details of the event beyond this overview can be found in several related papers.

Movie associated to Fig. 2 is available at https://www.aanda.org Title: Relationship Between Onsets of CME Acceleration and Magnetic Reconnection in CME-flare Events Authors: Zhu, Chunming; Balentine, Danny; Qiu, Jiong; Vievering, Juliana; Vourlidas, Angelos; Hu, Qiang Bibcode: 2021AGUFMSH25E2141Z Altcode: What role magnetic reconnection plays in the initiation of solar eruptions is still not clear. In this study, we focus on the initiation of ~10 CME-flare events by combining flare reconnection and CME kinematics. We measure CME kinematics in the early stage from two viewpoints of SDO (12s cadence) and STEREO (up to 75s cadence). We also measure the reconnection flux rate by evaluating magnetic fluxes swept by the flare foot-point brightenings on the solar disk observed from SDO, with the cadence of 12--24s. With these measurements, we determine the time and location of early signatures of magnetic reconnection with respect to the CME evolution. By exploring the related magnetic field configuration, we classify these early reconnection signatures based on their locations and evolutions, and discuss how the early reconnection signatures could be related to the initiation of the solar eruptions. Title: Internal Structure of the 2019 April 2 CME Authors: Wood, Brian E.; Braga, Carlos R.; Vourlidas, Angelos Bibcode: 2021ApJ...922..234W Altcode: 2021arXiv211014083W We present the first analysis of internal coronal mass ejection (CME) structure observed very close to the Sun by the Wide-field Imager for Solar PRobe (WISPR) instrument on board the Parker Solar Probe (PSP). The transient studied here is a CME observed during PSP's second perihelion passage on 2019 April 2, when PSP was only 40 R ⊙ from the Sun. The CME was also well observed from 1 au by the STEREO-A spacecraft, which tracks the event all the way from the Sun to 1 au. However, PSP/WISPR observes internal structure not apparent in the images from 1 au. In particular, two linear features are observed, one bright and one dark. We model these features as two loops within the CME flux rope (FR) channel. The loops can be interpreted as bundles of field lines, with the brightness of the bright loop indicative of lots of mass being loaded into those field lines, and with the dark loop being devoid of such mass loading. It is possible that these loops are actually representative of two independent FR structures within the overall CME outline. Title: Analysis of Coronal Mass Ejections Observed by Multiple Spacecraft, including by WISPR on Parker Solar Probe Authors: Liewer, Paulett; Hall, Jeffrey; Braga, Carlos; Hess, Phillip; Penteado, Paulo; Stenborg, Guillermo; Vourlidas, Angelos; Qiu, Jiong Bibcode: 2021AGUFMSH15A2019L Altcode: The Wide-field Imager for Solar Probe (WISPR) has provided high resolution images of multiple coronal mass ejections (CMEs) during its first seven encounters with the Sun and most of these have been observed by white-light instruments on either STEREO A or SOHO or both. The multiple viewpoints have been important in determining the source of the CMEs and their trajectories. Here we present results from the analysis of the origin and trajectories of several WISPR CMEs with some unexpected results. WISPR has a wide fixed angular field-of-view (FOV), extending radially from 13.5° to 108° from the Sun and approximately 50° in the transverse direction, but the physical extent of the imaged coronal region varies directly with the distance of the spacecraft from the Sun. We have developed tools for determining the trajectories of solar ejecta which take into account the rapid spacecraft motion. We have also developed tools to relate and compare the CMEs seen in the WISPR images to simultaneous observation from the other white light telescope (SOHO/LASCO or STEREO/SECCHI), making uses of the World Coordinate System information in the images FITS headers. This software allows us to project the trajectory determined from WISPR or features seen in the WISPR images onto images from the second white light telescope (or visa versa) to verify the trajectory determined from the WISPR data alone or to determine a CMEs location by triangulation. Utilizing the multiple viewpoints has led to a better understanding of the structure and evolution of the CMEs. Title: Large ensemble simulations of CMEs in the inner heliosphere: toward constraining distributions of CME parameters near the Sun Authors: Provornikova, Elena; Merkin, Viacheslav; Malanushenko, Anna; Gibson, Sarah; Vourlidas, Angelos; Arge, Charles; Dalmasse, Kevin Bibcode: 2021AGUFMSH32A..01P Altcode: In this work, we take a comprehensive approach which combines physics-based simulations, observations and statistical methods toward understanding the evolution of coronal mass ejections in the inner heliosphere and linking characteristics of CMEs near the Sun and their plasma and magnetic field properties as they would be observed at 1 AU. We simulate the propagation of ICMEs using a global model of the inner heliosphere driven at the coronal boundary by the Wang-Sheeley-Arge (WSA)-ADAPT model. ICMEs are initiated at 21.5 solar radii using an MHD analytical Gibson-Low (G&L) model of a self-similarly expanding magnetic bubble with defining parameters (e.g., latitude and longitude, magnetic field topology and strength, angular width, speed, orientation). The ICME propagation is simulated using the inner heliosphere version of the Grid Agnostic MHD for Extended Research Applications (GAMERA) MHD model, which is a reinvention of the high-heritage Lyon-Fedder-Mobarry (LFM) code. A set of values for each of the defining G&L parameters was constrained by the statistical representation of CME images near the Sun. Intending to span the solar cycle, we model ICME propagation in different solar wind backgrounds corresponding to rising, declining, and minimum solar cycle phases. A grid of CME parameters and three solar wind backgrounds constitute a parameter space for 50,000 ICME simulations. We describe types and a structure of the output data from simulations and an algorithm of automatic performance of many thousands of runs. We discuss methods to incorporate CME data from both solar observations and in-situ at 1 AU in a statistical study to construct posterior predictive distributions of CME model input parameters. Title: Connecting the Low to the High Corona: A Method to Isolate Transients in STEREO/COR1 Images Authors: Alzate, Nathalia; Morgan, Huw; Viall, Nicholeen; Vourlidas, Angelos Bibcode: 2021ApJ...919...98A Altcode: 2021arXiv210702644A We present a method that isolates time-varying components from coronagraph and extreme ultraviolet images, allowing substreamer transients propagating within streamers to be tracked from the low to the high corona. The method uses a temporal bandpass filter with a transmission bandwidth of ~2.5-10 hr that suppresses both high- and low-frequency variations in observations made by the STEREO/SECCHI suite. We demonstrate that this method proves crucial in linking features in the low corona, where the magnetic field is highly nonradial, to their counterparts in the high corona, where the magnetic field follows a radial path, through the COR1 instrument. We also apply our method to observations by the COR2 and EUVI instruments on board SECCHI and produce height-time profiles that reveal small density enhancements, associated with helmet streamers propagating from ~1.2 R⊙ out to beyond 5 R⊙. Our processing method reveals that these features are common during the period of solar minimum in this study. The features recur on timescales of hours, originate very close to the Sun, and remain coherent out into interplanetary space. We measure the speed of the features and classify them as slow (a few to tens of kilometers per second) or fast (~100 km s-1). Both types of features serve as an observable tracer of a variable component of the slow solar wind to its source regions. Our methodology helps overcome the difficulties in tracking small-scale features through COR1. As a result, it proves successful in measuring the connectivity between the low and high corona and in measuring the velocities of small-scale features. Title: Energetic particle evolution during coronal mass ejection passage from 0.3 to 1 AU Authors: Joyce, C. J.; McComas, D. J.; Schwadron, N. A.; Vourlidas, A.; Christian, E. R.; McNutt, R. L.; Cohen, C. M. S.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; Mitchell, D. G.; Hill, M. E.; Roelof, E. C.; Allen, R. C.; Szalay, J. R.; Rankin, J. S.; Desai, M. I.; Giacalone, J.; Matthaeus, W. H.; Niehof, J. T.; de Wet, W.; Winslow, R. M.; Bale, S. D.; Kasper, J. C. Bibcode: 2021A&A...651A...2J Altcode: We provide analysis of a coronal mass ejection (CME) that passed over Parker Solar Probe (PSP) on January 20, 2020 when the spacecraft was at just 0.32 AU. The Integrated Science Investigation of the Sun instrument suite measures energetic particle populations associated with the CME before, during, and after its passage over the spacecraft. We observe a complex evolution of energetic particles, including a brief ~2 h period where the energetic particle fluxes are enhanced and the nominal orientation of the energetic particle streaming outward from the Sun (from 30 to 100 keV nuc−1) abruptly reverses inward toward the Sun. This transient and punctuated evolution highlights the importance of magnetic field structures that connect the spacecraft to different acceleration sites, one of which is likely more distant from the Sun than PSP during the evolution of the CME. We discuss these characteristics and what they tell us about the source of the energetic particles. During this period, PSP was radially aligned with the Solar Terrestrial Relations Observatory A (STEREO-A), which measured the same CME when it passed 1 AU. The magnetic field measurements at both spacecraft are remarkably similar, indicating that the spacecraft are likely encountering the same portion of the magnetic structure that has not evolved significantly in transit. The energetic particle observations on the other hand, are quite different at STEREO-A, showing how transport effects have acted on the energetic particle populations and obscured the detailed properties present earlier in the development of the CME. This event provides a unique case study in how energetic particle populations evolve as CMEs propagate through the heliosphere. Title: Parker Solar Probe observations of He/H abundance variations in SEP events inside 0.5 au Authors: Cohen, C. M. S.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; Desai, M. I.; de Nolfo, G. A.; Giacalone, J.; Hill, M. E.; Joyce, C. J.; Labrador, A. W.; Leske, R. A.; Matthaeus, W. H.; McComas, D. J.; McNutt, R. L.; Mewaldt, R. A.; Mitchell, D. G.; Mitchell, J. G.; Rankin, J. S.; Roelof, E. C.; Schwadron, N. A.; Stone, E. C.; Szalay, J. R.; Wiedenbeck, M. E.; Vourlidas, A.; Bale, S. D.; Pulupa, M.; MacDowall, R. J. Bibcode: 2021A&A...650A..23C Altcode:
Aims: The Parker Solar Probe (PSP) orbit provides an opportunity to study the inner heliosphere at distances closer to the Sun than previously possible. Due to the solar minimum conditions, the initial orbits of PSP yielded only a few solar energetic particle (SEP) events for study. Recently during the fifth orbit, at distances from 0.45 to 0.3 au, the energetic particle suite on PSP, Integrated Science Investigation of the Sun (IS⊙IS), observed a series of six SEP events, adding to the limited number of SEP events studied inside of 0.5 au. Variations in the H and He spectra and the He/H abundance ratio are examined and discussed in relation to the identified solar source regions and activity.
Methods: IS⊙IS measures the energetic particle environment from ~20 keV to >100 MeV/nuc. Six events were selected using the ~1 MeV proton intensities, and while small, they were sufficient to calculate proton and helium spectra from ~1 to ~10 MeV/nuc. For the three larger events, the He/H ratio as a function of energy was determined. Using the timing of the associated radio bursts, solar sources were identified for each event and the eruptions were examined in extreme ultraviolet emission.
Results: The largest of the selected events has peak ~1 MeV proton intensities of 3.75 (cm2 sr s MeV)−1. Within uncertainties, the He and H spectra have similar power law forms with indices ranging from −2.3 to −3.3. For the three largest events, the He/H ratios are found to be relatively energy independent; however, the ratios differ substantially with values of 0.0033 ± 0.0013, 0.177 ± 0.047, and 0.016 ± 0.009. An additional compositional variation is evident in both the 3He and electron signatures. These variations are particularly interesting as the three larger events are likely a result of similar eruptions from the same active region.

Movies associated to Figs. 3 and 8 are only available at https://www.aanda.org Title: An Observational Study of a "Rosetta Stone" Solar Eruption Authors: Mason, E. I.; Antiochos, Spiro K.; Vourlidas, Angelos Bibcode: 2021ApJ...914L...8M Altcode: 2021arXiv210509164M This Letter reports observations of an event that connects all major classes of solar eruptions: those that erupt fully into the heliosphere versus those that fail and are confined to the Sun, and those that eject new flux into the heliosphere, in the form of a flux rope, versus those that eject only new plasma in the form of a jet. The event originated in a filament channel overlying a circular polarity inversion line and occurred on 2016 March 13 during the extended decay phase of the active region designated NOAA 12488/12501. The event was especially well observed by multiple spacecraft and exhibited the well-studied null-point topology. We analyze all aspects of the eruption using Solar Dynamics Observatory Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager, Solar-Terrestrial Relations Observatory Extreme Ultraviolet Imager, and Solar and Heliospheric Observatory Large Angle and Spectrometric Coronagraph (SOHO LASCO) imagery. One section of the filament undergoes a classic failed eruption with cool plasma subsequently draining onto the section that did not erupt, but a complex structured coronal mass ejection/jet is clearly observed by SOHO/LASCO C2 shortly after the failed filament eruption. We describe in detail the slow buildup to eruption, the lack of an obvious trigger, and the immediate reappearance of the filament after the event. The unique mixture of major eruption properties observed during this event places severe constraints on the structure of the filament channel field and, consequently, on the possible eruption mechanism. Title: Coronal mass ejections observed by heliospheric imagers at 0.2 and 1 au. The events on April 1 and 2, 2019 Authors: Braga, Carlos R.; Vourlidas, Angelos Bibcode: 2021A&A...650A..31B Altcode: 2020arXiv201105229B Context. We study two coronal mass ejections (CMEs) observed between April 1 to 2, 2019 by both the inner Wide-Field Imager for Parker Solar Probe (WISPR-I) onboard the Parker Solar Probe (PSP) spacecraft (located between about 46 and 38 solar radii during this period) and the inner heliospheric imager (HI-1) onboard the Solar Terrestrial Relations Observatory Ahead (STEREO-A) spacecraft, orbiting the Sun at about 0.96 au. This is the first study of CME observations from two viewpoints in similar directions but at considerably different solar distances.
Aims: Our objective is to derive CME kinematics from WISPR-I observations and to compare them with results from HI-1. This allows us to understand how the PSP observations affect the CME kinematics, especially due to its proximity to the Sun.
Methods: We estimated the CME positions, speeds, accelerations, propagation directions, and longitudinal deflections using imaging observations from two spacecrafts and a set of analytical expressions that consider the CME as a point structure and take the rapid change in spacecraft position into account. We derived the kinematics using each viewpoint independently and both viewpoints as a constraint.
Results: We found that both CMEs are slow (<400 km s−1), propagating eastward of the Sun-Earth line (westward of PSP and STEREO-A). The second CME seems to accelerate between ~0.1 and ~0.2 au and deflect westward with an angular speed consistent with the solar rotation speed. We found some discrepancies in the CME solar distance (up to 0.05 au, particularly for CME #1), latitude (up to ~10°), and longitude (up to 24°) when comparing results from different fit cases (different observations or set of free parameters).
Conclusions: Discrepancies in longitude are likely due to the feature that is tracked visually, rather than instrumental biases or fit assumptions. For similar reasons, the CME #1 solar distance, as derived from WISPR-I observations, is larger than the HI-1 result, regardless of the fit parameters considered. Error estimates for CME kinematics do not show any clear trend associated with the observing instrument. The source region location and the lack of any clear in situ counterparts (both at near-Earth and at PSP) support our estimate of the propagation direction for both events. Title: Periodic Solar Wind Density Structures Observed with Parker Solar Probe WISPR Authors: Viall, N. M.; Vourlidas, A.; Howard, R.; Linton, M.; Kepko, L.; Di Matteo, S.; Higginson, A. K. Bibcode: 2021AAS...23812305V Altcode: Periodic trains of mesoscale structures in solar wind density have been observed close to the Sun with in situ data from the Helios spacecraft, as well as remotely in STEREO/COR2 and STEREO/HI1 white light imaging data. While some periodic density structures may be a consequence of the development of dynamics en route, many are remnants of the formation and release of the solar wind, and thus provide important constraints on solar wind models. The instrument suite on Parker Solar Probe offers an unprecedented viewpoint of the ambient solar wind and structure therein, shortly after its formation and release from the solar corona. Here, we report on the first observations of periodic trains of mesoscale structures in solar wind density observed by the Wide-field Imager for Parker Solar PRobe (WISPR). We describe our open-source Fourier analysis and robust spectral background estimation technique used to identify the periodic density structures. The observation of periodic density structures so near to the Sun allows us to begin disentangling how much structure is created during solar wind formation, versus how much is due to evolution as the solar wind advects outward. Title: Mind The Gap: Observing The Jet/CME Continuum In A Hybrid Eruption Authors: Mason, E.; Antiochos, S.; Vourlidas, A. Bibcode: 2021AAS...23821316M Altcode: Coronal mass ejections, jets, prominence eruptions: solar eruptions are an active field with a broad range of accepted phenomena, and an even broader range of proposed mechanisms that cause the phenomena. This talk reports the observations of an event that connects the major eruption classes, and could provide a holistic explanation for all of them. The event originated in a filament channel overlying a circular polarity inversion line (PIL) and occurred on 2013 March 13 during the extended decay phase of the active region designated (sequentially) NOAA 12488/12501. This event was especially well-observed by multiple spacecraft and was seen to have the well-studied null-point topology. We analyze all aspects of the eruption using SDO AIA and HMI, STEREO-A, and SOHO LASCO imagery. One section of the filament undergoes a classic failed eruption with cool plasma subsequently draining onto the section that did not erupt, but a complex structured CME/jet is clearly observed by SOHO LASCO C2 shortly after the failed filament eruption. We describe in detail the long, slow buildup to eruption; the lack of an obvious trigger; and the immediate reappearance of the filament after the event. The unique mixture of major eruption properties that are observed in this event places severe constraints on the structure of the filament channel field and, consequently, on the possible eruption mechanism. Title: Analysis of Coronal Mass Ejections Observed by the Wide-field Imager (WISPR) on Parker Solar Probe Authors: Liewer, P. C.; Qiu, J.; Vourlidas, A.; Penteado, P.; Hall, J. R. Bibcode: 2021AAS...23832204L Altcode: The Wide-field Imager for Solar Probe (WISPR) has provided high resolution images of multiple coronal mass ejections (CMEs) during its first seven encounters with the Sun. Here we present results of the analysis of the origin and trajectories of several of these CMEs with some unexpected results. WISPR has a wide fixed angular field-of-view (FOV), extending radially from 13.5° to 108° from the Sun and approximately 50° in the transverse direction, but the physical extent of the imaged coronal region varies directly with the distance of the spacecraft from the Sun. We have developed tools for determining the trajectories of solar eject which take into account the rapid spacecraft motion. The CMEs analyzed have also been observed by either STEREO A or LASCO or both. To relate and compare the CMEs seen in the WISPR images to simultaneous observation from another white light telescope, it is necessary to relate the fields-of-view of the telescopes at any given time to a common inertial frame of reference, e.g., the Heliocentric Inertial coordinate frame. Using World Coordinate System information in the images' FITS headers, we project the trajectory determined from WISPR or features seen in the WISPR images onto images from the second white light telescope (or visa versa) to verify the trajectory determined from the WISPR data alone and to better understand the structure and evolution of the CMEs. Title: In-flight Calibration and Data Reduction for the WISPR Instrument On Board the PSP Mission Authors: Hess, Phillip; Howard, Russell A.; Stenborg, Guillermo; Linton, Mark; Vourlidas, Angelos; Thernisien, Arnaud; Colaninno, Robin; Rich, Nathan; Wang, Dennis; Battams, Karl; Kuroda, Natsuha Bibcode: 2021SoPh..296...94H Altcode: We present the calibration status and data reduction methodology for the Wide Field Imager for Solar Probe (WISPR) on board the Parker Solar Probe (PSP) mission. In particular, we describe the process for converting a raw image, measured in digital numbers (DN), to a calibrated image, measured in mean solar brightness (MSB). We also discuss details of the on board image processing including bias removal, the linearity of the electronics, pointing, geometric distortion, and photometric calibration using stellar measurements, and the characterization of vignetting and other instrumental artifacts. The analysis presented here is based on data from the first four WISPR orbits. As the PSP perihelia get progressively closer to the Sun and the WISPR concept of operation evolves to deal with the brighter scene, the calibration will likely need to be updated. Aging of the optics and the possibility of detector degradation may also occur. Hence, we consider the WISPR calibration as work in progress with updates reported as necessary. Title: Tracking solar wind flows from rapidly varying viewpoints by the Wide-field Imager for Parker Solar Probe Authors: Nindos, A.; Patsourakos, S.; Vourlidas, A.; Liewer, P. C.; Penteado, P.; Hall, J. R. Bibcode: 2021A&A...650A..30N Altcode: 2020arXiv201013140N
Aims: Our goal is to develop methodologies to seamlessly track transient solar wind flows viewed by coronagraphs or heliospheric imagers from rapidly varying viewpoints.
Methods: We constructed maps of intensity versus time and elongation (J-maps) from Parker Solar Probe (PSP) Wide-field Imager (WISPR) observations during the fourth encounter of PSP. From the J-map, we built an intensity on impact-radius-on-Thomson-surface map (R-map). Finally, we constructed a latitudinal intensity versus time map (Lat-map). Our methodology satisfactorily addresses the challenges associated with the construction of such maps from data taken from rapidly varying viewpoint observations.
Results: Our WISPR J-map exhibits several tracks, corresponding to transient solar wind flows ranging from a coronal mass ejection down to streamer blobs. The latter occurrence rate is about 4-5 per day, which is similar to the occurrence rate in a J-map made from ~1 AU data obtained with the Heliospheric Imager-1 (HI-1) on board the Solar Terrestrial Relations Observatory Ahead spacecraft (STEREO-A). STEREO-A was radially aligned with PSP during the study period. The WISPR J-map tracks correspond to angular speeds of 2.28 ± 0.7°/h (2.49 ± 0.95°/h), for linear (quadratic) time-elongation fittings, and radial speeds of about 150-300 km s−1. The analysis of the Lat-map reveals a bifurcating streamer, which implies that PSP was flying through a slightly folded streamer during perihelion.
Conclusions: We developed a framework to systematically capture and characterize transient solar wind flows from space platforms with rapidly varying vantage points. The methodology can be applied to PSP WISPR observations as well as to upcoming observations from instruments on board the Solar Orbiter mission.

Movie associated to Fig. 8 is available at https://www.aanda.org Title: Evolution of a streamer-blowout CME as observed by imagers on Parker Solar Probe and the Solar Terrestrial Relations Observatory Authors: Liewer, P. C.; Qiu, J.; Vourlidas, A.; Hall, J. R.; Penteado, P. Bibcode: 2021A&A...650A..32L Altcode: 2020arXiv201205174L Context. On 26-27 January 2020, the Wide-field Imager for Solar Probe on Parker Solar Probe (PSP) observed a coronal mass ejection (CME) from a distance of approximately 30 R⊙ as it passed through the instrument's 95° field-of-view, providing an unprecedented view of the flux rope morphology of the CME's internal structure. The same CME was seen by Solar Terrestrial Relations Observatory-Ahead (STEREO-A), beginning on 25 January.
Aims: Our goal is to understand the origin and determine the trajectory of this CME.
Methods: We analyzed data from three well-placed spacecrafts: PSP, STEREO-A, and Solar Dynamics Observatory (SDO). The CME trajectory was determined using a tracking-and-fitting technique and verified using simultaneous images of the CME propagation from STEREO-A. The fortuitous alignment with STEREO-A also provided views of coronal activity leading up to the eruption. Observations from SDO, in conjunction with potential magnetic field models of the corona, were used to analyze the coronal magnetic evolution for the three days leading up to the flux rope ejection from the corona on 25 January.
Results: We found that the 25 January CME is likely the end result of a slow magnetic flux rope eruption that began on 23 January and was observed by STEREO-A/Extreme Ultraviolet Imager. The analysis of these observations suggest that the flux rope was apparently constrained in the corona for more than a day before its final ejection on 25 January. STEREO-A/COR2 observations of swelling and brightening of the overlying streamer for several hours prior to eruption on 25 January led us to classify this as a streamer-blowout CME. The analysis of the SDO data suggests that restructuring of the coronal magnetic fields caused by an emerging active region led to the final ejection of the flux rope.

Movies associated to Figs. 3, 7-9 are available at https://www.aanda.org Title: Solar Physics and Solar Wind Authors: Raouafi, Nour E.; Vourlidas, Angelos Bibcode: 2021GMS...258.....R Altcode: No abstract at ADS Title: Improving the Medium-Term Forecasting of Space Weather: A Big Picture Review from a Solar Observer's Perspective Authors: Vourlidas, Angelos Bibcode: 2021FrASS...8...68V Altcode: Our scientific understanding of the solar drivers of Space Weather, i.e. Coronal Mass Ejections, flares, and solar energetic particles, has improved considerably in the last 20+ years thanks to a plethora of space missions and modeling advances. Yet, there has been no major breakthrough in assessing the geo-effectiveness of a given CME and associated phenomena, largely holding back actionable medium-term (up to 7 days) forecasting of Space Weather. Why is that?

To search for answers, I first summarise the results of the last 20+ years of research on solar drivers by collecting lessons-learned and identifying paradigm shifts in our view of solar activity, always in relation to Space Weather concerns. Then, I review the state of the key observational-based quantities used in forecasting, which allows me to identify the choke points and research gaps that drive the current medium-term forecasting performance. Finally, I outline a path forward consisting of the measurements with the strongest potential to improve space weather forecasting horizon and robustness. Title: The CME arrival prediction with the Effective Acceleration Model: Further testing with heliospheric imaging observations Authors: Paouris, Evangelos; Vourlidas, Angelos; Papaioannou, Athanasios; Anastasiadis, Anastasios Bibcode: 2021EGUGA..2310254P Altcode: The estimation of the Coronal Mass Ejection (CME) arrival is an open issue in the field of Space Weather. Many models have been developed to predict Time-of-Arrival (ToA). In this work, we utilize an updated version of the Effective Acceleration Model (EAM) to calculate the ToA. The EAM predicts the ToA of the CME-driven shock and the sheath's average speed at 1 AU. The model assumes that the interaction between the ambient solar wind and the interplanetary CME (ICME) results in constant acceleration or deceleration. We recently compared EAM against ENLIL and drag based models (DBEM) with a sample of 16 CMEs. We confirmed the well-known fact that the deceleration of fast ICMEs in the interplanetary medium is not captured by most models. We study further the deceleration of fast ICMEs by introducing, for the first time, wide-angle observations by the STEREO heliospheric imagers into the EAM model. The speed profiles for some test cases show deceleration in the interplanetary medium at greater distances compared with the field-of-view of the coronagraphs. Title: High fidelity spectroscopic imaging at low radio frequencies to estimate plasma parameters of solar coronal mass ejections at higher coronal heights Authors: Kansabanik, Devojyoti; Mondal, Surajit; Oberoi, Divya; Vourlidas, Angelos Bibcode: 2021EGUGA..2311089K Altcode: Coronal Mass Ejections (CMEs) are large-scale explosive eruptions of magnetised plasma from the Sun into the Heliosphere. Measuring the physical parameters of CMEs is crucial for understanding their physics and for assessing their geo-effectiveness. Radio observations offer the most direct means for estimating these plasma parameters when gyrosynchrotron (GS) emission is detected from the CME plasma. However, since the first detection by Bastian et al.2001, only a handful of studies have successfully detected GS emission from CME plasma. This is usually attributed to the challenges involved in obtaining the high dynamic range imaging required for observing this faint gyrosynchrotron emission in the vicinity of active solar emissions.The newly developed imaging pipeline (Mondal et al., 2019) designed for the data from Murchison Widefield Array (MWA) marks a significant improvement in metrewave solar radio imaging. Our work suggests that we should now be able to routinely detect GS emission from CME plasma. We present an example where we have successfully detected radio emission from CME plasma and modelled it as GS emission, leading to reliable estimates of CME magnetic field as well as the distribution of energetic electrons (Mondal et al. 2020). In a different example we are able to detect the radio emission from the CME plasma out to as far as 8.3 solar radii. We find that the observed spectra are not always consistent with simple GS models. This highlights that more complicated physics might be at play and points to the need for building more detailed models for interpreting these emissions. We hope that with the availability of polarimetric imaging capability, which we are in the process of developing, this technique will provide a robust way to routinely measure CME magnetic fields along with its other physical parameters. We note that these are the weakest detections of GS emissions from CME plasma reported yet. Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST) Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio, Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart; Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa, Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler, Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun, Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres, Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.; Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini, Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena; Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor; Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael; Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli, Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys, Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.; Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis, Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson, Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.; Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.; Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava, Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas, Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST Instrument Scientists; DKIST Science Working Group; DKIST Critical Science Plan Community Bibcode: 2021SoPh..296...70R Altcode: 2020arXiv200808203R The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. Title: Validation of Global EUV Wave MHD Simulations and Observational Techniques Authors: Downs, Cooper; Warmuth, Alexander; Long, David M.; Bloomfield, D. Shaun; Kwon, Ryun-Young; Veronig, Astrid M.; Vourlidas, Angelos; Vršnak, Bojan Bibcode: 2021ApJ...911..118D Altcode: Global EUV waves remain a controversial phenomenon more than 20 yr after their discovery by SOHO/EIT. Although consensus is growing in the community that they are most likely large-amplitude waves or shocks, the wide variety of observations and techniques used to identify and analyze them have led to disagreements regarding their physical properties and interpretation. Here, we use a 3D magnetohydrodynamic (MHD) model of the solar corona to simulate an EUV wave event on 2009 February 13 to enable a detailed validation of the various commonly used detection and analysis techniques of global EUV waves. The simulated event exhibits comparable behavior to that of a real EUV wave event, with similar kinematic behavior and plasma parameter evolution. The kinematics of the wave are estimated via visual identification and profile analysis, with both approaches providing comparable results. We find that projection effects can affect the derived kinematics of the wave, due to the variation in fast-mode wave speed with height in the corona. Coronal seismology techniques typically used for estimates of the coronal magnetic field are also tested and found to estimate fast-mode speeds comparable to those of the model. Plasma density and temperature variations of the wave front are also derived using a regularized inversion approach and found to be consistent with observed wave events. These results indicate that global waves are best interpreted as large-amplitude waves and that they can be used to probe the coronal medium using well-defined analysis techniques. Title: Addressing Gaps in Space Weather Operations and Understanding With Small Satellites Authors: Verkhoglyadova, O. P.; Bussy-Virat, C. D.; Caspi, A.; Jackson, D. R.; Kalegaev, V.; Klenzing, J.; Nieves-Chinchilla, J.; Vourlidas, A. Bibcode: 2021SpWea..1902566V Altcode: 2020arXiv201203343V Gaps in space weather observations that can be addressed with small satellites are identified. Potential improvements in solar inputs to space weather models, space radiation control, estimations of energy budget of the upper Earth's atmosphere, and satellite drag modeling are briefly discussed. Key observables, instruments, and observation strategies by small satellites are recommended. Tracking optimization for small satellites is proposed. Title: Estimating plasma parameters of solar coronal mass ejections at higher coronal heights using high fidelity low-frequency radio images Authors: Kansabanik, Devojyoti; Mondal, Surajit; Oberoi, Divya; Vourlidas, Angelos Bibcode: 2021csss.confE..36K Altcode: Coronal Mass Ejection (CMEs) are large scale explosive eruptions of magnetised plasma from Sun into Heliosphere. Measuring the physical parameters of CMEs is crucial for understanding their physics and for assessing their geoeffectiveness. Radio observations offer the most direct means for estimating these plasma parameters when gyrosynchrotron (GS) emission is detected from the CME. But only a handful of studies have successfully managed to detect this GS emissions (Bastian et al. 2001; Maia et al. 2007; and Demoulin et al. 2012).We will show that it is now routinely possible to detect these GS emissions using high dynamic range radio images produced by an automated imaging pipeline (Mondal et al. 2019a) using the data from Murchison Widefield Array. We have detected the radio emission from CME plasma at the largest distance (8.3 solar radii) till date. We will show that magnetic field and energetic electron distribution inside CME plasma can be estimated directly at higher coronal heights by fitting a model of GS emission to the observed spectra. On the other hand it is also observed that radio spectra always can not be represented by simple GS spectra. This indicates that a more complicated physics is involved for these radio emissions. Title: On the Rigidity Spectrum of Cosmic-Ray Variations within Propagating Interplanetary Disturbances: Neutron Monitor and SOHO/EPHIN Observations at ∼1-10 GV Authors: Belov, Anatoly; Papaioannou, Athanasios; Abunina, Maria; Dumbovic, Mateja; Richardson, Ian G.; Heber, Bernd; Kuhl, Patrick; Herbst, Konstantin; Anastasiadis, Anastasios; Vourlidas, Angelos; Eroshenko, Eugenia; Abunin, Artem Bibcode: 2021ApJ...908....5B Altcode: The rigidity dependence of all Forbush decreases (FDs) recorded from 1995 to 2015 has been determined using neutron monitor (NM) and Solar and Heliospheric Observatory (SOHO) (EPHIN) spacecraft data, covering the energy (rigidity) range from ∼433 MeV (1 GV) to 9.10 GeV (10 GV). We analyzed a total of 421 events and determined the spectrum in rigidity with an inverse power-law fit. As a result, the mean spectral index was identified to be ⟨γF⟩ = 0.46 ± 0.02. The majority (∼66%) of the FDs have γF within the range 0.3-0.7. The remaining one-third of the events (∼33%) have either (very) soft or hard FD spectra, with the latter being more common than the former. Significant variations of γF occur within almost every FD event. During the initial FD decay phase the spectrum becomes gradually harder, in contrast to the recovery phase, when it becomes softer. Additionally, low energies (rigidities) seem to be better suited for studying the fine structure of interplanetary disturbances (primarily interplanetary coronal mass ejections) that lead to FDs. In particular, FDs recorded by the EPHIN instrument on SOHO better capture a two-step structure than FDs observed by NMs. Finally, the ejecta of an ICME, especially when identified as a magnetic cloud, often leads to abrupt changes in the slope of γF. Title: Assessing the Projection Correction of Coronal Mass Ejection Speeds on Time of Arrival Prediction Performance Using the Effective Acceleration Model Authors: Paouris, Evangelos; Vourlidas, Angelos; Papaioannou, Athanasios; Anastasiadis, Anastasios Bibcode: 2021SpWea..1902617P Altcode: 2020arXiv201204703P White light images of coronal mass ejections (CMEs) are projections on the plane of sky (POS). As a result, CME kinematics are subject to projection effects. The error in the true (deprojected) speed of CMEs is one of the main causes of uncertainty to Space Weather forecasts, since all estimates of the CME time of arrival (ToA) at a certain location within the heliosphere require, as input, the CME speed. We use single viewpoint observations for 1,037 flare CME events between 1996 and 2017 and propose a new approach for the correction of the CME speed assuming radial propagation from the flare site. Our method is uniquely capable to produce physically reasonable deprojected speeds across the full range of source longitudes. We bound the uncertainty in the deprojected speed estimates via limits in the true angular width of a CME based on multiview point observations. Our corrections range up to 1.37-2.86 for CMEs originating from the center of the disk. On average, the deprojected speeds are 12.8% greater than their POS speeds. For slow CMEs (VPOS < 400 km/s) the full ice cream cone model performs better while for fast and very fast CMEs (VPOS > 700 km/s) the shallow ice cream model gives much better results. CMEs with 691-878 km/s POS speeds have a minimum ToA mean absolute error (MAE) of 11.6 h. This method, is robust, easy to use, and has immediate applicability to Space Weather forecasting applications. Moreover, regarding the speed of CMEs, our work suggests that single viewpoint observations are generally reliable. Title: Plasma heating induced by tadpole-like downflows in the flaring solar corona Authors: Samanta, T.; Tian, H.; Chen, B.; Reeves, K. K.; Cheung, M. C. M.; Vourlidas, A.; Banerjee, D. Bibcode: 2021Innov...200083S Altcode: 2021arXiv210314257S As one of the most spectacular energy release events in the solar system, solar flares are generally powered by magnetic reconnection in the solar corona. As a result of the re-arrangement of magnetic field topology after the reconnection process, a series of new loop-like magnetic structures are often formed and are known as flare loops. A hot diffuse region, consisting of around 5-10 MK plasma, is also observed above the loops and is called a supra-arcade fan. Often, dark, tadpole-like structures are seen to descend through the bright supra-arcade fans. It remains unclear what role these so-called supra-arcade downflows (SADs) play in heating the flaring coronal plasma. Here we show a unique flare observation, where many SADs collide with the flare loops and strongly heat the loops to a temperature of 10-20 MK. Several of these interactions generate clear signatures of quasi-periodic enhancement in the full-Sun-integrated soft X-ray emission, providing an alternative interpretation for quasi-periodic pulsations that are commonly observed during solar and stellar flares. Title: Propagating Conditions and the Time of ICME Arrival: A Comparison of the Effective Acceleration Model with ENLIL and DBEM Models Authors: Paouris, Evangelos; Čalogović, Jaša; Dumbović, Mateja; Mays, M. Leila; Vourlidas, Angelos; Papaioannou, Athanasios; Anastasiadis, Anastasios; Balasis, Georgios Bibcode: 2021SoPh..296...12P Altcode: 2020arXiv201205857P The Effective Acceleration Model (EAM) predicts the Time-of-Arrival (ToA) of the Coronal Mass Ejection (CME) driven shock and the average speed within the sheath at 1 AU. The model is based on the assumption that the ambient solar wind interacts with the interplanetary CME (ICME) resulting in constant acceleration or deceleration. The upgraded version of the model (EAMv3), presented here, incorporates two basic improvements: (i) a new technique for the calculation of the acceleration (or deceleration) of the ICME from the Sun to 1 AU and (ii) a correction for the CME plane-of-sky speed. A validation of the upgraded EAM model is performed via comparisons to predictions from the ensemble version of the Drag-Based model (DBEM) and the WSA-ENLIL+Cone ensemble model. A common sample of 16 CMEs/ICMEs, in 2013 - 2014, is used for the comparison. Basic performance metrics such as the mean absolute error (MAE), mean error (ME) and root mean squared error (RMSE) between observed and predicted values of ToA are presented. MAE for EAM model was 8.7 ±1.6 hours while for DBEM and ENLIL was 14.3 ±2.2 and 12.8 ±1.7 hours, respectively. ME for EAM was −1.4 ±2.7 hours in contrast with −9.7 ±3.4 and −6.1 ±3.3 hours from DBEM and ENLIL. We also study the hypothesis of stronger deceleration in the interplanetary (IP) space utilizing the EAMv3 and DBEM models. In particularly, the DBEM model perform better when a greater value of drag parameter, of order of a factor of 3, is used in contrast to previous studies. EAMv3 model shows a deceleration of ICMEs at greater distances, with a mean value of 0.72 AU. Title: Nonthermal electrons revealed by LOFAR Authors: Zucca, Pietro; Pellizzoni, Alberto; Krankowski, Andrzej; Rothkaehl, Hanna; Mann, Gottfried; Vocks, Christian; Magdalenic, Jasmina; Marque, Christophe; Jackson, Bernard; Fallows, Richard; Tomasik, Lukasz; Hamish; Reid, A. S.; Gallagher, Peter; Vourlidas, Angelos; Bisi, Mario M.; Carley, Eoin; Matyjasiak, Barbara; Kozarev, Kamen; Dabrowski, Bartosz; Morosan, Diana; Tiburzi, Caterina; Chang, Peijin Bibcode: 2021cosp...43E1065Z Altcode: During solar flares and CMEs, the corona is heated, plasma motion, waves and shocks are ignited, and particles are accelerated. The accelerated particles propagate through the solar corona causing a variety of plasma instabilities that lead to enhanced non-thermal radio emission, known as "radio bursts". By studying radio-bursts' characteristics we can gain insight into the properties of energetic particles and the ambient coronal plasma, and the properties of particle acceleration mechanisms, such as magnetic reconnection and/or shocks in the solar atmosphere. The Low Frequency aRray (LOFAR) can be used to study the fundamental plasma physics of solar radio bursts with unprecedented time resolution in dynamic spectra, as well as with both interferometric imaging and tied array imaging. In this talk, an overview of recent results obtained with the LOFAR telescope will be given, including observations of a different variety of radio bursts such as type II, III and IV. These observations were performed with simultaneous beam formed and interferometric imaging, resulting in unprecedented special resolution with baselines up to ~120 km. Finally, we will present the plan for future observations and the remaining challenges of solar-heliospheric low-frequency observations. Title: Gibson & Low Flux Rope Model: More Than a Spheromak! Authors: Malanushenko, Anna; Gibson, Sarah; Provornikova, Elena; Dalmasse, Kévin; Merkin, Viacheslav; Vourlidas, Angelos; Nychka, Doug; Flyer, Natasha; Arge, Charles Bibcode: 2021cosp...43E1736M Altcode: Modeling solar coronal mass ejections (CMEs) is very important for both understanding coronal physics and for improving the accuracy of space weather forecasts. While it is generally accepted that CMEs are primarily magnetic structures, the exact properties of these structures could differ in different models and events. A structure often considered is a spheromak, a toroidal twisted flux rope, which is ejected as a CME bubble. Another commonly considered structure is a twisted magnetic flux rope, which is anchored to the solar surface while its upper portion is ejected into interplanetary space. In this talk we will show how a well-known analytical magnetohydrodynamic CME model (Gibson \& Low, 1998), generally considered a spheromak-like model, can be extended to represent both standard spheromak and twisted flux tube configurations, as well as other topologically distinct magnetic structures. We will begin with the general parameters of the flux rope in this model (such as size and stretching parameters), and explore topologically different congurations possible with their variation. We then present several dimensionless parameters which can be varied to achieve these different configurations and consider how they relate to directly observable quantities. This work is particularly timely, as the Gibson \& Low model is been increasingly used as input to numerical models of the solar corona and the heliosphere. The ability to generate topologically different magnetic congurations within this analytic solution is of great value to such simulations, as well as for the studies of the flux ropes forming in the solar corona. Title: Constraining the physical parameters of coronal mass ejections at large coronal heights using high fidelity low radio frequency images Authors: Kansabanik, Devojyoti; Oberoi, Divya; Vourlidas, Angelos; Mondal, Surajit Bibcode: 2021cosp...43E1009K Altcode: Coronal Mass Ejections (CMEs) are large scale explosive eruptions of magnetised plasma from the Sun into the Heliosphere. Measuring the physical parameters of CMEs is crucial for understanding their physics and for assessing their geo-effectiveness. Radio observations offer the most direct means for estimating these plasma parameters when gyrosynchrotron (GS) emission is detected from the CME. However, since the first detection by Bastian et al.2001, only a handful of studies have successfully detected GS emission from CME plasma. This is usually attributed to the challenges involved in obtaining the high contrast imaging required for observing this faint emission in the vicinity of active solar emissions. Recent work using data from the Murchison Wide field Array (MWA), a low frequency radio interferometer, and the newly developed imaging pipeline designed for solar radio imaging (Mondal et al., 2019) marks a significant improvement in metrewave solar radio imaging. Our work suggests that we should now be able to routinely detect GS emission from CME plasma. We present an example where we have successfully detected radio emission from CME plasma and modelled it as GS emission, leading to reliable estimates of CME magnetic eld as well as the distribution of energetic electrons (Mondal et al.2020). In a different example, we find that the observed spectra are not always consistent with simple GS models. For this CME we are able to detect the radio emission from the CME plasma out to as far as 8.3 solar radii. This highlights that more complicated physics might be at play and points to the need for building more detailed models for interpreting these emissions. We note that these are the weakest detections of GS emissions from CME plasma reported yet. Title: Investigating the circumsolar wind with Parker Solar Probe near-imaging and in-situ high cadence observations Authors: Patsourakos, Spiros; Liewer, Paulett; Stenborg, Guillermo; Howard, Russell; Hess, Phillip; Stevens, Michael; Vourlidas, Angelos; Kasper, Justin; Nindos, Alexander; Penteado, Paulo; Korreck, Kelly; Case, Anthony Bibcode: 2021cosp...43E.940P Altcode: The proposition of the existence of the solar wind and its subsequent discovery were major milestones at the dawn of the Space Age. Since then, the solar wind has been extensively observed by in-situ instruments at various locations in the inner and outer heliosphere but mainly at 1 AU, and by remote sensing instruments at 1 AU. Despite significant progress in the characterization and understanding of the solar wind, important questions about the nature of the solar wind remain unsettled. These questions include the nature of the launch and acceleration of the solar wind and whether it is steady, quasi-steady, periodic or intermittent. The recently launched Parker Solar Probe (PSP) mission, which has been already plunged several times in the solar corona, is ideally suited to shed more light into these lingering questions. We present a coordinated analysis of up-close and high-cadence imaging observations of the solar wind taken by WISPR and of in-situ solar-wind observations taken inside the solar corona by SWEAP during the first solar encounters of PSP. A discussion of instrumental and orbital aspects of the WISPR observations pertinent to our analysis is also included. Imaging data of the solar wind from ~ 1 AU by COR2 on STEREO-A spacecraft is also analyzed. We submit the time-series of the imaging and in-situ solar wind data to an array of methods aiming to map their properties. We conclude with a discussion of future PSP (WISPR and SWEAP) and Solar Orbiter (SoloHI) observing and analysis strategies pertinent to our science questions. Title: Recent Advances with EUV Irradiance Inputs to the Upper Atmosphere Authors: Vourlidas, Angelos Bibcode: 2021cosp...43E.817V Altcode: The proliferation of satellites in low Earth orbits has increased the need for accurate tracking and orbit predictions. Those require reliable modeling of the atmospheric drag in the upper atmosphere, which, in turn, depends the quality of the solar forcing inputs to the atmospheric models. In this talk, I review the status of the solar focusing inputs with emphasis on the EUV irradiance measurements and indices. I discuss recent developments and the issues that prevent us from improving atmospheric drag prediction beyond a few days in the future. I finally offer possible mitigation strategies for consideration. Title: Unraveling the Internal Magnetic Field Structure of the Earth-directed Interplanetary Coronal Mass Ejections Authors: Nieves-Chinchilla, Teresa; Jian, Lan; Szabo, Adam; Vourlidas, Angelos; Balmaceda, Laura; Guedes Dos Santos, Luiz Fernando Bibcode: 2021cosp...43E1739N Altcode: The magnetic field configurations associated with interplanetary coronal mass ejections (ICMEs) are the in situ manifestations of the entrained magnetic structure associated with coronal mass ejections (CMEs). We present a comprehensive study of the internal magnetic field configurations of ICMEs observed at 1 AU by the Wind mission during 1995 - 2015. The goal is to unravel the internal magnetic structure associated with the ICMEs and establish the signatures that validate a flux-rope structure. We examine the expected magnetic field signatures by simulating spacecraft trajectories within a simple flux rope, i.e., with circular-cylindrical (CC) helical magnetic field geometry. By comparing the synthetic configurations with the 353 ICME in situ observations, we find that only 152 events (Fr) display the clear signatures of an expected axial-symmetric flux rope. Two more populations exhibit possible signatures of flux rope; 58 cases (F−) display a small rotation (<90$^{\circ}$) of the magnetic field direction, interpreted as a large separation of the spacecraft from the center, and, 62 cases (F+) exhibit larger rotations, possibly arising from more complex configuration. The categories, Cx (14$%$) and E events (9$%$), reveal signatures of complexity possibly related with evolutionary processes. We then reconstruct the flux ropes assuming CC geometry. We examine the orientation and geometrical properties during the solar activity levels at the end of Solar Cycle 22 (SC22), SC23 and part of SC24. The orientation exhibits solar cycle trends and follow the heliospheric current sheet orientation. We confirm previous studies that found a Hale cycle dependence of the poloidal field reversal. By comparing our results with the occurrence of CMEs with large angular width (AW> 60$^{\circ}$) we find a broad correlation suggesting that such events are highly inclined CMEs. The solar cycle distribution of bipolar vs. unipolar Bz configuration confirms that the CMEs may remove solar cycle magnetic field and helicity. Title: On the Quasi-Three Dimensional Configuration of Magnetic Clouds Authors: Hu, Qiang; He, Wen; Qiu, Jiong; Vourlidas, Angelos; Zhu, Chunming Bibcode: 2021GeoRL..4890630H Altcode: 2020arXiv201011889H We develop an optimization approach to model the magnetic field configuration of magnetic clouds, based on a linear force-free formulation in three dimensions. Such a solution, dubbed the Freidberg solution, is kin to the axisymmetric Lundquist solution, but with more general "helical symmetry." The merit of our approach is demonstrated via its application to two case studies of in situ measured magnetic clouds. Both yield results of reduced χ2 ≈ 1. Case 1 shows a winding flux rope configuration with one major polarity. Case 2 exhibits a double-helix configuration with two flux bundles winding around each other and rooted on regions of mixed polarities. This study demonstrates the three-dimensional complexity of the magnetic cloud structures. Title: Results from the LOFAR coordination with PSP Authors: Zucca, Pietro; Pellizzoni, Alberto; Krankowski, Andrzej; Rothkaehl, Hanna; Mann, Gottfried; Vocks, Christian; Magdalenic, Jasmina; Marque, Christophe; Jackson, Bernard; Fallows, Richard; Tomasik, Lukasz; Miteva, Rositsa; Hamish; Reid, A. S.; Gallagher, Peter; Vourlidas, Angelos; Bisi, Mario M.; Carley, Eoin; Matyjasiak, Barbara; Kozarev, Kamen; Dabrowski, Bartosz; Morosan, Diana; Tiburzi, Caterina; Zhabngm, Peijin Bibcode: 2021cosp...43E.945Z Altcode: Understanding and modelling the complex state of the Sun-solar wind-magnetosphere-ionosphere-thermosphere system, requires a comprehensive set of multiwavelength observations. LOFAR has unique capabilities in the radio domain. Some examples of these include: a) the ability to take high-resolution solar dynamic spectra and radio images of the Sun; b) observing the scintillation (interplanetary scintillation - IPS) of distant, compact, astronomical radio sources to determine the density, velocity and turbulence structure of the solar wind; and c) the use of Faraday rotation as a tool to probe the interplanetary magnetic-field strength and direction. However, to better understand and predict how the Sun, its atmosphere, and more in general the Heliosphere works and impacts Earth, the combination of in-situ spacecraft measurements and ground-based remote-sensing observations of coronal and heliospheric plasma parameters is extremely useful. Ground-based observations can be used to infer a global picture of the inner heliosphere, providing the essential context into which in-situ measurements from spacecraft can be placed. Conversely, remote-sensing observations usually contain information from extended lines of sight, with some deconvolution and modelling necessary to build up a three-dimensional (3-D) picture. Precise spacecraft measurements, when calibrated, can provide ground truth to constrain these models. The PSP mission is observing the solar corona and near-Sun interplanetary space. It has a highly-elliptical orbit taking the spacecraft as close as nearly 36 solar radii from the Sun centre on its first perihelion passage, and subsequent passages ultimately reaching as close as 9.8 solar radii. Four instruments are on the spacecraft's payload: FIELDS measuring the radio emission, electric and magnetic fields, Poynting flux, and plasma waves as well as the electron density and temperature; ISOIS measuring energetic electrons, protons, and heavy ions in the energy range 10 keV-100 MeV; SWEAP measuring the density, temperature, and flow speed of electrons, protons, and alphas in the solar wind; and finally, WISPR imaging coronal streamers, coronal mass ejections (CMEs), their associated shocks, and other solar wind structures in the corona and near-Sun interplanetary space, and provide context for the other three in-situ instruments. In this talk, several results of the joint LOFAR/PSP campaign will be presented, including fine structures of radio bursts, localization and kinematics of propagating radio sources in the heliosphere, and the challenges and plans for future observing campaigns including PSP and Solar Orbiter. Title: On the Quasi-Three Dimensional Configuration of Magnetic Clouds Authors: Hu, Q.; Jiong, Q.; Liewer, P. C.; Vourlidas, A.; Zhu, C. Bibcode: 2020AGUFMSH0440015H Altcode: Magnetic clouds (MCs) identified in the solar wind from in-situ spacecraft measurements represent a subset of interplanetary coronal mass ejections (ICMEs). They possess a specific set of observational signatures based on magnetic field and plasma parameters. In particular a relatively smooth rotation of the magnetic field and elevated field magnitude usually hint at a well-organized field configuration traversing the single-point observing platform. Additional evidence in support of such a configuration can be obtained from the solar source regions where they originate, generally taken in the form of a flux rope. Based on in-situ spacecraft measurements, various flux rope models in one-dimensional and two-dimensional configurations have been developed and applied to event studies, with the latter represented by the Grad-Shafranov reconstruction technique. However given the significant variability in the in-situ measurements, not all MC events can be modeled successfully by the existing methods. We develop a quasi-three dimensional model which is intrinsically three-dimensional. We demonstrate, in several case studies, that a satisfactory fitting to the in-situ spacecraft data along the path across such a magnetic structure is obtained as judged by the proper Chi^2 statistics, taking into account the underlying data uncertainties. Title: Constraining the Physical Parameters of Coronal Mass Ejections at Large Coronal Heights using Low Radio Frequency Gyrosynchrotron Emission Authors: Kansabanik, D.; Mondal, S.; Oberoi, D.; Vourlidas, A. Bibcode: 2020AGUFMSH0280017K Altcode: Coronal Mass Ejection (CMEs) are large scale explosive eruptions of magnetised plasma from the Sun into the Heliosphere. Measuring the physical parameters of CMEs is crucial for understanding their physics and for assessing their geo-effectiveness. Radio observations offer the most direct means for estimating these plasma parameters when gyrosynchrotron (GS) emission is detected from the CME. However, since the first detection by Bastian et al. in 2001, only a handful of studies have successfully detected GS emission from CME plasma.This is usually attributed to the challenges involved in obtaining the high contrast imaging required for observing this faint emission in the vicinity of active solar emissions. Title: Imaging the Solar Wind From Space: Where do we stand? Authors: Vourlidas, A. Bibcode: 2020AGUFMSH031..04V Altcode: Next year marks the 50th anniversary of the detection of Coronal Mass Ejections from space. The discovery and subsequent observations of thousands of events from a stream of coronagraph telescopes marked a paradigm shift of our view of the corona, from a physical system changing gradually over a solar cycle, to a system marked with explosive transient activity on timescales from seconds to days to months. Thanks to coronagraphs, and more recently EUV imagers, Space Weather forecasting and research have become strong research areas within the Heliophysics discipline. adding to that, the transients and even the more quiescent background wind can now be imaged directly in the inner heliosphere thanks to the advent of heliospheric imaging since the mid-2000s.

The recent deployment of the Parker Solar Probe and Solar Orbiter missions ushers a new era of coronal/heliospheric imaging from widely varying vantage points along with future missions, such as PUNCH, and operational mission at the L1 and L5 point. It is, therefore, an appropriate time to take stock of the lessons learned from the decades of imaging of the solar wind, both quiescent and transient. In this talk, I review those lessons/learned and discuss where to go next. Title: Investigation of a prominent solar wind structure observed by PSP on June 13, 2020 Authors: Niembro Hernandez, T.; Stevens, M. L.; Korreck, K. E.; Paulson, K. W.; Nieves-Chinchilla, T.; Szabo, A.; Balmaceda, L. A.; Vourlidas, A.; Horbury, T. S.; Luhmann, J. G.; Case, A. W.; Kasper, J. C.; Larson, D. E.; Livi, R.; Rahmati, A.; Huang, J.; Whittlesey, P. L.; Bale, S. D.; Pulupa, M.; Malaspina, D.; Bonnell, J. W.; Harvey, P.; Goetz, K.; Dudok de Wit, T.; MacDowall, R. J.; Koval, A. Bibcode: 2020AGUFMSH0490007N Altcode: In the early hours of June 13, 2020, just after the end of its 5 th solar encounter, the Faraday Cup on-board Parker Solar Probe (PSP) registered the passage of a prominent solar wind structure embedded in highly variable plasma and characterized by regions with distinct plasma conditions (speed, density, magnetic field, etc) and wave activity. From remote sensing observations, using spacecraft at different heliospheric locations, several transients were observed ejected from the Sun, including a coronal mass ejection (CME) oriented away from PSP that may have also influenced the solar wind conditions through which the structure in question has propagated. In this work, we report the PSP-SPC observations around this structure and identify possible solar sources relying on multi-spacecraft observations. We also characterized the propagation and evolution of the CME observed on June 12, 2020 and the role it played influencing the conditions of the unusual variable ambient solar wind. Title: Ensemble modeling of interplanetary CMEs with data-constrained internal magnetic flux rope Authors: Provornikova, E.; Merkin, V. G.; Malanushenko, A. V.; Gibson, S. E.; Vourlidas, A.; Arge, C. N. Bibcode: 2020AGUFMSH0030016P Altcode: Understanding the evolution of the CME magnetic structure as it propagates through the interplanetary space is a key aspect in the development of forecasting of magnetic properties of a CME arriving at Earth and thus its impact on space weather. To analyze processes of interplanetary CME (ICME)/solar-wind interactions and the role of CME flux rope specification and solar wind background structure, we take a statistical approach and perform thousands of data-driven MHD simulations of ICME propagation in the inner heliosphere. Data-driven modeling of ICMEs in the inner heliosphere (starting beyond the critical surface in the corona) presents an attractive and computationally feasible approach, since it bypasses the complex problem of CME initiation and eruption in the corona. We simulate the propagation of ICMEs in the inner heliosphere using a global model driven at the coronal boundary by the Wang-Sheeley-Arge (WSA)-ADAPT model. ICMEs are initiated at 21.5 solar radii using an MHD analytical Gibson-Low (G&L) model of a self-similarly expanding magnetic flux rope with defining parameters (e.g., location, magnetic topology, width, magnetic field strength, speed, orientation). The ICME propagation is simulated using the inner heliosphere version of the Grid Agnostic MHD for Extended Research Applications (GAMERA) MHD model, which is a reinvention of the high-heritage Lyon-Fedder-Mobarry (LFM) code. A set of values for each of the defining G&L parameters was constrained by statistical representation of solar CME observations. With the aim to span the solar cycle, we model ICME propagation in different solar wind backgrounds corresponding to rising, maximum, declining and minimum solar cycle phases. A grid of G&L parameters and four solar wind backgrounds constitute a parameter space for thousands of MHD ICME runs. For each of the simulations we extract synthetic in-situ observations of ICME as it passes Earth and synthetic white-light images of an ICME as it propagates in the interplanetary space. We present an analysis of produced distributions of ICME parameters and characteristics. Title: Analysis of Solar Wind Ejecta Observed by the Wide-field Imager (WISPR) on Parker Solar Probe Authors: Liewer, P. C.; Qiu, J.; Vourlidas, A.; Hall, J. R.; Penteado, P.; Howard, R. A. Bibcode: 2020AGUFMSH0490005L Altcode: The three-to-five-month highly elliptical orbit of Parker Solar Probe (PSP), approaching within 10 solar radii of the Sun, allows the Wide-field Imager for Solar Probe (WISPR) to view the corona with unprecedented spatial resolution. WISPR has a wide fixed angular field-of-view (FOV), extending radially from 13.5° to 108° from the Sun and approximately 50° in the transverse direction, but the physical extent of the imaged coronal region varies directly with the distance of the spacecraft from the Sun. We have developed tools for determining the trajectories of solar eject which take into account the spacecraft motion. Here, we present results of the analysis of the trajectory of several CMEs observed by WISPR using these tools, including CMEs observed on 2020 January 20 and 2020 January 26-27. The CMEs were also observed in white light by either STEREO A or LASCO or both. Observations from STEREO A, LASCO and SDO are used to study the origin and evolution of these events. To relate and compare the ejecta seen in the WISPR images to simultaneous observation from another white light telescope, it is necessary to relate the fields-of-view of the telescopes at any given time to a common frame of reference, such as the Heliocentric Inertial coordinate frame. Using World Coordinate System information in the images' FITS headers, we project the trajectory determined from WISPR or features seen in the WISPR images onto images from the second white light telescope to better understand the structure and evolution of the CMEs. Title: Relating Imaged Streamer Flows to the Slow Solar Winds measured by Solar Orbiter and Parker Solar Probe Authors: Rouillard, A. P.; Griton, L.; Louarn, P.; Fedorov, A.; Horbury, T. S.; Kouloumvakos, A.; Poirier, N.; Lavarra, M.; Vourlidas, A.; Howard, R. A.; Moncuquet, M.; Lavraud, B.; Fargette, N.; Réville, V.; Bruno, R.; Prech, L.; Livi, S. A.; Owen, C. J.; Angelini, V.; Bale, S. D.; Evans, V.; Kasper, J. C.; O'Brien, H.; Penou, E.; Pinto, R. Bibcode: 2020AGUFMSH0360002R Altcode: The physical mechanisms that produce the slow solar wind are still highly debated. Parker Solar Probe's (PSP's) recent solar encounters during Solar Orbiter's (SolO) cruise phase provide new opportunities to relate in situ measurements of the nascent slow solar wind with white-light images of the solar corona. We exploit data taken by the Solar and Heliospheric Observatory, the Solar TErrestrial RElations Observatory (STEREO), and the Wide Imager on Solar Probe to study the connection between real and pseudo-streamer flows with high-density plasma measured by the different spacecraft. We exploit these images to classify the different types of slow winds measured by PSP and SolO and investigate the magneto-plasma properties of these different winds. In this presentation a particular focus will be put on the interpretation of the high-cadence measurements taken by the Proton-Alpha Sensor on Solar Orbiter. Title: Decoding the Pre-Eruptive Magnetic Field Configurations of Coronal Mass Ejections Authors: Patsourakos, S.; Vourlidas, A.; Török, T.; Kliem, B.; Antiochos, S. K.; Archontis, V.; Aulanier, G.; Cheng, X.; Chintzoglou, G.; Georgoulis, M. K.; Green, L. M.; Leake, J. E.; Moore, R.; Nindos, A.; Syntelis, P.; Yardley, S. L.; Yurchyshyn, V.; Zhang, J. Bibcode: 2020SSRv..216..131P Altcode: 2020arXiv201010186P A clear understanding of the nature of the pre-eruptive magnetic field configurations of Coronal Mass Ejections (CMEs) is required for understanding and eventually predicting solar eruptions. Only two, but seemingly disparate, magnetic configurations are considered viable; namely, sheared magnetic arcades (SMA) and magnetic flux ropes (MFR). They can form via three physical mechanisms (flux emergence, flux cancellation, helicity condensation). Whether the CME culprit is an SMA or an MFR, however, has been strongly debated for thirty years. We formed an International Space Science Institute (ISSI) team to address and resolve this issue and report the outcome here. We review the status of the field across modeling and observations, identify the open and closed issues, compile lists of SMA and MFR observables to be tested against observations and outline research activities to close the gaps in our current understanding. We propose that the combination of multi-viewpoint multi-thermal coronal observations and multi-height vector magnetic field measurements is the optimal approach for resolving the issue conclusively. We demonstrate the approach using MHD simulations and synthetic coronal images. Title: Radio observations of coronal mass ejection initiation and development in the low solar corona Authors: Carley, Eoin P.; Vilmer, Nicole; Vourlidas, Angelos Bibcode: 2020FrASS...7...79C Altcode: Coronal mass ejections are large eruptions of plasma and magnetic field from the low solar corona into the heliosphere. These eruptions are often associated with energetic electrons that produce various kinds of radio emission. However, there is ongoing investigation into exactly where, when and how the electron acceleration occurs during flaring and eruption, and how the associated radio emission can be exploited as a diagnostic of both the particle acceleration and CME eruptive physics. Here, we review past and present developments in radio observations of flaring and eruption, from the destabilisation of flux ropes to development of a CME and the eventual driving of shocks in the corona. We concentrate primarily on the progress made in CME radio physics in the past two decades, and show how radio imaging spectroscopy provides the ability to diagnose the locations and kinds of electron acceleration during eruption, which provides insight into CME eruptive models in the early stages of their evolution (<10 Rsun). We finally discuss how new instrumentation in the radio domain will pave the way for a deeper understanding of CME physics in the near future. Title: Coordination within the remote sensing payload on the Solar Orbiter mission Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.; Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade, S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.; Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy, S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.; Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey, B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.; Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi, M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.; Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.; Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.; Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.; Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams, D.; Woch, J.; Zhukov, A. N.; Zouganelis, I. Bibcode: 2020A&A...642A...6A Altcode: Context. To meet the scientific objectives of the mission, the Solar Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing (RS) instruments designed for joint operations with inter-instrument communication capabilities. Indeed, previous missions have shown that the Sun (imaged by the RS instruments) and the heliosphere (mainly sampled by the IS instruments) should be considered as an integrated system rather than separate entities. Many of the advances expected from Solar Orbiter rely on this synergistic approach between IS and RS measurements.
Aims: Many aspects of hardware development, integration, testing, and operations are common to two or more RS instruments. In this paper, we describe the coordination effort initiated from the early mission phases by the Remote Sensing Working Group. We review the scientific goals and challenges, and give an overview of the technical solutions devised to successfully operate these instruments together.
Methods: A major constraint for the RS instruments is the limited telemetry (TM) bandwidth of the Solar Orbiter deep-space mission compared to missions in Earth orbit. Hence, many of the strategies developed to maximise the scientific return from these instruments revolve around the optimisation of TM usage, relying for example on onboard autonomy for data processing, compression, and selection for downlink. The planning process itself has been optimised to alleviate the dynamic nature of the targets, and an inter-instrument communication scheme has been implemented which can be used to autonomously alter the observing modes. We also outline the plans for in-flight cross-calibration, which will be essential to the joint data reduction and analysis.
Results: The RS instrument package on Solar Orbiter will carry out comprehensive measurements from the solar interior to the inner heliosphere. Thanks to the close coordination between the instrument teams and the European Space Agency, several challenges specific to the RS suite were identified and addressed in a timely manner. Title: When do solar erupting hot magnetic flux ropes form? Authors: Nindos, A.; Patsourakos, S.; Vourlidas, A.; Cheng, X.; Zhang, J. Bibcode: 2020A&A...642A.109N Altcode: 2020arXiv200804380N
Aims: We investigate the formation times of eruptive magnetic flux ropes relative to the onset of solar eruptions, which is important for constraining models of coronal mass ejection (CME) initiation.
Methods: We inspected uninterrupted sequences of 131 Å images that spanned more than eight hours and were obtained by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to identify the formation times of hot flux ropes that erupted in CMEs from locations close to the limb. The appearance of the flux ropes as well as their evolution toward eruptions were determined using morphological criteria.
Results: Two-thirds (20/30) of the flux ropes were formed well before the onset of the eruption (from 51 min to more than eight hours), and their formation was associated with the occurrence of a confined flare. We also found four events with preexisting hot flux ropes whose formations occurred a matter of minutes (from three to 39) prior to the eruptions without any association with distinct confined flare activity. Six flux ropes were formed once the eruptions were underway. However, in three of them, prominence material could be seen in 131 Å images, which may indicate the presence of preexisting flux ropes that were not hot. The formation patterns of the last three groups of hot flux ropes did not show significant differences. For the whole population of events, the mean and median values of the time difference between the onset of the eruptive flare and the appearance of the hot flux rope were 151 and 98 min, respectively.
Conclusions: Our results provide, on average, indirect support for CME models that involve preexisting flux ropes; on the other hand, for a third of the events, models in which the ejected flux rope is formed during the eruption appear more appropriate.

Movies attached to Figs. 2, 5, 8, and 10 are available at http://www.aanda.org Title: Models and data analysis tools for the Solar Orbiter mission Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.; Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.; Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.; Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi, N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla, T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.; Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.; Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.; Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.; Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot, V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.; Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.; Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp, E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud, B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.; Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.; Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti, S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.; Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez, L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca, L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.; Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov, A. N. Bibcode: 2020A&A...642A...2R Altcode: Context. The Solar Orbiter spacecraft will be equipped with a wide range of remote-sensing (RS) and in situ (IS) instruments to record novel and unprecedented measurements of the solar atmosphere and the inner heliosphere. To take full advantage of these new datasets, tools and techniques must be developed to ease multi-instrument and multi-spacecraft studies. In particular the currently inaccessible low solar corona below two solar radii can only be observed remotely. Furthermore techniques must be used to retrieve coronal plasma properties in time and in three dimensional (3D) space. Solar Orbiter will run complex observation campaigns that provide interesting opportunities to maximise the likelihood of linking IS data to their source region near the Sun. Several RS instruments can be directed to specific targets situated on the solar disk just days before data acquisition. To compare IS and RS, data we must improve our understanding of how heliospheric probes magnetically connect to the solar disk.
Aims: The aim of the present paper is to briefly review how the current modelling of the Sun and its atmosphere can support Solar Orbiter science. We describe the results of a community-led effort by European Space Agency's Modelling and Data Analysis Working Group (MADAWG) to develop different models, tools, and techniques deemed necessary to test different theories for the physical processes that may occur in the solar plasma. The focus here is on the large scales and little is described with regards to kinetic processes. To exploit future IS and RS data fully, many techniques have been adapted to model the evolving 3D solar magneto-plasma from the solar interior to the solar wind. A particular focus in the paper is placed on techniques that can estimate how Solar Orbiter will connect magnetically through the complex coronal magnetic fields to various photospheric and coronal features in support of spacecraft operations and future scientific studies.
Methods: Recent missions such as STEREO, provided great opportunities for RS, IS, and multi-spacecraft studies. We summarise the achievements and highlight the challenges faced during these investigations, many of which motivated the Solar Orbiter mission. We present the new tools and techniques developed by the MADAWG to support the science operations and the analysis of the data from the many instruments on Solar Orbiter.
Results: This article reviews current modelling and tool developments that ease the comparison of model results with RS and IS data made available by current and upcoming missions. It also describes the modelling strategy to support the science operations and subsequent exploitation of Solar Orbiter data in order to maximise the scientific output of the mission.
Conclusions: The on-going community effort presented in this paper has provided new models and tools necessary to support mission operations as well as the science exploitation of the Solar Orbiter data. The tools and techniques will no doubt evolve significantly as we refine our procedure and methodology during the first year of operations of this highly promising mission. Title: The Solar Orbiter Science Activity Plan. Translating solar and heliospheric physics questions into action Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.; Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra, A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.; Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.; Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.; Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.; Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.; Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio, L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun, A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso, F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.; Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.; Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.; van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi, L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine, D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot, S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham, G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier, K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins, J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis, I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.; Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis, G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.; Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.; Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis, K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien, H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.; Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.; Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines, J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.; Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.; Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.; Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.; Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.; Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula, G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio, A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.; Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann, T.; Young, P. R.; Zhukov, A. N. Bibcode: 2020A&A...642A...3Z Altcode: 2020arXiv200910772Z Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument suites, the coordination and planning of the operations are essential to address the following four top-level science questions: (1) What drives the solar wind and where does the coronal magnetic field originate?; (2) How do solar transients drive heliospheric variability?; (3) How do solar eruptions produce energetic particle radiation that fills the heliosphere?; (4) How does the solar dynamo work and drive connections between the Sun and the heliosphere? Maximising the mission's science return requires considering the characteristics of each orbit, including the relative position of the spacecraft to Earth (affecting downlink rates), trajectory events (such as gravitational assist manoeuvres), and the phase of the solar activity cycle. Furthermore, since each orbit's science telemetry will be downloaded over the course of the following orbit, science operations must be planned at mission level, rather than at the level of individual orbits. It is important to explore the way in which those science questions are translated into an actual plan of observations that fits into the mission, thus ensuring that no opportunities are missed. First, the overarching goals are broken down into specific, answerable questions along with the required observations and the so-called Science Activity Plan (SAP) is developed to achieve this. The SAP groups objectives that require similar observations into Solar Orbiter Observing Plans, resulting in a strategic, top-level view of the optimal opportunities for science observations during the mission lifetime. This allows for all four mission goals to be addressed. In this paper, we introduce Solar Orbiter's SAP through a series of examples and the strategy being followed. Title: Trajectory Determination for Coronal Ejecta Observed by WISPR/Parker Solar Probe Authors: Liewer, P. C.; Qiu, J.; Penteado, P.; Hall, J. R.; Vourlidas, A.; Howard, R. A. Bibcode: 2020SoPh..295..140L Altcode: 2020arXiv200909323L The Wide-field Imager for Solar Probe (WISPR) onboard the Parker Solar Probe (PSP), observing in white light, has a fixed angular field of view, extending from 13.5∘ to 108∘ from the Sun and approximately 50∘ in the transverse direction. Because of the highly elliptical orbit of PSP, the physical extent of the imaged coronal region varies directly as the distance from the Sun, requiring new techniques for analysis of the motions of observed density features. Here, we present a technique for determining the 3D trajectory of CMEs and other coronal ejecta moving radially at a constant velocity by first tracking the motion in a sequence of images and then applying a curve-fitting procedure to determine the trajectory parameters (distance vs. time, velocity, longitude, and latitude). To validate the technique, we have determined the trajectory of two CMEs observed by WISPR that were also observed by another white-light imager, either the Solar and Heliophysics Observatory (SOHO) / Large Angle and Spectrometric COronagraph (LASCO)-C3 or the Solar Terrestrial Relations Observatory (STEREO)-A/HI1. The second viewpoint was used to verify the trajectory results from this new technique and help determine its uncertainty. Title: Understanding the origins of the heliosphere: integrating observations and measurements from Parker Solar Probe, Solar Orbiter, and other space- and ground-based observatories Authors: Velli, M.; Harra, L. K.; Vourlidas, A.; Schwadron, N.; Panasenco, O.; Liewer, P. C.; Müller, D.; Zouganelis, I.; St Cyr, O. C.; Gilbert, H.; Nieves-Chinchilla, T.; Auchère, F.; Berghmans, D.; Fludra, A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.; Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.; Wimmer-Schweingruber, R. F.; Bale, S.; Kasper, J.; McComas, D. J.; Raouafi, N.; Martinez-Pillet, V.; Walsh, A. P.; De Groof, A.; Williams, D. Bibcode: 2020A&A...642A...4V Altcode: Context. The launch of Parker Solar Probe (PSP) in 2018, followed by Solar Orbiter (SO) in February 2020, has opened a new window in the exploration of solar magnetic activity and the origin of the heliosphere. These missions, together with other space observatories dedicated to solar observations, such as the Solar Dynamics Observatory, Hinode, IRIS, STEREO, and SOHO, with complementary in situ observations from WIND and ACE, and ground based multi-wavelength observations including the DKIST observatory that has just seen first light, promise to revolutionize our understanding of the solar atmosphere and of solar activity, from the generation and emergence of the Sun's magnetic field to the creation of the solar wind and the acceleration of solar energetic particles.
Aims: Here we describe the scientific objectives of the PSP and SO missions, and highlight the potential for discovery arising from synergistic observations. Here we put particular emphasis on how the combined remote sensing and in situ observations of SO, that bracket the outer coronal and inner heliospheric observations by PSP, may provide a reconstruction of the solar wind and magnetic field expansion from the Sun out to beyond the orbit of Mercury in the first phases of the mission. In the later, out-of-ecliptic portions of the SO mission, the solar surface magnetic field measurements from SO and the multi-point white-light observations from both PSP and SO will shed light on the dynamic, intermittent solar wind escaping from helmet streamers, pseudo-streamers, and the confined coronal plasma, and on solar energetic particle transport.
Methods: Joint measurements during PSP-SO alignments, and magnetic connections along the same flux tube complemented by alignments with Earth, dual PSP-Earth, and SO-Earth, as well as with STEREO-A, SOHO, and BepiColumbo will allow a better understanding of the in situ evolution of solar-wind plasma flows and the full three-dimensional distribution of the solar wind from a purely observational point of view. Spectroscopic observations of the corona, and optical and radio observations, combined with direct in situ observations of the accelerating solar wind will provide a new foundation for understanding the fundamental physical processes leading to the energy transformations from solar photospheric flows and magnetic fields into the hot coronal plasma and magnetic fields and finally into the bulk kinetic energy of the solar wind and solar energetic particles.
Results: We discuss the initial PSP observations, which already provide a compelling rationale for new measurement campaigns by SO, along with ground- and space-based assets within the synergistic context described above. Title: The Solar Orbiter Heliospheric Imager (SoloHI) Authors: Howard, R. A.; Vourlidas, A.; Colaninno, R. C.; Korendyke, C. M.; Plunkett, S. P.; Carter, M. T.; Wang, D.; Rich, N.; Lynch, S.; Thurn, A.; Socker, D. G.; Thernisien, A. F.; Chua, D.; Linton, M. G.; Koss, S.; Tun-Beltran, S.; Dennison, H.; Stenborg, G.; McMullin, D. R.; Hunt, T.; Baugh, R.; Clifford, G.; Keller, D.; Janesick, J. R.; Tower, J.; Grygon, M.; Farkas, R.; Hagood, R.; Eisenhauer, K.; Uhl, A.; Yerushalmi, S.; Smith, L.; Liewer, P. C.; Velli, M. C.; Linker, J.; Bothmer, V.; Rochus, P.; Halain, J. -P.; Lamy, P. L.; Auchère, F.; Harrison, R. A.; Rouillard, A.; Patsourakos, S.; St. Cyr, O. C.; Gilbert, H.; Maldonado, H.; Mariano, C.; Cerullo, J. Bibcode: 2020A&A...642A..13H Altcode:
Aims: We present the design and pre-launch performance of the Solar Orbiter Heliospheric Imager (SoloHI) which is an instrument prepared for inclusion in the ESA/NASA Solar Orbiter mission, currently scheduled for launch in 2020.
Methods: The goal of this paper is to provide details of the SoloHI instrument concept, design, and pre-flight performance to give the potential user of the data a better understanding of how the observations are collected and the sources that contribute to the signal.
Results: The paper discusses the science objectives, including the SoloHI-specific aspects, before presenting the design concepts, which include the optics, mechanical, thermal, electrical, and ground processing. Finally, a list of planned data products is also presented.
Conclusions: The performance measurements of the various instrument parameters meet or exceed the requirements derived from the mission science objectives. SoloHI is poised to take its place as a vital contributor to the science success of the Solar Orbiter mission. Title: Predicting the Time of Arrival of Coronal Mass Ejections at Earth From Heliospheric Imaging Observations Authors: Braga, Carlos Roberto; Vourlidas, Angelos; Stenborg, Guillermo; Dal Lago, Alisson; Mendonça, Rafael Rodrigues Souza de; Echer, Ezequiel Bibcode: 2020JGRA..12527885B Altcode: 2020arXiv200809005B The time of arrival (ToA) of coronal mass ejections (CMEs) at Earth is a key parameter due to the space weather phenomena associated with the CME arrival, such as intense geomagnetic storms. Despite the incremental use of new instrumentation and the development of novel methodologies, ToA estimated errors remain above 10 h on average. Here, we investigate the prediction of the ToA of CMEs using observations from heliospheric imagers, i.e., from heliocentric distances higher than those covered by the existent coronagraphs. In order to perform this work, we analyze 14 CMEs observed by the heliospheric imagers HI-1 onboard the twin STEREO spacecraft to determine their front location and speed. The kinematic parameters are derived with a new technique based on the Elliptical Conversion (ElCon) method, which uses simultaneous observations from the two viewpoints from STEREO. Outside the field of view of the instruments, we assume that the dynamics of the CME evolution is controlled by aerodynamic drag, i.e., a force resulting from the interaction with particles from the background solar wind. To model the drag force, we use a physical model that allows us to derive its parameters without the need to rely on drag coefficients derived empirically. We found a CME ToA mean error of 1.6 ± 8.0 h ToA and a mean absolute error of 6.9 ± 3.9 h for a set of 14 events. The results suggest that observations from HI-1 lead to estimates with similar errors to observations from coronagraphs. Title: The Coronal Mass Ejection Visibility Function of Modern Coronagraphs Authors: Vourlidas, Angelos; Balmaceda, L. A.; Xie, H.; St. Cyr, O. C. Bibcode: 2020ApJ...900..161V Altcode: 2020arXiv200803348V We analyze the detection capability of coronal mass ejections (CMEs) for all currently operating coronagraphs in space. We define as CMEs events that propagate beyond 10 solar radii with morphologies broadly consistent with a magnetic flux-rope presence. We take advantage of multi-viewpoint observations over five month-long intervals, corresponding to special orbital configurations of the coronagraphs aboard the Solar Terrestrial Relations Observatory (STEREO) and Solar and Heliospheric Observatory missions. This allows us to sort out CMEs from other outward-propagating features (e.g., waves or outflows), and thus to identify the total number of unique CMEs ejected during those periods. We determine the CME visibility functions (VFs) of the STEREO COR2-A/B and LASCO C2/C3 coronagraphs directly as the ratio of observed to unique CMEs. The VFs range from 0.71 to 0.92 for a 95% confidence interval. By comparing detections between coronagraphs on the same spacecraft and from multiple spacecraft, we assess the influence of field of view (FOV), instrument performance, and projection effects on the CME detection ability without resorting to proxies, such as flares or radio bursts. We find that no major CMEs are missed by any of the coronagraphs, that a few slow halo-like events may be missed in synoptic cadence movies, and that narrow FOV coronagraphs have difficulties discriminating between CMEs and other ejections, leading to "false" detection rates. We conclude that CME detection can only be validated with multi-viewpoint imaging—two coronagraphs in quadrature offer adequate detection capability. Finally, we apply the VFs to observed CME rates resulting in upward corrections of 40%. Title: The Science Case for the $4{\pi}$ Perspective: A Polar/Global View for Studying the Evolution & Propagation of the Solar Wind and Solar Transients Authors: Vourlidas, A.; Gibson, S.; Hassler, D.; Hoeksema, T.; Linton, M.; Lugaz, N.; Newmark, J. Bibcode: 2020arXiv200904880V Altcode: To make progress on the open questions on CME/CIR propagation, their interactions and the role and nature of the ambient solar wind, we need spatially resolved coverage of the inner heliosphere -- both in-situ and (critically) imaging -- at temporal scales matching the evolutionary timescales of these phenomena (tens of minutes to hours), and from multiple vantage points. The polar vantage is uniquely beneficial because of the wide coverage and unique perspective it provides. The ultimate goal is to achieve full $4\pi$ coverage of the solar surface and atmosphere by 2050. Title: Trigger Shy? Flare-less Active Region Circular Prominence Eruption Authors: Mason, E.; Antiochos, S.; Vourlidas, A. Bibcode: 2020SPD....5121001M Altcode: Prominence eruptions have been studied since the days of Skylab, and generally fall into two categories based on their locations: quiet Sun and active regions. Quiescent prominences are generally slow to grow and take can days to erupt, with or without any evidence of energization prior to eruption. By contrast, active region prominences generally erupt on time scales of hours or minutes, and are often accompanied by powerful flares. This study reports on an observation of an unusual circular prominence eruption located in an active region which occurs without any evidence of flaring as a trigger. The prominence is under the dome surface of a raining null point topology, which was part of the extended decay phase of the active region designated NOAA 12488/12501. One half of the prominence undergoes a partial eruption, and the cool plasma subsequently drains onto the side which did not erupt, followed by a poorly-structured CME observed by SOHO LASCO C2 shortly after the eruption. We analyze both the failed eruption and secondary CME using SDO AIA, STEREO-A, and SOHO LASCO imagery. The location of the null-point topology raises critical questions about the role of open/closed boundaries in eruptive phenomena and CME structure. The poor structure of the outflowing CME is likely the result of the destruction of the flux rope through reconnection as it passes through the null-point structure, and possibly through additional overlying closed field. The eruption does not show a trigger, but arcades and ribbons form over the erupted half of the prominence. Taken together, the failed eruption presents eruption characteristics of both a CME and a jet, with potential evidence of a low-energy reconnection mechanism driving failed eruptions in highly decayed but still topologically compact magnetic fields. Title: Radio Observations of Coronal Mass Ejections: Space Weather Aspects Authors: Vourlidas, Angelos; Carley, Eoin P.; Vilmer, Nicole Bibcode: 2020FrASS...7...43V Altcode: We review the current state-of-affairs in radio observations of Coronal Mass Ejections (CMEs) from a Space Weather perspective. In particular, we examine the role of radio observations in predicting or presaging an eruption, in capturing the formation stages of the CME, and in following the CME evolution in the corona and heliosphere. We then look to the future and identify capabilities and research areas where radio observations---particularly, spectropolarimetric imaging---offer unique advantages for Space Weather research on CMEs. We close with a discussion of open issues and possible strategies for enhancing the relevance and importance of radio astronomy for Space Weather science. Title: The Solar Origin of Particle Events Measured by Parker Solar Probe Authors: Kouloumvakos, Athanasios; Vourlidas, Angelos; Rouillard, Alexis P.; Roelof, Edmond C.; Leske, Rick; Pinto, Rui; Poirier, Nicolas Bibcode: 2020ApJ...899..107K Altcode: During the second solar encounter phase of Parker Solar Probe (PSP), two small solar energetic particle (SEP) events were observed by the Integrated Science Investigation of the Sun, on 2019 April 2 and 4. At the time, PSP was approaching its second perihelion at a distance of ∼24.8 million kilometers from the solar center, it was in near-radial alignment with STEREO-A and in quadrature with Earth. During the two SEP events multiple narrow ejections and a streamer-blowout coronal mass ejection (SBO-CME) originated from a solar region situated eastward of PSP. We analyze remote-sensing observations of the solar corona, and model the different eruptions and how PSP was connected magnetically to the solar atmosphere to determine the possible origin of the two SEP events. We find that the SEP event on April 2 was associated with the two homologous ejections from active region 12738 that included two surges and EUV waves occurring in quick succession. The EUV waves appear to merge and were fast enough to form a shock in the low corona. We show that the April 4 SEP event originates in the SBO-CME. Our modeling work suggests that formation of a weak shock is likely for this CME. Title: On the Expansion Speed of Coronal Mass Ejections: Implications for Self-Similar Evolution Authors: Balmaceda, L. A.; Vourlidas, A.; Stenborg, G.; St. Cyr, O. C. Bibcode: 2020SoPh..295..107B Altcode: A proper characterization of the kinematics of coronal mass ejections (CMEs) is important not only for practical purposes, i.e. space weather forecasting, but also to improve our current understanding of the physics behind their evolution in the middle corona and into the heliosphere. The first and core step toward this goal is the estimation of the three main components of the CME speeds, namely the expansion speed relative to the center of motion in both, the radial and lateral directions, and the propagation speed (i.e. Vfront, Vlat, Vbulk, respectively). To this aim, we exploit the observations obtained with COR2 onboard the Solar Terrestrial Relations Observatory (STEREO) from 2007 to 2014 to investigate the relationships among the different components as a function of the heliocentric distance of the CME events. Here, we analyze a sample of 475 CMEs. The selected events exhibit clear flux rope signatures as seen either edge on (i.e. F-CMEs: three-part structure, presence of a cavity) or face on (i.e. L- or loop CMEs) in white light images. Our main findings are: i) L-CMEs show almost twice as large expansion speeds compared to F-CMEs (Vfront ,L=367 kms−1, Vlat ,L=365 kms−1 vs. Vfront ,F=215 kms−1, Vlat ,F=182 kms−1); ii) the relationship between the two components of the expansion speeds is linear and does not change with height; iii) the ratio of the propagation speed to the lateral expansion speed is a function of the angular width that describes the self-similarity evolution of a CME; and iv) 65% of the CMEs exhibit a self-similar evolution at 10 solar radii, reaching 70% at 15 solar radii. Title: How Reliable are CME speeds derived from single viewpoint observations? Authors: Paouris, Evangelos; Vourlidas, Angelos; Papaioannou, Athanasios; Anastasiadis, Anastasios Bibcode: 2020EGUGA..22..625P Altcode: Images of Coronal Mass Ejections (CMEs) are primarily acquired by space-based coronagraphs. Such images capture the outward flow of density structures from the Sun by observing Thompson-scattered sunlight from the free electrons entrained in these structures. Because the emission is optically thin, CMEs images are projections of their real 3D structure on the field of view (FOV) of the coronagraph. As a result, the CME characteristics (e.g. linear speed, angular width) calculated from these images, suffer from projection effects and their reliability needs to be quantified. In this work we apply a geometrical method for the de-projection of the linear CME speeds of 4009 CMEs from the CDAW catalog, associated with solar flares (3225 C-class, 736 M-class and 48 X-class solar flares). Our aim is to provide a robust quantification of the reliability of the CME properties from L1 (SOHO/LASCO) single viewpoint measurements.In addition, we compare the intensity and location of solar flares with the CME kinematic characteristics. In particular, 482 M-class solar flares associated with CMEs with an angular width 30°< w < 120°, show a dependence of the mean CME linear speed with the longitude of the parent solar flare, indicating that projection effects of CMEs should be reduced near the solar limb. However, such deprojections tend to overcorrect the CME speed for sources near the solar meridian. They result in speeds of the order of 5000-7000 km/s, which seem physically unreasonable. By considering the 3D extent of the CMEs, we provide a novel geometrical correction of the deprojected CME linear speed. The resulting speeds range from a few 100 km/s up to almost 2600 km/s, a much more physically acceptable correction. This study has important implications for Space Weather applications since the reliable estimation of the CME linear speed has a direct effect on the time of arrival of CMEs at Earth and the quantification of the expected peak flux of solar radiation storms.Acknowledgement: This work was funded from the State Scholarships Foundation of Greece (I.K.Y.), in the framework of: "Funding Post-doctoral Researchers" of the b.p.: "Human Resources Development, Education and Lifelong Learning" from ESPA (2014-2020). Title: The forming slow solar wind imaged along streamer rays by the wide-angle imager on Parker Solar Probe Authors: Poirier, Nicolas; Kouloumvakos, Athanasios; Rouillard, Alexis P.; Pinto, Rui; Vourlidas, Angelos; Stenborg, Guillermo; Valette, Emeline; Howard, Russell A.; Hess, Phillip; Thernisien, Arnaud; Rich, Nathan; Griton, Léa; Indurain, Mikel; Raouafi, Nour-Edine; Lavarra, Michael; Réville, Victor Bibcode: 2020EGUGA..2211552P Altcode: The Wide-field Imager for Solar PRobe (WISPR) obtained the first high-resolution images of coronal rays at heights below 15 Rsun when Parker Solar Probe (PSP) was located inside 0.25 AU during the first encounter. We exploit these remarkable images to reveal the structure of coronal rays at scales that are not easily discernible in images taken from near 1 AU. To analyze and interpret WISPR observations which evolve rapidly both radially and longitudinally, we construct a latitude versus time map using full WISPR dataset from the first encounter. From the exploitation of this map and also from sequential WISPR images we show the presence of multiple sub-structures inside streamers and pseudo-streamers. WISPR unveils the fine-scale structure of the densest part of streamer rays that we identify as the solar origin of the heliospheric plasma sheet typically measured in situ in the solar wind. We exploit 3-D magneto-hydrodynamic (MHD) models and we construct synthetic white-light images to study the origin of the coronal structures observed by WISPR. Overall, including the effect of the spacecraft relative motion towards the individual coronal structures we can interpret several observed features by WISPR. Moreover, we relate some coronal rays to folds in the heliospheric current sheet that are unresolved from 1 AU. Other rays appear to form as a result of the inherently inhomogeneous distribution of open magnetic flux tubes. This work was funded by the European Research Council through the project SLOW_SOURCE - DLV-819189. Title: Estimation of the Physical Parameters of a CME at High Coronal Heights Using Low-frequency Radio Observations Authors: Mondal, Surajit; Oberoi, Divya; Vourlidas, Angelos Bibcode: 2020ApJ...893...28M Altcode: 2019arXiv190912041M Measuring the physical parameters of coronal mass ejections (CMEs), particularly their entrained magnetic field, is crucial for understanding their physics and for assessing their geoeffectiveness. At the moment, only remote sensing techniques can probe these quantities in the corona, the region where CMEs form and acquire their defining characteristics. Radio observations offer the most direct means for estimating the magnetic field when gyrosynchrotron emission is detected. In this work we measure various CME plasma parameters, including its magnetic field, by modeling the gyrosynchrotron emission from a CME. The dense spectral coverage over a wide frequency range provided by the Murchison Widefield Array (MWA) affords a much better spectral sampling than possible before. The MWA images also provide a much higher imaging dynamic range, enabling us to image these weak emissions. Hence we are able to detect radio emission from a CME at larger distances (∼4.73 R⊙) than have been reported before. The flux densities reported here are among the lowest measured in similar works. Our ability to make extensive measurements on a slow and otherwise unremarkable CME suggests that with the availability of data from the new-generation instruments like the MWA, it should now be possible to make routine, direct detections of radio counterparts of CMEs. Title: How Does Magnetic Reconnection Drive the Early-stage Evolution of Coronal Mass Ejections? Authors: Zhu, Chunming; Qiu, Jiong; Liewer, Paulett; Vourlidas, Angelos; Spiegel, Michael; Hu, Qiang Bibcode: 2020ApJ...893..141Z Altcode: 2020arXiv200311134Z Theoretically, coronal mass ejection (CME) kinematics are related to magnetic reconnection processes in the solar corona. However, the current quantitative understanding of this relationship is based on the analysis of only a handful of events. Here we report a statistical study of 60 CME-flare events from 2010 August to 2013 December. We investigate kinematic properties of CMEs and magnetic reconnection in the low corona during the early phase of the eruptions, by combining limb observations from STEREO with simultaneous on-disk views from SDO. For a subset of 42 events with reconnection rate evaluated by the magnetic fluxes swept by the flare ribbons on the solar disk observed from SDO, we find a strong correlation between the peak CME acceleration and the peak reconnection rate. Also, the maximum velocities of relatively fast CMEs (≳600 km s-1) are positively correlated with the reconnection flux, but no such correlation is found for slow CMEs. A time-lagged correlation analysis suggests that the distribution of the time lag of CME acceleration relative to reconnection rate exhibits three peaks, approximately 10 minutes apart, and on average, acceleration-led events have smaller reconnection rates. We further compare the CME total mechanical energy with the estimated energy in the current sheet. The comparison suggests that, for small-flare events, reconnection in the current sheet alone is insufficient to fuel CMEs. Results from this study suggest that flare reconnection may dominate the acceleration of fast CMEs, but for events of slow CMEs and weak reconnection, other mechanisms may be more important. Title: Solar physics in the 2020s: DKIST, parker solar probe, and solar orbiter as a multi-messenger constellation Authors: Martinez Pillet, V.; Tritschler, A.; Harra, L.; Andretta, V.; Vourlidas, A.; Raouafi, N.; Alterman, B. L.; Bellot Rubio, L.; Cauzzi, G.; Cranmer, S. R.; Gibson, S.; Habbal, S.; Ko, Y. K.; Lepri, S. T.; Linker, J.; Malaspina, D. M.; Matthews, S.; Parenti, S.; Petrie, G.; Spadaro, D.; Ugarte-Urra, I.; Warren, H.; Winslow, R. Bibcode: 2020arXiv200408632M Altcode: The National Science Foundation (NSF) Daniel K. Inouye Solar Telescope (DKIST) is about to start operations at the summit of Haleakala (Hawaii). DKIST will join the early science phases of the NASA and ESA Parker Solar Probe and Solar Orbiter encounter missions. By combining in-situ measurements of the near-sun plasma environment and detail remote observations of multiple layers of the Sun, the three observatories form an unprecedented multi-messenger constellation to study the magnetic connectivity inside the solar system. This white paper outlines the synergistic science that this multi-messenger suite enables. Title: Simulating White-Light Images of Coronal Structures for Parker Solar Probe/WISPR: Study of the Total Brightness Profiles Authors: Nisticò, Giuseppe; Bothmer, Volker; Vourlidas, Angelos; Liewer, Paulett C.; Thernisien, Arnaud F.; Stenborg, Guillermo; Howard, Russell A. Bibcode: 2020SoPh..295...63N Altcode: 2020arXiv200405447N The Wide-field Imager for Parker Solar Probe (WISPR) captures unprecedented white-light images of the solar corona and inner heliosphere. Thanks to the uniqueness of the Parker Solar Probe's (PSP) orbit, WISPR is able to image "locally" coronal structures at high spatial and time resolutions. The observed plane of sky, however, rapidly changes because of the PSP's high orbital speed. Therefore, the interpretation of the dynamics of the coronal structures recorded by WISPR is not straightforward. A first study, undertaken by Liewer et al. (Solar Phys.294, 93, 2019), shows how different coronal features (e.g., streamers, flux ropes) appear in the field-of-view of WISPR by means of raytracing simulations. In particular, they analyze the effects of the spatial resolution changes on both the images and the associated height-time maps, and introduce the fundamentals for geometric triangulation. In this follow-up paper, we focus on the study of the total brightness of a simple, spherical, plasma density structure, to understand how the analysis of Thomson-scattered emission by the electrons in a coronal feature can shed light into the determination of its kinematic properties. We investigate two cases: (i) a density sphere at a constant distance from the Sun for different heliographic longitudes; (ii) a density sphere moving outwardly with constant speed. The study allows us to characterize the effects of the varying heliocentric distance of the observer and scattering angle on the total brightness observed, which we exploit to contribute to a better determination of the position and speed of the coronal features observed by WISPR. Title: Relating Streamer Flows to Density and Magnetic Structures at the Parker Solar Probe Authors: Rouillard, Alexis P.; Kouloumvakos, Athanasios; Vourlidas, Angelos; Kasper, Justin; Bale, Stuart; Raouafi, Nour-Edine; Lavraud, Benoit; Howard, Russell A.; Stenborg, Guillermo; Stevens, Michael; Poirier, Nicolas; Davies, Jackie A.; Hess, Phillip; Higginson, Aleida K.; Lavarra, Michael; Viall, Nicholeen M.; Korreck, Kelly; Pinto, Rui F.; Griton, Léa; Réville, Victor; Louarn, Philippe; Wu, Yihong; Dalmasse, Kévin; Génot, Vincent; Case, Anthony W.; Whittlesey, Phyllis; Larson, Davin; Halekas, Jasper S.; Livi, Roberto; Goetz, Keith; Harvey, Peter R.; MacDowall, Robert J.; Malaspina, D.; Pulupa, M.; Bonnell, J.; de Witt, T. Dudok; Penou, Emmanuel Bibcode: 2020ApJS..246...37R Altcode: 2020arXiv200101993R The physical mechanisms that produce the slow solar wind are still highly debated. Parker Solar Probe's (PSP's) second solar encounter provided a new opportunity to relate in situ measurements of the nascent slow solar wind with white-light images of streamer flows. We exploit data taken by the Solar and Heliospheric Observatory, the Solar TErrestrial RElations Observatory (STEREO), and the Wide Imager on Solar Probe to reveal for the first time a close link between imaged streamer flows and the high-density plasma measured by the Solar Wind Electrons Alphas and Protons (SWEAP) experiment. We identify different types of slow winds measured by PSP that we relate to the spacecraft's magnetic connectivity (or not) to streamer flows. SWEAP measured high-density and highly variable plasma when PSP was well connected to streamers but more tenuous wind with much weaker density variations when it exited streamer flows. STEREO imaging of the release and propagation of small transients from the Sun to PSP reveals that the spacecraft was continually impacted by the southern edge of streamer transients. The impact of specific density structures is marked by a higher occurrence of magnetic field reversals measured by the FIELDS magnetometers. Magnetic reversals are associated with much stronger density variations inside than outside streamer flows. We tentatively interpret these findings in terms of magnetic reconnection between open magnetic fields and coronal loops with different properties, providing support for the formation of a subset of the slow wind by magnetic reconnection. Title: Modeling the Early Evolution of a Slow Coronal Mass Ejection Imaged by the Parker Solar Probe Authors: Rouillard, Alexis P.; Poirier, Nicolas; Lavarra, Michael; Bourdelle, Anthony; Dalmasse, Kévin; Kouloumvakos, Athanasios; Vourlidas, Angelos; Kunkel, Valbona; Hess, Phillip; Howard, Russ A.; Stenborg, Guillermo; Raouafi, Nour E. Bibcode: 2020ApJS..246...72R Altcode: 2020arXiv200208756R During its first solar encounter, the Parker Solar Probe (PSP) acquired unprecedented up-close imaging of a small coronal mass ejection (CME) propagating in the forming slow solar wind. The CME originated as a cavity imaged in extreme ultraviolet that moved very slowly (<50 km s-1) to 3-5 solar radii (R ⊙), where it then accelerated to supersonic speeds. We present a new model of an erupting flux rope (FR) that computes the forces acting on its expansion with a computation of its internal magnetic field in three dimensions. The latter is accomplished by solving the Grad-Shafranov equation inside two-dimensional cross sections of the FR. We use this model to interpret the kinematic evolution and morphology of the CME imaged by PSP. We investigate the relative role of toroidal forces, momentum coupling, and buoyancy for different assumptions on the initial properties of the CME. The best agreement between the dynamic evolution of the observed and simulated FR is obtained by modeling the two-phase eruption process as the result of two episodes of poloidal flux injection. Each episode, possibly induced by magnetic reconnection, boosted the toroidal forces accelerating the FR out of the corona. We also find that the drag induced by the accelerating solar wind could account for about half of the acceleration experienced by the FR. We use the model to interpret the presence of a small dark cavity, clearly imaged by PSP deep inside the CME, as a low-density region dominated by its strong axial magnetic fields. Title: Small, Low-energy, Dispersive Solar Energetic Particle Events Observed by Parker Solar Probe Authors: Hill, M. E.; Mitchell, D. G.; Allen, R. C.; de Nolfo, G. A.; Vourlidas, A.; Brown, L. E.; Jones, S. I.; McComas, D. J.; McNutt, R. L., Jr.; Mitchell, J. G.; Szalay, J. R.; Wallace, S.; Arge, C. N.; Christian, E. R.; Cohen, C. M. S.; Crew, A. B.; Desai, M. I.; Giacalone, J.; Henney, C. J.; Joyce, C. J.; Krimigis, S. M.; Leske, R. A.; Mewaldt, R. A.; Nelson, K. S.; Roelof, E. C.; Schwadron, N. A.; Wiedenbeck, M. E. Bibcode: 2020ApJS..246...65H Altcode: The Energetic Particle Instrument-Low Energy (EPI-Lo) experiment has detected several weak, low-energy (∼30-300 keV nucleon-1) solar energetic particle (SEP) events during its first two closest approaches to the Sun, providing a unique opportunity to explore the sources of low-energy particle acceleration. As part of the Parker Solar Probe (PSP) Integrated Science Investigation of the Sun (IS⊙IS) suite, EPI-Lo was designed to investigate the physics of energetic particles; however, in the special lowest-energy "time-of-flight only" product used in this study, it also responds to solar photons in a subset of approximately sunward-looking apertures lacking special light-attenuating foils. During the first three perihelia, in a frame rotating with the Sun, PSP undergoes retrograde motion, covering a 17° heliographic longitudinal range three times during the course of the ∼11-day perihelion passes, permitting a unique spatial and temporal study into the location, correlation, and persistence of previously unmeasurable SEPs. We examine the signatures of these SEPs (during the first PSP perihelion pass only) and the connection to possible solar sources using remote observations from the Solar Dynamics Observatory (SDO), the Solar TErrestrial RElations Observatory (STEREO), and the ground-based Global Oscillation Network Group (GONG). The orientation of the Sun relative to STEREO, SDO, and GONG makes such identifications challenging, but we do have several candidates, including an equatorial coronal hole at a Carrington longitude of ∼335°. To analyze observations from EPI-Lo, which is a new type of particle instrument, we examine instrumental effects and provide a preliminary separation of the ion signal from the photon background. Title: Observations of the 2019 April 4 Solar Energetic Particle Event at the Parker Solar Probe Authors: Leske, R. A.; Christian, E. R.; Cohen, C. M. S.; Cummings, A. C.; Davis, A. J.; Desai, M. I.; Giacalone, J.; Hill, M. E.; Joyce, C. J.; Krimigis, S. M.; Labrador, A. W.; Malandraki, O.; Matthaeus, W. H.; McComas, D. J.; McNutt, R. L., Jr.; Mewaldt, R. A.; Mitchell, D. G.; Posner, A.; Rankin, J. S.; Roelof, E. C.; Schwadron, N. A.; Stone, E. C.; Szalay, J. R.; Wiedenbeck, M. E.; Vourlidas, A.; Bale, S. D.; MacDowall, R. J.; Pulupa, M.; Kasper, J. C.; Allen, R. C.; Case, A. W.; Korreck, K. E.; Livi, R.; Stevens, M. L.; Whittlesey, P.; Poduval, B. Bibcode: 2020ApJS..246...35L Altcode: 2019arXiv191203384L A solar energetic particle event was detected by the Integrated Science Investigation of the Sun (IS⊙IS) instrument suite on Parker Solar Probe (PSP) on 2019 April 4 when the spacecraft was inside of 0.17 au and less than 1 day before its second perihelion, providing an opportunity to study solar particle acceleration and transport unprecedentedly close to the source. The event was very small, with peak 1 MeV proton intensities of ∼0.3 particles (cm2 sr s MeV)-1, and was undetectable above background levels at energies above 10 MeV or in particle detectors at 1 au. It was strongly anisotropic, with intensities flowing outward from the Sun up to 30 times greater than those flowing inward persisting throughout the event. Temporal association between particle increases and small brightness surges in the extreme-ultraviolet observed by the Solar TErrestrial RElations Observatory, which were also accompanied by type III radio emission seen by the Electromagnetic Fields Investigation on PSP, indicates that the source of this event was an active region nearly 80° east of the nominal PSP magnetic footpoint. This suggests that the field lines expanded over a wide longitudinal range between the active region in the photosphere and the corona. Title: Detailed Imaging of Coronal Rays with the Parker Solar Probe Authors: Poirier, Nicolas; Kouloumvakos, Athanasios; Rouillard, Alexis P.; Pinto, Rui F.; Vourlidas, Angelos; Stenborg, Guillermo; Valette, Emeline; Howard, Russell A.; Hess, Phillip; Thernisien, Arnaud; Rich, Nathan; Griton, Lea; Indurain, Mikel; Raouafi, Nour-Edine; Lavarra, Michael; Réville, Victor Bibcode: 2020ApJS..246...60P Altcode: 2019arXiv191209345P The Wide-field Imager for Solar PRobe (WISPR) obtained the first high-resolution images of coronal rays at heights below 15 R⊙ when the Parker Solar Probe (PSP) was located inside 0.25 au during the first encounter. We exploit these remarkable images to reveal the structure of coronal rays at scales that are not easily discernible in images taken from near 1 au. To analyze and interpret WISPR observations, which evolve rapidly both radially and longitudinally, we construct a latitude versus time map using the full WISPR data set from the first encounter. From the exploitation of this map and also from sequential WISPR images. we show the presence of multiple substructures inside streamers and pseudostreamers. WISPR unveils the fine-scale structure of the densest part of streamer rays that we identify as the solar origin of the heliospheric plasma sheet typically measured in situ in the solar wind. We exploit 3D magnetohydrodynamic models, and we construct synthetic white-light images to study the origin of the coronal structures observed by WISPR. Overall, including the effect of the spacecraft relative motion toward the individual coronal structures, we can interpret several observed features by WISPR. Moreover, we relate some coronal rays to folds in the heliospheric current sheet that are unresolved from 1 au. Other rays appear to form as a result of the inherently inhomogeneous distribution of open magnetic flux tubes. Title: Imaging the Solar Corona From Within Authors: Hess, P.; Howard, R.; Vourlidas, A.; Bothmer, V.; Colaninno, R.; DeForest, C.; Gallagher, B.; Hall, J. R.; Higginson, A.; Korendyke, C.; Kouloumvakos, A.; Lamy, P.; Liewer, P.; Linker, J.; Linton, M.; Penteado, P.; Plunkett, S.; Poirer, N.; Raouafi, N.; Rich, N.; Rochus, P.; Rouillard, A.; Socker, D.; Stenborg, G.; Thernisien, A.; Viall, N. Bibcode: 2020AAS...23514907H Altcode: Parker Solar Probe (PSP), launched, in August 2018 is humanity's first probe of a stellar atmosphere. It will make measurements of the near-Sun plasma from 'within' the outer corona with gradually reduced perihelia from its first perihelia of 35 Rs in 2018-19 to 9.8 Rs in 2025. Here we report the results from the imaging observations of the electron and dust corona, whe PSP was 35-54 Rs from the solar surface, taken by the Wide-field Imager for Solar Probe (WISPR). The spacecraft was near-corotating with the solar corona throughout the observing window, which is an unprecedented situation for any type of coronal imaging. Our initial analysis uncovers a long-hypothesized depletion of the primordial dust orbiting near the Sun, reveals the plasma structure of small-scale ejections, and provides a strict test for validating model predictions of the large-scale configuration of the coronal plasma. Thus, WISPR imaging allows the study of near-Sun dust dynamics as the mission progresses. The high-resolution images of small transients, largely unresolved from 1 AU orbits, unravel the sub-structures of small magnetic flux ropes and show that the Sun continually releases helical magnetic fields in the background wind. Finally, WISPR's observations of the coronal streamer evolution confirm the large-scale topology of the solar corona but they also reveal that, as recently predicted, streamers are composed of yet smaller sub-streamers channeling continual density fluctuations at all visible scales. Title: A "Classic" Z-Rich Solar Energetic Particle Event Observed by Parker Solar Probe at 0.2AU (April 2-3, 2019) Authors: Roelof, E. C.; Allen, R. C.; Bale, S. D.; Christian, E. R.; Cohen, C.; Cummings, A. C.; Hill, M. E.; Leske, R. A.; McComas, D. J.; McNutt, R. L., Jr.; Mewaldt, R. A.; Mitchell, D. G.; Pulupa, M.; Schwadron, N.; Stone, E. C.; Szalay, J. R.; Wiedenbeck, M. E.; Vourlidas, A. Bibcode: 2019AGUFMSH21B..09R Altcode: An impulsive solar energetic particle event displaying enhanced abundances of heavy ions was observed on 02 April 2019 from 0.2 AU by the EPI-Lo ion spectrometer of the ISOIS instrument suite on the Parker Solar Probe (PSP). It was associated with brightenings and south-westerly surges from the active region (2738) east of central meridian as viewed in 193 nm images from STEREO-A (fortuitously only10.7deg eastward of PSP). Compared to a subsequent impulsive SEP event observed by ISOIS/EPI-Hi/EPI-Lo (only two days later on 04 April 2019), the enhancements (by species) were: 1-to-1 for ~60 keV H; 20-fold for ~210 keV He; and >50-fold for both ~375 keV O and ~1500 keV Fe (i.e., unmeasurable above background on 04 April). The velocity-dispersed ion onset ~1200 UT on 02 April implied that impulsive ion injection began at about same time as a type iii burst group (0850-1905 UT) observed by PSP/FIELDS. The ion event began with beam-like pitch-angle anisotropies. The event was abruptly terminated by a dramatic flux dropout ~0750 UT on 03 April, in close coincidence with what appears to be a tangential discontinuity (or separatrix) in the local magnetic field lines at PSP. We seem to have observed a "classic" Z-rich ion event, as first identified during the decline of Solar Cycle 20 (Hurford et al., ApJLett, 1975; Zwickl et al., ApJ, 1978). These were characterized by normal ion spectra, normal SW conditions, association with small H-alpha flares, but with long-lasting (~1 day) beam-like highly anisotropic pitch-angle distributions. Because the ion spectra were similar to impulsive events with normal ion abundances, Zwickl et al. argued that these events were Z-rich as a consequence of enhanced abundances in the seed population, rather than differences in the acceleration mechanism itself. Recently, Mason and Klecker (ApJ, 2017) have suggested a very efficient abundance enrichment process, whereby propagation of all ions through a material thickness of ~20 micrograms/cm2 produces a selective (Z-rich) enhancement, because of the heavies' greater affinity for electrons that mitigates the Z^2/A energy loss rate. At low-coronal H-densities of 10^8-10^9 /cc, this thickness would imply an ion path length of 0.2-2.0 solar radii, which might produce a seed population consistent with the constraints of our PSP observations. Title: Parker Solar Probe Observations of the 4 April 2019 Solar Energetic Particle Event Near Perihelion Authors: Leske, R. A.; Christian, E. R.; Cohen, C.; Cummings, A. C.; Davis, A. D.; Hill, M. E.; Labrador, A. W.; McComas, D. J.; McNutt, R. L., Jr.; Mewaldt, R. A.; Mitchell, D. G.; Roelof, E. C.; Schwadron, N.; Stone, E. C.; Szalay, J. R.; Wiedenbeck, M. E.; Bale, S. D.; MacDowall, R. J.; Pulupa, M.; Vourlidas, A. Bibcode: 2019AGUFMSH23C3357L Altcode: A solar energetic particle (SEP) event was detected by the ISOIS instrument suite on Parker Solar Probe (PSP) on 4 April 2019 when the spacecraft was almost at its second perihelion of 0.17 AU, providing an opportunity to study solar particle acceleration and transport unprecedentedly close to the source. The event was small, with peak 1 MeV proton intensities at PSP of ~0.3 protons/(cm2 sr s MeV), and was not observed above background levels in either STEREO or ACE particle detectors at 1 AU. It was strongly anisotropic, with intensities flowing outward from the Sun ~30 times greater than those flowing inward. Curiously, although the event was clearly observed in the ISOIS EPI-Hi instrument at proton energies of a few MeV, it was much less pronounced at energies of a few hundred keV in EPI-Lo. Conversely, an event two days earlier on 2 April was observed in EPI-Lo, with almost no detectable signature in EPI-Hi except for a significant (though statistically limited) enhancement in heavy ions up to Fe at energies of several MeV/nucleon. Based on STEREO/EUVI observations of small brightness surges (several of which were also associated with type III emission seen by both STEREO/WAVES and PSP/FIELDS), the source of both these events appears to be an active region that was later numbered Region 2738 when it rotated over the east limb and became visible from Earth several days later. This region was far (nearly 90 degrees) to the east of the nominal PSP magnetic footpoint, raising the question of how these particles traveled to the observer.

We present EPI-Hi and EPI-Lo observations of the time profiles, spectra, composition, and anisotropy of this event, compare it with the earlier 2 April event, and examine the associated solar activity and interplanetary environment to assess the implications for particle acceleration and transport.

This work was supported by NASA under contract NNN06AA01C. Title: Observations of Magnetic Island Formation by the Wide Field Imager on Parker Solar Probe (WISPR/PSP) Authors: Linton, M.; Stenborg, G.; Howard, R. A.; Ko, Y. K.; Vourlidas, A.; Higginson, A. K.; Tenerani, A.; Velli, M.; Liewer, P. C. Bibcode: 2019AGUFMSH33D3397L Altcode: We report on observations by the Wide Field Imager on Parker Solar Probe of possible magnetic island formation in a solar coronal streamer current sheet. Remote sensing observations during the second perihelion of Parker Solar Probe show the formation and ejection of an elliptical structure in the center of the streamer current sheet. The morphology and evolution of this candidate magnetic island is consistent with magnetohydrodynamical simulations of island formation and ejection in solar wind current sheets. We will review the relevant theory and simulations as they relate to this observation, and will compare and contrast these observations with corresponding remote sensing observation of candidate island formation events made from 1 AU by the SOHO and STEREO spacecraft.

This work was supported by the NASA Parker Solar Probe Program Office. Title: Imaging the Solar Corona from Within: First Results from the Parker Solar Probe Telescope Authors: Howard, R. A.; Vourlidas, A.; Bothmer, V.; Colaninno, R. C.; DeForest, C.; Gallagher, B.; Hall, J. R.; Hess, P.; Higginson, A. K.; Korendyke, C.; Kouloumvakos, A.; Lamy, P.; Liewer, P. C.; Linker, J.; Linton, M.; Penteado, P. F.; Plunkett, S. P.; Poirier, N.; Raouafi, N.; Rich, N.; Rochus, P. L.; Rouillard, A. P.; Socker, D. G.; Stenborg, G.; Thernisien, A.; Viall, N. M. Bibcode: 2019AGUFMSH11A..04H Altcode: Parker Solar Probe (PSP) launched in August 2018 is humanity's first probe of a stellar atmosphere. It will make measurements of the near-Sun plasma from 'within' the outer corona with gradually reduced perihelia from its first perihelia of 35 Rs in 2018-19 to 9.8 Rs in 2025. Here we report the results from the imaging observations of the electron and dust corona, whe PSP was 35-54 Rs from the solar surface, taken by the Wide-field Imager for Solar Probe (WISPR). The spacecraft was near-corotating with the solar corona throughout the observing window, which is an unprecedented situation for any type of coronal imaging. Our initial analysis uncovers a long-hypothesized depletion of the primordial dust orbiting near the Sun, reveals the plasma structure of small-scale ejections, and provides a strict test for validating model predictions of the large-scale configuration of the coronal plasma. Thus, WISPR imaging allows the study of near-Sun dust dynamics as the mission progresses. The high-resolution images of small transients, largely unresolved from 1 AU orbits, unravel the sub-structures of small magnetic flux ropes and show that the Sun continually releases helical magnetic fields in the background wind. Finally, WISPR's observations of the coronal streamer evolution confirm the large-scale topology of the solar corona but they also reveal that, as recently predicted, streamers are composed of yet smaller sub-streamers channeling continual density fluctuations at all visible scales. Title: Evolution of the geoeffective April 5, 2010 CME in the inner heliosphere: A global MHD model with a data-constrained magnetic flux rope specification. Authors: Provornikova, E.; Merkin, V. G.; Gibson, S. E.; Malanushenko, A. V.; Arge, C. N.; Vourlidas, A. Bibcode: 2019AGUFMSH42A..03P Altcode: Modeling the evolution of internal magnetic structure of interplanetary coronal mass ejections (ICMEs) is important both for space weather prediction and for basic understanding of magnetized space plasma interactions. Data-driven modeling of ICMEs in the inner heliosphere (starting beyond the critical surface in the corona) presents an attractive and computationally feasible approach, since it bypasses the complex problem of CME initiation and eruption in the corona. Using this approach, we simulate the propagation of ICMEs through the inner heliosphere using a global model driven at the coronal boundary by the Wang-Sheeley-Arge (WSA)-ADAPT model. ICMEs are initiated at 20 solar radii (Rs) using a magnetohydrodynamic (MHD) analytical Gibson-Low (GL) model of a self-similarly expanding magnetic flux rope with parameters (e.g., location, geometry, speed, orientation) constrained by white-light coronograph observations. The ICME propagation is simulated using the Grid Agnostic MHD for Extended Research Applications (GAMERA) MHD model, which is a recent reinvention of the high-heritage Lyon-Fedder-Mobarry (LFM) code. We apply this approach to the study of a geoeffective ICME which arrived at Earth on April 5, 2010. This ICME appeared bright in SOHO/LASCO and STEREO coronagraphs allowing derivation of its parameters near the Sun thus constraining its properties in our model. However, the orientation of the flux rope was not determined uniquely from the observations. It was also not clear which part of the ICME hit Earth and caused the severe geomagnetic storm. By comparing synthetic white-light images derived from our MHD modeling with images from SOHO/LASCO and STEREO/HI1 and HI2, we shed light on the ICME initial orientation and it evolution due to the interaction with the background solar wind. We further compare the modeling results with ACE observations at 1 AU and discuss which part of the CME was probed by the spacecraft. Title: Estimating the Visibility Function of Modern Coronagraphs Authors: Balmaceda, L. A.; Xie, H.; Vourlidas, A.; St Cyr, O. C. Bibcode: 2019AGUFMSH41F3331B Altcode: Estimates of the coronal mass ejection (CME) rate have been well-documented and are quasi-continuous since the mid-1970s based on coronagraph observations operating from ground and space. However, because coronagraphs detect CMEs via the scattering of photospheric emission from the electrons in the CME plasma, the visibility of a given CME depends strongly on its direction of propagation. Moreover, the detection of a CME by a given coronagraph depends both on the event-observer geometry and on the instrumental sensitivity and stray-light level of the detecting instrument. This dependence is called the CME Visibility Function (VF), and is specific to a given instrument. Here we determine and compare the visibility functions for SOHO LASCO and STEREO COR1/COR2 coronagrpahs. Our goal is to provide a thorough analysis of CME detectability for all currently operating coronagraphs, over different phases of the solar cycle, and to interpret the VF results both in terms of instrument design, performance, and effects of projection. Taking advantage of the multi-viewpoint observations available since the launch of STEREO we are able to obtain new estimates of the global CME rate. We provide the results based on specific periods of interest. Title: Gibson & Low Flux Rope Model: More Than a Spheromak! Authors: Malanushenko, A. V.; Gibson, S. E.; Provornikova, E.; Merkin, V. G.; Vourlidas, A.; Arge, C. N.; Dalmasse, K.; Nychka, D. W.; Flyer, N. Bibcode: 2019AGUFMSH11C3397M Altcode: Modeling solar coronal mass ejections (CMEs) is very important for both understanding coronal physics and for improving the accuracy of space weather forecasts. While it is generally accepted that CMEs are primarily magnetic structures, the exact properties of these structures could differ in different models and events. A structure often considered is a spheromak, a toroidal twisted flux rope, which is ejected as a CME bubble. Another commonly considered structure is a twisted magnetic flux rope, which is anchored to the solar surface while its upper portion is ejected into interplanetary space. In this talk we will show how a well-known analytical magnetohydrodynamic CME model (Gibson&Low, 1998), generally considered a spheromak-like model, can be extended to represent both standard spheromak and twisted flux tube configurations, as well as other topologically distinct magnetic structures. We will begin with the general parameters of the flux rope in this model (such as size and stretching parameters), and explore topologically different configurations possible with their variation. We then present several dimensionless parameters which can be varied to achieve these different configurations and consider how they relate to directly observable quantities. This work is particularly timely, as the Gibson&Low model is been increasingly used as input to numerical models of the solar corona and the heliosphere. The ability to generate topologically different magnetic configurations within this analytic solution is of great value to such simulations, as well as for the studies of the flux ropes forming in the solar corona. Title: Combining Remote and in situ Parker Solar Probe and STEREO Data to Understand Solar Wind Density Structures Authors: Viall, N. M.; Howard, R. A.; Vourlidas, A.; DeForest, C.; Kasper, J. C.; Korreck, K. E.; Case, A. W.; Stevens, M. L.; Whittlesey, P. L.; Larson, D. E.; Livi, R.; Szabo, A.; Kepko, L.; Lavraud, B.; Rouillard, A. P.; Velli, M. Bibcode: 2019AGUFMSH13C3432V Altcode: The instrument suite on Parker Solar Probe offers an unprecedented viewpoint of the ambient solar wind and structure therein, shortly after its formation and release from the solar corona. We take advantage of the synergistic observations of the first Parker Solar Probe encounters and the STEREO COR2 deep field campaigns covering the same time periods to study mesoscale solar wind density structures. They often occur in a quasi-periodic train, especially near the heliospheric current sheet. Some may be a consequence of the development of dynamics en route; many are remnants of the formation and release of the solar wind, and provide important constraints on solar wind models. The opportunity to combine the different observing angles and fields of view of the white light WISPR observations and white light STEREO COR2 observations with in situ density and plasma measurements from SWEAP allows better understanding of the characteristics and properties of mesoscale density structures. The in situ data measure precise size scales, plasma boundaries, and relationships between density and other parameters. They help in the interpretation of the structures seen in white light images and in unraveling projection effects. The white light images enhance the in situ data by providing global heliospheric context, as well as the occurrence rate and 2-D size scales of structures as a function of latitude and distance from the Sun. Together, these observations provide crucial constraints on the formation of structures in the solar wind. Title: The Solar Orbiter Heliospheric Imager (SoloHI) for the Solar Orbiter Mission: Science and Instrument Status Authors: Vourlidas, A.; Howard, R. A.; Colaninno, R. C.; Korendyke, C.; Thernisien, A.; Linton, M.; Tun Beltran, S.; Liewer, P. C.; Velli, M.; Linker, J.; Bothmer, V.; Rochus, P. L.; Lamy, P. L. Bibcode: 2019AGUFMSH24A..08V Altcode: The SoloHI instrument has completed its development effort and has been integrated onto the Solar Orbiter spacecraft. The mission, scheduled for launch in February 2020, will undergo gravity assist maneuvers around Venus to change both the perihelion distance as well as the plane of the orbit to ultimately achieve a minimum perihelion of 0.28 AU and an orbital inclination of about 35° relative to the ecliptic plane. The remote sensing instruments will operate for three 10-day periods out of the nominal 6-month orbit. SoloHI detects sunlight scattered by free electrons in the corona and solar wind from 5° to 45° elongation in visible wavelengths, providing linkage between solar and solar wind observations. The science investigation focuses mainly on the solar wind, including streamers, small-scale intensity and density fluctuations, jets, and Coronal Mass Ejections (CMEs). SoloHI is very similar to the HI-1 instrument on STEREO/SECCHI but with double the FOV of HI-1. In this paper, we present our preparations for the mission including the instrument status, our science planning strategy, our observing plans for cruise phase, calibrations, early science and our low-latency and science data products

This work has been supported by NASA. Title: Challenges in the Analysis of Images from the Wide-field Imager (WISPR) on Parker Solar Probe Authors: Liewer, P. C.; Hall, J. R.; Penteado, P.; Vourlidas, A.; Thernisien, A.; Howard, R. A.; Qiu, J.; Nistico, G.; Bothmer, V. Bibcode: 2019AGUFMSH23A..09L Altcode: The three-to-five-month highly elliptical orbit of Parker Solar Probe (PSP), approaching within 10 solar radii of the Sun, will allow the Wide-field Imager for Solar Probe (WISPR) to view the corona with unprecedented spatial resolution from multiple viewpoints. WISPR, located on the ram side of PSP, will image and fly through structures sample by the in situ instruments. WISPR has a wide fixed angular field-of-view (FOV), extending radially from 13.5° to 108° from the Sun and approximately 50° in the transverse direction, but the physical extent of the imaged coronal region varies directly with the distance of the spacecraft from the Sun. Challenges to interpreting the motion of density features seen in the WISPR images come from the wide and changing field-of-view and the unknown extent of the region of the coronal that co-rotates with the Sun. To relate and compare features seen in the images to observation by other instruments and spacecraft with other locations and viewpoints, it is necessary to relate the field-of-view of the WISPR telescopes at any given time to other frames of reference, such as the various Heliographic and Heliocentric coordinate systems. Here we discuss re-projections of WISPR images into several frames, made utilizing the World Coordinate System, which relies on information in the images' FITS headers (see W. T. Thompson, 2006, DOI: 10.1051/0004 6361:20054262). We will present methods for creating elongation vs. time images (J-maps) for WISPR images and also a technique for tracking observed density features to determine their 3D trajectories. These methods will be illustrated using data from WISPR's first encounters with the Sun. Title: Near-Sun observations of an F-corona decrease and K-corona fine structure Authors: Howard, R. A.; Vourlidas, A.; Bothmer, V.; Colaninno, R. C.; DeForest, C. E.; Gallagher, B.; Hall, J. R.; Hess, P.; Higginson, A. K.; Korendyke, C. M.; Kouloumvakos, A.; Lamy, P. L.; Liewer, P. C.; Linker, J.; Linton, M.; Penteado, P.; Plunkett, S. P.; Poirier, N.; Raouafi, N. E.; Rich, N.; Rochus, P.; Rouillard, A. P.; Socker, D. G.; Stenborg, G.; Thernisien, A. F.; Viall, N. M. Bibcode: 2019Natur.576..232H Altcode: Remote observations of the solar photospheric light scattered by electrons (the K-corona) and dust (the F-corona or zodiacal light) have been made from the ground during eclipses1 and from space at distances as small as 0.3 astronomical units2-5 to the Sun. Previous observations6-8 of dust scattering have not confirmed the existence of the theoretically predicted dust-free zone near the Sun9-11. The transient nature of the corona has been well characterized for large events, but questions still remain (for example, about the initiation of the corona12 and the production of solar energetic particles13) and for small events even its structure is uncertain14. Here we report imaging of the solar corona15 during the first two perihelion passes (0.16-0.25 astronomical units) of the Parker Solar Probe spacecraft13, each lasting ten days. The view from these distances is qualitatively similar to the historical views from ground and space, but there are some notable differences. At short elongations, we observe a decrease in the intensity of the F-coronal intensity, which is suggestive of the long-sought dust free zone9-11. We also resolve the fine-scale plasma structure of very small eruptions, which are frequently ejected from the Sun. These take two forms: the frequently observed magnetic flux ropes12,16 and the predicted, but not yet observed, magnetic islands17,18 arising from the tearing-mode instability in the current sheet. Our observations of the coronal streamer evolution confirm the large-scale topology of the solar corona, but also reveal that, as recently predicted19, streamers are composed of yet smaller substreamers channelling continual density fluctuations at all visible scales. Title: Unraveling the Internal Magnetic Field Structure of the Earth-directed Interplanetary Coronal Mass Ejections During 1995 - 2015 Authors: Gilbert, H. R.; Nieves-Chinchilla, T.; Jian, L.; Balmaceda, L.; Vourlidas, A.; Szabo, A.; St Cyr, O. C.; Guedes dos Santos, L. F. Bibcode: 2019AGUFMSH43C3377G Altcode: The magnetic field configurations associated with interplanetary coronal mass ejections (ICMEs) are the in situ manifestations of the entrained magnetic structure associated with coronal mass ejections (CMEs). We present a comprehensive study of the internal magnetic field configurations of ICMEs observed at 1 AU by the Wind mission during 1995 - 2015. The goal is to unravel the internal magnetic structure associated with the ICMEs and establish the signatures that validate a flux-rope structure. We examine the expected magnetic field signatures by simulating spacecraft trajectories within a simple flux rope, i.e., with circular-cylindrical (CC) helical magnetic field geometry. By comparing the synthetic configurations with the 353 ICME in situ observations, we find that only 152 events (Fr) display the clear signatures of an expected axial-symmetric flux rope. Two more populations exhibit possible signatures of flux rope; 58 cases (F-) display a small rotation (<90◦) of the magnetic field direction, interpreted as a large separation of the spacecraft from the center, and, 62 cases (F+) exhibit larger rotations, possibly arising from more complex configuration.

The categories, Cx (14%) and E events (9%), reveal signatures of complexity possibly related with evolutionary processes. We then reconstruct the flux ropes assuming CC geometry. We examine the orientation and geometrical properties during the solar activity levels at the end of Solar Cycle 22 (SC22), SC23 and part of SC24. The orientation exhibits solar cycle trends and follow the heliospheric current sheet orientation. We confirm previous studies that found a Hale cycle dependence of the poloidal field reversal. By comparing our results with the occurrence of CMEs with large angular width (AW> 60◦) we find a broad correlation suggesting that such events are highly inclined CMEs. The solar cycle distribution of bipolar vs. unipolar Bz configuration confirms that the CMEs may remove solar cycle magnetic field and helicity. Title: Impacts of small coronal transients at Parker Solar Probe at times of density increases and burst of magnetic switchbacks Authors: Rouillard, A. P.; Kouloumvakos, A.; Vourlidas, A.; Raouafi, N. E.; Lavraud, B.; Stenborg, G.; Kasper, J. C.; Bale, S.; Poirier, N.; Howard, R. A.; Viall, N. M.; Lavarra, M.; Stevens, M. L.; Korreck, K. E.; Case, A. W.; Whittlesey, P. L.; Larson, D. E.; Halekas, J. S.; Livi, R.; Goetz, K.; Harvey, P.; MacDowall, R. J.; Malaspina, D.; Pulupa, M.; Bonnell, J. W.; Dudok de Wit, T. Bibcode: 2019AGUFMSH12A..04R Altcode: A subset at least of the slow solar wind is released in the form of transients ejected continually along streamer rays. The physical mechanisms responsible for these transient releases of dense material are not yet fully understood. We exploit a period when the NASA Solar-TErrestrial RElations Observatory-A (STEREO-A) was in orbital quadrature with Parker Solar Probe (PSP) to track the release and propagation of dense material from the corona to PSP. At the time PSP had passed its second perihelion and was located near the Thomson sphere of the inner Heliospheric Imager (HI-1) onboard STEREO-A. This provided optimal observing conditions to track dense and therefore bright structures from the corona to the Sun-approaching spacecraft. We show that the streamers were continually ejecting bursts of dense structures (so-called 'blobs') many of which exhibiting V-shapes that are reminiscent of either magnetic kinks and/or the well-known back ends of small magnetic flux ropes. The wide-angle imager on Parker Solar Probe imaged similar structures at other locations of the streamers during this second encounter suggesting a global nature of this transient activity. We find evidence in STEREO ultraviolet images for slow reconfigurations of the corona near the estimated source regions of these structures but no one-to-one association is yet clearly established between the lower and upper corona. The exploitation of height-time maps ('J-maps') built from COR-2 and HI-1 images of the solar wind allow us to track the dense features all the way to PSP. We show that the spacecraft was repeatedly impacted by the southern edge of these structures. The passage of the bright coronal material at PSP is associated with clear density increases measured by the plasma instrument as expected. We also find evidence that the impact of the specific dense structures are correlated with a higher occurrence of magnetic field reversals. Part of this work was funded by the European Research Council through the project SLOW_SOURCE - DLV-819189 Title: A Comparative Study of 2017 July and 2012 July Complex Eruptions: Are Solar Superstorms "Perfect Storms" in Nature? Authors: Liu, Y. D.; Zhao, X.; Hu, H.; Vourlidas, A.; Zhu, B. Bibcode: 2019AGUFMSH32A..02L Altcode: It is paramount from both scientific and societal perspectives to understand the generation of extreme space weather. We discuss the formation of solar superstorms based on a comparative study of the 2012 July 23 and 2017 July 23 eruptions. The first one is Carrington-class, and the second could rival the 1989 March event that caused the most intense geomagnetic storm of the space age. Observations of these events in the historically weak solar cycle 24 indicate that a solar superstorm can occur in any solar cycle and at any phase of the cycle. Recurrent patterns are identified in both cases, including the long-lived eruptive nature of the active region, a complex event composed of successive eruptions from the same active region, and in-transit interaction between the successive eruptions resulting in exceptionally strong ejecta magnetic fields at 1 AU. Each case also shows unique characteristics. Preconditioning of the upstream solar wind leading to unusually high solar wind speeds at 1 AU is observed in the first case whereas not in the latter. This may suggest that the concept of "preconditioning" appears to be necessary for making a Carrington-class storm. We find a considerable deflection by nearby coronal holes in the second case but not in the first. On the basis of these results, we propose a hypothesis for further investigation that superstorms are "perfect storms" in nature, i.e., a combination of circumstances that results in an event of unusual magnitude. Historical records of some extreme events seem to support our hypothesis. Title: Tracking Outward Propagating Small-Scale Structures from EUVI through COR1 and COR2 Authors: Viall, N. M.; Alzate, N.; Morgan, H.; Vourlidas, A. Bibcode: 2019AGUFMSH13A..07V Altcode: The challenge of connecting slow solar wind variability to its source at the Sun is primarily due to the limitations on observational data of the low corona. Instrumental light scattering is higher in coronagraph observations very close to the solar surface, resulting in poor signal-to-noise ratios. Additionally, the non-radial nature of the coronal structures in this region hampers the tracking of small-scale structures in observations, since they produce weaker signals. Our work focuses on developing and applying advanced image processing techniques to solar imaging data in an effort to connect the low corona to the high corona with a focus on the identification of the sources of small-scale structures in the slow solar wind. The inner coronagraph, COR1, onboard the STEREO spacecraft, observes the low corona from ~1.1 to 4 Rs, imaging the important connection between the solar wind, its source, and the formation of the solar wind structures. We have developed an approach for processing COR1 that allows the tracking of small-scale structures. The core process is a bandpass filter of the data over time, where the signal from high frequency noise is suppressed, as well as slowly evolving structures. We applied this method to a 10-day period of observations during solar minimum and compared them to observations from the imager EUVI and outer coronagraph COR2. Height-time profiles reveal structures propagating through the different fields of view, establishing a connection between the low and high corona. Further analysis will allow us to characterize these structures and determine occurrence frequencies, size scales, formation height and mechanism. Our method for processing COR1 opens the door to ~13 years of STEREO/COR1 data for studies in general of the connection between the low and high corona, and specifically of small-scale coronal structures. Title: The Forming Slow Solar Wind Imaged along Streamer Rays by the Wide-Angle Imager on Parker Solar Probe Authors: Poirier, N.; Rouillard, A. P.; Kouloumvakos, A.; Vourlidas, A.; Stenborg, G.; Pinto, R.; Réville, V.; Valette, E.; Howard, R. A.; Hess, P.; Thernisien, A.; Rich, N.; Raouafi, N. E.; Lavarra, M.; Liewer, P. C.; Qiu, J.; Indurain, M. Bibcode: 2019AGUFMSH12A..08P Altcode: The Wide-field Imager for Solar PRobe (WISPR) recorded the first detailed imaging of streamer rays when Parker Solar Probe was in quasi-corotation with the corona. We exploit these new images to reveal the time and space variability in these streamers at scales that are not easily discernible in images taken from near 1AU, this provides new insights on the forming slow solar wind. WISPR images are projected into Carrington like maps to reveal the multiple white-light structures of a streamer observed during the first perihelion passage. We exploit 3-D magneto-hydrodynamic models to study the origin of these sub-structures and interpret them as small corrugation in the streamers and heliospheric current sheets. High-resolution simulations explain a number of observational features observed by WISPR including the effect of the spacecraft moving at high speed towards the individual streamer rays that make up a streamer. Finally we highlight the level of temporal variability in the streamers induced by propagating density structures likely induced by time-dependent processes occurring in the corona. This work was funded by the European Research Council through the project SLOW_SOURCE - DLV-819189. Title: LOCKYER: Large Optimized Coronagraphs for KeY Emission line Research Authors: Laming, J. M.; Vourlidas, A. Bibcode: 2019AGUFMSH31B..15L Altcode: LOCKYER will investigate the birth region of the Solar Wind, CMEs, SEPs, and Space Weather. The mission will explore this critical coronal region by acquiring spectroscopic and imaging observations of the off-limb corona, from 1.2 to 12 Rs, across the EUV-UV-Visible spectrum. The science investigation addresses two key long-standing science questions

1. What powers the Solar Wind?

2. How do CMEs form and acquire their defining characteristics?

The sun-pointed payload consists of three telescopes mounted on a LEOstar spacecraft in a 650 km Sun-Sync orbit. Observations are taken continuously, except during the brief eclipses, and downlinked through a Ka-band link once daily. LOCKYER observes over the western solar limb, synoptically, with either a single or dual slit system. Visible and EUV images are obtained at a 1-5 minute cadence, depending on the objective. The spacecraft rotates to the east limb every 30 min to acquire a full image of the equatorial corona for Space Weather purposes. LOCKYER comprises three telescopes:

1. A spectroscopic coronagraph in the EUV-UV range (70 - 170 nm)

2. A visible coronagraph with a FOV of 1.5-12 Rs with polarization and emission line filter capabilities

3. A broadband EUV (17-20 nm) coronagraph with FOV of 1.5 to 5 Rs.

All three instruments use the same occulter mounted on an 8.5m boom. We will describe how this instrument suite will be used to measure waves and dynamics, coronal element abundances, and solar wind acceleration as three coupled sets of phenomena, and used to investigate the various regimes of the background solar wind, coronal mass ejections, and their associated shock waves.

LOCKYER is a collaborative project between JHU APL, NRL, SAO, Univ. of New Hampshire, Univ. of Colorado, Univ. of Montana, SWRI, IAS, and IRAP. Title: Multi-species modelling of the forming solar wind from the upper chromosphere to Parker Solar Probe Authors: Lavarra, M.; Rouillard, A. P.; Blelly, P. L.; Pinto, R.; Poirier, N.; Indurain, M.; Réville, V.; Stevens, M. L.; Kasper, J. C.; Korreck, K. E.; Case, A. W.; Whittlesey, P. L.; Larson, D. E.; Bale, S.; Halekas, J. S.; Livi, R.; Raouafi, N. E.; Goetz, K.; Harvey, P.; MacDowall, R. J.; Malaspina, D.; Pulupa, M.; Bonnell, J. W.; Dudok de Wit, T.; Lavraud, B.; Vourlidas, A.; Howard, R. A. Bibcode: 2019AGUFMSH11C3401L Altcode: The effects of coronal heating on the properties of the escaping solar wind are still debated. We investigate the development of temperature anisotropies in the middle corona measured by past coronal spectrometers by using a 1-D multi-species model of the forming solar wind. The model assumes a bi-Maxwellian distribution function for all species, couples neutral (hydrogen, helium) and charged particles (electrons, protons, charged helium) and includes a self-consistent treatment of ionisation processes in the upper chromosphere and low corona. Our simulations extend to 70 solar radii and we compare our first results with the bulk properties and anisotropies of the ions and electrons measured in situ by Helios and Parker Solar Probe. We study the effects of ion and electron heating separately as well as wave transport and dissipation on the resulting solar wind properties for different coronal topologies including streamers, pseudo-streamers and interplume regions. A first multi-tube implementation of this kinetic-fluid code allows us to compare our results with past spectroscopic measurements by the Solar and Heliospheric Observatory and the future Solar Orbiter mission. Part of this work was funded by the European Research Council through the project SLOW_SOURCE - DLV-819189 Title: Lyα science from the LST aboard the ASO-S mission Authors: Vourlidas, Angelos Bibcode: 2019RAA....19..168V Altcode: We review the status of solar Lyα science in anticipation of the upcoming Advanced Space-based Solar Observatory (ASO-S) mission, planned for a late 2021 (or 2022) launch. The mission carries a pair of the Lyα Solar Telescopes (LST) capable of high resolution disk and off-limb imaging, which will provide the first synoptic Lyα imaging observations of the solar atmosphere. We discuss the history of Lyα imaging and latest results, and outline the open questions that ASO-S could address. ASO-S will launch at an optimal time for Lyα science. Several other Lyα telescopes will be in operation. We identify the synergies between ASO-S and other missions as well as serendipitous non-solar science opportunities. We conclude that ASO-S has the potential for breakthrough observations and discoveries in the chromosphere-corona interface where the Lyα emission is the major player. Title: Comparing extrapolations of the coronal magnetic field structure at 2.5 R⊙ with multi-viewpoint coronagraphic observations Authors: Sasso, C.; Pinto, R. F.; Andretta, V.; Howard, R. A.; Vourlidas, A.; Bemporad, A.; Dolei, S.; Spadaro, D.; Susino, R.; Antonucci, E.; Abbo, L.; Da Deppo, V.; Fineschi, S.; Frassetto, F.; Landini, F.; Naletto, G.; Nicolini, G.; Nicolosi, P.; Pancrazzi, M.; Romoli, M.; Telloni, D.; Ventura, R. Bibcode: 2019A&A...627A...9S Altcode: 2019arXiv190509005S The magnetic field shapes the structure of the solar corona, but we still know little about the interrelationships between the coronal magnetic field configurations and the resulting quasi-stationary structures observed in coronagraphic images (such as streamers, plumes, and coronal holes). One way to obtain information on the large-scale structure of the coronal magnetic field is to extrapolate it from photospheric data and compare the results with coronagraphic images. Our aim is to verify whether this comparison can be a fast method to systematically determine the reliability of the many methods that are available for modeling the coronal magnetic field. Coronal fields are usually extrapolated from photospheric measurements that are typically obtained in a region close to the central meridian on the solar disk and are then compared with coronagraphic images at the limbs, acquired at least seven days before or after to account for solar rotation. This implicitly assumes that no significant changes occurred in the corona during that period. In this work, we combine images from three coronagraphs (SOHO/LASCO-C2 and the two STEREO/SECCHI-COR1) that observe the Sun from different viewing angles to build Carrington maps that cover the entire corona to reduce the effect of temporal evolution to about five days. We then compare the position of the observed streamers in these Carrington maps with that of the neutral lines obtained from four different magnetic field extrapolations to evaluate the performances of the latter in the solar corona. Our results show that the location of coronal streamers can provide important indications to distinguish between different magnetic field extrapolations. Title: Predicting the geoeffective properties of coronal mass ejections: current status, open issues and path forward Authors: Vourlidas, A.; Patsourakos, S.; Savani, N. P. Bibcode: 2019RSPTA.37780096V Altcode: Much progress has been made in the study of coronal mass ejections (CMEs), the main drivers of terrestrial space weather thanks to the deployment of several missions in the last decade. The flow of energy required to power solar eruptions is beginning to be understood. The initiation of CMEs is routinely observed with cadences of tens of seconds with arc-second resolution. Their inner heliospheric evolution can now be imaged and followed routinely. Yet relatively little progress has been made in predicting the geoeffectiveness of a particular CME. Why is that? What are the issues holding back progress in medium-term forecasting of space weather? To answer these questions, we review, here, the measurements, status and open issues on the main CME geoeffective parameters; namely, their entrained magnetic field strength and configuration, their Earth arrival time and speed, and their mass (momentum). We offer strategies for improving the accuracy of the measurements and their forecasting in the near and mid-term future. To spark further discussion, we incorporate our suggestions into a top-level draft action plan that includes suggestions for sensor deployment, technology development and modelling/theory improvements.

This article is part of the theme issue `Solar eruptions and their space weather impact'. Title: Unraveling the Internal Magnetic Field Structure of the Earth-directed Interplanetary Coronal Mass Ejections During 1995 - 2015 Authors: Nieves-Chinchilla, Teresa; Jian, Lan K.; Balmaceda, Laura; Vourlidas, Angelos; dos Santos, Luiz F. G.; Szabo, Adam Bibcode: 2019SoPh..294...89N Altcode: The magnetic field configurations associated with interplanetary coronal mass ejections (ICMEs) are the in situ manifestations of the entrained magnetic structure associated with coronal mass ejections (CMEs). We present a comprehensive study of the internal magnetic field configurations of ICMEs observed at 1 AU by the Wind mission during 1995 - 2015. The goal is to unravel the internal magnetic structure associated with the ICMEs and establish the signatures that validate a flux-rope structure. We examine the expected magnetic field signatures by simulating spacecraft trajectories within a simple flux rope, i.e., with circular-cylindrical (CC) helical magnetic field geometry. By comparing the synthetic configurations with the 353 ICME in situ observations, we find that only 152 events (Fr) display the clear signatures of an expected axial-symmetric flux rope. Two more populations exhibit possible signatures of flux rope; 58 cases (F−) display a small rotation (<90∘) of the magnetic field direction, interpreted as a large separation of the spacecraft from the center, and, 62 cases (F+) exhibit larger rotations, possibly arising from more complex configuration. The categories, Cx (14%) and E events (9%), reveal signatures of complexity possibly related with evolutionary processes. We then reconstruct the flux ropes assuming CC geometry. We examine the orientation and geometrical properties during the solar activity levels at the end of Solar Cycle 22 (SC22), SC23 and part of SC24. The orientation exhibits solar cycle trends and follow the heliospheric current sheet orientation. We confirm previous studies that found a Hale cycle dependence of the poloidal field reversal. By comparing our results with the occurrence of CMEs with large angular width (AW>60∘) we find a broad correlation suggesting that such events are highly inclined CMEs. The solar cycle distribution of bipolar vs. unipolar Bz configuration confirms that the CMEs may remove solar cycle magnetic field and helicity. Title: Element Abundances: A New Diagnostic for the Solar Wind Authors: Laming, J. Martin; Vourlidas, Angelos; Korendyke, Clarence; Chua, Damien; Cranmer, Steven R.; Ko, Yuan-Kuen; Kuroda, Natsuha; Provornikova, Elena; Raymond, John C.; Raouafi, Nour-Eddine; Strachan, Leonard; Tun-Beltran, Samuel; Weberg, Micah; Wood, Brian E. Bibcode: 2019ApJ...879..124L Altcode: 2019arXiv190509319L We examine the different element abundances exhibited by the closed loop solar corona and the slow speed solar wind. Both are subject to the first ionization potential (FIP) effect, the enhancement in coronal abundance of elements with FIP below 10 eV (e.g., Mg, Si, Fe) with respect to high-FIP elements (e.g., O, Ne, Ar), but with subtle differences. Intermediate elements, S, P, and C, with FIP just above 10 eV, behave as high-FIP elements in closed loops, but are fractionated more like low-FIP elements in the solar wind. On the basis of FIP fractionation by the ponderomotive force in the chromosphere, we discuss fractionation scenarios where this difference might originate. Fractionation low in the chromosphere where hydrogen is neutral enhances the S, P, and C abundances. This arises with nonresonant waves, which are ubiquitous in open field regions, and is also stronger with torsional Alfvén waves, as opposed to shear (i.e., planar) waves. We discuss the bearing these findings have on models of interchange reconnection as the source of the slow speed solar wind. The outflowing solar wind must ultimately be a mixture of the plasma in the originally open and closed fields, and the proportions and degree of mixing should depend on details of the reconnection process. We also describe novel diagnostics in ultraviolet and extreme ultraviolet spectroscopy now available with these new insights, with the prospect of investigating slow speed solar wind origins and the contribution of interchange reconnection by remote sensing. Title: Simulating White Light Images of Coronal Structures for WISPR/ Parker Solar Probe: Effects of the Near-Sun Elliptical Orbit Authors: Liewer, P.; Vourlidas, A.; Thernisien, A.; Qiu, J.; Penteado, P.; Nisticò, G.; Howard, R.; Bothmer, V. Bibcode: 2019SoPh..294...93L Altcode: The three-to-five-month elliptical orbit of Parker Solar Probe (PSP), approaching within 10 solar radii of the Sun, will allow the Wide-field Imager for Solar Probe (WISPR) to view the corona with unprecedented spatial resolution from multiple viewpoints. WISPR has a wide fixed angular field of view, extending from 13.5∘ to 108∘ from the Sun and approximately 50∘ in the transverse direction, but the physical extent of the imaged coronal region varies directly with the distance of the spacecraft from the Sun. In a solar encounter period of approximately 10 days around perihelion, PSP covers over 100 - 200° of heliographic longitude and the distance from the Sun varies by a factor of two to five. In this paper, we use synthetic white-light images to study the effects of the rapid elliptical orbit on the images that can be anticipated for WISPR's observations. We find that sequences of images can help identify coronal density features that will be sampled by in-situ instruments. We also find that the multiple viewpoints, provided by the rapid motion near perihelion, can be used to obtain three-dimensional information on the coronal density features. Title: Solar energetic particles in the inner heliosphere: status and open questions Authors: Anastasiadis, Anastasios; Lario, David; Papaioannou, Athanasios; Kouloumvakos, Athanasios; Vourlidas, Angelos Bibcode: 2019RSPTA.37780100A Altcode: Solar energetic particle (SEP) events are related to both solar flares and coronal mass ejections (CMEs) and they present energy spectra that span from a few keV up to several GeV. A wealth of observations from widely distributed spacecraft have revealed that SEPs fill very broad regions of the heliosphere, often all around the Sun. High-energy SEPs can sometimes be energetic enough to penetrate all the way down to the surface of the Earth and thus be recorded on the ground as ground level enhancements (GLEs). The conditions of the radiation environment are currently unpredictable due to an as-yet incomplete understanding of solar eruptions and their corresponding relation to SEP events. This is because the complex nature and the interplay of the injection, acceleration and transport processes undergone by the SEPs in the solar corona and the interplanetary space prevent us from establishing an accurate understanding (based on observations and modelling). In this work, we review the current status of knowledge on SEPs, focusing on GLEs and multi-spacecraft events. We extensively discuss the forecasting and nowcasting efforts of SEPs, dividing these into three categories. Finally, we report on the current open questions and the possible direction of future research efforts.

This article is part of the theme issue `Solar eruptions and their space weather impact'. Title: Tomography of the Solar Corona with the Wide-Field Imager for the Parker Solar Probe Authors: Vásquez, Alberto M.; Frazin, Richard A.; Vourlidas, Angelos; Manchester, Ward B.; van der Holst, Bart; Howard, Russell A.; Lamy, Philippe Bibcode: 2019SoPh..294...81V Altcode: The Wide-field Imager for the Parker Solar Probe (PSP/WISPR) comprises two telescopes that record white-light total brightness [B ] images of the solar corona. Their fields of view cover a widely changing range of heliocentric heights over the 24 highly eccentric orbits planned for the mission. In this work, the capability of PSP/WISPR data to carry out tomographic reconstructions of the three-dimensional (3D) distribution of the coronal electron density is investigated. Based on the precise orbital information of the mission, B -images for Orbits 1, 12, and 24 are synthesized from a 3D magnetohydrodynamic model of the corona. For each orbit, the time series of synthetic images is used to carry out a tomographic reconstruction of the coronal electron density and results are compared with the model. As the PSP perihelion decreases, the range of heights that can be tomographically reconstructed progressively shifts to lower values, and the period required to gather the data decreases. For Orbit 1 tomographic reconstruction is not possible. For Orbit 12, tomographic reconstruction is possible in the heliocentric height range ≈5 -15 R⊙, over a region spanning up to ≈160∘ in Carrington longitude, with data gathered over a ≈3.4 day-long period. For Orbit 24, tomographic reconstruction is possible in the heliocentric height range ≈3 -10 R⊙, over a region spanning up to ≈170∘ in Carrington longitude, with data gathered over a ≈2.8 day-long period. Title: Radio Propagation Diagnostics of the Inner Heliosphere in the Era of the Parker Solar Probe Authors: Kobelski, Adam; Bastian, Timothy S.; Vourlidas, Angelos Bibcode: 2019AAS...23410706K Altcode: The solar wind offers and extraordinary laboratory for studying turbulence, turbulent dissipation, and heating. The Parker Solar Probe (PSP) was launched in August 2018 to study these and other important processes in the inner heliosphere. One type of observation that will complement those of PSP are radio propagation measurements of solar wind turbulence in the outer corona and the inner heliosphere. This type of observation can provide measurements of the angular broadening of distant spatially coherent background sources that transilluminate the foreground solar wind plasma. This well-known technique can be used to measure the spatial spectrum of electron density inhomogeneities in the solar wind on scales of 100s of meters to 10s of kilometers inside of 10-15 solar radii over a wide range of position angles.

Here we report the results of a pilot study of background sources using the Jansky Very Large Array (JVLA) in summer 2015. Unlike previous studies of this kind, the JVLA's much greater sensitivity allows fainter and more numerous sources to be used as probes of the foreground medium. We observed 11 background sources in 16 sessions at apparent radial distances of 2-7 solar radii. We confirm previous findings: that the spectrum is flatter than Kolmogorov and that is highly anisotropic. Unlike previous studies we find breaks into steeper spectra for some sources on short spatial scales, suggestive of a transition to dissipation.

Looking forward, we describe observations planned in August 2019 in support of the third PSP perihelion passage (35.7 solar radii). The VLA will be used to observe the corona and inner heliosphere along 70 pierce points <10 solar radii. These observations will not only provide global context about the state of the inner heliosphere at time of perihelion passage, they will also baseline key solar wind parameters that can be compared directly with PSP measurements. These include turbulence level, spectral index, degree of anisotropy, and the orientation of the magnetic field. The PSP measurements will, in turn, provide measurements that will validate key assumptions made in interpreting the radio data. Title: Sheared Magnetic Arcades and the Pre-eruptive Magnetic Configuration of Coronal Mass Ejections: Diagnostics, Challenges and Future Observables Authors: Patsourakos, Spiros; Vourlidas, A.; Anthiochos, S. K.; Archontis, V.; Aulanier, G.; Cheng, X.; Chintzoglou, G.; Georgoulis, M. K.; Green, L. M.; Kliem, B.; Leake, J.; Moore, R. L.; Nindos, A.; Syntelis, P.; Torok, T.; Yardley, S. L.; Yurchyshyn, V.; Zhang, J. Bibcode: 2019shin.confE.194P Altcode: Our thinking about the pre-eruptive magnetic configuration of Coronal Mass Ejections has been effectively dichotomized into two opposing and often fiercely contested views: namely, sheared magnetic arcades and magnetic flux ropes. Finding a solution to this issue will have important implications for our understanding of CME initiation. We first discuss the very value of embarking into the arcade vs. flux rope dilemma and illustrate the corresponding challenges and difficulties to address it. Next, we are compiling several observational diagnostics of pre-eruptive sheared magnetic arcades stemming from theory/modeling, discuss their merits, and highlight potential ambiguities that could arise in their interpretation. We finally conclude with a discussion of possible new observables, in the frame of upcoming or proposed instrumentation, that could help to circumvent the issues we are currently facing. Title: MHD modeling of evolving ICME magnetic structure in the inner heliosphere Authors: Provornikova, Elena; Merkin, Vyacheslav; Malanushenko, Anna; Gibson, Sarah; Arge, Nick; Vourlidas, Angelos Bibcode: 2019shin.confE.230P Altcode: As CME propagates through the inner heliosphere, evolution of its structure is influenced by the interaction with the solar wind streams. I will present our recent simulations with GAMERA code of propagating flux rope-CME from 0.1 to 1 AU in the background solar wind. We evaluate self-similarly an erupting CME at 0.1 AU based on the Gibson-Low model and insert it into our global inner heliosphere model driven by the Wang-Sheeley-Arge (WSA) model of the corona, while WSA, in turn, is driven by ADAPT global photospheric magnetic field maps. To simulate the ICME propagation in the inner heliosphere, we use the GAMERA (Grid Agnostic MHD for Extended Research Applications) magnetohydrodynamic (MHD) code which is a reinvention of the high-heritage Lyon-Fedder-Mobarry (LFM) code. We present modeling results and focus on the evolution of the large-scale structure of the CME from the outer solar corona to Earth. In particular I will present a simulation of the April 3, 2010 CME event. Title: Deriving the Near-Sun Magnetic Field of Coronal Mass Ejections from Magnetic Helicity Conservation Authors: Patsourakos, Spiros; Georgoulis, M. K.; Petroulea, G.; Vourlidas, A.; Nieves-Chinchilla, T. Bibcode: 2019shin.confE.222P Altcode: The near-Sun magnetic field of Coronal Mass Ejections represents a key parameter for assessing their energetics and structuring, and additionally, it is a major element of methods/applications/simulations aiming to predict the magnetic field of Earth-directed CMEs upon impact at geospace. Diagnostics of CME magnetic fields in the corona can be achieved via observations in the radio domain, which however, are currently not available on a regular basis. Therefore, several methods to infer the CME magnetic field in the corona have recently emerged. We developed one such method which is based on the magnetic helicity conservation principle applied to flux rope CMEs. Its input parameters could be readily retrieved from the analysis of HMI magnetograms and SOHO/STEREO WL coronagraph images. We present parametric and case-study applications of this method, and discuss how it be could be used to predict the CME magnetic field magnitude at 1 AU. Title: Unraveling the internal magnetic field structure of the Earth-directed interplanetary coronal mass ejections during 1995-2015.? Authors: Nieves-Chinchilla, Teresa; Jian, Lan K.; Balmaceda, Laura; Vourlidas, Angelos; dos Santos, Luiz F. G.; Szabo, Adam Bibcode: 2019shin.confE..19N Altcode: The magnetic field configurations associated with interplanetary coronal mass ejections (ICMEs) are the in-situ manifestations of the entrained magnetic structure associated with the coronal mass ejections (CMEs). The prediction of such configurations is essential to Space Weather in order to forecast any resulting geomagnetic disturbances. The main hypothesis in such predictions is to assume that such structure is a flux rope. We present a comprehensive study of the internal magnetic field configurations of ICMEs observed at 1 AU in the period 1995-2015 in order to unravel the internal magnetic structure associated with the CMEs and establish under what signatures a flux rope model is valid. In the first part of the presentation, we examine the expected magnetic field configurations by simulating various spacecraft trajectories within an ICME. This simulation is based on the assumption of a flux rope with the simplest flux rope geometry, i.e. circular-cylindrical helical magnetic field configuration. In the second part of the paper, we reconstruct the flux ropes by using the technique described on Nieves-Chinchilla et al. 2016. We examine the orientation and geometrical properties during the solar activity levels at the end of solar cycle 22, solar cycle 23 and part of solar cycle 24. Title: COHERENT: Studying the corona as a holistic environment Authors: Caspi, Amir; Seaton, Daniel B.; Case, Traci; Cheung, Mark; Cranmer, Steven; DeForest, Craig E.; de Toma, Giuliana; Downs, Cooper; Elliott, Heather; Gold, Anne U.; Longcope, Dana; Savage, Sabrina L.; Sullivan, Susan; Viall, Nicholeen; Vourlidas, Angelos; West, Matthew J. Bibcode: 2019shin.confE.241C Altcode: The solar corona and the heliosphere must be part of a single physical system, but because the dominant physical processes change dramatically from the magnetically-dominated low corona, through the sparsely-observed middle corona, and into the plasma flow-dominated outer corona and heliospheric interface, unified frameworks to study the corona as a whole are essentially nonexistent. Understanding how physical processes shape and drive the dynamics of the corona as a global system, on all spatiotemporal scales, is critical for solving many fundamental problems in solar and heliospheric physics. However, the lack of unifying observations and models has led to a fragmentation of the community into distinct regimes of plasma parameter space, largely clustering around regions where existing instrumentation has made observations widely available and where models can be sufficiently self-contained to be tractable. We describe COHERENT, the 'Corona as a Holistic Environment' Research Network, a focused effort to facilitate interdisciplinary collaborative research to develop frameworks for unifying existing and upcoming observations, theory, models, and analytical tools to study the corona as a holistic system. Title: Coronal Mass Ejections from Sun to Earth: Recent Advances in Modeling and Statistical Approaches Authors: Malanushenko, Anna; Gibson, S.; Dalmasse, K.; Merkin, V.; Provornikova, E.; Vourlidas, A.; Arge, C.; Nychka, D.; Wiltberger, M.; Flyer, N. Bibcode: 2019shin.confE.206M Altcode: Solar coronal mass ejections (CMEs) are violent eruptive phenomena which originate on the Sun; their heliospheric extensions, called interplanetary CMEs, are known for their potential to impact the whole heliosphere and, in particular, the Earth. While not all CMEs are launched in such a way as to hit the Earth, those that do can have big impacts on Earth's magnetosphere. The magnitude of such impact depends upon many factors such as the CME launch location and velocity, its positioning within the background solar wind, its mass, and its magnetic properties such as the orientation of its front with respect to the Earth's magnetic field.

Case studies of how iCMEs propagate through the heliosphere are complicated by many factors, including often incomplete input for models. We present and discuss a different approach. Rather than focusing on modeling a particular event, we intend to carry out a large statistical study in the event parameter space. Further, Bayesian statistics will be used along with large statistical databases of near-Sun and near-Earth observables, to infer statistical distributions of relevant CME input parameters, which are capable of yielding given distributions of observables, for a given stage of the the solar cycle.

We use a analytical flux rope model (Gibson&Low model) and a background solar wind boundary (Wang-Sheeley-Arge model) as inputs for a new MHD heliospheric simulation code (Gamera). We give an overview and update of the project and show first modeling results. Title: Reconstructing Extreme Space Weather From Planet Hosting Stars Authors: Airapetian, Vladimir; Adibekyan, V.; Ansdell, M.; Alexander, D.; Barklay, T.; Bastian, T.; Boro Saikia, S.; Cohen, O.; Cuntz, M.; Danchi, W.; Davenport, J.; DeNolfo, G.; DeVore, R.; Dong, C. F.; Drake, J. J.; France, K.; Fraschetti, F.; Herbst, K.; Garcia-Sage, K.; Gillon, M.; Glocer, A.; Grenfell, J. L.; Gronoff, G.; Gopalswamy, N.; Guedel, M.; Hartnett, H.; Harutyunyan, H.; Hinkel, N. R.; Jensen, A. G.; Jin, M.; Johnstone, C.; Kahler, S.; Kalas, P.; Kane, S. R.; Kay, C.; Kitiashvili, I. N.; Kochukhov, O.; Kondrashov, D.; Lazio, J.; Leake, J.; Li, G.; Linsky, J.; Lueftinger, T.; Lynch, B.; Lyra, W.; Mandell, A. M.; Mandt, K. E.; Maehara, H.; Miesch, M. S.; Mickaelian, A. M.; Mouschou, S.; Notsu, Y.; Ofman, L.; Oman, L. D.; Osten, R. A.; Oran, R.; Petre, R.; Ramirez, R. M.; Rau, G.; Redfield, S.; Réville, V.; Rugheimer, S.; Scheucher, M.; Schlieder, J. E.; Shibata, K.; Schnittman, J. D.; Soderblom, David; Strugarek, A.; Turner, J. D.; Usmanov, A.; Van Der Holst, B.; Vidotto, A.; Vourlidas, A.; Way, M. J.; Wolk, Scott J.; Zank, G. P.; Zarka, P.; Kopparapu, R.; Babakhanova, S.; Pevtsov, A. A.; Lee, Y.; Henning, W.; Colón, K. D.; Wolf, E. T. Bibcode: 2019BAAS...51c.564A Altcode: 2019astro2020T.564A; 2019arXiv190306853A The goal of this white paper is to identify and describe promising key research goals to aid the theoretical characterization and observational detection of ionizing radiation from quiescent and flaring upper atmospheres of planet hosts as well as properties of stellar coronal mass ejections (CMEs) and stellar energetic particle (SEP) events. Title: Radio Observational Constraints on Turbulent Astrophysical Plasmas Authors: Bastian, Tim; Cordes, James; Kasper, Justin; Kobelski, Adam; Korreck, Kelly; Howes, Gregory; Salem, Chadi; Spangler, Steve; Vourlidas, Angelos Bibcode: 2019astro2020T.307B Altcode: 2019arXiv190405807B Using radio observations of background sources, scattering phenomena may be used to characterize the properties of foreground turbulent plasma. We discuss the potential of such techniques to explore turbulence in the solar wind and interstellar medium. The Next Generation VLA will be an ideal instrument to exploit these techniques. Title: Challenges in the Analysis of Images from the Wide-field Imager (WISPR) on Parker Solar Probe Authors: Liewer, Paulett; Penteado, Paulo; Hall, Jeff; Vourlidas, Angelos; Qiu, Jiong; Howard, Russ Bibcode: 2019shin.confE.133L Altcode: The three-to-five-month elliptical orbit of Parker Solar Probe (PSP), approaching within 10 solar radii of the Sun, will allow the Wide-field Imager for Solar Probe (WISPR) to view the corona with unprecedented spatial resolution from multiple viewpoints. WISPR, located on the ram side of PSP, will image and fly through structures sample by the in situ instruments. WISPR has a wide fixed angular field-of-view (FOV), extending radially from 13.5? to 108? from the Sun and approximately 50? in the transverse direction, but the physical extent of the imaged coronal region varies directly with the distance of the spacecraft from the Sun. To relate and compare features seen in the images to observation by other instruments and spacecraft with other locations and viewpoints, it is first necessary to relate the field-of-view of the WISPR telescopes at any given time to other frames of reference, such as the various Heliographic and Heliocentric coordinate systems. Here we present projections of WISPR images in several frames, made utilizing the World Coordinate System which relies on information in the images’ FITS headers (see W. T. Thompson, 2006, DOI: 10.1051/0004-6361:20054262). Specifically, the projection software uses the SolarSoft Sunpice package ($SSW/sunspice), developed by W. Thompson to obtain the proper SPICE information on spacecraft location, orientation, and the pointing of the WISPR telescopes relative to the spacecraft pointing. The changing size of the FOV relative to the Sun must be considered when analyzing tracks of density features in a sequence of images. We discuss how to create elongation (angle from the Sun as seen by the observer) vs. time images from WISPR and show J-maps created from data on WISPR’s first encounter. Title: Connecting the Low Corona to the High Corona: Outward Propagating Small-Scale Transients Tracked from EUVI Through COR1 and COR2 Authors: Alzate, Nathalia; Viall, Nicholeen; Morgan, Huw; Vourlidas, Angelos Bibcode: 2019shin.confE..59A Altcode: Identification of the source of the slow solar wind has been hampered by the complexity of plasma structures in the very low corona and data limitations in terms of noise reduction. Application of state-of-the-art image processing techniques has revealed very faint structures in the low corona that have an impact on the structure of the extended corona. These techniques, which overcome faint signals and noise in the data, allow us to identify and characterize the sources of the slow solar wind as we explore the variability of coronal density structures over a distance range starting from the solar surface out to tens of radii and beyond using data from the STEREO spacecraft. Having successfully conquered the noise issues in the COR1 instrument, as a proof of concept we revisited a 10-day period in January 2008 in which density enhancements were previously identified as sources of the slow solar wind in in situ, HI2 and COR2 data. Our preliminary results show transients present in the EUVI, COR1 and COR2 FOVs, with several transients propagating through at least two FOVs. Further analysis will enable us to properly determine the exact formation heights of ambient solar wind structures, formation mechanisms, and the features in the low corona they connect to. We will include data from other instruments to study different coronal configurations in order to characterize solar wind structures low in the corona as a function of coronal magnetic complexity, which will be an essential test for theories of solar wind formation. Our method for processing COR1 data opens the door to 12 years of data for studies of small-scale coronal structures and their geoeffectiveness. This work is part of the broad effort in Heliospheric physics to understand the different types of transient structures created in the solar wind as it is formed. Title: A Statistical Study of CME Kinematics and its Relationship to the Magnetic Reconnection Flux Authors: Zhu, Chunming; Qiu, Jiong; Spiegel, Michael; Liewer, Paulett; Vourlidas, Angelos; Hu, Qiang Bibcode: 2019shin.confE..84Z Altcode: It is well known that CME kinematics are strongly related to the magnetic reconnection process in the solar corona. However, a quantitative understanding of this relationship still remains elusive. To determine the role of reconnection in CME initiation and acceleration, we carry out a statistical study of the CME kinematics relative to the onset and progress of magnetic reconnection, using 56 eruptions. The CMEs are measured utilizing the EUV and white light observations at the solar limb viewed from STEREO, while the magnetic reconnection processes are evaluated by the magnetic fluxes which are swept by the flare ribbons on the solar disk observed from SDO. With these measurements, we explore the duration and magnitude of the CME accelerations and the correlation to those of the magnetic reconnection flux. The distributions of the heights at which the CMEs are initiated and which the peak acceleration is reached are addressed. Based on these observational results, the triggering mechanisms for the CMEs are discussed. Title: Connecting the Properties of Coronal Shock Waves with Those of Solar Energetic Particles Authors: Kouloumvakos, Athanasios; Rouillard, Alexis P.; Wu, Yihong; Vainio, Rami; Vourlidas, Angelos; Plotnikov, Illya; Afanasiev, Alexandr; Önel, Hakan Bibcode: 2019ApJ...876...80K Altcode: We develop and exploit a new catalog of coronal pressure waves modeled in 3D to study the potential role of these waves in accelerating solar energetic particles (SEPs) measured in situ. Our sample comprises modeled shocks and SEP events detected during solar cycle 24 observed over a broad range of longitudes. From the 3D reconstruction of shock waves using coronagraphic observations we derived the 3D velocity along the entire front as a function of time. Combining new reconstruction techniques with global models of the solar corona, we derive the 3D distribution of basic shock parameters such as Mach numbers, compression ratios, and shock geometry. We then model in a time-dependent manner how the shock wave connects magnetically with spacecraft making in situ measurements of SEPs. This allows us to compare modeled shock parameters deduced at the magnetically well-connected regions, with different key parameters of SEPs such as their maximum intensity. This approach accounts for projection effects associated with remote-sensing observations and constitutes the most extensive study to date of shock waves in the corona and their relation to SEPs. We find a high correlation between the maximum flux of SEPs and the strength of coronal shock waves quantified, for instance, by the Mach number. We discuss the implications of that work for understanding particle acceleration in the corona. Title: TRAcking interplanetary Coronal mass Ejections with foRbush decreases (TRACER) Authors: Papaioannou, Athanasios; Belov, Anatoly; Vourlidas, Angelos; Anastasiadis, Anastasios Bibcode: 2019EGUGA..2117133P Altcode: During their travel from Sun to Earth, coronal mass ejections (CMEs) interact with Galactic cosmic rays (GCRs) that fill the interplanetary (IP) space. The leading shock wave when present and the following CME structure modulate GCRs, which results in a reduction of the cosmic ray (CR) intensity, known as Forbush decrease (FD). CMEs are regularly observed via both remote sensing (coronagraph and heliospheric imaging instruments) and in-situ measurements of plasma and magnetic field. However, this two way approach can be augmented with the identification of FDs in the measurements of GCRs; one may detect interplanetary CMEs passing by the observational site. Thereby, the recordings of FDs at different points within the heliosphere could be used as tracers of the IP evolution of CMEs. In this work, we present FD events that have been recorded at Earth by neutron monitors and in the inner heliosphere by the Helios 1 and 2 spacecraft. Using these FDs as a tracer of the agent CMEs, we identify their kinematics from 0.3 to 1 AU and quantify the effect of the CME physical parameters to the recorded intensity decrease during the FDs. Title: A Comparative Study of 2017 July and 2012 July Complex Eruptions: Are Solar Superstorms “Perfect Storms” in Nature? Authors: Liu, Ying D.; Zhao, Xiaowei; Hu, Huidong; Vourlidas, Angelos; Zhu, Bei Bibcode: 2019ApJS..241...15L Altcode: 2019arXiv190203416L It is paramount from both scientific and societal perspectives to understand the generation of extreme space weather. We discuss the formation of solar superstorms based on a comparative study of the 2012 July 23 and 2017 July 23 eruptions. The first one is Carrington-class, and the second could rival the 1989 March event that caused the most intense geomagnetic storm of the space age. Observations of these events in the historically weak solar cycle 24 indicate that a solar superstorm can occur in any solar cycle and at any phase of the cycle. Recurrent patterns are identified in both cases, including the long-lived eruptive nature of the active region, a complex event composed of successive eruptions from the same active region, and in-transit interaction between the successive eruptions resulting in exceptionally strong ejecta magnetic fields at 1 au. Each case also shows unique characteristics. Preconditioning of the upstream solar wind leading to unusually high solar wind speeds at 1 au is observed in the first case, but not in the latter. This may suggest that the concept of “preconditioning” appears to be necessary for making a Carrington-class storm. We find a considerable deflection by nearby coronal holes in the second case, but not in the first. On the basis of these results, we propose a hypothesis for further investigation that superstorms are “perfect storms” in nature, i.e., a combination of circumstances that results in an event of an unusual magnitude. Historical records of some extreme events seem to support our hypothesis. Title: The Parker Solar Probe WISPR Instrument: Status and Observations Authors: Howard, Russell; Vourlidas, Angelos; Colaninno, Robin; Stenborg, Guillermo; Hess, Phillip; Liewer, Paulett; Rich, Nathan; Dennison, Hillary Bibcode: 2019EGUGA..2110704H Altcode: The PSP mission was launched Aug 12, 2018 into orbit about the Sun. In Oct/Nov it performed its first perihelion pass at 0.16 AU (36 solar radii). We present the plans and first observations of the corona for the WISPR instrument on the PSP mission. Observing the corona/solar wind from 0.25 AU to the ultimate perihelion distance of 0.04 AU is absolutely unique, but presents new challenges due to the rapidly changing heliocentric distance. WISPR, a heliospheric imager type of instrument, consists of two telescopes, which together observe in the spacecraft ram direction along the ecliptic plane from 13.5 - 108 deg from the Sun. This range of elongations encompasses the Thomson circle (the locus of points of maximum Thomson scattering efficiency) thereby transitioning from remote observations of structures close to the Sun to local observations of structures close to the spacecraft. Three different types of observations are envisioned: synoptic full field, partial field high cadence shock studies and partial field turbulence studies. The last one is a sequence of images at a 10-second cadence for which a power spectrum of intensity or electron density will be generated at selected heights in the corona, to see where wave energy is being deposited. In these preliminary images we anticipate that the view will be quite different as PSP plunges into the corona than the view from 1 AU. The spatial resolution will be greatly increased as we fly through the coronal structures and will reveal fine-scale details such as fluctuations in the plasma sheet, perhaps indicating individual flux tubes or magnetic islands or maybe something totally unexpected. The vantage points will remove a large fraction of the circumsolar dust contributing to the F-corona, perhaps also revealing the first dust to sublimate. To prepare for the mission, techniques have been developed to determine the background, track features that are moving through the field of view, among others. Due to the relative positions of PSP, Earth and the Sun, only a small fraction of the data has been received on ground, but WISPR has worked well through the first perihelion. We gratefully acknowledge support from the NASA Parker Solar Probe Project. Title: Raytracing simulations of Parker Solar Probe/WISPR images Authors: Nisticò, Giuseppe; Liewer, Paulett; Vourlidas, Angelos; Thernisien, Arnaud; Howard, Russell; Bothmer, Volker Bibcode: 2019EGUGA..2114202N Altcode: The Wide-field Imager for Parker Solar Probe (WISPR) provides unprecedented white-light images of the solar corona and inner heliosphere from unconventional viewpoints thanks to the close perihelion transits of Parker Solar Probe. WISPR images coronal structures at high spatial and time resolutions, but the data analysis needs to consider the continuous change of the observation's plane-of-sky and hence of the projection due to PSP's fast orbital speed and high orbital eccentricity. Therefore, it is important to understand how these factors affect the images. Here, we present an analysis of simulated WISPR images and discuss how WISPR data can be analyzed to study the physical conditions of the corona and the near-Sun environment. Title: Combined geometrical modelling and white-light mass determination of coronal mass ejections Authors: Pluta, Adam; Mrotzek, Niclas; Vourlidas, Angelos; Bothmer, Volker; Savani, Neel Bibcode: 2019A&A...623A.139P Altcode: Context. We use forward modelling on multi-viewpoint coronagraph observations to estimate the 3-dimensional morphology, initial speed and deprojected masses of Coronal Mass Ejections (CMEs). The CME structure is described via the Graduated Cylindrical Shell (GCS) model, which enables the measurement of CME parameters in a consistent and comparable manner.
Aims: This is the first large-scale use of the GCS model to estimate CME masses, so we discuss inherent peculiarities and implications for the mass determination with a special focus on CME events emerging from close to the observer's central meridian. Further, we analyse the CME characteristics best suited to estimate the CME mass in a timely manner to make it available to CME arrival predictions.
Methods: We apply the method to a set of 122 bright events observed simultaneously from two vantage points with the COR2 coronagraphs onboard of the twin NASA STEREO spacecraft. The events occurred between January 2007 and December 2013 and are compiled in an online catalogue within the EU FP7 project HELCATS. We statistically analyse the derived CME parameters, their mutual connection and their relation to the solar cycle.
Results: We show that the derived morphology of intense disk events is still systematically overestimated by up to a factor of 2 with stereoscopic modelling, which is the same order of magnitude as for observations from only one vantage point. The overestimation is very likely a combination of projection effects as well as the increased complexity of separating CME shocks and streamers from CME fronts for such events. We further show that CME mass determination of disk events can lead to overestimation of the mass by about a factor of 10 or more, in case of overlapping bright structures.
Conclusions: We conclude that for stereoscopic measurements of disk events, the measurement of the initial CME speed is the most reliable one. We further suggest that our presented CME speed-mass correlation is most suited to estimate the CME mass early from coronagraph observations. Title: Solar Physics from Unconventional Viewpoints Authors: Gibson, Sarah E.; Vourlidas, Angelos; Hassler, Donald M.; Rachmeler, Laurel A.; Thompson, Michael J.; Newmark, Jeffrey; Velli, Marco; Title, Alan; McIntosh, Scott W. Bibcode: 2018FrASS...5...32G Altcode: 2018arXiv180509452G We explore new opportunities for solar physics that could be realized by future missions providing sustained observations from vantage points away from the Sun-Earth line. These include observations from the far side of the Sun, at high latitudes including over the solar poles, or from near-quadrature angles relative to the Earth (e.g., the Sun-Earth L4 and L5 Lagrangian points). Such observations fill known holes in our scientific understanding of the three-dimensional, time-evolving Sun and heliosphere, and have the potential to open new frontiers through discoveries enabled by novel viewpoints. Title: How Reliable Are the Properties of Coronal Mass Ejections Measured from a Single Viewpoint? Authors: Balmaceda, Laura A.; Vourlidas, Angelos; Stenborg, Guillermo; Dal Lago, Alisson Bibcode: 2018ApJ...863...57B Altcode: We present an analysis of widths and kinematic properties of coronal mass ejections (CMEs) obtained via a supervised image segmentation algorithm, the CORonal SEgmentation Technique (CORSET), on simultaneous observations from the two COR2 telescopes on the Solar Terrestrial Relations Observatory (STEREO) mission, from 2007 May to 2014 September. The sample of 460 events with measurements from two vantage points offers the opportunity to test the accuracy and constraints of single-viewpoint properties that underlie the bulk of CME research to date. In addition, we examine the dependence of the properties on the morphology of the events. The main findings are as follows. (1) The radial speeds derived from different perspectives are in good agreement with a relatively low intrinsic uncertainty of 39%. (2) Projection effects are more important for determination of CME width rather than for speed. (3) The expansion speeds depend on CME morphology, with loop-type CMEs expanding twice as fast as flux-rope CMEs, possibly underpinning the more explosive nature. (4) Triangulations of CME speed and propagation direction are optimal from viewpoints separated by 60°-90° e.g., between the Lagrangian points L1 and L5 (or L4). (5) The projected speeds are underestimated, on average, by at least 20% when compared to their deprojected (triangulated) values. We also discuss in detail the lessons learned from the application of the CORSET algorithm to event tracking. Our findings should hopefully be a useful guide in the use of (semi)automated algorithms for extraction of CME physical parameters and in the interpretation of single-viewpoint observations (likely to be the norm after the end of the STEREO mission). Title: Streamer-blowout Coronal Mass Ejections: Their Properties and Relation to the Coronal Magnetic Field Structure Authors: Vourlidas, Angelos; Webb, David F. Bibcode: 2018ApJ...861..103V Altcode: 2018arXiv180600644V We present a comprehensive analysis of a particular class of coronal mass ejection (CME) event called streamer-blowout CMEs (SBOs). The events are characterized by a gradual swelling of the overlying streamer, lasting hours to days, followed by a slow, wide CME, generally exhibiting a three-part structure, which leaves the streamer significantly depleted in its wake. We identify 909 SBO events in the LASCO/C2 observations between 1996 and 2015. The average blowout lasts for 40.5 hr, but the evacuation can take days for some events. The SBO CMEs are wider and more massive than the average CME. Their properties generally vary during and between solar cycles. Their minimum (maximum) monthly occurrence rate of one (six) events in cycle 23 has doubled in cycle 24—a probable manifestation of the weaker global fields in the current cycle. The locations of SBOs follow the tilt of the global dipole (but not from 2014 onward), do not correlate with sunspot numbers, and exhibit flux rope morphology at a much higher rate (61%) than regular CMEs (40%). We propose that these characteristics are consistent with SBOs arising from extended polarity inversion lines outside active regions (e.g., quiet Sun and polar crown filaments) through the release via reconnection of magnetic energy, likely accumulated via differential rotation. Title: Connecting Shock Waves Properties in the Solar Corona with the Characteristics of Solar Energetic Particle Events Authors: Kouloumvakos, Athanasios; Rouillard, A. P.; Vainio, R.; Vourlidas, A.; Plotnikov, I.; Wu, Y.; Afanasiev, A. Bibcode: 2018shin.confE.114K Altcode: We exploit a new catalog of coronal pressure waves modeled in 3-D to study the potential role of shock waves as accelerators of Solar Energetic Particle events (SEPs) measured in situ. Our samples of modeled shocks and SEPs are related to events detected during solar cycle 24 that were observed over a broad range of longitudes. From the 3D-reconstruction of shock waves using multi-viewpoint coronagraphic observations we estimated the 3-D velocity of the entire front as a function of time. We then used the method presented in Rouillard et al. (2016) for the derivation of the 3D-distribution of Alfvenic Mach number and other key shock properties including the density compression ratio. We present for the first time a comparison of modeled shock parameters such as the shock speed, the Alfvenic Mach number and the compression ratio deduced at the magnetically well-connected regions, with different key parameters of SEPs such as their maximum intensity, spectral index, and element abundance and for a large number of events. We discuss the implications of our results for our understanding of particle acceleration at shocks waves. Title: Alfvenic critical point inferred from coronal shock and wave properties Authors: Kwon, Ryun Young; Vourlidas, Angelos Bibcode: 2018shin.confE.137K Altcode: We compare an empirical solar wind speed profile from Sheeley et al. (1997) with Alfven speed profiles derived from coronal shock and wave properties to infer the possible height of the Alfvenic critical point. We derive the Alfven speed profiles with three different techniques. (1) We estimate the shock density compression ratios at different heights using fits of a sheath electron density model to shock fronts observed in coronagraphic images (Kwon et al. 2018). The three-dimensional geometry is considered to examine the electron density jump along the shock normal. The Rankine-Hugoniot (jump) relation is used to estimate the Alfvenic Mach number, i.e., the ratio between the shock speeds and local Alfven speeds, from the density compression ratios. Since the 3D kinematics of the shocks is known at the points where we determined the density compression ratios, the Alfvenic Mach numbers are also derived. (2) We assume that the lower part (lateral flank) of a spherical shock front degenerates into a linear fast-mode wave (or weak shock wave) and fit the time-dependent geometric solution of a linear fast-mode wave given in Uchida (1970) to the lateral flanks. We select the Alfven speed profile associated with the best fits. (3) We use a measure of Alfvenic Mach numbers obtained from the standoff distances (Gopalswamy & Yashiro 2011; Poomvises et al. 2012). In general, we assume that an empirical model gives the upstream electron density, the adiabatic index is 5/3, and the Alfven speed at 1 AU is 50 km/s. The height of the Alfvenic critical point is found to be around 15 - 25 Rs [solar radii], whereas the peak of the Alfven speed profile is located at 2 - 3 Rs. Title: Preparing for Parker Solar Probe: Tracking Moving Solar Wind Features in Images from the Wide-field Imager for Parker Solar Probe (WISPR) Authors: Liewer, Paulett C.; Qiu, Jiong; Nisticò, Giuseppe; Vourlidas, Angelos; Penteado, Paulo; Thernisien, Arnaud; Howard, Russell; Bothmer, Volker Bibcode: 2018shin.confE..43L Altcode: The Parker Solar Probe (PSP) trajectory, approaching within 10 solar radii, will allow the white light imager, WISPR, to view the inner corona with unprecedented spatial resolution. WISPR, with a field of view extending from 13.5° to 108° elongation angle from the Sun, will image the fine-scale coronal structure with arcminute resolution at high cadence ( 5 - 60 min). The dependency of Thomson scattering on the distance between the observer and the Sun dictates that WISPR will be a “local" heliospheric imager, and thus can provide a crucial link between the visible corona and PSP's in-situ measurements. To prepare for this unprecedented viewing of the structures in the inner corona, we are creating synthetic white light images and animations, viewed from the PSP trajectory, using the white-light ray-tracing package developed at NRL (available through SolarSoft). We will present results for small flux ropes moving outward through the corona as well as fly-throughs of finely structured coronal streamers. We also investigated whether the 3-D trajectory (direction and velocity) of a density enhancement (flux rope or Title: Understanding the initiation and early evolution of the 2012 July 12 CME Authors: Nikou, Eleni; Kwon, Ryun-Young; Vourlidas, Angelos; Zhang, Jie Bibcode: 2018shin.confE.141N Altcode: The early evolution of Coronal Mass Ejections (CMEs), particularly the fast, highly Title: Simulations of PSP/WISPR observations of the corona/inner heliosphere with raytracing software Authors: Nisticò, Giuseppe; Liewer, Paulett; Qiu, Jiong; Vourlidas, Angelos; Bothmer, Volker; Thernisien, Arnaud Bibcode: 2018shin.confE..40N Altcode: The Wide-Field Imager for Parker Solar Probe (WISPR) will observe the Thomson scattered emission of the corona/inner heliosphere, covering a range of elongation angles from 13.5 to 108 deg, at high temporal (0.05-60 min) and spatial resolution (plate scale of 1.2-1.7 arcmin per pixel). Such images will be taken from unprecedented points of observation thanks to the highly-eccentric orbits of Parker Solar Probe (PSP), which will reach the minimum perihelion distance below 10 solar radii from the Sun's centre. Title: Probing the Properties and Effects of Coronal Shocks Using Modeling, Simulations and Observations Authors: Rouillard, Alexis; Kouloumvakos, A.; Kwon, R. -K. .; Vourlidas, A.; Vainio, R.; Wu, Y.; Afanasiev, A.; Önel, H.; Mann, G.; Warmuth, A.; Vilmer, N.; Share, G. Bibcode: 2018shin.confE.140R Altcode: We start with the 3D reconstruction of evolving shock waves based on remote-sensing observations that provide the shock's outermost extent, 3-D expansion speeds, geometry, Mach and a new technique to derive compression ratio. We compare the results of these reconstructions with other techniques. We then carried out case studies and surveys to study the link between these shock waves and electromagnetic emissions at radio, X-ray and gamma-ray frequencies. We focus on the onsets of radio type II bursts and exploit a new modeling framework that includes particle acceleration and transport effects to study the onset of a number of hard X-ray and gamma-ray events. Title: Preparing for Parker Solar Probe: Synthetic White-light Imagery and Analysis for the Wide-field Imager (WISPR) Authors: Liewer, Paulett; Nisticó, Giuseppe; Howard, Russell; Bothmer, Volker; Thernisien, Arnaud; Vourlidas, Angelos; Penteado, Paulo Bibcode: 2018cosp...42E2010L Altcode: The Parker Solar Probe (PSP) trajectory, approaching within 10 solar radii, will allow the white light imager, WISPR, to view the inner corona with unprecedented spatial resolution. WISPR, with a field of view extending from 13.5° to 108° elongation angle from the Sun, will image the fine-scale coronal structure with arcminute resolution. The dependency of the Thomson scattering on the imaging geometry (distance and angle from the Sun) dictates that WISPR will be very sensitive to the emission from plasma close to the spacecraft, in contrast to the situation for imaging from 1 AU. Thus, WISPR will be the first 'local' imager providing a crucial link between the large-scale corona and PSP's in-situ measurements. To prepare for this unprecedented viewing of the structures in the inner corona, we are creating synthetic white light images and animations, viewed from the PSP trajectory, using the white-light ray-tracing package developed at NRL (available through SolarSoft). We will present results for small flux ropes moving outward through the corona as well as fly-throughs of finely structured coronal streamers. Using the synthetic images, analysis techniques similar to traditional white light "jmaps" are used to find the "track" of a flux rope's elongation versus time. The "track" is compared with predictions using simple geometric expressions to gain information on the 3D trajectory of the flux rope. Additional analysis techniques, such as re-projections of the images, will also be discussed. Title: The Highly Structured Outer Solar Corona Authors: DeForest, C. E.; Howard, R. A.; Velli, M.; Viall, N.; Vourlidas, A. Bibcode: 2018ApJ...862...18D Altcode: We report on the observation of fine-scale structure in the outer corona at solar maximum, using deep-exposure campaign data from the Solar Terrestrial Relations Observatory-A (STEREO-A)/COR2 coronagraph coupled with postprocessing to further reduce noise and thereby improve effective spatial resolution. The processed images reveal radial structure with high density contrast at all observable scales down to the optical limit of the instrument, giving the corona a “woodgrain” appearance. Inferred density varies by an order of magnitude on spatial scales of 50 Mm and follows an f -1 spatial spectrum. The variations belie the notion of a smooth outer corona. They are inconsistent with a well-defined “Alfvén surface,” indicating instead a more nuanced “Alfvén zone”—a broad trans-Alfvénic region rather than a simple boundary. Intermittent compact structures are also present at all observable scales, forming a size spectrum with the familiar “Sheeley blobs” at the large-scale end. We use these structures to track overall flow and acceleration, finding that it is highly inhomogeneous and accelerates gradually out to the limit of the COR2 field of view. Lagged autocorrelation of the corona has an enigmatic dip around 10 R ⊙, perhaps pointing to new phenomena near this altitude. These results point toward a highly complex outer corona with far more structure and local dynamics than has been apparent. We discuss the impact of these results on solar and solar-wind physics and what future studies and measurements are necessary to build upon them. Title: Connecting Shock Waves Properties in the Solar Corona with the Characteristics of Solar Energetic Particle Events Authors: Kouloumvakos, Athanasios; Rouillard, A. P.; Vainio, R.; Vourlidas, A.; Plotnikov, I.; Wu, T.; Afanasiev, A. Bibcode: 2018shin.confE.113K Altcode: We exploit a new catalog of coronal pressure waves modeled in 3-D to study the potential role of shock waves as accelerators of Solar Energetic Particle events (SEPs) measured in situ. Our samples of modeled shocks and SEPs are related to events detected during solar cycle 24 that were observed over a broad range of longitudes. From the 3D-reconstruction of shock waves using multi-viewpoint coronagraphic observations we estimated the 3-D velocity of the entire front as a function of time. We then used the method presented in Rouillard et al. (2016) for the derivation of the 3D-distribution of Alfvenic Mach number and other key shock properties including the density compression ratio. We present for the first time a comparison of modeled shock parameters such as the shock speed, the Alfvenic Mach number and the compression ratio deduced at the magnetically well-connected regions, with different key parameters of SEPs such as their maximum intensity, spectral index, and element abundance and for a large number of events. We discuss the implications of our results for our understanding of particle acceleration at shocks waves. Title: Assessing the Geo-effectiveness of CMEs: Where do we stand at the end of Solar Cycle 24 Authors: Vourlidas, Angelos Bibcode: 2018cosp...42E3563V Altcode: As the minimum of Cycle 24 nears, the database of CME observations from the LASCO coronagraphs will encompass two full solar cycles. This unprecedented coverage of the eruptive sun is complemented by 10+ years of stereoscopic observations from STEREO, sub-minute imaging of the EUV corona from SDO/AIA, and a plethora of high-resolution spectroscopic observations in many atmospheric layers from Hinode and IRIS. So, what have we learned from these missions about the geo-effective potential of CMEs and their sources? In this talk, I will discuss that current status, identify some of the gaps and offer strategies for improving our understanding of geo-effective CMEs in the future. Title: Elliptic-cylindrical Analytical Flux Rope Model for Magnetic Clouds Authors: Nieves-Chinchilla, T.; Linton, M. G.; Hidalgo, M. A.; Vourlidas, A. Bibcode: 2018ApJ...861..139N Altcode: In this paper, we present the elliptic-cylindrical analytical flux rope model, which constitutes the first level of complexity above that of a circular-cylindrical geometry. The framework of this series of models was established by Nieves-Chinchilla et al. with the circular-cylindrical analytical flux rope model. The model describes the magnetic flux rope topology with distorted cross section as a possible consequence of the flux rope interaction with the solar wind. In this model, for the first time, a flux rope is completely described by a nonorthogonal geometry. The Maxwell equations can be consistently solved using tensorial analysis, and relevant physical quantities can be derived, such as magnetic fluxes, number of turns, or Lorentz force distribution. The model is generalized in terms of the radial dependence of the poloidal and axial current density components. The circular-cylindrical reconstruction technique has been adapted to the new geometry for a specific case of the model and tested against an interplanetary coronal mass ejection observed by the Wind spacecraft on 2005 June 12. In this specific case, from the comparative analysis between the circular-cylindrical and elliptic-cylindrical models, the inclusion of the cross-section distortion in the 3D reconstruction results in significant changes in the derived axis orientation, size, central magnetic field, magnetic fluxes, and force-freeness. The case studied in this paper exemplifies the use of the model and reconstruction technique developed. Furthermore, the novel mathematical formulation to model flux ropes in heliophysics paves the way to the inclusion of more complex magnetic field configurations. Title: Solar Observations Away from the Sun-Earth Line Authors: Gibson, Sarah E.; McIntosh, Scott William; Rachmeler, Laurel; Thompson, Michael J.; Title, Alan M.; Velli, Marco C. M.; Vourlidas, Angelos Bibcode: 2018tess.conf40340G Altcode: Observations from satellite missions have transformed the field of solar physics. High-resolution observations with near-continuous temporal coverage have greatly extended our capability for studying long-term and transient phenomena, and the opening of new regions of the solar spectrum has made detailed investigation of the solar atmosphere possible.

However, to date most solar space-based missions have been restricted to an observational vantage in the vicinity of the Sun-Earth line, either in orbit around the Earth or from the L1 Lagrangian point. As a result, observations from these satellites represent the same geometrical view of the Sun that is accessible from the Earth.

Understanding the deep interior structure of the Sun and the full development of solar activity would really benefit from fully three-dimensional monitoring of the solar atmosphere and heliosphere. On the one hand, simultaneous spacecraft observations from multiple vantage points would allow studies of the deep interior structure of the sun via stereoscopic helioseismology; on the other, distributed observations would allow the understanding of the complete evolution of activity complexes and enhance space weather predictions dramatically.

Presently, observations of the Sun away from Earth are obtained by the STEREO pair of satellites, which have provided an unprecedented global view by orbiting around to the far side of the Sun, and the Ulysses mission, which achieved a high-inclination (80˚) near-polar orbit (but which, however, did not include any solar imaging instruments). The forthcoming Solar Orbiter mission, which will orbit the sun and reach a maximum inclination of 34˚ out of the ecliptic should provide the first detailed mapping of the sun's polar fields. In addition, Solar Probe Plus will explore the outer corona and inner Heliosphere with very rapid solar encounters at a minimum perihelion 9.86 solar radii from the center of the Sun.

We explore some of the new opportunities for solar physics that can be realized by future missions that provide sustained observations from vantage points away from the Sun-Earth line (and in some cases the ecliptic plane): observations from the far side of the Sun, over its poles, or from the L5 Lagrangian point. Title: Information theoretical approach to discovering causalities in solar cycle Authors: Wing, Simon; Johnson, Jay; Vourlidas, Angelos Bibcode: 2018tess.conf22407W Altcode: The causal parameters and response lag times of the solar cycle dynamics are investigated with transfer entropy, which can determine the amount of information transfer from one variable to another. The causal dependency of the solar cycle parameters is bidirectional. The transfer of information from the solar polar field to the sunspot number (SSN) peaks at lag time (t) ~ 30-40 months, but thereafter it remains at a persistent low level for at least 400 months (~ 3 solar cycles) for the period 1906-2014. The latter may indicate the persistency of the polar fields from cycle to cycle. It may lend support to the idea that the polar fields from the last 3 or more solar cycles can affect the production of SSN of the subsequent cycle. There is also a similarly long term information transfer from the SSN to the polar field. Both the meridional flow speed and flux emergence (proxied by the SSN) transfer information to the polar field, but one transfers more information than the other, depending on the lag times. The meridional flow speed transfers more information to the polar field than SSN at t ~28-30 months and at t ~90-110 months, which may be consistent with some flux transfer dynamo models and some surface flux transport models. However, the flux emergence transfers more information to the polar field than the meridional flow at t ~60-80 months, which may be consistent with a recently developed surface flux transport model. The transfer of information from the meridional flow to SSN peaks at t ~110-120 months (~1 solar cycle), suggesting that the meridional flow can be used to predict SSN one cycle ahead. Title: Solar Polar Diamond Explorer (SPDEx): Understanding the Origins of Solar Activity Using a New Perspective Authors: Vourlidas, A.; Liewer, P. C.; Velli, M.; Webb, D. Bibcode: 2018arXiv180504172V Altcode: Our knowledge of the Sun, its atmosphere, long term activity and space weather potential is severely limited by the lack of good observations of the polar and far-side regions. Observations from a polar vantage point would revolutionize our understanding of the mechanism of solar activity cycles, polar magnetic field reversals, the internal structure and dynamics of the Sun and its atmosphere. Only with extended (many day) observations of the polar regions can the polar flows be determined down to the tachocline where the dynamo is thought to originate. Rapid short period polar orbits, using in situ and remote sensing instrumentation, distributed over a small number of spacecraft, will provide continuous 360o coverage of the solar surface and atmosphere in both longitude and latitude for years on end. This unprecedented full coverage will enable breakthrough studies of the physical connection between the solar interior, the solar atmosphere, the solar wind, solar energetic particles and the inner heliosphere at large. A potential implementation, the Solar Polar Diamond Explorer (SPDEx) built upon the Solar Polar Imager mission design, involves up to four small spacecraft in a 0.48-AU orbit with an inclination of 75o. The orbit is achieved using solar sails or ion engines, both technologies already demonstrated in space. Title: Turtles All The Way Down: The finely structured outer corona, and its implications for PSP Authors: DeForest, Craig E.; Howard, Russell A.; Velli, Marco C. M.; Viall, Nicholeen M.; Vourlidas, Angelos Bibcode: 2018tess.conf30928D Altcode: Based on optical resolution of the starfield with SOHO/LASCO, STEREO/COR, and other coronagraphs, there is widespread intuition that the solar corona becomes more smooth with altitude. This is an optical illusion, caused by the interplay between signal-to-noise ratio (SNR) and feature size in typical coronal images. Processed, low-noise, deep-field COR2 images of the outer corona reveal rich structure at all observable scales, with surprising time variability and very short spatial correlation scales under 50 Mm, at altitudes near 10 Rs. This has deep implications not only for the solar wind and outer coronal physics, but also for the types of structure that Parker Solar Probe will encounter. We will present and discuss the fundamental result, and explore its implications for in-situ science and required context imaging from PSP. We will also make specific predictions about the environment PSP will encounter at solar altitudes of 10-15 Rs. Title: Using Solar Wind Structures as a Rosetta Stone for Understanding Solar Wind Formation Authors: Viall, Nicholeen M.; Kepko, Larry; Antiochos, Spiro K.; Higginson, Aleida Katherine; Vourlidas, Angelos; Lepri, Susan T. Bibcode: 2018tess.conf31702V Altcode: In the inner heliosphere, the slow solar wind is often comprised of mesoscale structures: structures with timescales of hours and length scales of hundreds of mega meters. White light coronagraph data suggest that these mesoscale structures are formed and embedded in the solar wind within the first several solar radii above the solar surface, which is still below even the closest approach of Parker Solar Probe at nine solar radii. We argue that these mesoscale structures represent a 'Rosetta Stone' for using the embedded solar wind plasma signatures to understand the fundamental release and acceleration of solar wind plasma. We study events identified in data from current missions to demonstrate how mesoscale structures can link dynamics observed remotely in the lower corona with in situ observations. We discuss the observations that Parker Solar Probe will make and how to capitalize on this remote-to-in situ data connection. Title: Opportunities for Space Weather Research from Parker Solar Probe and Solar Orbiter Imaging Authors: Vourlidas, Angelos Bibcode: 2018tess.conf41101V Altcode: <span class="s1" <p class="p2" <span class="s1" One of the most exciting NASA missions is scheduled to be launch in summer 2018. The Parker Solar Probe (PSP) will be the first spacecraft to enter the atmosphere of a star, reaching within 6 million km from the solar surface. It will be followed by another inner heliospheric probe, ESA's Solar Orbiter (SO), which will imagef the solar atmosphere from above the ecliptic for the first time.The two probes will revolutionize our understanding of the origins and structure of the quiescent and transient solar wind (CMEs, CIRs, etc) thanks to their comprehensive package of remote sensing and in-situ instrumentation, <p class="p2" <span class="s1" Both are encounter missions and hence unsuited for Space Weather monitoring, Their Space Weather research potential, on the other hand, is extremely high. In this talk, I'll discuss how PSP and SO can address current gaps in our understanding of the source of Space Weather and guide the development of future Space Weather systems and models. Title: Distributed Mission Concepts to Achieve Comprehensive Coverage of Solar Activity Authors: Vourlidas, Angelos Bibcode: 2018tess.conf41205V Altcode: <span class="s1" Accurate terrestrial weather forecasting relies on comprehensive coverage of the terrestrial system provided by a huge number of distributed surface, air and space sensors. Space weather is no different. We need to research and monitor solar disturbances throughout the inner heliosphere. Unfortunately, achieving coverage at the same level as in the terrestrial system is unfeasible for the Sun-Earth system due to its scale. We need is a clear strategy and 'outside the box' thinking for the deployment of our sensors to optimize coverage within a reasonable timetable and budget.<p class="p1" <span class="s1" In this talk, I discuss multi-point and multi-viewpoint "string-of-pearls" concepts for achieving nearly complete coverage of solar activity. The concepts are driven by the needs of SpW research and operations and take advantage of uncommon orbits and mission designs. Their implementation is not straightforward and I outline the challenges that lay ahead for moving forward with such ideas. Title: Understanding the Internal Magnetic Field Configurations of ICMEs using more than 20 years of Wind Observations Authors: Nieves-Chinchilla, Teresa; Vourlidas, Angelos; Raymond, John C.; Linton, Mark; Al-Haddad, Nada A.; Savani, Neel; Szabo, A.; Hidalgo, Miguel A. UAH Bibcode: 2018tess.conf10415N Altcode: The magnetic topology, structure, and geometry of the magnetic obstacles embedded within interplanetary coronal mass ejections (ICMEs) are not yet fully and consistently described by in situ models and reconstruction techniques. The main goal of this work is to understand better the status of the internal magnetic field of ICMEs and to explore in situ signatures to identify clues to develop a more accurate and reliable in situ analytical model. We take advantage of more than 20 years of Wind observations of transients at 1~AU to compile a comprehensive database of ICMEs through three solar cycles, from 1995 to 2015. The catalog is publicly available at wind.gsfc.nasa.gov and fully described in this article. We identify and collect the properties of 337 ICMEs of which 298 show organized magnetic field signatures. To allow for departures from idealized magnetic configurations, we introduce the term of 'magnetic obstacle' (MO) to signify the possibility of more complex configurations.To quantify the asymmetry of the magnetic field strength profile within these events, we introduce the distortion parameter (DiP) and calculate the expansion velocity within the magnetic obstacle. Circular-cylindrical geometry is assumed when the magnetic field strength displays a symmetric profile. We perform a statistical study of these two parameters, to find that: (1) Only 35% of the events show symmetric magnetic profiles and a small enough expansion velocity to be compatible with the assumption of an idealized cylindrical static flux rope. (2) 41% of the events do not show the expected relationship between expansion and magnetic field compression in the front, with the maximum magnetic field closer to the first encounter of the spacecraft with the magnetic obstacle; 18% show contractions (i.e. apparent negative expansion velocity) and 30% show magnetic field compression in the back.

In summary, our main results demonstrate that the assumed correlation between expanding structure and asymmetric magnetic field is not always valid. Although 59% of the cases could be described by circular-cylindrical geometry, with or without expansion, the remaining cases show significant in situ signatures of departures from circular-cylindrical geometry. These results will aid in the development of more accurate in situ models to reconcile image. Title: Coronal properties inferred from the measure of shock Mach numbers from the coronal base to the Alfvenic critical point Authors: Kwon, RyunYoung; Vourlidas, Angelos Bibcode: 2018tess.conf30927K Altcode: We estimate the radial profiles of coronal parameters, such as local Alfvén (fast-mode) speed, magnetic field, electron density, temperature, plasma beta, polytropic index, and magnetic/gas pressure, from the coronal shock Mach numbers (density compression ratios). We employ five methodologies to determine the Mach numbers; (1) fits of a sheath electron density model to coronagraphic images (Kwon et al. 2018), (2) fits of a linear fast magnetosonic wave model to observed shock wave fronts in the corona (Kwon et al. 2017), (3) measures of standoff distance at the shock noses (Gopalswamy & Yashiro 2011), (4) comparisons of 3D shock properties with MHD models (Rouillard et al. 2016), and (5) comparisons of 3D shock kinematics with empirical coronal magnetic field and electron density models. The 3D geometry and kinematics of coronal shock waves are determined with the ellipsoid model using successive multi-perspective observations. We discuss its physical implications for the characteristics of solar wind and solar energetic particle acceleration in the sub-Alfvénic region. Title: Simulating observations of the corona/inner heliosphere with the Wide-Field Imager for Parker Solar Probe by raytracing software Authors: Nisticò, Giuseppe; Liewer, Paulett; Bothmer, Volker; Vourlidas, Angelos Bibcode: 2018EGUGA..2018677N Altcode: The Wide-Field Imager for Parker Solar PRobe (WISPR) will provide us with white-light images of the corona/inner heliosphere offset from the Sun, covering a range of elongation angles from 13.5 to 108 deg, with a high temporal (0.05-60 min) and spatial resolution (plate scale of 1.2-1.7 arcmin per pixel). Such images will be taken from unprecedented points of observation thanks to the highly-eccentric orbits of Parker Solar Probe (PSP), which will reach the minimum perihelion distance below 10 solar radii from the Sun's centre. Therefore, it is important to understand how WISPR images will look during the perihelion phases and when PSP will eventually fly throughout various coronal structures, e.g. streamers, expanding flux ropes, and jets. In this talk we will provide a collection of synthetic WISPR images for different coronal structures by using the raytracing tools available with the SolarSoftWare package. We will discuss the effects due to the varying radial distance and the high orbital speed ( 200 km/s) of PSP on the WISPR images, including the possibility of 3D reconstruction and the determination of the correct kinematics for expanding flux ropes and jets. Title: Evolution of CME Mass in the Corona Authors: Howard, Russell A.; Vourlidas, Angelos Bibcode: 2018SoPh..293...55H Altcode: The idea that coronal mass ejections (CMEs) pile up mass in their transport through the corona and heliosphere is widely accepted. However, it has not been shown that this is the case. We perform an initial study of the volume electron density of the fronts of 13 three-part CMEs with well-defined frontal boundaries observed with the Solar and Heliospheric Observatory/Large Angle and Spectrometric COronagraph (SOHO/LASCO) white-light coronagraphs. We find that, in all cases, the volume electron density decreases as the CMEs travel through the LASCO-C2 and -C3 fields of view, from 2.6 -30 R⊙. The density decrease follows closely a power law with an exponent of −3, which is consistent with a simple radial expansion. This indicates that in this height regime there is no observed pile-up. Title: Evolution of CME Mass in The Corona Authors: Howard, Russell A.; Vourlidas, Angelos Bibcode: 2018EGUGA..2018390H Altcode: The idea that Coronal Mass Ejections (CMEs) pile up mass in their transport through the corona and heliosphere is widely accepted. However, it has not been shown that this is the case. We perform an initial study of the volume electron density of the fronts of thirteen 3-part CMEs with well defined frontal boundaries observed with the SOHO/LASCO white light coronagraphs. We find that, in all cases, the volume electron density decreases as the CMEs travel through the LASCO/C2 & C3 fields of view, from 2.6 - 30 Rs. The density decrease follows closely a power law with an exponent of -3, which is consistent with a simple radial expansion. This indicates that in this height regime there is no observed pileup. This work was supported by NASA. Title: Bridging the Gap: Capturing the Lyα Counterpart of a Type-II Spicule and Its Heating Evolution with VAULT2.0 and IRIS Observations Authors: Chintzoglou, Georgios; De Pontieu, Bart; Martínez-Sykora, Juan; Pereira, Tiago M. D.; Vourlidas, Angelos; Tun Beltran, Samuel Bibcode: 2018ApJ...857...73C Altcode: 2018arXiv180303405C We present results from an observing campaign in support of the VAULT2.0 sounding rocket launch on 2014 September 30. VAULT2.0 is a Lyα (1216 Å) spectroheliograph capable of providing spectroheliograms at high cadence. Lyα observations are highly complementary to the IRIS observations of the upper chromosphere and the low transition region (TR) but have previously been unavailable. The VAULT2.0 data provide new constraints on upper-chromospheric conditions for numerical models. The observing campaign was closely coordinated with the IRIS mission. Taking advantage of this simultaneous multi-wavelength coverage of target AR 12172 and by using state-of-the-art radiative-MHD simulations of spicules, we investigate in detail a type-II spicule associated with a fast (300 km s-1) network jet recorded in the campaign observations. Our analysis suggests that spicular material exists suspended high in the atmosphere but at lower temperatures (seen in Lyα) until it is heated and becomes visible in TR temperatures as a network jet. The heating begins lower in the spicule and propagates upwards as a rapidly propagating thermal front. The front is then observed as fast, plane-of-the-sky motion typical of a network jet, but contained inside the pre-existing spicule. This work supports the idea that the high speeds reported in network jets should not be taken as real mass upflows but only as apparent speeds of a rapidly propagating heating front along the pre-existing spicule. Title: Information Theoretic Approach to Discovering Causalities in the Solar Cycle Authors: Wing, Simon; Johnson, Jay R.; Vourlidas, Angelos Bibcode: 2018ApJ...854...85W Altcode: The causal parameters and response lag times of the solar cycle dynamics are investigated with transfer entropy, which can determine the amount of information transfer from one variable to another. The causal dependency of the solar cycle parameters is bidirectional. The transfer of information from the solar polar field to the sunspot number (SSN) peaks at lag time (τ) ∼ 30-40 months, but thereafter it remains at a persistently low level for at least 400 months (∼3 solar cycles) for the period 1906-2014. The latter may lend support to the idea that the polar fields from the last three or more solar cycles can affect the production of the SSN of the subsequent cycle. There is also a similarly long-term information transfer from the SSN to the polar field. Both the meridional flow speed and flux emergence (proxied by the SSN) transfer information to the polar field, but one transfers more information than the other, depending on the lag times. The meridional flow speed transfers more information than the SSN to the polar field at τ ∼ 28-30 months and at τ ∼ 90-110 months, which may be consistent with some flux transfer dynamo models and some surface flux transport models. However, the flux emergence transfers more information than the meridional flow to the polar field at τ ∼ 60-80 months, which may be consistent with a recently developed surface flux transport model. The transfer of information from the meridional flow to the SSN peaks at τ ∼ 110-120 months (∼1 solar cycle). Title: The density compression ratio of shock fronts associated with coronal mass ejections Authors: Kwon, Ryun-Young; Vourlidas, Angelos Bibcode: 2018JSWSC...8A...8K Altcode: 2018JSWSC...8A..08K; 2018arXiv180104355K We present a new method to extract the three-dimensional electron density profile and density compression ratio of shock fronts associated with coronal mass ejections (CMEs) observed in white light coronagraph images. We demonstrate the method with two examples of fast halo CMEs (∼2000 km s-1) observed on 2011 March 7 and 2014 February 25. Our method uses the ellipsoid model to derive the three-dimensional geometry and kinematics of the fronts. The density profiles of the sheaths are modeled with double-Gaussian functions with four free parameters, and the electrons are distributed within thin shells behind the front. The modeled densities are integrated along the lines of sight to be compared with the observed brightness in COR2-A, and a χ2 approach is used to obtain the optimal parameters for the Gaussian profiles. The upstream densities are obtained from both the inversion of the brightness in a pre-event image and an empirical model. Then the density ratio and Alfvénic Mach number are derived. We find that the density compression peaks around the CME nose, and decreases at larger position angles. The behavior is consistent with a driven shock at the nose and a freely propagating shock wave at the CME flanks. Interestingly, we find that the supercritical region extends over a large area of the shock and lasts longer (several tens of minutes) than past reports. It follows that CME shocks are capable of accelerating energetic particles in the corona over extended spatial and temporal scales and are likely responsible for the wide longitudinal distribution of these particles in the inner heliosphere. Our results also demonstrate the power of multi-viewpoint coronagraphic observations and forward modeling in remotely deriving key shock properties in an otherwise inaccessible regime. Title: Using the Deep Space Gateway to Build the Next Generation Heliophysics Research Grid Authors: Vourlidas, A.; Ho, G. C.; Cohen, I. J.; Korendyke, C. M.; Tun-Beltran, S.; Plunkett, S. P.; Newmark, J.; St Cyr, O. C.; Hoeksema, T. Bibcode: 2018LPICo2063.3055V Altcode: The Heliophysics Research Grid (HRG) consists of in situ and imaging sensors, distributed in key locations in the heliosphere for research and to support space exploration needs. The Deep Space Gateway enables the HRG as a storage and staging hub for HRG launches. Title: Understanding the Internal Magnetic Field Configurations of ICMEs Using More than 20 Years of Wind Observations Authors: Nieves-Chinchilla, T.; Vourlidas, A.; Raymond, J. C.; Linton, M. G.; Al-haddad, N.; Savani, N. P.; Szabo, A.; Hidalgo, M. A. Bibcode: 2018SoPh..293...25N Altcode: The magnetic topology, structure, and geometry of the magnetic obstacles embedded within interplanetary coronal mass ejections (ICMEs) are not yet fully and consistently described by in situ models and reconstruction techniques. The main goal of this work is to better understand the status of the internal magnetic field of ICMEs and to explore in situ signatures to identify clues to develop a more accurate and reliable in situ analytical models. We take advantage of more than 20 years of Wind observations of transients at 1 AU to compile a comprehensive database of ICMEs through three solar cycles, from 1995 to 2015. The catalog is publicly available at wind.gsfc.nasa.gov and is fully described in this article. We identify and collect the properties of 337 ICMEs, of which 298 show organized magnetic field signatures. To allow for departures from idealized magnetic configurations, we introduce the term "magnetic obstacle" (MO) to signify the possibility of more complex configurations. To quantify the asymmetry of the magnetic field strength profile within these events, we introduce the distortion parameter (DiP) and calculate the expansion velocity within the magnetic obstacle. Circular-cylindrical geometry is assumed when the magnetic field strength displays a symmetric profile. We perform a statistical study of these two parameters and find that only 35% of the events show symmetric magnetic profiles and a low enough expansion velocity to be compatible with the assumption of an idealized cylindrical static flux rope, and that 41% of the events do not show the expected relationship between expansion and magnetic field compression in the front, with the maximum magnetic field closer to the first encounter of the spacecraft with the magnetic obstacle; 18% show contractions (i.e. apparent negative expansion velocity), and 30% show magnetic field compression in the back. We derive an empirical relation between DiP and expansion velocity that is the first step toward improving reconstructions with possible applications to space weather studies. In summary, our main results demonstrate that the assumed correlation between expanding structure and asymmetric magnetic field is not always valid. Although 59% of the cases could be described by circular-cylindrical geometry, with or without expansion, the remaining cases show significant in situ signatures of departures from circular-cylindrical geometry. These results will aid in the development of more accurate in situ models to reconcile image. Title: The Deep Space Gateway Opportunity for Next Generation Space Weather Measurements Authors: Ho, G. C.; Vourlidas, A.; Westlake, J. H.; Cohen, I. J. Bibcode: 2018LPICo2063.3046H Altcode: The near-Earth vicinity of the Deep Space Gateway could represent the first step in formulation of a new space weather system, potentially providing a broad range of infrastructure to enable a paradigm-shifting approach to how measurements are made. Title: EUV Irradiance Inputs to Thermospheric Density Models: Open Issues and Path Forward Authors: Vourlidas, A.; Bruinsma, S. Bibcode: 2018SpWea..16....5V Altcode: 2018arXiv180106092V One of the objectives of the NASA Living With a Star Institute on "Nowcasting of Atmospheric Drag for low Earth orbit (LEO) Spacecraft" was to investigate whether and how to increase the accuracy of atmospheric drag models by improving the quality of the solar forcing inputs, namely, extreme ultraviolet (EUV) irradiance information. In this focused review, we examine the status of and issues with EUV measurements and proxies, discuss recent promising developments, and suggest a number of ways to improve the reliability, availability, and forecast accuracy of EUV measurements in the next solar cycle. Title: The Solar Orbiter Heliospheric Imager (SoloHI) for the Solar Orbiter Mission Authors: Howard, R.; Colaninno, R. C.; Plunkett, S. P.; Thernisien, A. F.; Wang, D.; Rich, N.; Korendyke, C.; Socker, D. G.; Linton, M.; McMullin, D. R.; Vourlidas, A.; Liewer, P. C.; De Jong, E.; Velli, M.; Mikic, Z.; Bothmer, V.; Philippe, L.; Carter, M. T. Bibcode: 2017AGUFMSH23D2681H Altcode: The SoloHI instrument has completed its development effort and has been integrated onto the Solar Orbiter (SolO) spacecraft. The SolO mission, scheduled for launch in February 2019, will undergo gravity assist maneuvers around Venus to change both the perihelion distance as well as the plane of the orbit to ultimately achieve a minimum perihelion of 0.28 AU and an orbital inclination of about 35° relative to the ecliptic plane. The remote sensing instruments will operate for three 10-day periods out of the nominal 6-month orbit. SoloHI will observe sunlight scattered by free electrons in the corona/solar wind from 5° to 45° elongation in visible wavelengths and will provide a coupling between remote sensing and in situ observations. It is very similar to the HI-1 instrument on STEREO/SECCHI except that the FOV is twice the size at 40o. We present our efforts to prepare for the mission including our observing plans, quick-look plans and some results of the calibration activities. We gratefully acknowledge the support of the NASA Solar Orbiter Collaboration project. Title: The Wide-Field Imager for the Parker Solar Probe Mission (WISPR) Authors: Plunkett, S. P.; Howard, R.; Chua, D. H.; Crump, N. A.; Dennison, H.; Korendyke, C.; Linton, M.; Rich, N.; Socker, D. G.; Thernisien, A. F.; Wang, D.; Vourlidas, A.; Baugh, R.; Van Duyne, J. P.; Liewer, P. C.; De Jong, E.; Boies, M. T.; Mikic, Z.; Bothmer, V.; Rochus, P.; Halain, J. P. Bibcode: 2017AGUFMSH23D2693P Altcode: The Parker Solar Probe (PSP) mission will be humanity's first visit to the atmosphere of our nearest star, the Sun, when it is launched in July 2018. PSP will complete 24 orbits between the Sun and Venus with diminishing perihelia reaching as close as 7 million km (9.86 solar radii) from Sun center. In addition to a suite of in-situ probes for the magnetic field, plasma, and energetic particles, the payload includes the Wide Field Imager for Solar Probe (WISPR) that will record unprecedented visible light images of the solar corona and the inner heliosphere. WISPR is the smallest heliospheric imager to date, and comprises two nested wide-field telescopes with large-format (2K x 2K) APS CMOS detectors to optimize the performance over a combined 95º radial by 58º transverse field of view and to minimize the risk of dust damage, which may be considerable close to the Sun. WISPR will discover - in this never-before explored region of the heliosphere - the fundamental nature of coronal structures and the source regions of the solar wind as the PSP flies through them, and will determine whether a dust-free zone exists near the Sun. WISPR has completed its development effort and has been integrated onto the PSP spacecraft. In this paper, we will present our efforts to prepare for the mission including our observing plans and some results of the calibration activities. Title: Combining Remote and In Situ Observations with MHD models to Understand the Formation of the Slow Solar Wind Authors: Viall, N. M.; Kepko, L.; Antiochos, S. K.; Lepri, S. T.; Vourlidas, A.; Linker, J. Bibcode: 2017AGUFMSH21C..05V Altcode: Connecting the structure and variability in the solar corona to the Heliosphere and solar wind is one of the main goals of Heliophysics and space weather research. The instrumentation and viewpoints of the Parker Solar Probe and Solar Orbiter missions will provide an unprecedented opportunity to combine remote sensing with in situ data to determine how the corona drives the Heliosphere, especially as it relates to the origin of the slow solar wind. We present analysis of STEREO coronagraph and heliospheric imager observations and of in situ ACE and Wind measurements that reveal an important connection between the dynamics of the corona and of the solar wind. We show observations of quasi-periodic release of plasma into the slow solar wind occurring throughout the corona - including regions away from the helmet streamer and heliospheric current sheet - and demonstrate that these observations place severe constraints on the origin of the slow solar wind. We build a comprehensive picture of the dynamic evolution by combining remote imaging data, in situ composition and magnetic connectivity information, and MHD models of the solar wind. Our results have critical implications for the magnetic topology involved in slow solar wind formation and magnetic reconnection dynamics. Crucially, this analysis pushes the limits of current instrument resolution and sensitivity, showing the enormous potential science to be accomplished with the Parker Solar Probe and Solar Orbiter missions. Title: Investigating the ability of solar coronal shocks to accelerate solar energetic particles Authors: Kwon, R. Y.; Vourlidas, A. Bibcode: 2017AGUFMSH31B2734K Altcode: We estimate the density compression ratio of shocks associated with coronal mass ejections (CMEs) and investigate whether they can accelerate solar energetic particles (SEPs). Using remote-sensing, multi-viewpoint coronagraphic observations, we have developed a method to extract the sheath electron density profiles along the shock normal and estimate the density compression ratio. Our method uses the ellipsoid model to derive the 3D geometry of the sheaths, including the line-of-sight (LOS) depth. The sheath density profiles along the shock normal are modeled with double-Gaussian functions, and the modeled densities are integrated along the LOSs to be compared with the observed brightness in STEREO COR2-Ahead. The upstream densities are derived from either the pB-inversion of the brightness in a pre-event image or an empirical model. We analyze two fast halo CMEs observed on 2011 March 7 and 2014 February 25 that are associated with SEP events detected by multiple spacecraft located over a broad range of heliolongitudes. We find that the density compression peaks around the CME nose and decreases at larger position angles. Interestingly, we find that the supercritical region extends over a large area of the shock and lasts longer (several tens of minutes) than past reports. This finding implies that CME shocks may be capable of accelerating energetic particles in the corona over extended spatial and temporal scales and may, therefore, be responsible for the wide longitudinal distribution of these particles in the inner heliosphere. Title: A model for heliospheric flux-ropes Authors: Nieves-Chinchilla, T.; Linton, M.; Vourlidas, A.; Hidalgo, M. A. U. Bibcode: 2017AGUFMSH12B..08N Altcode: This work is presents an analytical flux-rope model, which explores different levels of complexity starting from a circular-cylindrical geometry. The framework of this series of models was established by Nieves-Chinchilla et al. 2016 with the circular-cylindrical analytical flux rope model. The model attempts to describe the magnetic flux rope topology with distorted cross-section as a possible consequence of the interaction with the solar wind. In this model, the flux rope is completely described in a non-orthogonal geometry. The Maxwell equations are solved using tensor calculus consistent with the geometry chosen, invariance along the axial direction, and with the assumption of no radial current density. The model is generalized in terms of the radial and azimuthal dependence of the poloidal current density component and axial current density component. The misalignment between current density and magnetic field is studied in detail for several example profiles of the axial and poloidal current density components. This theoretical analysis provides a map of the force distribution inside of the flux-rope. For reconstruction of the heliospheric flux-ropes, the circular-cylindrical reconstruction technique has been adapted to the new geometry and applied to in situ ICMEs with a flux-rope entrained and tested with cases with clear in situ signatures of distortion. The model adds a piece in the puzzle of the physical-analytical representation of these magnetic structures that should be evaluated with the ultimate goal of reconciling in-situ reconstructions with imaging 3D remote sensing CME reconstructions. Other effects such as axial curvature and/or expansion could be incorporated in the future to fully understand the magnetic structure. Title: Bridging the Gap: Capturing the Lyα Counterpart of a Type-II Spicule and its Heating Evolution with VAULT2.0 and IRIS Campaign Observations Authors: Chintzoglou, G.; De Pontieu, B.; Martinez-Sykora, J.; Mendes Domingos Pereira, T.; Vourlidas, A.; Tun Beltran, S. Bibcode: 2017AGUFMSH43A2794C Altcode: We present the analysis of data from the observing campaign in support to the VAULT2.0 sounding rocket launch on September 30, 2014. VAULT2.0 is a Lyα (1216 Å) spectroheliograph capable of providing fast cadence spectroheliograms of high-spectral purity. High resolution Lyα observations are highly complementary with the IRIS observations of the upper chromosphere and the low transition region but have previously been unavailable. The VAULT2.0 data provide critical, new upper-chromospheric constraints for numerical models. The observing campaign was closely coordinated with the IRIS mission. Taking advantage of this simultaneous multi-wavelength coverage of target AR 12172 and by using state-of-the-art radiative-MHD simulations of spicules, we are able to perform a detailed investigation of a type-II spicule associated with a fast apparent network jet recorded in the campaign observations during the VAULT2.0 flight. Our unique analysis suggests that spicular material exists suspended in lower temperatures until it rapidly gets heated and becomes visible in transition-region temperatures as an apparent network jet. Title: Mapping The Territory: What Current Remote Sensing Tells Us To Expect For PSP Authors: DeForest, C. E.; McComas, D. J.; Vourlidas, A.; Howard, R. Bibcode: 2017AGUFMSH21C..06D Altcode: Remote sensing with current coronagraphs affords the best current estimate of plasma conditions PSP will encounter. Over the past few years, analyses of the synoptic data sets from the STEREO/COR2 and STEREO/HI1 imagers have yielded rough locations for critical loci such as the Alfvén and β=1 surfaces. We now present new results from the deepest-field coronagraph sequence made to date: the STEREO-A deep-field campaign. Recently-developed noise reduction techniques and the unique deep-exposure data set reveal small scale motions and fluctuations throughout the visible corona and give new insight into the structure of the outer corona. Title: Turbulent Density Fluctuations and Proton Heating Rate in the Solar Wind from 9-20 R ⊙ Authors: Sasikumar Raja, K.; Subramanian, Prasad; Ramesh, R.; Vourlidas, Angelos; Ingale, Madhusudan Bibcode: 2017ApJ...850..129S Altcode: 2017arXiv171006295S We obtain scatter-broadened images of the Crab Nebula at 80 MHz as it transits through the inner solar wind in 2017 and 2016 June. These images are anisotropic, with the major axis oriented perpendicular to the radially outward coronal magnetic field. Using these data, we deduce that the density modulation index (δ {N}e/{N}e) caused by turbulent density fluctuations in the solar wind ranges from 1.9× {10}-3 to 7.7× {10}-3 between 9 and 20 R ⊙. We also find that the heating rate of solar wind protons at these distances ranges from 2.2× {10}-13 to 1.0× {10}-11 {erg} {{cm}}-3 {{{s}}}-1. On two occasions, the line of sight intercepted a coronal streamer. We find that the presence of the streamer approximately doubles the thickness of the scattering screen. Title: Is There a CME Rate Floor? CME and Magnetic Flux Values for the Last Four Solar Cycle Minima Authors: Webb, D. F.; Howard, R. A.; St. Cyr, O. C.; Vourlidas, A. Bibcode: 2017ApJ...851..142W Altcode: The recent prolonged activity minimum has led to the question of whether there is a base level of the solar magnetic field evolution that yields a “floor” in activity levels and also in the solar wind magnetic field strength. Recently, a flux transport model coupled with magneto-frictional simulations has been used to simulate the continuous magnetic field evolution in the global solar corona for over 15 years, from 1996 to 2012. Flux rope eruptions in the simulations are estimated (Yeates), and the results are in remarkable agreement with the shape of the SOlar Heliospheric Observatory/Large Angle and Spectrometric Coronagraph Experiment coronal mass ejection (CME) rate distribution. The eruption rates at the two recent minima approximate the observed-corrected CME rates, supporting the idea of a base level of solar magnetic activity. In this paper, we address this issue by comparing annual averages of the CME occurrence rates during the last four solar cycle minima with several tracers of the global solar magnetic field. We conclude that CME activity never ceases during a cycle, but maintains a base level of 1 CME every 1.5 to ∼3 days during minima. We discuss the sources of these CMEs. Title: CME Dynamics Using STEREO and LASCO Observations: The Relative Importance of Lorentz Forces and Solar Wind Drag Authors: Sachdeva, Nishtha; Subramanian, Prasad; Vourlidas, Angelos; Bothmer, Volker Bibcode: 2017SoPh..292..118S Altcode: 2017arXiv170504871S We seek to quantify the relative contributions of Lorentz forces and aerodynamic drag on the propagation of solar coronal mass ejections (CMEs). We use Graduated Cylindrical Shell (GCS) model fits to a representative set of 38 CMEs observed with the Solar and Heliospheric Observatory (SOHO) and the Solar and Terrestrial Relations Observatory (STEREO) spacecraft. We find that the Lorentz forces generally peak between 1.65 and 2.45 R⊙ for all CMEs. For fast CMEs, Lorentz forces become negligible in comparison to aerodynamic drag as early as 3.5 - 4 R⊙. For slow CMEs, however, they become negligible only by 12 - 50 R⊙. For these slow events, our results suggest that some of the magnetic flux might be expended in CME expansion or heating. In other words, not all of it contributes to the propagation. Our results are expected to be important in building a physical model for understanding the Sun-Earth dynamics of CMEs. Title: Three-dimensional characteristics of solar coronal shocks determined from observations; Geometry, Kinematics, and Compression ratio Authors: Kwon, Ryun Young; Vourlidas, Angelos Bibcode: 2017SPD....4820102K Altcode: We investigate the three-dimensional (3D) characteristics of coronal shocks associated with Coronal Mass Ejections (CMEs), in terms of geometry, kinematics, and density compression ratio, employing a new method we have developed. The method uses multi-viewpoint observations from the STEREO-A, -B and SOHO coronagraphs. The 3D structure and kinematics of coronal shock waves and the driving CMEs are derived separately using a forward modeling method. We analyze two CMEs that are observed as halos by the three spacecraft, and the peak speeds are over 2000 km s-1. From the 3D modeling, we find (1) the coronal shock waves are spherical apparently enclosing the Sun, in which the angular widths are much wider than those of CMEs (92° and 252° versus 58° and 91°), indicating shock waves are propagating away from the CMEs in the azimuthal directions, and (2) the speeds of the shock waves around the CME noses are comparable to those of the CME noses, but the speeds at the lateral flanks seem to be limited to the local fast magnetosonic speed. Applying our new method, we determine electron densities in the shock sheaths, the downstream-upstream density ratios, and the Mach numbers. We find (1) the sheath electron densities decrease with height in general but have the maximum near the CME noses, (2) the density ratios and Mach numbers also seem to depend on the position angle from the CME nose to the far-flank but are more or less constant in time, while the sheath electron densities and speeds decrease with time, because of the reduced local Alfven speed with height, and (3) the shocks could be supercritical in a wider spatial range, and it lasts longer, than those of what have been reported in the past. We conclude that the shock wave associated with an energetic CME is a phenomenon that is becoming a non-driven (blast-type), nearly freely propagating wave at the flank from a driven (bow- and/or piston-type) wave near the CME nose. Title: Observation of an Extremely Large-Density Heliospheric Plasma Sheet Compressed by an Interplanetary Shock at 1 AU Authors: Wu, Chin-Chun; Liou, Kan; Lepping, R. P.; Vourlidas, Angelos; Plunkett, Simon; Socker, Dennis; Wu, S. T. Bibcode: 2017SoPh..292..109W Altcode: At 11:46 UT on 9 September 2011, the Wind spacecraft encountered an interplanetary (IP) fast-forward shock. The shock was followed almost immediately by a short-duration (∼ 35 minutes) extremely dense pulse (with a peak ∼ 94 cm−3). The pulse induced an extremely large positive impulse (SYM-H = 74 nT and Dst = 48 nT) on the ground. A close examination of other in situ parameters from Wind shows that the density pulse was associated with i) a spike in the plasma β (ratio of thermal to magnetic pressure), ii) multiple sign changes in the azimuthal component of the magnetic field (Bϕ), iii) a depressed magnetic field magnitude, iv) a small radial component of the magnetic field, and v) a large (> 90°) change in the suprathermal (∼ 255 eV) electron pitch angle across the density pulse. We conclude that the density pulse is associated with the heliospheric plasma sheet (HPS). The thickness of the HPS is estimated to be ∼8.2 ×105km. The HPS density peak is about five times the value of a medium-sized density peak inside the HPS (∼ 18 cm−3) at 1 AU. Our global three-dimensional magnetohydrodynamic simulation results (Wu et al. in J. Geophys. Res. 212, 1839, 2016) suggest that the extremely large density pulse may be the result of the compression of the HPS by an IP shock crossing or an interaction between an interplanetary shock and a corotating interaction region. Title: Magnetic flux-rope configurations embedded in the Coronal Mass Ejections Authors: Nieves-Chinchilla, Teresa; Vourlidas, A.; Raymond, J.; Linton, M.; Savani, P. N.; Al-haddad, N.; Szabo, A. Bibcode: 2017shin.confE..37N Altcode: Interplanetary coronal mass ejections (ICMEs) are manifestations of magnetized plasma moving from the Sun throughout the heliosphere. The understanding of the magnetic field topology, structure, global morphology and the effect of the evolution from the first stages of the heliospheric journey of the CMEs are still a challenge. Today the reconciliation between local and global ICMEs reconstruction are far to converge systematically in a unique scenario and vision. Also the lack of consensus between in-situ models, lead to the need to revisit the heliospheric definition of the magnetic obstacle embedded in the ICMEs. In this work we approach this discussion from the point of view of in-situ observations of the ICMEs using the catalogues of ICMEs provided by Heliospheric observatories. We address three questions: 1) Can we find any relationship between the in-situ observed magnetic field strength compression and the apparent Vexp?, 2) Can we quantify the flux-rope distortion, curvatures or deformations at any heliospheric distance?, and finally, 3) can we quantify the forces that govern the internal evolution of the ICMEs in the inner heliosphere?. Title: Magnetic Flux Rope Shredding By a Hyperbolic Flux Tube: The Detrimental Effects of Magnetic Topology on Solar Eruptions Authors: Chintzoglou, Georgios; Vourlidas, Angelos; Savcheva, Antonia; Tassev, Svetlin; Tun Beltran, Samuel; Stenborg, Guillermo Bibcode: 2017ApJ...843...93C Altcode: 2017arXiv170600057C We present the analysis of an unusual failed eruption captured in high cadence and in many wavelengths during the observing campaign in support of the Very high Angular resolution Ultraviolet Telescope (VAULT2.0) sounding rocket launch. The refurbished VAULT2.0 is a Lyα (λ 1216 Å) spectroheliograph launched on 2014 September 30. The campaign targeted active region NOAA AR 12172 and was closely coordinated with the Hinode and IRIS missions and several ground-based observatories (NSO/IBIS, SOLIS, and BBSO). A filament eruption accompanied by a low-level flaring event (at the GOES C-class level) occurred around the VAULT2.0 launch. No coronal mass ejection was observed. The eruption and its source region, however, were recorded by the campaign instruments in many atmospheric heights ranging from the photosphere to the corona in high cadence and spatial resolution. This is a rare occasion that enabled us to perform a comprehensive investigation on a failed eruption. We find that a rising Magnetic Flux Rope (MFR)-like structure was destroyed during its interaction with the ambient magnetic field, creating downflows of cool plasma and diffuse hot coronal structures reminiscent of “cusps.” We employ magnetofrictional simulations to show that the magnetic topology of the ambient field is responsible for the destruction of the MFR. Our unique observations suggest that the magnetic topology of the corona is a key ingredient for a successful eruption. Title: The Density Structure of Shock Sheaths Associated with Coronal Mass Ejections Authors: Kwon, Ryun Young; Vourlidas, Angelos Bibcode: 2017shin.confE..23K Altcode: We present the three-dimensional (3D) geometry and property of coronal mass ejections (CMEs) focusing on the density structure of the shock sheaths. We have developed a new method utilizing remote-sensing, multi-viewpoint coronagraphic observations, to extract the 3D electron density profiles and thus the density compression ratio of shock sheaths associated with CMEs close to the Sun.

We analyze two fast halo CMEs observed on 2011 March 7 and 2014 February 25. Our method uses the ellipsoid model to derive the 3D geometry of the sheaths, including the line-of-sight (LOS) depth. The density profiles of the sheaths are modeled with double-Gaussian functions, with four free parameters. The modeled densities are integrated along the 3D LOSs and compared with the observed brightness in COR2-A, using a chi-squares approach to obtain the optimal parameters for the Gaussian profiles. The upstream densities are derived from both the inversion of the brightness in a pre-event image and an empirical model. Then the density ratio and Alfvenic Mach number are calculated across the shock front.

We find that the density compression peaks around the CME nose and decreases at larger position angles. It is consistent with a driven shock at the nose and a free-propagating wave at the CME flanks. Interestingly, we find that the compression ratio and hence the supercritical region extend over a large area of the shock and last longer (several tens of minutes) than past reports. Our results demonstrate the power of multi-viewpoint coronagraphic observations and forward modeling in remotely deriving key shock properties in an otherwise inaccessible regime. They also show that CME shocks are capable of accelerating energetic particles in the corona over extended spatial and temporal scales and may, therefore, be responsible for the wide longitudinal distribution of these particles in the inner heliosphere. Title: The 'baby' steps of CMEs: What can we learn about their future journey to the heliosphere? Authors: Guedes dos Santos, Luiz Fernando; Nieves-Chinchilla, Teresa; Vourlidas, Angelos; Uritsky, Vadim M. Bibcode: 2017shin.confE..24G Altcode: Coronal mass ejections (CMEs) are large-scale explosions of magnetic field and plasma from the Sun's corona and the primary drivers of terrestrial space weather. The fastest CMEs can reach Earth in 1-5 days expanding in size as they travel due to their strong entrained magnetic fields. Title: SOLARIS: Solar Sail Investigation of the Sun Authors: Appourchaux, Thierry; Auchère, Frédéric; Antonucci, Ester; Gizon, Laurent; MacDonald, Malcolm; Hara, Hirohisa; Sekii, Takashi; Moses, Daniel; Vourlidas, Angelos Bibcode: 2017arXiv170708193A Altcode: In this paper, we detail the scientific objectives and outline a strawman payload of the SOLAR sail Investigation of the Sun (SOLARIS). The science objectives are to study the 3D structure of the solar magnetic and velocity field, the variation of total solar irradiance with latitude, and the structure of the corona. We show how we can meet these science objective using solar-sail technologies currently under development. We provide a tentative mission profile considering several trade-off approaches. We also provide a tentative mass budget breakdown and a perspective for a programmatic implementation. Title: Multi-viewpoint Coronal Mass Ejection Catalog Based on STEREO COR2 Observations Authors: Vourlidas, Angelos; Balmaceda, Laura A.; Stenborg, Guillermo; Dal Lago, Alisson Bibcode: 2017ApJ...838..141V Altcode: We present the first multi-viewpoint coronal mass ejection (CME) catalog. The events are identified visually in simultaneous total brightness observations from the twin SECCHI/COR2 coronagraphs on board the Solar Terrestrial Relations Observatory mission. The Multi-View CME Catalog differs from past catalogs in three key aspects: (1) all events between the two viewpoints are cross-linked, (2) each event is assigned a physics-motivated morphological classification (e.g., jet, wave, and flux rope), and (3) kinematic and geometric information is extracted semi-automatically via a supervised image segmentation algorithm. The database extends from the beginning of the COR2 synoptic program (2007 March) to the end of dual-viewpoint observations (2014 September). It contains 4473 unique events with 3358 events identified in both COR2s. Kinematic properties exist currently for 1747 events (26% of COR2-A events and 17% of COR2-B events). We examine several issues, made possible by this cross-linked CME database, including the role of projection on the perceived morphology of events, the missing CME rate, the existence of cool material in CMEs, the solar cycle dependence on CME rate, speeds and width, and the existence of flux rope within CMEs. We discuss the implications for past single-viewpoint studies and for Space Weather research. The database is publicly available on the web including all available measurements. We hope that it will become a useful resource for the community. Title: Investigating the Wave Nature of the Outer Envelope of Halo Coronal Mass Ejections Authors: Kwon, Ryun-Young; Vourlidas, Angelos Bibcode: 2017ApJ...836..246K Altcode: We investigate the nature of the outer envelope of halo coronal mass ejections (H-CMEs) using multi-viewpoint observations from the Solar Terrestrial Relations Observatory-A, -B, and SOlar and Heliospheric Observatory coronagraphs. The 3D structure and kinematics of the halo envelopes and the driving CMEs are derived separately using a forward modeling method. We analyze three H-CMEs with peak speeds from 1355 to 2157 km s-1 sufficiently fast to drive shocks in the corona. We find that the angular widths of the halos range from 192° to 252°, while those of the flux ropes range between only 58° and 91°, indicating that the halos are waves propagating away from the CMEs. The halo widths are in agreement with widths of Extreme Ultraviolet (EUV) waves in the low corona further demonstrating the common origin of these structures. To further investigate the wave nature of the halos, we model their 3D kinematic properties with a linear fast magnetosonic wave model. The model is able to reproduce the position of the halo flanks with realistic coronal medium assumptions but fails closer to the CME nose. The CME halo envelope seems to arise from a driven wave (or shock) close to the CME nose, but it is gradually becoming a freely propagating fast magnetosonic wave at the flanks. This interpretation provides a simple unifying picture for CME halos, EUV waves, and the large longitudinal spread of solar energetic particles. Title: Structure, Propagation, and Expansion of a CME-driven Shock in the Heliosphere: A Revisit of the 2012 July 23 Extreme Storm Authors: Liu, Ying D.; Hu, Huidong; Zhu, Bei; Luhmann, Janet G.; Vourlidas, Angelos Bibcode: 2017ApJ...834..158L Altcode: 2016arXiv161104239L We examine the structure, propagation, and expansion of the shock associated with the 2012 July 23 extreme coronal mass ejection. Characteristics of the shock determined from multi-point imaging observations are compared to in situ measurements at different locations and a complex radio type II burst, which according to our definition has multiple branches that may not all be fundamental-harmonic related. The white-light shock signature can be modeled reasonably well by a spherical structure and was expanding backward even on the opposite side of the Sun. The expansion of the shock, which was roughly self-similar after the first ∼1.5 hr from launch, largely dominated over the translation of the shock center for the time period of interest. Our study also suggests a bow-shock morphology around the nose at later times due to the outward motion in combination with the expansion of the ejecta. The shock decayed and failed to reach Mercury in the backward direction and the Solar Terrestrial Relations Observatory B (STEREO B) and Venus in the lateral directions, as indicated by the imaging and in situ observations. The shock in the nose direction, however, may have persisted to the far outer heliosphere, with predicted impact on Dawn around 06:00 UT on July 25 and on Jupiter around 23:30 UT on July 27 by a magnetohydrodynamic model. The type II burst shows properties generally consistent with the spatial/temporal variations of the shock deduced from imaging and in situ observations. In particular, the low-frequency bands agree well with the in situ measurements of a very low density ahead of the shock at STEREO A. Title: Understanding the Physical Nature of Coronal "EIT Waves" Authors: Long, D. M.; Bloomfield, D. S.; Chen, P. F.; Downs, C.; Gallagher, P. T.; Kwon, R. -Y.; Vanninathan, K.; Veronig, A. M.; Vourlidas, A.; Vršnak, B.; Warmuth, A.; Žic, T. Bibcode: 2017SoPh..292....7L Altcode: 2016arXiv161105505L For almost 20 years the physical nature of globally propagating waves in the solar corona (commonly called "EIT waves") has been controversial and subject to debate. Additional theories have been proposed over the years to explain observations that did not agree with the originally proposed fast-mode wave interpretation. However, the incompatibility of observations made using the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory with the fast-mode wave interpretation was challenged by differing viewpoints from the twin Solar Terrestrial Relations Observatory spacecraft and data with higher spatial and temporal resolution from the Solar Dynamics Observatory. In this article, we reexamine the theories proposed to explain EIT waves to identify measurable properties and behaviours that can be compared to current and future observations. Most of us conclude that the so-called EIT waves are best described as fast-mode large-amplitude waves or shocks that are initially driven by the impulsive expansion of an erupting coronal mass ejection in the low corona. Title: Chromosphere to 1 AU Simulation of the 2011 March 7th Event: A Comprehensive Study of Coronal Mass Ejection Propagation Authors: Jin, M.; Manchester, W. B.; van der Holst, B.; Sokolov, I.; Tóth, G.; Vourlidas, A.; de Koning, C. A.; Gombosi, T. I. Bibcode: 2017ApJ...834..172J Altcode: 2016arXiv161108897J We perform and analyze the results of a global magnetohydrodynamic simulation of the fast coronal mass ejection (CME) that occurred on 2011 March 7. The simulation is made using the newly developed Alfvén Wave Solar Model (AWSoM), which describes the background solar wind starting from the upper chromosphere and extends to 24 R⊙. Coupling AWSoM to an inner heliosphere model with the Space Weather Modeling Framework extends the total domain beyond the orbit of Earth. Physical processes included in the model are multi-species thermodynamics, electron heat conduction (both collisional and collisionless formulations), optically thin radiative cooling, and Alfvén-wave turbulence that accelerates and heats the solar wind. The Alfvén-wave description is physically self-consistent, including non-Wentzel-Kramers-Brillouin reflection and physics-based apportioning of turbulent dissipative heating to both electrons and protons. Within this model, we initiate the CME by using the Gibson-Low analytical flux rope model and follow its evolution for days, in which time it propagates beyond STEREO A. A detailed comparison study is performed using remote as well as in situ observations. Although the flux rope structure is not compared directly due to lack of relevant ejecta observation at 1 au in this event, our results show that the new model can reproduce many of the observed features near the Sun (e.g., CME-driven extreme ultraviolet [EUV] waves, deflection of the flux rope from the coronal hole, “double-front” in the white light images) and in the heliosphere (e.g., shock propagation direction, shock properties at STEREO A). Title: Why are Solar Energetic Particle Intensities so Much Lower in Solar Cycle 24, Especially at High Energies? Authors: Mewaldt, R. A.; Li, G.; Cohen, C.; Mason, G. M.; von Rosenvinge, T. T.; Smith, C. W.; Vourlidas, A. Bibcode: 2016AGUFMSH41D..01M Altcode: Measurements by ACE, STEREO, and GOES show that the number of large Solar Energetic Particle (SEP) events in the first 7 years of solar cycle 24 is reduced by a factor of 2 compared to this point of solar cycle 23, while the fluences of >10 MeV/nucleon ions from H to Fe are reduced by factors ranging from 5 to >10. Compared to solar cycles 22 and 23, the fluence of >100 MeV protons is reduced by factors of 7 to 10 in the current cycle. A common aspect of these observations is that the energy spectra of accelerated ions in cycle-24 have suddenly steepen at "breaks" that are 2 to 4 times lower in energy/nucleon than in cycle 23. We investigate the origin of these cycle-to-cycle intensity and spectral differences by evaluating possible factors that control the acceleration efficiency and maximum energy of CME-shock-accelerated particles in the last two cycles, including seed-particle densities of suprathermal ions, the interplanetary magnetic field strength and turbulence level, and properties of coronal mass ejections (CMEs) and their associated shocks. The effects of these conditions will be evaluated with a state-of-the-art SEP acceleration model and by comparing SEP data with earlier analytic evaluations of the maximum kinetic energy to which CME shocks can accelerate solar energetic ions from H to Fe. Title: Elliptic-cylindrical analytical flux-rope model for ICMEs Authors: Nieves-Chinchilla, T.; Linton, M.; Hidalgo, M. A. U.; Vourlidas, A. Bibcode: 2016AGUFMSH51F2648N Altcode: We present an analytical flux-rope model for realistic magnetic structures embedded in Interplanetary Coronal Mass Ejections. The framework of this model was established by Nieves-Chinchilla et al. (2016) with the circular-cylindrical analytical flux rope model and under the concept developed by Hidalgo et al. (2002). Elliptic-cylindrical geometry establishes the first-grade of complexity of a series of models. The model attempts to describe the magnetic flux rope topology with distorted cross-section as a possible consequence of the interaction with the solar wind. In this model, the flux rope is completely described in the non-euclidean geometry. The Maxwell equations are solved using tensor calculus consistently with the geometry chosen, invariance along the axial component, and with the only assumption of no radial current density. The model is generalized in terms of the radial dependence of the poloidal current density component and axial current density component. The misalignment between current density and magnetic field is studied in detail for the individual cases of different pairs of indexes for the axial and poloidal current density components. This theoretical analysis provides a map of the force distribution inside of the flux-rope. The reconstruction technique has been adapted to the model and compared with in situ ICME set of events with different in situ signatures. The successful result is limited to some cases with clear in-situ signatures of distortion. However, the model adds a piece in the puzzle of the physical-analytical representation of these magnetic structures. Other effects such as axial curvature, expansion and/or interaction could be incorporated in the future to fully understand the magnetic structure. Finally, the mathematical formulation of this model opens the door to the next model: toroidal flux rope analytical model. Title: LOCKYER (Large Optimized Coronagraph for KeY Emission line Research): A SMEX Mission to Provide Crucial Measurements of the Genesis of the Solar Wind and CMEs Authors: Ko, Y. K.; Vourlidas, A.; Korendyke, C.; Laming, J. M. Bibcode: 2016AGUFMSH43B2569K Altcode: The LOCKYER mission is designed to uncover the physical processes of acceleration and heating of the quiescent and transient solar wind. It builds on the success of the Ultraviolet Coronagraph Spectrometer (UVCS) on SOHO with a massive increase in effective area at Lyman-alpha (200x larger than UVCS), thanks to a modern optical design and the use of a 4m boom. The larger effective area enables spectral line observations from many ions, including He II (at 1640 Å), allowing us to access the region where the coronal plasma transitions from fluid to kinetic behavior. In addition, a visible light channel provides simultaneous high-resolution coronagraphic images for the global coronal structure and dynamics creating a greatly-expanded UVCS-LASCO `hybrid' instrument within the tight constraints of a SMEX mission. The LOCKYER mission aims to answer the following questions: 1) What are the physical processes responsible for the heating and acceleration of the primary (proton, electron, helium) and secondary (minor ion) plasma components of the fast and slow solar wind? 2) How are CMEs heated and accelerated? LOCKYER would greatly advance our knowledge of how and where the solar wind is formed, and how the variations in coronal microphysics impact the solar wind and heliosphere. The LOCKYER measurements are highly complementary to the Solar Probe Plus and Solar Orbiter measurements and provide detailed empirical descriptions of the coronal plasma at heights where the primary energy and momentum addition occur. Title: LASCO White-Light Observations of Eruptive Current Sheets Trailing CMEs Authors: Webb, David F.; Vourlidas, Angelos Bibcode: 2016SoPh..291.3725W Altcode: 2016SoPh..tmp..178W Many models of eruptive flares or coronal mass ejections (CMEs) involve formation of a current sheet connecting the ejecting CME flux rope with a magnetic loop arcade. However, there is very limited observational information on the properties and evolution of these structures, hindering progress in understanding eruptive activity from the Sun. In white-light images, narrow coaxial rays trailing the outward-moving CME have been interpreted as current sheets. Here, we undertake the most comprehensive statistical study of CME-rays to date. We use SOHO/LASCO data, which have a higher cadence, larger field of view, and better sensitivity than any previous coronagraph. We compare our results to a previous study of Solar Maximum Mission (SMM) CMEs, in 1984 - 1989, having candidate magnetic disconnection features at the CME base, about half of which were followed by coaxial bright rays. We examine all LASCO CMEs during two periods of minimum and maximum activity in Solar Cycle 23, resulting in many more events, ∼130 CME-rays, than during SMM. Important results include: The occurrence rate of the rays is ∼11 % of all CMEs during solar minimum, but decreases to ∼7 % at solar maximum; this is most likely related to the more complex coronal background. The rays appear on average 3 - 4 hours after the CME core, and are typically visible for three-fourths of a day. The mean observed current sheet length over the ray lifetime is ∼12 R⊙, with the longest current sheet of 18.5 R⊙. The mean CS growth rates are 188 kms−1 at minimum and 324 kms−1 at maximum. Outward-moving blobs within several rays, which are indicative of reconnection outflows, have average velocities of ∼350 kms−1 with small positive accelerations. A pre-existing streamer is blown out in most of the CME-ray events, but half of these are observed to reform within ∼1 day. The long lifetime and long lengths of the CME-rays challenge our current understanding of the evolution of the magnetic field in the aftermath of CMEs. Title: Spherically-shaped coronal shock waves associated with Coronal Mass Ejections Authors: Kwon, R. Y.; Vourlidas, A. Bibcode: 2016AGUFMSH43B2563K Altcode: Knowing the three-dimensional (3D) geometry of Coronal mass ejections (CMEs) and associated shock waves is crucial for interpretations of in-situ measurements close to the Sun that will be carried out by Solar Probe Plus and Solar Orbiter. Here, we obtain the 3D geometries of three CMEs and associated shock waves using multiple perspective observations from STEREO-Ahead, -Behind, SDO, and SOHO. These CMEs appeared as halo CMEs in all three viewing perspectives and were accompanied by solar energetic particle (SEP) events. The 3D structures and kinematics of the halo fronts were determined by applying a forward modeling method. We find that the angular widths of the halos are at least 192 degrees while those of the CMEs are at most 100 degrees, implying the presence of a spherically-shaped wave, extending out much further than the CME. The peak speeds of the CMEs are in the range of 1355- 2157 km/s, but the speeds of the halo flanks seem to reach the local fast-mode speed of the coronal medium 500 km/s. To further investigate the physical nature of the halo flanks, we compare the 3D properties of the halos with a fast-mode wave model given in Uchida (1970). The model reproduced the halo flanks with the local fast-mode speed profiles of the coronal medium. The modeled waves refract toward the lower altitudes as propagating through the inhomogeneous medium, and these fast-mode waves lead to the spherically-shaped fronts. In addition, the azimuthal extents of the halos are consistent with the SEP injection sites far away from the flare sites, supporting that the halo fronts are truly the signatures of the fast-mode wave. Our results suggest that the halo-shaped fronts are likely spherically-shaped fast-mode waves, extending out much further than the CMEs. The unprecedented in-situ measurements of Solar Probe Plus and Solar Orbiter will probe into the detailed physical properties of such large-scale disturbances in the corona. Title: A Heliospheric Plasma Sheet Crossing at 1 AU that Contains an Unusually High Density Just Downstream of Shock Wave Authors: Liou, K.; Wu, C. C.; Lepping, R. P.; Vourlidas, A.; Plunkett, S. P.; Socker, D. G.; Wu, S. T. Bibcode: 2016AGUFMSH51A2574L Altcode: On the 9th of September 2011 the Wind spacecraft encountered an interplanetary (IP) fast forward shock at 11:46 UT. The shock was followed almost immediately ( 5 minutes) by a short ( 35 minutes) duration, extremely large density pulse with a density peak of 94 cm-3. The density pulse induced an extremely large positive impulse (SYM-H = 74 nT and Dst = 48 nT) on the ground. A close examination of other in situ parameters from Wind, we find that the density pulse was associated with (1) a spike in the plasma beta (β, ratio of thermal to magnetic pressure), (2) multiple sign changes in the azimuthal angle of magnetic field, Bϕ, (3) a depressed magnetic field magnitude, (4) a small radial component of magnetic field, and (5) a large ( > 90º) pitch angle change in suprathermal electrons (> 200 eV) across the density pulse. We conclude that the density pulse is associated with the heliospheric plasma sheet (HPS). The thickness of the HPS is estimated to be 8.2x105 km. The HPS density peak is about five times the value of the median size density peak inside the HPS ( 18 cm-3). Our global three-dimensional magnetohydrodynamic simulation suggests that the unusually large density pulse was a result of the compression by the IP shock from behind. During this time Geotail was in the dawn sheath region and did not see the density pulse, suggesting the transient and localized nature of the density pulse. (Work of CCW is supported by the Chief of Naval Research.) Title: Investigation of Streamer Blowout Events Observed by LASCO Authors: Webb, D. F.; Vourlidas, A. Bibcode: 2016AGUFMSH33A..04W Altcode: We investigate the properties of the class of large-scale coronal eruption in which a pre-existing streamer brightens and swells for hours or days before being removed or disrupted during a coronal mass ejection (CME). Such events are important as a stage in the evolution of streamers, which are associated with the heliospheric current sheet and the separatrix (S)-web. Streamer blowouts (SBOs) represent large-scale ejections of mass and magnetic field into the heliosphere and are likely important for restructuring of the global solar fields over a solar cycle. Some questions we address are: What are the general properties of SBOs, e.g., speeds, durations, spans, masses and energies? Do SBOs depend on their formative structures, e.g., pseudostreamer/ quadrupolar arcades, active regions, polar crown filaments? How are SBOs related to magnetic flux transport to the solar poles? What roles do SBO/CMEs play in the Sun's shedding of its magnetic flux and helicity built up over the solar cycle, and in balancing the magnetic flux in the heliosphere? We summarize the properties of these events as observed by the SOHO/LASCO white light coronagraphs over solar cycle 23 from 1996-2011. Title: Deriving the Properties of Coronal Pressure Fronts in 3D: Application to the 2012 May 17 Ground Level Enhancement Authors: Rouillard, A. P.; Plotnikov, I.; Pinto, R. F.; Tirole, M.; Lavarra, M.; Zucca, P.; Vainio, R.; Tylka, A. J.; Vourlidas, A.; De Rosa, M. L.; Linker, J.; Warmuth, A.; Mann, G.; Cohen, C. M. S.; Mewaldt, R. A. Bibcode: 2016ApJ...833...45R Altcode: 2016arXiv160505208R We study the link between an expanding coronal shock and the energetic particles measured near Earth during the ground level enhancement of 2012 May 17. We developed a new technique based on multipoint imaging to triangulate the three-dimensional (3D) expansion of the shock forming in the corona. It uses images from three vantage points by mapping the outermost extent of the coronal region perturbed by the pressure front. We derive for the first time the 3D velocity vector and the distribution of Mach numbers, M FM, of the entire front as a function of time. Our approach uses magnetic field reconstructions of the coronal field, full magnetohydrodynamic simulations and imaging inversion techniques. We find that the highest M FM values appear near the coronal neutral line within a few minutes of the coronal mass ejection onset; this neutral line is usually associated with the source of the heliospheric current and plasma sheet. We illustrate the variability of the shock speed, shock geometry, and Mach number along different modeled magnetic field lines. Despite the level of uncertainty in deriving the shock Mach numbers, all employed reconstruction techniques show that the release time of GeV particles occurs when the coronal shock becomes super-critical (M FM > 3). Combining in situ measurements with heliospheric imagery, we also demonstrate that magnetic connectivity between the accelerator (the coronal shock of 2012 May 17) and the near-Earth environment is established via a magnetic cloud that erupted from the same active region roughly five days earlier. Title: Are non-driven fast-mode shocks responsible for the wide longitudinal spread of SEP events? Authors: Kwon, R. Y.; Vourlidas, A. Bibcode: 2016AGUFMSH32A..02K Altcode: Fast-mode shock waves are believed to be the primary agent in the acceleration of solar energetic particles (SEPs) over a wide range of energies across the solar corona and heliosphere. In this regard, the spatial distribution of the initial SEP injections from the solar corona should depend on the three-dimensional (3D) geometry of coronal shock waves. Using remote-sensing observations by STEREO-Ahead, -Behind, SDO, and SOHO, we determine the 3D structure and properties of the shock waves initially driven by coronal mass ejections (CMEs). As the shock wave expands, we distinguish two types of shock waves: One is the driven shock wave that is observed in white light observations as propagating ahead of the CME leading edge from the low corona into the interplanetary space. The other is the non-driven shock wave that is observed as a nearly-circular propagating disturbance seen in EUV observations of the low corona (i.e., the so-called EUV wave) and also observed as a halo-shaped disturbance in white light observations far from the eruption site. While the super-Alfvenic CME drivers constantly energize the driven shock waves, and the angular widths are limited to those of the drivers, the non-driven shock waves propagate in a very broad spatial range with deceleration. The magnetic connection of the spacecraft with the different proportions of the shock determines the properties of the observed SEP events. Spacecraft magnetically connected to the non-driven shock will see SEP events with intensities peaking at the prompt component and falling off rapidly. By contrast, spacecraft continuously connecting to driven shock waves will observe SEP events that increase in intensity with time and that may peak at the arrival of the shock. We suggest that the non-driven shock waves propagating far from the eruption site contribute to the broad longitudinal spread of SEPs. Illustrative examples of SEP events observed by STEREO and near-Earth spacecraft and how each spacecraft establishes magnetic connection with the different portions of the shock will be shown. Title: The Wide-Field Imager for Solar Probe Plus (WISPR) Authors: Vourlidas, Angelos; Howard, Russell A.; Plunkett, Simon P.; Korendyke, Clarence M.; Thernisien, Arnaud F. R.; Wang, Dennis; Rich, Nathan; Carter, Michael T.; Chua, Damien H.; Socker, Dennis G.; Linton, Mark G.; Morrill, Jeff S.; Lynch, Sean; Thurn, Adam; Van Duyne, Peter; Hagood, Robert; Clifford, Greg; Grey, Phares J.; Velli, Marco; Liewer, Paulett C.; Hall, Jeffrey R.; DeJong, Eric M.; Mikic, Zoran; Rochus, Pierre; Mazy, Emanuel; Bothmer, Volker; Rodmann, Jens Bibcode: 2016SSRv..204...83V Altcode: 2015SSRv..tmp....8V; 2015SSRv..tmp...66B The Wide-field Imager for Solar PRobe Plus (WISPR) is the sole imager aboard the Solar Probe Plus (SPP) mission scheduled for launch in 2018. SPP will be a unique mission designed to orbit as close as 7 million km (9.86 solar radii) from Sun center. WISPR employs a 95∘ radial by 58∘ transverse field of view to image the fine-scale structure of the solar corona, derive the 3D structure of the large-scale corona, and determine whether a dust-free zone exists near the Sun. WISPR is the smallest heliospheric imager to date yet it comprises two nested wide-field telescopes with large-format (2 K × 2 K) APS CMOS detectors to optimize the performance for their respective fields of view and to minimize the risk of dust damage, which may be considerable close to the Sun. The WISPR electronics are very flexible allowing the collection of individual images at cadences up to 1 second at perihelion or the summing of multiple images to increase the signal-to-noise when the spacecraft is further from the Sun. The dependency of the Thomson scattering emission of the corona on the imaging geometry dictates that WISPR will be very sensitive to the emission from plasma close to the spacecraft in contrast to the situation for imaging from Earth orbit. WISPR will be the first `local' imager providing a crucial link between the large-scale corona and the in-situ measurements. Title: Scientific challenges in thermosphere-ionosphere forecasting - conclusions from the October 2014 NASA JPL community workshop Authors: Mannucci, Anthony J.; Hagan, Maura E.; Vourlidas, Angelos; Huang, Cheryl Y.; Verkhoglyadova, Olga P.; Deng, Yue Bibcode: 2016JSWSC...6E..01M Altcode: Interest in forecasting space weather in the thermosphere and ionosphere (T-I) led to a community workshop held at NASA's Jet Propulsion Laboratory in October, 2014. The workshop focus was "Scientific Challenges in Thermosphere-Ionosphere Forecasting" to emphasize that forecasting presumes a sufficiently advanced state of scientific knowledge, yet one that is still evolving. The purpose of the workshop, and this topical issue that arose from the workshop, was to discuss research frontiers that will lead to improved space weather forecasts. Three areas are discussed in some detail in this paper: (1) the role of lower atmosphere forcing in the response of the T-I to geomagnetic disturbances; (2) the significant deposition of energy at polar latitudes during geomagnetic disturbances; and (3) recent developments in understanding the propagation of coronal mass ejections through the heliosphere and prospects for forecasting the north-south component of the interplanetary magnetic field (IMF) using observations at the Lagrangian L5 point. We describe other research presented at the workshop that appears in the topical issue. The possibility of establishing a "positive feedback loop" where improved scientific knowledge leads to improved forecasts is described (Siscoe 2006, Space Weather, 4, S01003; Mannucci 2012, Space Weather, 10, S07003). Title: Relationship of EUV Irradiance Coronal Dimming Slope and Depth to Coronal Mass Ejection Speed and Mass Authors: Mason, James Paul; Woods, Thomas N.; Webb, David F.; Thompson, Barbara J.; Colaninno, Robin C.; Vourlidas, Angelos Bibcode: 2016ApJ...830...20M Altcode: 2016arXiv160705284M Extreme ultraviolet (EUV) coronal dimmings are often observed in response to solar eruptive events. These phenomena can be generated via several different physical processes. For space weather, the most important of these is the temporary void left behind by a coronal mass ejection (CME). Massive, fast CMEs tend to leave behind a darker void that also usually corresponds to minimum irradiance for the cooler coronal emissions. If the dimming is associated with a solar flare, as is often the case, the flare component of the irradiance light curve in the cooler coronal emission can be isolated and removed using simultaneous measurements of warmer coronal lines. We apply this technique to 37 dimming events identified during two separate two-week periods in 2011 plus an event on 2010 August 7, analyzed in a previous paper to parameterize dimming in terms of depth and slope. We provide statistics on which combination of wavelengths worked best for the flare-removal method, describe the fitting methods applied to the dimming light curves, and compare the dimming parameters with corresponding CME parameters of mass and speed. The best linear relationships found are v CME km s ≈ 2.36 × 10 6 km % × s dim % s m CME [ g ] ≈ 2.59 × 10 15 g % × d dim [ % ] . These relationships could be used for space weather operations of estimating CME mass and speed using near-real-time irradiance dimming measurements. Title: Understanding the Physical Nature of Coronal "EIT Waves" Authors: Long, D. M.; Bloomfield, D. S.; Chen, P. -F.; Downs, C.; Gallagher, P. T.; Kwon, R. -Y.; Vanninathan, K.; Veronig, A.; Vourlidas, A.; Vrsnak, B.; Warmuth, A.; Zic, T. Bibcode: 2016usc..confE..24L Altcode: For almost 20 years the physical nature of globally-propagating waves in the solar corona (commonly called "EIT waves") has been controversial and subject to debate. Additional theories have been proposed throughout the years to explain observations that did not fit with the originally proposed fast-mode wave interpretation. However, the incompatibility of observations made using the Extreme-ultraviolet Imaging Telescope (EIT) on the Solar and Heliospheric Observatory with the fast-mode wave interpretation have been challenged by differing viewpoints from the Solar Terrestrial Relations Observatory spacecraft and higher spatial/temporal resolution data from the Solar Dynamics Observatory. In this paper, we reexamine the theories proposed to explain "EIT waves" to identify measurable properties and behaviours that can be compared to current and future observations. Most of us conclude that "EIT waves" are best described as fast-mode large-amplitude waves/shocks, which are initially driven by the impulsive expansion of an erupting coronal mass ejection in the low corona. Title: Using ForeCAT Deflections and Rotations to Constrain the Early Evolution of CMEs Authors: Kay, C.; Opher, M.; Colaninno, R. C.; Vourlidas, A. Bibcode: 2016ApJ...827...70K Altcode: 2016arXiv160603460K To accurately predict the space weather effects of the impacts of coronal mass ejection (CME) at Earth one must know if and when a CME will impact Earth and the CME parameters upon impact. In 2015 Kay et al. presented Forecasting a CME’s Altered Trajectory (ForeCAT), a model for CME deflections based on the magnetic forces from the background solar magnetic field. Knowing the deflection and rotation of a CME enables prediction of Earth impacts and the orientation of the CME upon impact. We first reconstruct the positions of the 2010 April 8 and the 2012 July 12 CMEs from the observations. The first of these CMEs exhibits significant deflection and rotation (34° deflection and 58° rotation), while the second shows almost no deflection or rotation (<3° each). Using ForeCAT, we explore a range of initial parameters, such as the CME’s location and size, and find parameters that can successfully reproduce the behavior for each CME. Additionally, since the deflection depends strongly on the behavior of a CME in the low corona, we are able to constrain the expansion and propagation of these CMEs in the low corona. Title: Real time tests for long lead-time forecasting of the magnetic field vectors within CMEs Authors: Savani, Neel; Vourlidas, Angelos; Pulkkinen, Antti; Wold, Alexandra M. Bibcode: 2016cosp...41E1724S Altcode: The direction of magnetic vectors within coronal mass ejections, CMEs, has significant importance for forecasting terrestrial behavior. We have developed a technique to estimate the time-varying magnetic field at Earth for periods within CMEs (Savani et al 2015, 2016). This technique reduces the complex dynamics in order to create a reliable prediction methodology to operate everyday under robust conditions. In this presentation, we focus on the results and skill scores of the forecasting technique calculated from 40 historical CME events from the pre-STEREO mission. Since these results provided substantial improvements in the long lead-time Kp index forecasts, we have now begun testing under real-time conditions. We will also show the preliminary results of our methodology under these real-time conditions within the CCMC hosted at NASA Goddard Space Flight Center. Title: Lessons Learned from Flux-ropes Observed by Wind spacecraft 1995-2015 Authors: Nieves-Chinchilla, Teresa; Vourlidas, A.; Raymond, J.; Al-Haddad, N.; Linton, M.; Savani, N. P.; Szabo, A. Bibcode: 2016shin.confE..59N Altcode: It is well known that the geoeffectiveness of interplanetary coronal mass ejections (ICMEs) depends on their magnetic field topology and global geometry. The observed in-situ magnetic signatures are more complex than a simple flux-rope magnetic topology. Sometimes these events are called Ejectas or Magnetic flux-rope like. On the other hand, imaging observations of CMEs close to the Sun suggest that the entrained flux-rope undergo significant evolutionary changes, such as deformation or distortion, during their heliospheric propagation.

The goal of this paper is to explore the magnetic field and plasma parameter observations in order to get information about the magnetic field configuration, structure and geometry of the magnetic obstacles embedded in the ICMEs. This goal can be also spread on questions as: Can we quantify the Flux-Rope distortion at any heliospheric distance? Can we predict axial curvature or deformations? How is the expansion affecting to the compression in the magnetic obstacle front? Can we find any relationship between the magnetic field strength compression and the expansion velocity?. The answers to these questions will aid to address the final question: can we quantify the forces that govern the ICME evolution?

To accomplish this study, we have selected Earth-directed CMEs observed by in-situ instruments onboard on Wind spacecraft (wind.nasa.gov) in the period 1995-2015. Title: Magnetic Flux Rope Shredding by Quasi-Separatrix Layers: The Detrimental Effects of Magnetic Topology on Solar Eruptions Authors: Chintzoglou, Georgios; Stenborg, Guillermo; Savcheva, Antonia; Vourlidas, Angelos; Tassev, Svetlin; Tun Beltran, Samuel Bibcode: 2016cosp...41E.348C Altcode: We present the analysis of an unusual failed eruption event observed in high cadence and in many wavelengths during the campaign in support of the VAULT2.0 sounding rocket launch. The refurbished Very high Angular resolution Ultraviolet Telescope (VAULT2.0) is a Lyalpha (1216AA) spectroheliograph launched on September 30, 2014. The objective of the VAULT2.0 project is the study of the chromosphere-corona interface. The observing campaign targeted active region AR 12172 and was closely coordinated with the textsl{Hinode/} and textsl{IRIS/} missions and several ground-based observatories (NSO/IBIS an SOLIS, and BBSO) ). A filament eruption accompanied by small level heating (at the GOES C-class level) occurred around the VAULT2.0 launch. No CME was observed. The eruption and its source region, however, was recorded by the campaign instruments in all atmospheric heights ranging from the photosphere to the corona in high cadence and spatial resolution. This is a rare occasion which enables us to perform a comprehensive investigation on a failed eruption. We find that a rising Magnetic Flux Rope-like (MFR) structure was destroyed during its interaction with the overlying magnetic field creating downflows of cool plasma and diffuse hot coronal structures reminiscent of 'spines'. We employ MHD simulations to show that the magnetic topology of the overlying field is responsible for the destruction of the MFR. Our unique observations suggest that the magnetic topology of the corona is a key ingredient for a successful eruption. Title: Three-dimensional Geometry of a Current Sheet in the High Solar Corona: Evidence for Reconnection in the Late Stage of the Coronal Mass Ejections Authors: Kwon, Ryun-Young; Vourlidas, Angelos; Webb, David Bibcode: 2016ApJ...826...94K Altcode: Motivated by the standard flare model, ray-like structures in the wake of coronal mass ejections (CMEs) have been often interpreted as proxies of the reconnecting current sheet connecting the CME with the postflare arcade. We present the three-dimensional properties of a post-CME ray derived from white light images taken from three different viewing perspectives on 2013 September 21. By using a forward modeling method, the direction, cross section, and electron density are determined within the heliocentric distance range of 5-9 R ⊙. The width and depth of the ray are 0.42 ± 0.08 R ⊙ and 1.24 ± 0.35 R ⊙, respectively, and the electron density is (2.0 ± 0.5) × 104 cm-3, which seems to be constant with height. Successive blobs moving outward along the ray are observed around 13 hr after the parent CME onset. We model the three-dimensional geometry of the parent CME with the Gradual Cylindrical Shell model and find that the CME and ray are coaxial. We suggest that coaxial post-CME rays, seen in coronagraph images, with successive formation of blobs could be associated with current sheets undergoing magnetic reconnection in the late stage of CMEs. Title: Three-Dimensional Geometry of a Current Sheet in the High Solar Corona: Evidence for Reconnection in the Late Stage of Coronal Mass Ejections Authors: Kwon, Ryun Young; Vourlidas, Angelos; Webb, David Bibcode: 2016shin.confE.108K Altcode: Motivated by the standard flare model, ray-like structures in the wake of coronal mass ejections (CMEs) have been often interpreted as proxies of the reconnecting current sheet connecting the CME with the post flare arcade. We present the three-dimensional properties of a post-CME ray derived from white light images taken from three different viewing perspectives on 2013 September 21. By using a forward modeling method, the direction, cross section, and electron density are determined within the heliocentric distance range of 5-9 Rs. The width and depth of the ray are 0.42 +/- 0.08 Rs and 1.24 +/- 0.35 Rs, respectively, and the electron density is (2.0 +/- 0.5) x 10^4 cm^-3, which seems to be constant with height. Successive blobs moving outward along the ray are observed around 13 hours after the parent CME onset. We model the 3D geometry of the parent CME with the Gradual Cylindrical Shell model, and find that the CME and ray are coaxial. We suggest that coaxial post-CME rays, seen in coronagraph images, with successive formation of blobs could be associated with current sheets undergoing magnetic reconnection in the late stage of CMEs. Title: The acceleration sites of solar energetic particles inferred from the three-dimensional geometry of shock waves associated with coronal mass ejections Authors: Kwon, Ryun Young; Vourlidas, Angelos; Lario, David Bibcode: 2016shin.confE..19K Altcode: The observation of solar energetic particle (SEP) events by spacecraft widely separated in longitude results from processes associated with the acceleration, release and transport of SEPs on the Sun and in the inner heliosphere. We analyze the possibility that the distribution of SEPs in the inner heliosphere results from their injection by shocks associated with coronal mass ejections (CMEs). We pay especial attention to a very widespread SEP event observed on 2014 February 25 that originated from a single flare-CME event. The SEPs were detected by near-Earth spacecraft (SOHO and ACE) located at 82° west of the flare site and STEREO-Ahead and -Behind, located at 1 AU from the Sun, and 125° east and 78° east of the flare site, respectively. The 3D geometric modeling of the shock wave associated with the parent CME reveals that the shock wave propagated laterally over 45° in longitude and intercepted the field lines nominally connecting the Sun with STEREO-Ahead and -Behind, below 4 solar radii (Rs) with an angle between the magnetic field and the shock normal ranging between 24°-79°, at the times estimated for the initial release of the SEPs. In contrast, the in-situ measurements indicate that the spacecraft located on the west of the flare established magnetic connection with the shock driven when its leading edge was already in the high corona (> 14 Rs). The shock properties measured at the spacecraft and the electron peak intensities of the SEPs were well correlated with the longitudinal separations of the spacecraft with respect to the flare site. We conclude that the shock wave propagating around the solar surface was responsible for the initial injection of SEPs in the low corona (< 4 Rs), whereas the CME-driven shock in the interplanetary space played a major role in the observed SEP intensity-time profiles. Title: 3D reconstruction and particle acceleration properties of Coronal Shock Waves During Powerful Solar Particle Events Authors: Plotnikov, Illya; Vourlidas, Angelos; Tylka, Allan J.; Pinto, Rui; Rouillard, Alexis; Tirole, Margot Bibcode: 2016cosp...41E1570P Altcode: Identifying the physical mechanisms that produce the most energetic particles is a long-standing observational and theoretical challenge in astrophysics. Strong pressure waves have been proposed as efficient accelerators both in the solar and astrophysical contexts via various mechanisms such as diffusive-shock/shock-drift acceleration and betatron effects. In diffusive-shock acceleration, the efficacy of the process relies on shock waves being super-critical or moving several times faster than the characteristic speed of the medium they propagate through (a high Alfven Mach number) and on the orientation of the magnetic field upstream of the shock front. High-cadence, multipoint imaging using the NASA STEREO, SOHO and SDO spacecrafts now permits the 3-D reconstruction of pressure waves formed during the eruption of coronal mass ejections. Using these unprecedented capabilities, some recent studies have provided new insights on the timing and longitudinal extent of solar energetic particles, including the first derivations of the time-dependent 3-dimensional distribution of the expansion speed and Mach numbers of coronal shock waves. We will review these recent developments by focusing on particle events that occurred between 2011 and 2015. These new techniques also provide the opportunity to investigate the enigmatic long-duration gamma ray events. Title: Circular-cylindrical flux-rope analytical model for Magnetic Clouds Authors: Nieves-Chinchilla, Teresa; Linton, Mark; Hidalgo, Miguel A.; Vourlidas, Angelos; Savani, Neel P.; Szabo, Adam; Farrugia, Charlie; Yu, Wenyuan Bibcode: 2016SPD....4710203N Altcode: We present an analytical model to describe magnetic flux-rope topologies. When these structures are observed embedded in Interplanetary Coronal Mass Ejections (ICMEs) with a depressed proton temperature, they are called Magnetic Clouds ( MCs). The model extends the circular-cylindrical concept of Hidalgo et al. (2000) by introducing a general form for the radial dependence of the current density. This generalization provides information on the force distribution inside the flux rope in addition to the usual parameters of MC geometrical information and orientation.The generalized model provides flexibility for implementation in 3D MHD simulations. Here, we evaluate its performance in the reconstruction of MCs in in-situ observations. Four Earth directed ICME events, observed by the Wind spacecraft, are used to validate the technique. The events are selected from the ICME Wind list with the magnetic obstacle boundaries chosen consistently with the magnetic fi eld and plasma in situ observations and with a new parameter (EPP, Electron Pitch angle distribution Parameter) which quantifies the bidirectionally of theplasma electrons. The goodness of the fit is evaluated with a single correlation parameter to enable comparative analysis of the events. In general, at first glance, the model fits the selected events very well. However, a detailed analysis of events with signatures of significant compression indicates the need to explore geometries other than the circular-cylindrical. Title: A Circular-cylindrical Flux-rope Analytical Model for Magnetic Clouds Authors: Nieves-Chinchilla, T.; Linton, M. G.; Hidalgo, M. A.; Vourlidas, A.; Savani, N. P.; Szabo, A.; Farrugia, C.; Yu, W. Bibcode: 2016ApJ...823...27N Altcode: We present an analytical model to describe magnetic flux-rope topologies. When these structures are observed embedded in Interplanetary Coronal Mass Ejections (ICMEs) with a depressed proton temperature, they are called Magnetic Clouds (MCs). Our model extends the circular-cylindrical concept of Hidalgo et al. by introducing a general form for the radial dependence of the current density. This generalization provides information on the force distribution inside the flux rope in addition to the usual parameters of MC geometrical information and orientation. The generalized model provides flexibility for implementation in 3D MHD simulations. Here, we evaluate its performance in the reconstruction of MCs in in situ observations. Four Earth-directed ICME events, observed by the Wind spacecraft, are used to validate the technique. The events are selected from the ICME Wind list with the magnetic obstacle boundaries chosen consistently with the magnetic field and plasma in situ observations and with a new parameter (EPP, the Electron Pitch angle distribution Parameter) which quantifies the bidirectionally of the plasma electrons. The goodness of the fit is evaluated with a single correlation parameter to enable comparative analysis of the events. In general, at first glance, the model fits the selected events very well. However, a detailed analysis of events with signatures of significant compression indicates the need to explore geometries other than the circular-cylindrical. An extension of our current modeling framework to account for such non-circular CMEs will be presented in a forthcoming publication. Title: An Analysis of Interplanetary Solar Radio Emissions Associated with a Coronal Mass Ejection Authors: Krupar, V.; Eastwood, J. P.; Kruparova, O.; Santolik, O.; Soucek, J.; Magdalenić, J.; Vourlidas, A.; Maksimovic, M.; Bonnin, X.; Bothmer, V.; Mrotzek, N.; Pluta, A.; Barnes, D.; Davies, J. A.; Martínez Oliveros, J. C.; Bale, S. D. Bibcode: 2016ApJ...823L...5K Altcode: 2016arXiv160604301K Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma that may cause severe geomagnetic storms if Earth directed. Here, we report a rare instance with comprehensive in situ and remote sensing observations of a CME combining white-light, radio, and plasma measurements from four different vantage points. For the first time, we have successfully applied a radio direction-finding technique to an interplanetary type II burst detected by two identical widely separated radio receivers. The derived locations of the type II and type III bursts are in general agreement with the white-light CME reconstruction. We find that the radio emission arises from the flanks of the CME and are most likely associated with the CME-driven shock. Our work demonstrates the complementarity between radio triangulation and 3D reconstruction techniques for space weather applications. Title: Multi-viewpoint Observations of a Widely distributed Solar Energetic Particle Event: The Role of EUV Waves and White-light Shock Signatures Authors: Kouloumvakos, A.; Patsourakos, S.; Nindos, A.; Vourlidas, A.; Anastasiadis, A.; Hillaris, A.; Sandberg, I. Bibcode: 2016ApJ...821...31K Altcode: On 2012 March 7, two large eruptive events occurred in the same active region within 1 hr from each other. Each consisted of an X-class flare, a coronal mass ejection (CME), an extreme-ultraviolet (EUV) wave, and a shock wave. The eruptions gave rise to a major solar energetic particle (SEP) event observed at widely separated (∼120°) points in the heliosphere. From multi-viewpoint energetic proton recordings we determine the proton release times at STEREO B and A (STB, STA) and the first Lagrange point (L1) of the Sun-Earth system. Using EUV and white-light data, we determine the evolution of the EUV waves in the low corona and reconstruct the global structure and kinematics of the first CME’s shock, respectively. We compare the energetic proton release time at each spacecraft with the EUV waves’ arrival times at the magnetically connected regions and the timing and location of the CME shock. We find that the first flare/CME is responsible for the SEP event at all three locations. The proton release at STB is consistent with arrival of the EUV wave and CME shock at the STB footpoint. The proton release time at L1 was significantly delayed compared to STB. Three-dimensional modeling of the CME shock shows that the particle release at L1 is consistent with the timing and location of the shock’s western flank. This indicates that at L1 the proton release did not occur in low corona but farther away from the Sun. However, the extent of the CME shock fails to explain the SEP event observed at STA. A transport process or a significantly distorted interplanetary magnetic field may be responsible. Title: Longitudinal Properties of a Widespread Solar Energetic Particle Event on 2014 February 25: Evolution of the Associated CME Shock Authors: Lario, D.; Kwon, R. -Y.; Vourlidas, A.; Raouafi, N. E.; Haggerty, D. K.; Ho, G. C.; Anderson, B. J.; Papaioannou, A.; Gómez-Herrero, R.; Dresing, N.; Riley, P. Bibcode: 2016ApJ...819...72L Altcode: We investigate the solar phenomena associated with the origin of the solar energetic particle (SEP) event observed on 2014 February 25 by a number of spacecraft distributed in the inner heliosphere over a broad range of heliolongitudes. These include spacecraft located near Earth; the twin Solar TErrestrial RElations Observatory spacecraft, STEREO-A and STEREO-B, located at ∼1 au from the Sun 153° west and 160° east of Earth, respectively; the MErcury Surface Space ENvironment GEochemistry and Ranging mission (at 0.40 au and 31° west of Earth); and the Juno spacecraft (at 2.11 au and 48° east of Earth). Although the footpoints of the field lines nominally connecting the Sun with STEREO-A, STEREO-B and near-Earth spacecraft were quite distant from each other, an intense high-energy SEP event with Fe-rich prompt components was observed at these three locations. The extent of the extreme-ultraviolet wave associated with the solar eruption generating the SEP event was very limited in longitude. However, the white-light shock accompanying the associated coronal mass ejection extended over a broad range of longitudes. As the shock propagated into interplanetary space it extended over at least ∼190° in longitude. The release of the SEPs observed at different longitudes occurred when the portion of the shock magnetically connected to each spacecraft was already at relatively high altitudes (≳2 R⊙ above the solar surface). The expansion of the shock in the extended corona, as opposite to near the solar surface, determined the SEP injection and SEP intensity-time profiles at different longitudes. Title: Numerical simulation of multiple CME-driven shocks in the month of 2011 September Authors: Wu, Chin-Chun; Liou, Kan; Vourlidas, Angelos; Plunkett, Simon; Dryer, Murray; Wu, S. T.; Socker, Dennis; Wood, Brian E.; Hutting, Lynn; Howard, Russell A. Bibcode: 2016JGRA..121.1839W Altcode: A global, three-dimensional (3-D) numerical simulation model has been employed to study the Sun-to-Earth propagation of multiple (12) coronal mass ejections (CMEs) and their associated shocks in September 2011. The inputs to the simulation are based on actual solar observations, which include the CME speeds, source locations, and photospheric magnetic fields. The simulation result is fine tuned with in situ solar wind data observations at 1 AU by matching the arrival time of CME-driven shocks. During this period three CME-driven interplanetary (IP) shocks induced three sizable geomagnetic storms on 9, 17, and 26 September, with Dst values reaching -69, -70, and -101 nT, respectively. These storm events signify the commencement of geomagnetic activity in the solar cycle 24. The CME propagation speed near the Sun (e.g., < 30 RS) has been widely used to estimate the interplanetary CME (ICME)/Shock arrival time at 1 AU. Our simulation indicates that the background solar wind speed, as expected, is an important controlling parameter in the propagation of IP shocks and CMEs. Prediction of the ICME/shock arrival time at 1 AU can be more problematic for slow (e.g., < 500 km s-1) than fast CMEs (>1000 km s-1). This is because the effect of the background solar wind is more pronounced for slow CMEs. Here we demonstrate this difficulty with a slow (400 km s-1) CME event that arrived at the Earth in 3 days instead of the predicted 4.3 days. Our results also demonstrate that a long period (a month in this case) of simulation may be necessary to make meaningful solar source geomagnetic storm associations. Title: Investigation of the Chromosphere-Corona Interface with the Upgraded Very High Angular Resolution Ultraviolet Telescope (VAULT2.0) Authors: Vourlidas, Angelos; Beltran, Samuel Tun; Chintzoglou, Georgios; Eisenhower, Kevin; Korendyke, Clarence; Feldman, Ronen; Moser, John; Shea, John; Johnson-Rambert, Mary; McMullin, Don; Stenborg, Guillermo; Shepler, Ed; Roberts, David Bibcode: 2016JAI.....540003V Altcode: Very high angular resolution ultraviolet telescope (VAULT2.0) is a Lyman-alpha (Lyα; 1216Å) spectroheliograph designed to observe the upper chromospheric region of the solar atmosphere with high spatial (<0.5‧‧) and temporal (8s) resolution. Besides being the brightest line in the solar spectrum, Lyα emission arises at the temperature interface between coronal and chromospheric plasmas and may, hence, hold important clues about the transfer of mass and energy to the solar corona. VAULT2.0 is an upgrade of the previously flown VAULT rocket and was launched successfully on September 30, 2014 from White Sands Missile Range (WSMR). The target was AR12172 midway toward the southwestern limb. We obtained 33 images at 8s cadence at arc second resolution due to hardware problems. The science campaign was a resounding success, with all space and ground-based instruments obtaining high-resolution data at the same location within the AR. We discuss the science rationale, instrument upgrades, and performance during the first flight and present some preliminary science results. Title: Waves and Magnetism in the Solar Atmosphere (WAMIS) Authors: Ko, Yuan-Kuen; Moses, John; Laming, John; Strachan, Leonard; Tun Beltran, Samuel; Tomczyk, Steven; Gibson, Sarah; Auchere, Frederic; Casini, Roberto; Fineschi, Silvano; Knoelker, Michael; Korendyke, Clarence; McIntosh, Scott; Romoli, Marco; Rybak, Jan; Socker, Dennis; Vourlidas, Angelos; Wu, Qian Bibcode: 2016FrASS...3....1K Altcode: Comprehensive measurements of magnetic fields in the solar corona have a long history as an important scientific goal. Besides being crucial to understanding coronal structures and the Sun’s generation of space weather, direct measurements of their strength and direction are also crucial steps in understanding observed wave motions. In this regard, the remote sensing instrumentation used to make coronal magnetic field measurements is well suited to measuring the Doppler signature of waves in the solar structures. In this paper, we describe the design and scientific values of the Waves and Magnetism in the Solar Atmosphere (WAMIS) investigation. WAMIS, taking advantage of greatly improved infrared filters and detectors, forward models, advanced diagnostic tools and inversion codes, is a long-duration high-altitude balloon payload designed to obtain a breakthrough in the measurement of coronal magnetic fields and in advancing the understanding of the interaction of these fields with space plasmas. It consists of a 20 cm aperture coronagraph with a visible-IR spectro-polarimeter focal plane assembly. The balloon altitude would provide minimum sky background and atmospheric scattering at the wavelengths in which these observations are made. It would also enable continuous measurements of the strength and direction of coronal magnetic fields without interruptions from the day-night cycle and weather. These measurements will be made over a large field-of-view allowing one to distinguish the magnetic signatures of different coronal structures, and at the spatial and temporal resolutions required to address outstanding problems in coronal physics. Additionally, WAMIS could obtain near simultaneous observations of the electron scattered K-corona for context and to obtain the electron density. These comprehensive observations are not provided by any current single ground-based or space observatory. The fundamental advancements achieved by the near-space observations of WAMIS on coronal field would point the way for future ground based and orbital instrumentation. Title: Global magnetohydrodynamic simulation of the 15 March 2013 coronal mass ejection event—Interpretation of the 30-80 MeV proton flux Authors: Wu, Chin-Chun; Liou, Kan; Vourlidas, Angelos; Plunkett, Simon; Dryer, Murray; Wu, S. T.; Mewaldt, Richard A. Bibcode: 2016JGRA..121...56W Altcode: The coronal mass ejection (CME) event on 15 March 2013 is one of the few solar events in Cycle 24 that produced a large solar energetic particle (SEP) event and severe geomagnetic activity. Observations of SEP from the ACE spacecraft show a complex time-intensity SEP profile that is not easily understood with current empirical SEP models. In this study, we employ a global three-dimensional (3-D) magnetohydrodynamic (MHD) simulation to help interpret the observations. The simulation is based on the H3DMHD code and incorporates extrapolations of photospheric magnetic field as the inner boundary condition at a solar radial distance (r) of 2.5 solar radii. A Gaussian-shaped velocity pulse is imposed at the inner boundary as a proxy for the complex physical conditions that initiated the CME. It is found that the time-intensity profile of the high-energy (>10 MeV) SEPs can be explained by the evolution of the CME-driven shock and its interaction with the heliospheric current sheet and the nonuniform solar wind. We also demonstrate in more detail that the simulated fast-mode shock Mach number at the magnetically connected shock location is well correlated (rcc ≥ 0.7) with the concurrent 30-80 MeV proton flux. A better correlation occurs when the 30-80 MeV proton flux is scaled by r-1.4(rcc = 0.87). When scaled by r-2.8, the correlation for 10-30 MeV proton flux improves significantly from rcc = 0.12 to rcc = 0.73, with 1 h delay. The present study suggests that (1) sector boundary can act as an obstacle to the propagation of SEPs; (2) the background solar wind is an important factor in the variation of IP shock strength and thus plays an important role in manipulation of SEP flux; (3) at least 50% of the variance in SEP flux can be explained by the fast-mode shock Mach number. This study demonstrates that global MHD simulation, despite the limitation implied by its physics-based ideal fluid continuum assumption, can be a viable tool for SEP data analysis. Title: The Major Geoeffective Solar Eruptions of 2012 March 7: Comprehensive Sun-to-Earth Analysis Authors: Patsourakos, S.; Georgoulis, M. K.; Vourlidas, A.; Nindos, A.; Sarris, T.; Anagnostopoulos, G.; Anastasiadis, A.; Chintzoglou, G.; Daglis, I. A.; Gontikakis, C.; Hatzigeorgiu, N.; Iliopoulos, A. C.; Katsavrias, C.; Kouloumvakos, A.; Moraitis, K.; Nieves-Chinchilla, T.; Pavlos, G.; Sarafopoulos, D.; Syntelis, P.; Tsironis, C.; Tziotziou, K.; Vogiatzis, I. I.; Balasis, G.; Georgiou, M.; Karakatsanis, L. P.; Malandraki, O. E.; Papadimitriou, C.; Odstrčil, D.; Pavlos, E. G.; Podlachikova, O.; Sandberg, I.; Turner, D. L.; Xenakis, M. N.; Sarris, E.; Tsinganos, K.; Vlahos, L. Bibcode: 2016ApJ...817...14P Altcode: During the interval 2012 March 7-11 the geospace experienced a barrage of intense space weather phenomena including the second largest geomagnetic storm of solar cycle 24 so far. Significant ultra-low-frequency wave enhancements and relativistic-electron dropouts in the radiation belts, as well as strong energetic-electron injection events in the magnetosphere were observed. These phenomena were ultimately associated with two ultra-fast (>2000 km s-1) coronal mass ejections (CMEs), linked to two X-class flares launched on early 2012 March 7. Given that both powerful events originated from solar active region NOAA 11429 and their onsets were separated by less than an hour, the analysis of the two events and the determination of solar causes and geospace effects are rather challenging. Using satellite data from a flotilla of solar, heliospheric and magnetospheric missions a synergistic Sun-to-Earth study of diverse observational solar, interplanetary and magnetospheric data sets was performed. It was found that only the second CME was Earth-directed. Using a novel method, we estimated its near-Sun magnetic field at 13 R⊙ to be in the range [0.01, 0.16] G. Steep radial fall-offs of the near-Sun CME magnetic field are required to match the magnetic fields of the corresponding interplanetary CME (ICME) at 1 AU. Perturbed upstream solar-wind conditions, as resulting from the shock associated with the Earth-directed CME, offer a decent description of its kinematics. The magnetospheric compression caused by the arrival at 1 AU of the shock associated with the ICME was a key factor for radiation-belt dynamics. Title: Modeling AWSoM CMEs with EEGGL: A New Approach for Space Weather Forecasting Authors: Jin, M.; Manchester, W.; van der Holst, B.; Sokolov, I.; Toth, G.; Vourlidas, A.; de Koning, C. A.; Gombosi, T. I. Bibcode: 2015AGUFMSH43C..02J Altcode: The major source of destructive space weather is coronal mass ejections (CMEs). However, our understanding of CMEs and their propagation in the heliosphere is limited by the insufficient observations. Therefore, the development of first-principals numerical models plays a vital role in both theoretical investigation and providing space weather forecasts. Here, we present results of the simulation of CME propagation from the Sun to 1AU by combining the analytical Gibson & Low (GL) flux rope model with the state-of-art solar wind model AWSoM. We also provide an approach for transferring this research model to a space weather forecasting tool by demonstrating how the free parameters of the GL flux rope can be prescribed based on remote observations via the new Eruptive Event Generator by Gibson-Low (EEGGL) toolkit. This capability allows us to predict the long-term evolution of the CME in interplanetary space. We perform proof-of-concept case studies to show the capability of the model to capture physical processes that determine CME evolution while also reproducing many observed features both in the corona and at 1 AU. We discuss the potential and limitations of this model as a future space weather forecasting tool. Title: Synthetic White-light Imagery for the Wide-field Imager for Solar Probe Plus (WISPR) Authors: Liewer, P. C.; Thernisien, A. F.; Vourlidas, A.; Howard, R.; DeForest, C. E.; DeJong, E.; Desai, A. Bibcode: 2015AGUFMSH31C2426L Altcode: The Solar Probe Plus trajectory, approaching within 10 solar radii, will enable the white light imager, WISPR, to fly through corona features now only imaged remotely. The dependency of the Thomson scattering on the imaging geometry (distance and angle from the Sun) dictates that the outer WISPR telescope will be sensitive to the emission from plasma close to the spacecraft, in contrast to the situation for imaging from Earth orbit. Thus WISPR will be the first 'local' imager providing a crucial link between the large-scale corona and SPP's in-situ measurements. The high speed at perihelion will provide tomographic-like views of coronal structures at ≤1° resolution. As SPP approaches perihelion, WISPR, with a 95° radial by 58° transverse field of view, will resolve the fine-scale structure with high spatial resolution. To prepare for this unprecedented viewing of the structure of the inner corona, we are creating synthetic white light images and animations from the WISPR viewpoint using the white-light ray-tracing package developed at NRL (available through SolarSoft). We will present simulated observations of multi-strand models of coronal streamers and flux ropes of various size and make comparisons with views from Earth, Solar Orbiter and SPP. Analysis techniques for WISPR images will also be discussed. Title: Using Multiple-viewpoint Observations to Determine the Interaction of Three Coronal Mass Ejections Observed on 2012 March 5 Authors: Colaninno, Robin C.; Vourlidas, Angelos Bibcode: 2015ApJ...815...70C Altcode: We examine the interaction of three coronal mass ejections (CMEs) that took place on 2012 March 5 at heights less than 20 R ⊙ in the corona. We used a forward fitting model to reconstruct the three-dimensional trajectories and kinematics of the CMEs and determine their interaction in the observations from three viewpoints: Solar and Heliospheric Observatory (SOHO), STEREO-A, and STEREO-B. The first CME (CME-1), a slow-rising eruption near disk center, is already in progress at 02:45 UT when the second CME (CME-2) erupts from AR 11429 on the east limb. These two CMEs are present in the corona not interacting when a third CME (CME-3) erupts from AR 11429 at 03:34 UT. CME-3 has a constant velocity of 1456[±31] km s-1 and drives a shock that is observed as a halo from all viewpoints. We find that the shock driven by CME-3 passed through CME-1 with no observable change in the geometry, trajectory, or velocity of CME-1. However, the elevated temperatures detected in situ when CME-1 reached Earth indicate that the plasma inside CME-1 may have been heated by the passage of the shock. CME-2 is accelerated by CME-3 to more than twice its initial velocity and remains a separate structure ahead of the CME-3 front. CME-2 is deflected 24° northward by CME-3 for a total deflection of 40° from its source region. These results suggest that the collision of CME-2 and CME-3 is superelastic. This work demonstrates the capability and utility of fitting forward models to complex and interacting CMEs observed in the corona from multiple viewpoints. Title: A STEREO/SECCHI COR2 Catalog of CME Properties Built via a 'Hybrid' (manual-automatic) Event Detection and Measurement Technique Authors: Balmaceda, L. A.; Vourlidas, A.; Stenborg, G.; Dal Lago, A. Bibcode: 2015AGUFMSH21B2409B Altcode: Catalogs of Coronal Mass Ejection (CME) properties are an efficient and popular way to research the CME phenomenon. Up to now, all CME catalogs were based on observations from a single viewpoint and hence subject to the same projection effects. However, simultaneous CME observations from the two vantage points of the STEREO/SECCHI coronagraphs raises several issues: Is a CME always visible in both telescopes? Does it look the same, etc? To answer these questions, we compiled a cross-linked STEREO COR2 A/B catalog. First, we built, by visual inspection, a preliminary list of CME events observed by each of the two COR2 instruments, starting in 2007. The CME detection and tracking is carried out by a state-of-the-art supervised image segmentation technique named CORSET. Using a supervised technique, we seek to overcome the intrinsic caveats that both fully automated and fully manual methodologies exhibit, in particular when dealing with a bi-segmentation problem where the features of interest show different intensity levels, morphologies, and texture embedded in an ever-changing noisy background. We have successfully applied CORSET to about 30% of the total number of events in our list. The catalog contains a comprehensive list of the temporal evolution of the relevant morphological, kinematical, and dynamical properties of the CMEs uniquely identified and cross-referenced in both datasets. Here, we briefly review the technique, and present the first results on the analysis of the main characteristics of this set of CMEs throughout the whole period of the mission. Title: Observational Evidence for High-Mach Number Regime of Coronal Shock Waves During Powerful Solar Particle Events Authors: Rouillard, A. P.; Illya, P.; Zucca, P.; Tylka, A. J.; Vainio, R. O.; Vourlidas, A. Bibcode: 2015AGUFMSH32B..03R Altcode: Identifying the physical mechanisms that produce the most energetic particles is a long-standing observational and theoretical challenge in astrophysics. Strong shock waves have been proposed as efficient accelerators both in the solar physics and astrophysical contexts via various acceleration mechanisms. The proposed processes rely on shock waves being super-critical or moving several times faster than the characteristic speed of the medium they propagate through (a high MA). Using recent imaging of the NASA STEREO, SOHO and SDO spacecraft, we provide the first observations of the time-dependent 3-dimensional distribution of the expansion speed and MA of a coronal shock wave. These observations show that the high-energy particles measured near Earth are produced at the time of the sharp rise in the shock Mach number (>10) magnetically connected to Earth. These findings provide direct evidence to energetic particles being accelerated during the formation of a strong coronal shock. Using our new technique, we study the longitudinal spread and timing of a number of other energetic particle events during cycle 24. Title: Radio Triangulation of Type II Bursts Associated with a CME - CME Interaction Authors: Krupar, V.; Bothmer, V.; Davies, J. A.; Eastwood, J. P.; Forsyth, R. J.; Kruparova, O.; Magdalenic, J.; Maksimovic, M.; Santolik, O.; Soucek, J.; Vourlidas, A. Bibcode: 2015AGUFMSH53B2498K Altcode: Coronal Mass Ejections (CMEs) are large-scale magnetized plasma disturbances propagating through the corona and the interplanetary (IP) medium. Along their path, some CMEs can drive shock waves, which accelerate ions and electrons. These fast electrons can generate type II radio bursts at the local plasma frequency and/or its first harmonic. In this study we use data from the two STEREO spacecraft which carry both imaging and radio instruments with direction-finding capabilities allowing us to track energetic electrons responsible for radio bursts. We present an analysis of type II bursts observed on the November 29 - 30, 2013. The shock wave signatures were possibly generated by an interaction of two consecutive CMEs. We have investigated three time-frequency intervals when received radio waves were sufficiently intense for direction-finding analysis. The obtained positions of triangulated radio sources suggest that the CMEs propagate towards the STEREO-A. The IP shock associated with this event has been also observed in situ by the MESSENGER and STEREO-A spacecraft. Title: Modeling Magnetic Flux-Ropes Structures Authors: Nieves-Chinchilla, T.; Linton, M.; Hidalgo, M. A. U.; Vourlidas, A.; Savani, N.; Szabo, A.; Farrugia, C. J.; Yu, W. Bibcode: 2015AGUFMSH11B2388N Altcode: Flux-ropes are usually associated with magnetic structures embedded in the interplanetary Coronal Mass Ejections (ICMEs) with a depressed proton temperature (called Magnetic Clouds, MCs). However, small-scale flux-ropes in the solar wind are also identified with different formation, evolution, and dynamic involved. We present an analytical model to describe magnetic flux-rope topologies. The model is generalized to different grades of complexity. It extends the circular-cylindrical concept of Hidalgo et al. (2002) by introducing a general form for the radial dependence of the current density. This generalization provides information on the force distribution inside the flux rope in addition to the usual parameters of flux-rope geometrical information and orientation. The generalized model provides flexibility for implementation in 3-D MHD simulations. Title: Why is the Sun No Longer Accelerating Particles to High Energy in Solar Cycle 24? Authors: Mewaldt, R. A.; Cohen, C. M.; Li, G.; Mason, G. M.; Smith, C. W.; von Rosenvinge, T. T.; Vourlidas, A. Bibcode: 2015AGUFMSH33D..03M Altcode: Why is the Sun No Longer Accelerating Particles to High Energy in Solar Cycle 24?Measurements by ACE, STEREO, and GOES show that the number of large Solar Energetic Particle (SEP) events in solar cycle 24 is reduced by a factor of ~2 compared to this point of solar cycle 23, while the fluences of >10 MeV/nuc ions from H to Fe are reduced by factors ranging from ~4 to ~10. Compared to solar Cycle 22 and 23, the fluence of >100 MeV protons is reduced by factors of ~7 to ~10 in the current cycle. A common element of these observations is that the observed Cycle-24 energy spectra have "breaks" that suddenly steepen 2 to 4 times lower in energy/nucleon than in Cycle 23. We investigate the origin of these cycle-to-cycle spectral differences by evaluating possible factors that control the maximum energy of CME-shock-accelerated particles in the two cycles, including seed-particle densities of suprathermal ions, the interplanetary magnetic field strength and turbulence level, and properties of the associated CMEs. The effect of these conditions will be evaluated in the context of existing SEP acceleration models by comparing SEP data with simulations and with analytic evaluations of the maximum kinetic energy to which CME shocks can accelerate solar energetic ions from H to Fe. Understanding the properties that control the maximum kinetic energy of CME-shock accelerated particles has important implications for predicting future solar activity. Title: Longitudinal Properties of a Widespread Solar Energetic Particle Event on 2014 February 25: Evolution of the Parent CME and Associated Shock Authors: Lario, D.; Kwon, R. Y.; Papaioannou, A.; Dresing, N.; Raouafi, N. E.; Gomez-Herrero, R.; Ho, G. C.; Vourlidas, A.; Riley, P. Bibcode: 2015AGUFMSH33B2464L Altcode: We investigate the solar phenomena associated with the origin of the solar energetic particle (SEP) event observed on 2014 February 25 by a number of spacecraft distributed in the inner heliosphere over a broad range of heliolongitudes. These include a number of near-Earth spacecraft, the twin Solar TErrestrial RElations Observatory spacecraft, STEREO-A and STEREO-B, located at ~1 AU from the Sun 153 deg ahead and 160 deg behind Earth, respectively; the MErcury Surface Space ENvironment GEochemistry and Ranging (MESSENGER) mission (at 0.40 AU and 31 deg west of Earth), and the Juno spacecraft (at 2.11 AU and 48 deg east of Earth). Although the footpoints of the field lines nominally connecting the Sun with STEREO-A, STEREO-B and near-Earth spacecraft were quite distant one from each other, an intense Fe-rich SEP event with fast rising intensities was observed at all three locations. The extent of the Extreme UltraViolet (EUV) wave associated with the solar eruption generating the SEP event was very limited in longitude, but the white-light shock accompanying the associated coronal mass ejection (CME) extended over a broad range of longitudes. As the shock propagated into interplanetary space it extended over at least 190 deg in longitude when it arrived at ~1 AU. The release of the SEPs observed at different longitudes occurred when the shock associated with the CME was already high in the corona (>~2 solar radii above the solar surface). We argue that the expanding shock in the extended corona played a fundamental role in the injection of SEPs at different longitudes. Title: Open issues in connecting magnetospheric dynamics to their solar drivers Authors: Vourlidas, A. Bibcode: 2015AGUFMSH43C..01V Altcode: The inner heliospheric evolution of CMEs, the main drivers of Space Weather, is no longer a mystery, thanks to the STEREO observations. The initiation of these events can now be observed with cadence of tens of seconds with arc second resolution, thanks to SDO. The flow of energy required to power solar eruptions is beginning to be understood, thanks to Hinode and IRIS. Yet, there is relatively little progress in predicting the geoeffectiveness of a particular CME. Why is that? What are the issues that holding back progress in medium-term forecasting of Space Weather? I discuss some of the issues (e.g., Bz, drag) and possible mitigation strategies in this talk. Title: Heliospheric Imaging from SO and SPP: Linking the solar wind to its solar origins Authors: Vourlidas, A. Bibcode: 2015AGUFMSH24A..04V Altcode: Deciphering the complexities of the solar wind structure has been hampered by the 'disconnected' nature of the observations; imaging of the near-Sun corona, in-situ sampling at 1 AU. The STEREO observations closed this gap and contributed significantly in understanding the evolution of large scale transients. However, the solar wind origin and evolution, especially at small spatial scales, remains a mystery. Two upcoming missions, Solar Orbiter and Solar Probe Plus, are designed to address this problem head-on with comprehensive suites of remote sensing and in-situ instruments. Coronal and heliospheric imaging plays a crucial role in connecting the activity in the solar corona with the in-situ measurements. The SO and SPP telescopes image the large scale structures measured subsequently by their in-situ suites. Never before available, this tight coupling of white light imaging and in-situ instrumentation may be the key for understanding the solar wind. In this talk, I review the current ideas for linking hemispheric structures to their solar origin and discuss the opportunities for new science from the upcoming So and SPP missions. Title: Requirements for an Operational Coronagraph Authors: Howard, R.; Vourlidas, A.; Harrison, R. A.; Bisi, M. M.; Plunkett, S. P.; Socker, D. G.; Eyles, C. J.; Webb, D. F.; DeForest, C. E.; Davies, J. A.; Howard, T. A.; de Koning, C. A.; Gopalswamy, N.; Davila, J. M.; Tappin, J.; Jackson, B. V. Bibcode: 2015AGUFMSH14A..02H Altcode: Coronal mass ejections (CMEs) have been shown to be the major driver of the non-recurrent space weather events and geomagnetic storms. The utility of continuously monitoring such events has been very effectively demonstrated by the LASCO experiment on the SOHO mission. However SOHO is aging, having been launched 20 years ago on Dec 2, 1995. The STEREO mission, in which two spacecraft in orbits about the sun are drifting away from earth, has shown the utility of multiple viewpoints off the sun-earth line. Up to now the monitoring of CMES has been performed by scientific instruments such as LASCO and SECCHI with capabilities beyond those required to record the parameters that are needed to forecast the impact at earth. However, there is great interest within the US NOAA and the UK Met Office to launch operational coronagraphs to L1 and L5. An ad-hoc group was formed to define the requirements of the L5 coronagraph. In this paper we present some requirements that must be met by operational coronagraphs. The Office of Naval Research is gratefully acknowledged. Title: Observations and Analysis of the Non-Radial Propagation of Coronal Mass Ejections Near the Sun Authors: Liewer, Paulett; Panasenco, Olga; Vourlidas, Angelos; Colaninno, Robin Bibcode: 2015SoPh..290.3343L Altcode: 2015SoPh..tmp..177L The trajectories of coronal mass ejection (CME) are often observed to deviate from radial propagation from the source while within the coronagraph field of view (R<15 -30 Rsun). To better understand nonradial propagation within the corona, we first analyze the trajectories of five CMEs for which both the source and 3D trajectory (latitude, longitude, and velocity) can be well determined from solar imaging observations, primarily using observations from the twin Solar TErrestrial RElations Observatory (STEREO) spacecraft. Next we analyze the cause of any nonradial propagation using a potential field source surface (PFSS) model to determine the direction of the magnetic pressure forces exerted on the CME at various heights in the corona. In two cases, we find that the CME deviation from radial propagation primarily occurs before it reaches the coronagraph field of view (below 1.5 solar radii). Based on the observations and the magnetic pressure forces calculated from the PFSS model, we conclude that for these cases the deviation is the result of strong active-region fields causing an initial asymmetric expansion of the CME that gives rise to the apparent rapid deflection and nonradial propagation from the source. Within the limitations of the PFSS model, the magnetic fields for all five cases appear to guide the CMEs out of the corona through the weak-field region around the heliospheric current sheet even when the current sheet is inclined and warped. Title: Waves and Magnetism in the Solar Atmosphere (WAMIS) Authors: Strachan, L.; Ko, Y. -K.; Moses, J. D.; Laming, J. M.; Auchere, F.; Casini, R.; Fineschi, S.; Gibson, S.; Knoelker, M.; Korendyke, C.; Mcintosh, S.; Romoli, M.; Rybak, J.; Socker, D.; Tomczyk, S.; Vourlidas, A.; Wu, Q. Bibcode: 2015IAUS..305..121S Altcode: Magnetic fields in the solar atmosphere provide the energy for most varieties of solar activity, including high-energy electromagnetic radiation, solar energetic particles, flares, and coronal mass ejections, as well as powering the solar wind. Despite the fundamental role of magnetic fields in solar and heliospheric physics, there exist only very limited measurements of the field above the base of the corona. What is needed are direct measurements of not only the strength and orientation of the magnetic field but also the signatures of wave motions in order to better understand coronal structure, solar activity, and the role of MHD waves in heating and accelerating the solar wind. Fortunately, the remote sensing instrumentation used to make magnetic field measurements is also well suited to measure the Doppler signature of waves in the solar structures. We present here a mission concept for the Waves And Magnetism In the Solar Atmosphere (WAMIS) experiment which is proposed for a NASA long-duration balloon flight. Title: CME Propagation: Where does Aerodynamic Drag 'Take Over'? Authors: Sachdeva, Nishtha; Subramanian, Prasad; Colaninno, Robin; Vourlidas, Angelos Bibcode: 2015ApJ...809..158S Altcode: 2015arXiv150705199S We investigate the Sun-Earth dynamics of a set of eight well observed solar coronal mass ejections (CMEs) using data from the Solar Terrestrial Relations Observatory spacecraft. We seek to quantify the extent to which momentum coupling between these CMEs and the ambient solar wind (i.e., the aerodynamic drag) influences their dynamics. To this end, we use results from a 3D flux rope model fit to the CME data. We find that solar wind aerodynamic drag adequately accounts for the dynamics of the fastest CME in our sample. For the relatively slower CMEs, we find that drag-based models initiated below heliocentric distances ranging from 15 to 50 {R}⊙ cannot account for the observed CME trajectories. This is at variance with the general perception that the dynamics of slow CMEs are influenced primarily by solar wind drag from a few {R}⊙ onwards. Several slow CMEs propagate at roughly constant speeds above 15-50 {R}⊙ . Drag-based models initiated above these heights therefore require negligible aerodynamic drag to explain their observed trajectories. Title: Formation of Magnetic Flux Ropes during a Confined Flaring Well before the Onset of a Pair of Major Coronal Mass Ejections Authors: Chintzoglou, Georgios; Patsourakos, Spiros; Vourlidas, Angelos Bibcode: 2015ApJ...809...34C Altcode: 2015arXiv150701165C NOAA active region (AR) 11429 was the source of twin super-fast coronal mass ejections (CMEs). The CMEs took place within an hour from each other, with the onset of the first taking place in the beginning of 2012 March 7. This AR fulfills all the requirements for a “super active region” namely, Hale's law incompatibility and a δ-spot magnetic configuration. One of the biggest storms of Solar Cycle 24 to date ({D}{st}=-143 nT) was associated with one of these events. Magnetic flux ropes (MFRs) are twisted magnetic structures in the corona, best seen in ∼10 MK hot plasma emission and are often considered the core of erupting structures. However, their “dormant” existence in the solar atmosphere (i.e., prior to eruptions), is an open question. Aided by multi-wavelength observations by the Solar Dynamics Observatory (SDO) and by the Solar Terrestrial Relations Observatory (STEREO) and a nonlinear force-free model for the coronal magnetic field, our work uncovers two separate, weakly twisted magnetic flux systems which suggest the existence of pre-eruption MFRs that eventually became the seeds of the two CMEs. The MFRs could have been formed during confined (i.e., not leading to major CMEs) flaring and sub-flaring events which took place the day before the two CMEs in the host AR 11429. Title: How Common Are Hot Magnetic Flux Ropes in the Low Solar Corona? A Statistical Study of EUV Observations Authors: Nindos, A.; Patsourakos, S.; Vourlidas, A.; Tagikas, C. Bibcode: 2015ApJ...808..117N Altcode: 2015arXiv150703766N We use data at 131, 171, and 304 Å from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to search for hot flux ropes in 141 M-class and X-class solar flares that occurred at solar longitudes equal to or larger than 50°. Half of the flares were associated with coronal mass ejections. The goal of our survey is to assess the frequency of hot flux ropes in large flares irrespective of their formation time relative to the onset of eruptions. The flux ropes were identified in 131 Å images using morphological criteria and their high temperatures were confirmed by their absence in the cooler 171 and 304 Å passbands. We found hot flux ropes in 45 of our events (32% of the flares); 11 of them were associated with confined flares while the remaining 34 were associated with eruptive flares. Therefore almost half (49%) of the eruptive events involved a hot flux rope configuration. The use of supplementary Hinode X-Ray Telescope data indicates that these percentages should be considered as lower limits of the actual rates of occurrence of hot flux ropes in large flares. Title: An Investigation of the Causes of Solar-Cycle Variations in SEP Fluences and Composition Authors: Mewaldt, R.; Cohen, C.; Mason, G.; von Rosenvinge, T.; Li, G.; Smith, C. W.; Vourlidas, A. Bibcode: 2015ICRC...34...30M Altcode: 2015PoS...236...30M No abstract at ADS Title: Periodic Density Structures and the Origin of the Slow Solar Wind Authors: Viall, Nicholeen M.; Vourlidas, Angelos Bibcode: 2015ApJ...807..176V Altcode: The source of the slow solar wind has challenged scientists for years. Periodic density structures (PDSs), observed regularly in the solar wind at 1 AU, can be used to address this challenge. These structures have length scales of hundreds to several thousands of megameters and frequencies of tens to hundreds of minutes. Two lines of evidence indicate that PDSs are formed in the solar corona as part of the slow solar wind release and/or acceleration processes. The first is corresponding changes in compositional data in situ, and the second is PDSs observed in the inner Heliospheric Imaging data on board the Solar Terrestrial Relations Observatory (STEREO)/Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) suite. The periodic nature of these density structures is both a useful identifier as well as an important physical constraint on their origin. In this paper, we present the results of tracking periodic structures identified in the inner Heliospheric Imager in SECCHI back in time through the corresponding outer coronagraph (COR2) images. We demonstrate that the PDSs are formed around or below 2.5 solar radii—the inner edge of the COR2 field of view. We compute the occurrence rates of PDSs in 10 days of COR2 images both as a function of their periodicity and location in the solar corona, and we find that this set of PDSs occurs preferentially with a periodicity of ∼90 minutes and occurs near streamers. Lastly, we show that their acceleration and expansion through COR2 is self-similar, thus their frequency is constant at distances beyond 2.5 solar radii. Title: The Interaction of Three Coronal Mass Ejections Observed on 2012 March 5 from Multiple Viewpoints Authors: Colaninno, Robin C.; Vourlidas, Angelos Bibcode: 2015shin.confE.162C Altcode: We examined three CMEs that were observed together on 2012 March 5 in the corona at heights less than 20 Rsun. We analyzed observations from three viewpoints: Earth, STEREO-A and STEREO-B to reconstruct their three-dimensional (3D) geometry and kinematics and determine their interaction. The observations combined with our analysis show an initial slow raising CME (CME-1) that originated from a prominence eruption near the center of the solar disk as viewed from Earth. A second CME (CME-2) then erupts from an active region (AR) near the NE limb. These two CMEs are present in the corona not interacting when a third CME (CME-3) erupts from the same AR as CME-2. CME-3 is extremely impulsive and drives a shock that is observed as a halo from the all viewpoints. We find that the shock driven by CME-3 passed through CME-1 with no observable change in the geometry, trajectory, or velocity of CME-1. A possible signature of CME-1 in situ indicates that the plasma inside the flux rope was heated by the passage of the shock. CME-2 is accelerated by CME-3 to more than twice its initial velocity yet remains a separate structure ahead of the CME-3 front. CME-2 is deflect by CME-3 24 deg northward for a total deflection of 40 deg north of its SR. CME-3 interacts with both CME-1 and CME-2 with very different results due to the locations of their magnetic structures. CME-CME interactions such as these could have profound effects on the Earth-impact of such CMEs. Title: Predicting the magnetic vectors within coronal mass ejections arriving at Earth: 1. Initial architecture Authors: Savani, N. P.; Vourlidas, A.; Szabo, A.; Mays, M. L.; Richardson, I. G.; Thompson, B. J.; Pulkkinen, A.; Evans, R.; Nieves-Chinchilla, T. Bibcode: 2015SpWea..13..374S Altcode: 2015arXiv150202067S The process by which the Sun affects the terrestrial environment on short timescales is predominately driven by the amount of magnetic reconnection between the solar wind and Earth's magnetosphere. Reconnection occurs most efficiently when the solar wind magnetic field has a southward component. The most severe impacts are during the arrival of a coronal mass ejection (CME) when the magnetosphere is both compressed and magnetically connected to the heliospheric environment. Unfortunately, forecasting magnetic vectors within coronal mass ejections remain elusive. Here we report how, by combining a statistically robust helicity rule for a CME's solar origin with a simplified flux rope topology, the magnetic vectors within the Earth-directed segment of a CME can be predicted. In order to test the validity of this proof-of-concept architecture for estimating the magnetic vectors within CMEs, a total of eight CME events (between 2010 and 2014) have been investigated. With a focus on the large false alarm of January 2014, this work highlights the importance of including the early evolutionary effects of a CME for forecasting purposes. The angular rotation in the predicted magnetic field closely follows the broad rotational structure seen within the in situ data. This time-varying field estimate is implemented into a process to quantitatively predict a time-varying Kp index that is described in detail in paper II. Future statistical work, quantifying the uncertainties in this process, may improve the more heuristic approach used by early forecasting systems. Title: Investigating the Causes of Solar-Cycle Variations in Solar Energetic Particle Fluences and Composition Authors: Mewaldt, Richard; Cohen, Christina; Mason, Glenn M.; von Rosenvinge, Tycho; Li, Gang; Smith, Charles; Vourlidas, Angelos Bibcode: 2015TESS....140106M Altcode: Measurements with ACE, STEREO, and GOES show that the number of large Solar Energetic Particle (SEP) events in solar cycle 24 is reduced by a factor of ~2 compared to this point of cycle 23, while the fluences of >10 MeV/nuc ions from H to Fe are reduced by factors ranging from ~4 to ~10. We investigate the origin of these cycle-to-cycle differences by evaluating possible factors that include properties of the associated CMEs, seed particle densities, and the interplanetary magnetic field strength and turbulence levels. These properties will be evaluated in the context of existing SEP acceleration models. Title: Observations and Analysis of the Non-Radial Propagation of Coronal Mass Ejections Near the Sun Authors: Liewer, Paulett C.; Colaninno, Robin; Panasenco, Olga; Vourlidas, Angelos Bibcode: 2015TESS....111405L Altcode: Coronal Mass Ejection (CME) trajectories are often observed to deviate from radial propagation from the source while within the coronagraph fields-of-view (R < 15-30 Rsun). To better understand non-radial propagation within the corona, we analyze the trajectories of five CMEs for which both the source and 3-D trajectory can be well determined from solar imaging observations, primarily using observations from the twin Solar TErrestrial RElations Observatory (STEREO) spacecraft. A potential field source surface model is used to determine the direction of the magnetic pressure force exerted on the CMEs at various heights in the corona. One case shows the familiar gradual deflection of a polar crown filament CME towards the heliospheric current sheet and streamer belt by the large-scale coronal magnetic fields. In two cases, we find that strong active region fields cause an initial asymmetric expansion of the CME that gives rise to apparent rapid deflection and non-radial propagation from the source. For all five cases, within the limitations of the potential field source surface model, the coronal magnetic fields appear to guide the CMEs out through the weak field region around the heliospheric current sheet even when the current sheet is highly inclined and warped. Title: Are Halo-Like Solar Coronal Mass Ejections Merely a Matter of Geometric Projection Effect? Authors: Kwon, Ryun Young; Vourlidas, Angelos; Zhang, Jie Bibcode: 2015TESS....111406K Altcode: We investigated the physical nature of halo coronal mass ejections (CMEs) based on the stereoscopic observations from two STEREO Ahead and Behind (hereafter A and B) and SOHO spacecraft. There occurred 62 halo CMEs as observed by SOHO LASCO C2 for the three-year period from 2010 to 2012 during which the separation angles between SOHO and STEREOs were nearly 90 degrees. In such quadrature configuration, the coronagraphs of STEREOs, COR2-A and -B, showed the side view of those halo CMEs seen by C2. It has been widely believed that the halo appearance of a CME is caused by the geometric projection effect, i.e., a CME moves along the Sun-observer line. In other words, it would appear as a non-halo CME if viewed from the side. However, to our surprise, we found that 41 out of 62 events (66%) were observed as halo CMEs by all coronagraphs. This result suggests that a halo CME is not only a matter of the propagating direction. In addition, we show that a CME propagating normal to the line of sight can be observed as a halo CME due to the associated fast magnetosonic wave or shock front. We conclude that the apparent width of CMEs, especially halos or partial halos is driven by the existence, and the extent, of the associated waves or shocks and does not represent an accurate measure of the CME ejecta size. This effect needs to be taken into careful consideration in Space Weather predictions and modeling efforts. Title: Current STEREO Status on the Far Side of the Sun Authors: Thompson, William T.; Gurman, Joseph; Ossing, Daniel; Luhmann, Janet; Curtis, David; Schroeder, Peter; Mewaldt, Richard; Davis, Andrew; Wortman, Kristin; Russell, Christopher; Galvin, Antoinette; Kistler, Lynn; Ellis, Lorna; Howard, Russell; Vourlidas, Angelos; Rich, Nathan; Hutting, Lynn; Maksimovic, Milan; Bale, Stuart D.; Goetz, Keith Bibcode: 2015TESS....140205T Altcode: The current positions of the two STEREO spacecraft on the opposite side of the Sun from Earth (superior solar conjunction) has forced some significant changes in the spacecraft and instrument operations. No communications are possible when the spacecraft is within 2 degrees of the Sun, requiring that the spacecraft be put into safe mode until communications can be restored. Unfortunately, communications were lost with the STEREO Behind spacecraft on October 1, 2014, during testing for superior solar conjunction operations. We will discuss what is known about the causes of loss of contact, the steps being taken to try to recover the Behind spacecraft, and what has been done to prevent a similar occurrence on STEREO Ahead.We will also discuss the effect of being on the far side of the Sun on the science operations of STEREO Ahead. Starting on August 20, 2014, the telemetry rate from the STEREO Ahead spacecraft has been tremendously reduced due to the need to keep the temperature of the feed horn on the high gain antenna below acceptable limits. However, the amount of telemetry that can be brought down has been highly reduced. Even so, significant science is still possible from STEREO's unique position on the solar far side. We will discuss the science and space weather products that are, or will be, available from each STEREO instrument, when those products will be available, and how they will be used. Some data, including the regular space weather beacon products, are brought down for an average of a few hours each day during the daily real-time passes, while the in situ and radio beacon data are being stored on the onboard recorder to provide a continuous 24-hour coverage for eventual downlink once the spacecraft is back to normal operations. Title: Earth-directed ICME magnetic field configurations Authors: Nieves-Chinchilla, Teresa; Vourlidas, Angelos; Szabo, Adam; Savani, Neel; Mays, M. Leila; Hidalgo, Miguel Angel; Wenyuan, Yu Bibcode: 2015TESS....121004N Altcode: It is known that the geoeffectiveness of interplanetary coronal mass ejections (ICMEs) depends on their magnetic field configuration. However, it remains unclear how the ICME interactions with the solar wind or other solar transient structures affect their magnetic configuration through, say, distortion of their cross-section, or deformation of their front. Obviously, precise space weather forecasting is depended on precise understanding of the evolution of the ICME internal magnetic topology.The goal of this study is to identify the ambient solar wind parameters that affect the flux-rope geometry and magnetic field configuration. Title: Investigation of a failed Filament Eruption During the VAULT2.0 Campaign Observations Authors: Chintzoglou, Georgios; Vourlidas, Angelos; Tun-Beltran, Samuel; Stenborg, Guillermo Bibcode: 2015TESS....130217C Altcode: We report the first results from an observing campaign in support of the VAULT2.0 sounding rocket launch on September 30, 2014. VAULT2.0 is a Lya (1216Å) spectroheliograph capable of 0.4” (~300 km) spatial resolution. The objective of the VAULT2.0 project is the study of the chromosphere-corona interface. VAULT2.0 observations probe temperatures between 10000 and 50000 K, a regime not accessible by Hinode or SDO. Lyα observations are, therefore, ideal, for filling in this gap. The observing campaign was closely coordinated with the Hinode and IRIS missions. Several ground-based observatories also provided important observations (IBIS, BBSO, SOLIS). Taking advantage of this simultaneous multi-wavelength coverage of target AR 12172 we are able to perform a detailed investigation on a failed eruption of a Magnetic Flux Rope-like structure that was recorded in the joint observations, starting before VAULT2.0's flight. Title: Are Halo-like Solar Coronal Mass Ejections Merely a Matter of Geometric Projection Effects? Authors: Kwon, Ryun-Young; Zhang, Jie; Vourlidas, Angelos Bibcode: 2015ApJ...799L..29K Altcode: We investigated the physical nature of halo coronal mass ejections (CMEs) based on the stereoscopic observations from the two STEREO spacecraft, Ahead and Behind (hereafter A and B), and the SOHO spacecraft. Sixty-two halo CMEs occurred as observed by SOHO LASCO C2 for the three-year period from 2010 to 2012 during which the separation angles between SOHO and STEREO were nearly 90°. In such quadrature configuration, the coronagraphs of STEREO, COR2-A and -B, showed the side view of those halo CMEs seen by C2. It has been widely believed that the halo appearance of a CME is caused by the geometric projection effect, i.e., a CME moves along the Sun-observer line. In other words, it would appear as a non-halo CME if viewed from the side. However, to our surprise, we found that 41 out of 62 events (66%) were observed as halo CMEs by all coronagraphs. This result suggests that a halo CME is not just a matter of the propagating direction. In addition, we show that a CME propagating normal to the line of sight can be observed as a halo CME due to the associated fast magnetosonic wave or shock front. We conclude that the apparent width of CMEs, especially halos or partial halos is driven by the existence and the extent of the associated waves or shocks and does not represent an accurate measure of the CME ejecta size. This effect needs to be taken into careful consideration in space weather predictions and modeling efforts. Title: The VAULT2.0 Observing Campaign: A Comprehensive Investigation of the Chromosphere-Corona Interface at Sub-arcsecond scales Authors: Vourlidas, A.; Korendyke, C.; Tun-Beltran, S. D.; Ugarte-Urra, I.; Morrill, J. S.; Warren, H. P.; Young, P.; De Pontieu, B.; Gauzzi, G.; Reardon, K. Bibcode: 2014AGUFMSH41C4155V Altcode: We report the first results from an observing campaign in support of the VAULT2.0 sounding rocket launch on September 30, 2014. VAULT2.0 is a Lya (1216Å) spectroheliograph capable of 0.3" (~250 km) spatial resolution. The objective of the VAULT2.0 project is the study of the chromosphere-corona interface. This interface has acquired renewed emphasis over the last few years, thanks to high-resolution observations from Hinode/SOT and EIS instruments and the Lya imaging from the two VAULT flights. The observations have shown that the upper chromosphere may play a more important role in heating the corona and in affecting EUV observations that previously thought: (1) by supplying the mass via Type-II spicules and, (2) by absorbing coronal emission. Many of the required clues for further progress are located in sub-arcsecond structures with temperatures between 10000 and 50000 K, a regime not accessible by Hinode or SDO. Lyman-alpha observations are, therefore, ideal, for filling in this gap. The observing campaign in support of the VAULT2.0 is closely coordinated with the Hinode and IRIS missions to study the mass/energy flow from the chromosphere to the corona with joint observations of type-II spicules, and the magnetic connectivity of coronal loops using the full imaging and spectral capabilities of IRIS, Hinode and SDO. Several ground-based observatories also provide important observations (IBIS, BBSO, SOLIS). The VAULT2.0 project is funded by the NASA LCAS program. Title: Synthetic White-light Imagery for the Wide-field Imager for Solar Probe Plus (WISPR) Authors: Liewer, P. C.; Su, Y.; Vourlidas, A.; Thernisien, A. F.; Howard, R.; Hall, J. R.; DeJong, E. Bibcode: 2014AGUFMSH21B4101L Altcode: The Solar Probe Plus trajectory, approaching within 10 solar radii, will allow the white light imager, WISPR, to view the inner corona with unprecedented spatial resolution. WISPR, with a 95° radial by 58° transverse field of view, will image the fine-scale structure with arcminute-scale resolution. The dependency of the Thomson scattering on the imaging geometry (distance and angle from the Sun) dictates that WISPR will be very sensitive to the emission from plasma close to the spacecraft, in contrast to the situation for imaging from Earth orbit. Thus WISPR will be the first 'local' imager providing a crucial link between the large-scale corona and SPP's in-situ measurements. The high speed at perihelion will provide tomographic-like views of coronal structures. To prepare for this unprecedented viewing of the structure of the inner corona, we are creating synthetic white light images and animations from the WISPR viewpoint using the white-light ray-tracing package developed at NRL (available through SolarSoft). We will present results from multi-strand models of coronal streamers and currents sheets as well as images of coronal mass ejections as seen simultaneously from Earth, Solar Orbiter and SPP. Title: When the Sun Gets in the Way: Stereo Science Observations on the Far Side of the Sun Authors: Vourlidas, A.; Thompson, W. T.; Gurman, J. B.; Luhmann, J. G.; Curtis, D. W.; Schroeder, P. C.; Mewaldt, R. A.; Davis, A. J.; Wortman, K.; Russell, C. T.; Galvin, A. B.; Popecki, M.; Kistler, L. M.; Ellis, L.; Howard, R.; Rich, N.; Hutting, L.; Maksimovic, M.; Bale, S. D.; Goetz, K. Bibcode: 2014AGUFMSH53A4202V Altcode: With the two STEREO spacecraft on the opposite side of the Sun from Earth, pointing the high gain antenna at Earth means that it's also pointed very close to the Sun. This has resulted in unexpectedly high temperatures in the antenna feed horns on both spacecraft, and is forcing the mission operations team to take corrective action, starting in August 2014 for STEREO Ahead, and December 2014 for STEREO Behind. By off-pointing the antennas to use one of the lower power side lobes instead of the main lobe, the feed horn temperatures can be kept at a safe level while still allowing reliable communication with the spacecraft. However, the amount of telemetry that can be brought down will be highly reduced. Even so, significant science will still be possible from STEREO's unique position on the solar far side. We will discuss the science and space weather products that will be available from each STEREO instrument, when those products will be available, and how they will be used. Some data, including the regular space weather beacon products, will be brought down for an average of a few hours each day during the daily real-time passes, while the in situ and radio beacon data will be stored on the onboard recorder to provide a continuous 24-hour coverage for eventual downlink once the spacecraft is back to normal operations. Title: Evolution of Three Geoeffective Shock-CME pairs in September 2011 Authors: Wu, S. T.; Liou, K.; Wu, C. C.; Vourlidas, A.; Plunkett, S. P.; Dryer, Ph D., M.; Socker, D. G.; Wood, B. E. Bibcode: 2014AGUFMSH43A4179W Altcode: Three sizable geomagnetic storms were recorded in September 2011. The intensity of geomagnetic storms (Dstmin: minimum Dst) are -69, -70, -101 nT and the storms' onset time are September 9, 17, and 26, respectively. A sequence of coronal mass ejections (CMEs) correspond causing these three geomagnetic storms. The severe geomagnetic storm (Dstmin < -100 nT) on 26 September was caused by a couple of CMEs erupted on 24 September. Wind spacecraft detected an interplanetary (IP) shock at ~11:18 UT on 26 September but no magnetic cloud was recorded behind the IP shock. A severe geomagnetic storm was recorded ~6 hours after the IP shock passed through the Wind spacecraft. Geomagnetic index (Dst) dropped to -101 nT which was due to the z-component of interplanetary magnetic field (Bz) dropped to ~ -20 nT. Both September 9th and 17th IP shocks have followed by a magnetic hole with a very sharp change in both magnetic field and density. Inside the magnetic holes, both solar wind velocity and temperature are almost constant, and the peak of density and dip of magnetic field occurred near the centre of the magnetic field hole. Peak densities were close to ~94, ~60 cm-3 near the centre of the hole on Sept. 09, 17, respectively. A global, three-dimensional (3-D) magnetohydrodynamic (MHD) numerical model with inputs based on actual solar observations (e.g., velocity of the CME) is used to simulate the responses of the 3-D heliosphere. These velocity pulses are deduced from STEREO-A which are used to minic the initiation of the observed 15 CMEs at lower boundary (2.5 Rs) to investigate the CME evolution from the Sun to the Earth during September 03-30, 2011.Simulated background solar wind parameters (velocity, density, magnetic field, and temperature) are matched well with 1 AU in-situ measurement from Wind spacecraft. In summary, we have successfully simulated these CMEs' evolution and the IP shocks arrival time at 1 AU by comparison with Wind measurement.It is found that background solar wind is an important factor on the propagation of IP shocks and CMEs. The simulation results are also useful for explaining "How were the magnetic holes formed behind the IP shocks?" *Work of CCW was supported by ONR 6.1 program Title: Cycle-to-Cycle Variations in the Properties of Solar Energetic Particle Events Authors: Mewaldt, R. A.; Cohen, C. M.; Mason, G. M.; von Rosenvinge, T. T.; Vourlidas, A. Bibcode: 2014AGUFMSH41D..09M Altcode: We report on a cycle-to-cycle survey of Solar Energetic Particle (SEP) events using data from ACE, STEREO, GOES, SOHO, and other near-Earth spacecraft. We have compared the characteristics of solar proton events during cycles 21 - 24, including peak-intensity, fluence, spectral and compositional signatures. As of July 2014, a total of 72 cycle-24 events have met the NOAA criterion >10 protons/cm2-sr-s for >10 MeV proton intensities at either GOES, STEREO-A, or STEREO-B, including 33 at GOES. Most were observed at multiple longitudes. Compared to the first 5.7 years of cycles 22 and 23 the number of near-Earth GOES-class SEP events in cycle 24 is reduced by ~40%, and the total fluence of >10 MeV protons is a factor of ~4 lower. At >100 MeV the cycle 23 fluence is lower by a factor of >7. The two STEREOs make it possible to test whether Earth was simply in an anomalous location. There are also significant compositional differences between cycles 23 and 24 in abundance ratios such as Fe/O and Fe/H. We discuss factors that may have affected the intensity, spectra, and composition of SEPs during cycle 23, including the interplanetary magnetic field and solar wind properties, CME and shock properties, and seed particle abundances. Title: Observations of Near-Sun Turbulent Density Fluctuations with the Wide Field Imager for Solar Probe Plus (WISPR) Authors: Plunkett, S. P.; Howard, R.; Vourlidas, A.; Korendyke, C.; Rich, N.; Thernisien, A. F.; Wang, D.; Liewer, P. C. Bibcode: 2014AGUFMSH32A..05P Altcode: The trajectory of Solar Probe Plus (SPP) as it transits through the solar corona with a perihelion of < 10 Rs will allow much higher contrast observations of small-scale density fluctuations with higher cadence than is possible from 1 AU. The WISPR instrument will implement a high-cadence mode (up to 1 second) in which it will obtain images of the corona and inner heliosphere with high spatial resolution over a restricted field of view around specified regions of interest. Two-dimensional power spectra of the density fluctuations can then be constructed with variable cadences for direct comparison to similar spectra obtained by in-situ instruments on SPP and Solar Orbiter (SO). WISPR will provide density power spectra at or below the spectral break between inertial and injection scales, even at the closest perihelion approach, for different coronal structures. When combined with tomographic information from synoptic images, the WISPR turbulence program will be a major enhancement to the turbulence measurements from the SPP and SO in-situ instruments resulting in a much more robust understanding of the near-Sun turbulence. We will present details of the planned observations and will discuss the coordinated science objectives that can be addressed using these observations. Title: Open Issues on CME Propagation in the Inner Heliosphere Authors: Vourlidas, A. Bibcode: 2014AGUFMSH42A..07V Altcode: Over the last few years, the SECCHI imagers aboard the STEREO mission have revealed the inner heliosphere in unprecedented detail. We can image and track CMEs from their birth in the solar corona to their impact on Earth and beyond. We can routinely compare imaging observations with in-situ measurements of the same event and at the same time. It is tempting to think that the understanding the evolution of CMEs in the inner heliosphere should be straighforward. This is not the case. Although the prediction of the time of arrival of CMEs at Earth has improved somewhat, there are many outliers. Predicting the speed of the transient at Earth remain hit-or-miss. Clearly, the details of the propagation of CMEs in the inner heliosphere still elude us, preventing progress in Space Weather forecasting amongh other things. In this talk, I review the open issues, as revealed by joint imaging and in-situ analyses, and discuss strategies for making progress on the subject. Title: Global MHD Simulation of the Coronal Mass Ejection on 2011 March 7: from Chromosphere to 1 AU Authors: Jin, M.; Manchester, W.; van der Holst, B.; Sokolov, I.; Toth, G.; Vourlidas, A.; de Koning, C. A.; Gombosi, T. I. Bibcode: 2014AGUFMSH43A4176J Altcode: Performing realistic simulations of solar eruptions and validating those simulations with observations are important goals in order to achieve accurate space weather forecasts. Here, we perform and analyze results of a global magnetohydrodyanmic (MHD) simulation of the fast coronal mass ejection (CME) that occurred on 2011 March 7. The simulation is made using the newly developed Alfven Wave Solar Model (AWSoM), which describes the background solar wind starting from the upper chromosphere and expands to 24 Rs. Coupling of AWSoM to an inner heliosphere (IH) model with the Space Weather Modeling Framework (SWMF) extends the total domain beyond the orbit of Earth. Physical processes included in the model are multi-species thermodynamics, electron heat conduction (both collisional and collisionless formulations), optically thin radiative cooling, and Alfven-wave pressure that accelerates the solar wind. The Alfven-wave description is physically consistent, including non-WKB reflection and physics-based apportioning of turbulent dissipative heating to both electrons and protons. Within this model, we initiate the CME by using the Gibson-Low (GL) analytical flux rope model and follow its evolution for days, in which time it propagates beyond 1 AU. A comprehensive validation study is performed using remote as well as in-situ observations from SDO, SOHO, STEREOA/B, and OMNI. Our results show that the new model can reproduce many of the observed features near the Sun (e.g., CME-driven EUV waves, deflection of the flux rope from the coronal hole, "double-front" in the white light images) and in the heliosphere (e.g., CME-CIR interaction, shock properties at 1 AU). The CME-driven shock arrival time is within 1 hour of the observed arrival time, and nearly all the in-situ parameters are correctly simulated, which suggests the global MHD model as a powerful tool for the space weather forecasting. Title: Coronal shocks properties and their associations with energetic particle events measured near 1AU. Authors: Rouillard, A. P.; Vourlidas, A.; Tylka, A. J.; Ng, C. K.; Cohen, C. M. Bibcode: 2014AGUFMSH43A4170R Altcode: We combine ultraviolet and white-light images obtained by the Solar Dynamics Observatory (SDO) and the Solar-Terrestrial Relations Observatory (STEREO) to track, in the lower corona, the spatial and temporal evolution of pressure waves and shocks associated with the onset of Coronal Mass Ejections (CMEs). We use ideal geometrical 3-D surfaces to follow with time the location of the global disturbance observed in EUV and white-light images. This fitting technique provides a tracking of the evolution of shocks from the Sun to 20 solar radii. We combine potential field source surface calculations with simple models of the distribution of interplanetary magnetic field lines in the interplanetary medium to determine the magnetic connectivity of the shock with spacecraft located near 1AU. We extract the 3-D shock velocity vector, the shock geometry and, by using empirical functions of temperature and density variations in the corona, the local Alfven speed at the point of magnetic connectivity with STEREO-A, STEREO-B and L1 spacecraft. The properties of the tracked coronal shocks are compared with the properties of SEPs measured in situ. We concentrate on the proton-rich events detected by the near-Earth spacecraft as well as the STEREO spacecraft from 2011 to 2014. We use the onset of solar energetic particle events (SEPs) to determine their release time near the Sun. We show that the shock speed at the point of magnetic connectivity is a determining factor for the intensity of the SEP measured in situ with a steep relation between coronal shock speed and SEP maximum intensity. This analysis naturally removes projection effects associated with single viewpoint analysis presented in previous studies. We discuss how the interplay between the radial dependence of the Alfven speed and the complex topology of magnetic field lines in the corona is likely to control the onset time of SEPs at 1AU. We discuss the successes and challenges faced when interpreting SEP events in terms of the speed and geometry of coronal shocks. Title: Earth-Directed ICME Magnetic Field Configurations Authors: Nieves-Chinchilla, T.; Szabo, A.; Vourlidas, A.; Savani, N.; Hidalgo, M. A. U.; Yu, W. Bibcode: 2014AGUFMSH23D..08N Altcode: It is known that the geoeffectiveness of interplanetary coronal mass ejections (ICMEs) depends on their magnetic field configuration. However, it remains unclear how the ICME interactions with the solar wind or other solar transient structures affect their magnetic configuration through, say, distortion of their cross-section, or deformation of their front. Obviously, precise space weather forecasting is depended on precise understanding of the evolution of the ICME internal magnetic topology. The goal of this study is to identify the ambient solar wind parameters that affect the flux-rope geometry and magnetic field configuration Title: An Unusual Heliospheric Plasma Sheet Crossing at 1 AU Authors: Wu, C. C.; Liou, K.; Vourlidas, A.; Lepping, R. P.; Wang, Y. M.; Plunkett, S. P.; Socker, D. G.; Wu, S. T. Bibcode: 2014AGUFMSH43A4166W Altcode: At 11:46UT on September 9, 2011, the Wind spacecraft encountered an interplanetary (IP) fast forward shock. The shock was followed almost immediately (~5 minutes) by a short duration (~35 minutes), extremely large density pulse with a density peak of ~100 cm-3. While a sharp increase in the solar wind density is typical of an IP shock downstream, the unusual large density increase prompts a further investigation. After a close examination of other in situ data from Wind, we find the density pulse was associated with (1) a spike in the plasma beta (ratio of thermal to magnetic pressure), (2) multiple sign changes in the azimuthal angle of magnetic field, (3) depressed magnetic field, (4) a small radial component of magnetic field, and (5) a large (>90 degrees) pitch-angle change in suprathermal electrons (>200 eV) across the density pulse. We conclude that the density pulse is the heliospheric plasma sheet and the estimated thickness is ~820,000km. The unusually large density pulse is likely to be a result of the shock compression from behind. This view is supported by our 3D magnetohydrodynamic simulation. The detailed result and implications will be discussed. *This work is supported partially by ONR 6.1 program Title: The CME event on 07 January 2014: Why was it a geomagnetic dud? Authors: Raouafi, N. E.; Colaninno, R. C.; Vourlidas, A.; Stenborg, G.; Lario, D.; Merkin, V. G. Bibcode: 2014AGUFMSH51E..05R Altcode: The X-class flare-associated CME event on 07 January 2014 originated from a large sunspot group near disk center and reached > 2000 km s-1 at its initial phases. In-situ measurements at 1 AU show a strong solar proton event. The CME was expected to cause a significant geomagnetic response. However, arriving at 1 AU the CME was significantly slower than expected (~500 km s-1) and was a complete dud in terms of geomagnetic activity. We present a comprehensive analysis of the CME using EUV and white light observations as well as in-situ measurements to understand why it was not geo-effective. We particularly study CME deflection caused by coronal holes and eventual interaction with other pre-existing and slower CMEs. Title: Forecasting the magnetic vectors within a CME at L1 by using solar observations. Authors: Savani, N.; Vourlidas, A.; Szabo, A.; Mays, M. L.; Evans, R. M.; Thompson, B. J.; Richardson, I. G.; Pulkkinen, A. A.; Nieves-Chinchilla, T. Bibcode: 2014AGUFMSH43B4213S Altcode: The direction of magnetic vectors within coronal mass ejections has important consequences to forecasting terrestrial behaviour, however forecasting these vectors remains predominately elusive. Here, we report that a simplified system is capable of replicating the broad field rotations seen within flux rope CMEs at L1 monitors. The predictions are performed under three main themes: 1) The majority of the field rotations can be simplified to the constant-alpha force-free (CAFF) flux model first implemented circa 1990. 2) The helicity will follow the Bothmer & Schwenn system that relies on a reliable helicity prediction of active regions during solar cycle. Which has been recently confirmed by Wang [2013 ApJ]. 3) The majority of the distortions, deflections and rotations will have already occurred within coronagraphic field of view, thereby allowing the creation of a projected "volume-of-influence" on the Sun, from which Earth's position relative to the CME can be estimated. This presentation will compare predicted results to the observations from 7 CME events and then estimate the sources of uncertainty. As an example, the difference in robust statistics from 2 solar cycles of CAFF model fittings for the field magnitude will be compared to estimates generated from simulated CME-sheaths within forecasting Enlil runs. The figure displays an example field vector forecast from the techniques employed above. Title: Waves and Magnetism in the Solar Atmosphere (WAMIS) Authors: Ko, Y. K.; Auchere, F.; Casini, R.; Fineschi, S.; Gibson, S. E.; Knoelker, M.; Korendyke, C.; Laming, J. M.; Mcintosh, S. W.; Moses, J. D.; Romoli, M.; Rybak, J.; Socker, D. G.; Strachan, L.; Tomczyk, S.; Vourlidas, A.; Wu, Q. Bibcode: 2014AGUFMSH53B4221K Altcode: Magnetic fields in the solar atmosphere provide the energy for most varieties of solar activity, including high-energy electromagnetic radiation, solar energetic particles, flares, and coronal mass ejections, as well as powering the solar wind. Despite the fundamental role of magnetic fields in solar and heliospheric physics, there exists only very limited measurements of the field above the base of the corona. What is needed are direct measurements of not only the strength and orientation of the magnetic field but also the signatures of wave motions in order to better understand coronal structure, solar activity and the role of MHD waves in heating and accelerating the solar wind. Fortunately, the remote sensing instrumentation used to make magnetic field measurements is also well suited for measuring the Doppler signature of waves in the solar structures. With this in mind, we are proposing the WAMIS (Waves and Magnetism in the Solar Atmosphere) investigation. WAMIS will take advantage of greatly improved infrared (IR) detectors, forward models, advanced diagnostic tools and inversion codes to obtain a breakthrough in the measurement of coronal magnetic fields and in the understanding of the interaction of these fields with space plasmas. This will be achieved with a high altitude balloon borne payload consisting of a coronagraph with an IR spectro-polarimeter focal plane assembly. The balloon platform provides minimum atmospheric absorption and scattering at the IR wavelengths in which these observations are made. Additionally, a NASA long duration balloon flight mission from the Antarctic can achieve continuous observations over most of a solar rotation, covering all of the key time scales for the evolution of coronal magnetic fields. With these improvements in key technologies along with experience gained from current ground-based instrumentation, WAMIS will provide a low-cost mission with a high technology readiness leve. Title: Periodic Density Structures and the Origin of the Slow Solar Wind Authors: Viall, N. M.; Vourlidas, A. Bibcode: 2014AGUFMSH21B4114V Altcode: Periodic density structures with length-scales of hundreds to several thousands of Mm and frequencies of tens to hundreds of minutes are observed regularly in the solar wind at 1 AU. These structures coexist with, but are not due to, fluctuations in the plasma resulting from the turbulent cascade. Two lines of evidence - one identifying corresponding changes in compositional data in situ, and another identifying periodic density structures in the inner Heliospheric Imaging data onboard the Solar Terrestrial Relations Observatory (STEREO)/ Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) suite - indicate that periodic density structures are formed in the solar corona as part of the slow solar wind release and/or acceleration processes. The periodic nature of these density structures is an important physical constraint on their origin. In this presentation, we present the results of tracking periodic structures identified in the SECCHI/HI1 images down through the corresponding SECCHI/COR2 images. We demonstrate that the periodic density structures are formed around or below 2.5 solar radii - the inner edge of the COR2 field of view. Further, we compute the occurrence rate of periodic density structures in 10 days of COR2 images as a function of location in the solar corona. We find that this set of periodic density structures occurs preferentially in relation to coronal streamers. Periodic density structures are tracers of solar wind origin and/or acceleration; this study is a pilot for the kinds of investigations that we can carry out with the better temporal and spatial resolution of the heliospheric imagers on Solar Orbiter and Solar Probe Plus. Title: Solar Sources of Interplanetary Coronal Mass Ejections During the Solar Cycle 23/24 Minimum Authors: Kilpua, E. K. J.; Mierla, M.; Zhukov, A. N.; Rodriguez, L.; Vourlidas, A.; Wood, B. Bibcode: 2014SoPh..289.3773K Altcode: 2014SoPh..tmp...92K We examine solar sources for 20 interplanetary coronal mass ejections (ICMEs) observed in 2009 in the near-Earth solar wind. We performed a detailed analysis of coronagraph and extreme ultraviolet (EUV) observations from the Solar Terrestrial Relations Observatory (STEREO) and Solar and Heliospheric Observatory (SOHO). Our study shows that the coronagraph observations from viewpoints away from the Sun-Earth line are paramount to locate the solar sources of Earth-bound ICMEs during solar minimum. SOHO/LASCO detected only six CMEs in our sample, and only one of these CMEs was wider than 120∘. This demonstrates that observing a full or partial halo CME is not necessary to observe the ICME arrival. Although the two STEREO spacecraft had the best possible configuration for observing Earth-bound CMEs in 2009, we failed to find the associated CME for four ICMEs, and identifying the correct CME was not straightforward even for some clear ICMEs. Ten out of 16 (63 %) of the associated CMEs in our study were "stealth" CMEs, i.e. no obvious EUV on-disk activity was associated with them. Most of our stealth CMEs also lacked on-limb EUV signatures. We found that stealth CMEs generally lack the leading bright front in coronagraph images. This is in accordance with previous studies that argued that stealth CMEs form more slowly and at higher coronal altitudes than non-stealth CMEs. We suggest that at solar minimum the slow-rising CMEs do not draw enough coronal plasma around them. These CMEs are hence difficult to discern in the coronagraphic data, even when viewed close to the plane of the sky. The weak ICMEs in our study were related to both intrinsically narrow CMEs and the non-central encounters of larger CMEs. We also demonstrate that narrow CMEs (angular widths ≤ 20∘) can arrive at Earth and that an unstructured CME may result in a flux rope-type ICME. Title: Self-similar Expansion of Solar Coronal Mass Ejections: Implications for Lorentz Self-force Driving Authors: Subramanian, Prasad; Arunbabu, K. P.; Vourlidas, Angelos; Mauriya, Adwiteey Bibcode: 2014ApJ...790..125S Altcode: 2014arXiv1406.0286S We examine the propagation of several coronal mass ejections (CMEs) with well-observed flux rope signatures in the field of view of the SECCHI coronagraphs on board the STEREO satellites using the graduated cylindrical shell fitting method of Thernisien et al. We find that the manner in which they propagate is approximately self-similar; i.e., the ratio (κ) of the flux rope minor radius to its major radius remains approximately constant with time. We use this observation of self-similarity to draw conclusions regarding the local pitch angle (γ) of the flux rope magnetic field and the misalignment angle (χ) between the current density J and the magnetic field B. Our results suggest that the magnetic field and current configurations inside flux ropes deviate substantially from a force-free state in typical coronagraph fields of view, validating the idea of CMEs being driven by Lorentz self-forces. Title: Solar Energetic Particle Events in Different Types of Solar Wind Authors: Kahler, S. W.; Vourlidas, A. Bibcode: 2014ApJ...791....4K Altcode: We examine statistically some properties of 96 20 MeV gradual solar energetic proton (SEP) events as a function of three different types of solar wind (SW) as classified by Richardson and Cane. Gradual SEP (E > 10 MeV) events are produced in shocks driven by fast (V >~ 900 km s-1) and wide (W > 60°) coronal mass ejections (CMEs). We find no differences among the transient, fast, and slow SW streams for SEP 20 MeV proton event timescales. It has recently been found that the peak intensities Ip of these SEP events scale with the ~2 MeV proton background intensities, which may be a proxy for the near-Sun shock seed particles. Both the intensities Ip and their 2 MeV backgrounds are significantly enhanced in transient SW compared to those of fast and slow SW streams, and the values of Ip normalized to the 2 MeV backgrounds only weakly correlate with CME V for all SW types. This result implies that forecasts of SEP events could be improved by monitoring both the Sun and the local SW stream properties and that the well known power-law size distributions of Ip may differ between transient and long-lived SW streams. We interpret an observed correlation between CME V and the 2 MeV background for SEP events in transient SW as a manifestation of enhanced solar activity. Title: Predicting the magnetic vectors within coronal mass ejections arriving at Earth Authors: Savani, Neel P.; Vourlidas, Angelos; Szabo, Adam; Mays, M. Leila; Thompson, Barbara; Richardson, Ian; Evans, Rebekah; Pulkkinen, Antti; Nieves-Chinchilla, Teresa Bibcode: 2014shin.confE.164S Altcode: The process by which the Sun affects the terrestrial environment on short timescales is predominately driven by the amount of magnetic reconnection between the solar wind and Earth's magnetosphere. Reconnection occurs most efficiently when the solar wind magnetic field has a southward component. The most severe impacts are during the arrival of a coronal mass ejection (CME) when the magnetosphere is both compressed and magnetically connected to the heliospheric environment, leading to disruptions to, for example, power grids and satellite navigation. Unfortunately, forecasting magnetic vectors within coronal mass ejections remains elusive. Here we report how, by combining a statistically robust helicity rule for a CME's solar origin with a simplified flux rope topology the magnetic vectors within the Earth-directed segment of a CME can be predicted. These magnetic vectors can be incorporated into forecasting procedures to predict the global response measured by the Kp index more reliably. In particular, false predictions of strong geomagnetic events made without magnetic field information are considerably reduced. As an example, the forecast strength of a geomagnetic storm following a CME on 7 January 2014, is reduced from G3 (strong) to G1 (minor) on the NOAA scale when magnetic vectors are taken into account. Title: Global Magnetohydrodynamics Simulation of the Coronal Mass Ejection on 2011 March 7: from Chromosphere to 1 AU Authors: Jin, Meng; Manchester, W. B.; van der Holst, B.; Sokolov, I.; Toth, G.; Vourlidas, A.; de Koning, C.; Gombosi, T. I. Bibcode: 2014shin.confE..10J Altcode: Performing realistic simulations of solar eruptions and validating those simulations with observations are important goals in order to achieve accurate space weather forecasts. Here, we analyze results of a global magnetohydrodyanmic (MHD) simulation of the fast coronal mass ejection (CME) that occurred on 2011 March 7. The simulation is made using the newly developed Alfven Wave Solar Model (AWSoM), which describes the background solar wind starting from the upper chromosphere and expends to 24 Rs. Coupling of AWSoM to an inner heliosphere (IH) model with the Space Weather Modeling Framework extends the total domain beyond the orbit of Earth. Physical processes included in the model are multi-species thermodynamics, electron heat conduction (both collisional and collisionless formulation), optically thin radiative cooling and Alfven-wave pressure that accelerates the solar wind. The Alfven-wave description is physically self-consistent, including non-WKB reflection and physics-based apportioning of turbulent dissipative heating to both electrons and protons. Within this model, we initiate the CME by using the Gibson-Low (GL) analytical flux rope model and follow its evolution for days, in which time it propagates beyond 1 AU. A comprehensive validation study is performed using remote as well as the in situ observations from SDO, SOHO, STEREOA/B, and OMNI. Our results show that the new model can reproduce many of the observed features near the Sun (e.g., CME-driven EUV waves, deflection of the flux rope from the coronal hole, double-front in the white light images) and in the heliosphere (e.g., CME-CIR interaction, shock properties at 1 AU). By fitting the CME speeds near the Sun with observations, the CME-driven shock arrival time is within 1 hour of the observed arrival time and all the in situ parameters are correctly simulated, which suggests the global MHD model as a powerful tool for the space weather forecasting. Title: CME Expansion as the Driver of Metric Type II Shock Emission as Revealed by Self-consistent Analysis of High-Cadence EUV Images and Radio Spectrograms Authors: Kouloumvakos, A.; Patsourakos, S.; Hillaris, A.; Vourlidas, A.; Preka-Papadema, P.; Moussas, X.; Caroubalos, C.; Tsitsipis, P.; Kontogeorgos, A. Bibcode: 2014SoPh..289.2123K Altcode: 2013arXiv1311.5159K On 13 June 2010, an eruptive event occurred near the solar limb. It included a small filament eruption and the onset of a relatively narrow coronal mass ejection (CME) surrounded by an extreme ultraviolet (EUV) wave front recorded by the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) at high cadence. The ejection was accompanied by a GOES M1.0 soft X-ray flare and a Type-II radio burst; high-resolution dynamic spectra of the latter were obtained by the Appareil de Routine pour le Traitement et l'Enregistrement Magnetique de l'Information Spectral (ARTEMIS IV) radio spectrograph. The combined observations enabled a study of the evolution of the ejecta and the EUV wave front and its relationship with the coronal shock manifesting itself as metric Type-II burst. By introducing a novel technique, which deduces a proxy of the EUV compression ratio from AIA imaging data and compares it with the compression ratio deduced from the band-split of the Type-II metric radio burst, we are able to infer the potential source locations of the radio emission of the shock on that AIA images. Our results indicate that the expansion of the CME ejecta is the source for both EUV and radio shock emissions. Early in the CME expansion phase, the Type-II burst seems to originate in the sheath region between the EUV bubble and the EUV shock front in both radial and lateral directions. This suggests that both the nose and the flanks of the expanding bubble could have driven the shock. Title: Rapid CME Cavity Formation and Expansion Authors: Kliem, Bernhard; Forbes, Terry G.; Patsourakos, Spiros; Vourlidas, Angelos Bibcode: 2014AAS...22421206K Altcode: A cavity is supposed to be a general feature of well-developed CMEs at the stage they can be imaged by white-light coronagraphs (in the outer corona and solar wind). The cavity is interpreted as the cross section of the CME flux rope in the plane of sky. Preexisting cavities are observed around some quiescent erupting prominences, but usually not in active regions. Observations of CME cavities in the inner corona, where most of them appear to form, have become possible only with the STEREO and SDO missions. These reveal a very rapid formation and expansion of "EUV cavities" in fast and impulsively commencing eruptions early in the phase of main CME acceleration and impulsive flare rise. Different from the white-light observations, the EUV cavity initially appears to be larger than the CME flux rope. However, it evolves into the white-light cavity subsequently. MHD simulations of flux rope eruptions conform to this picture of initially larger cavity but subsequently approaching cavity and flux rope size. The initial expansion of ambient flux can be understood as a "reverse pinch effect", driven by decreasing flux rope current as the rope rises. Title: Solar Energetic Particle Events in Different Types of Solar Wind Authors: Kahler, Stephen W.; Vourlidas, Angelos Bibcode: 2014AAS...22432358K Altcode: We examine statistically some properties of 96 20 MeV gradual solar energetic proton (SEP) events as a function of three different types of solar winds (SWs) as classified by Richardson and Cane (2012). Gradual SEP (E > 10 MeV) events are produced in shocks driven by fast (V > 900 km/s) and wide (W > 60 deg) coronal mass ejections (CMEs). We find no differences between transient and fast or slow SW streams for SEP 20-MeV event timescales. It has recently been found that the peak intensities Ip of these SEP events scale with the ~ 2 MeV proton background intensities, which may be a proxy for the near-Sun shock seed particles. Both the intensities Ip and their 2 MeV backgrounds are significantly enhanced in transient SW compared to those of fast and slow SW streams, and the values of Ip normalized to the 2 MeV backgrounds only weakly correlate with CME V for all SW types. This result implies that forecasts of SEP events could be improved by monitoring both the Sun and the local SW stream properties and that the well known power-law size distributions of Ip may differ between transient and long-lived SW streams. We interpret an observed correlation between CME V and the 2 MeV background for SEP events in transient SW as a manifestation of enhanced solar activity. Title: Periodic Density Structures and the Source of the Slow Solar Wind Authors: Viall, Nicholeen; Vourlidas, Angelos Bibcode: 2014AAS...22440202V Altcode: Periodic density structures with length-scales of hundreds to several thousands of megameters, and frequencies of tens to hundreds of minutes, are observed regularly in the solar wind at 1 AU. These structures coexist with, but are not due to, fluctuations in the plasma resulting from the turbulent cascade. Two lines of evidence suggest that periodic density structures are formed in the solar corona as part of the slow solar wind release and/or acceleration processes. The first is the identification of corresponding changes in compositional data in situ, and the other is the identification of periodic density structures in the inner Heliospheric Imaging data onboard the STEREO/SECCHI suite. In this presentation, we show the results of tracking periodic structures identified in the SECCHI/Hi1 images down through the corresponding SECCHI/Cor2 images. We demonstrate that the periodic density structures are formed around or below 2.5 Rs - the inner edge of the Cor2 field of view. Further, we compute the occurrence rate of periodic density structures in 10 days of Cor2 images as a function of location in the solar corona. We find that periodic density structures do not occur throughout the entire space-filling volume of the solar wind; rather, there are particular places where they occur preferentially, suggesting source locations for periodic density structures in the slow solar wind. Title: A plasma β transition within a propagating flux rope Authors: Savani, Neel; Vourlidas, Angelos; Shiota, Daikou; Linton, Mark; Kusano, Kanya; Lugaz, Noe; Rouillard, Alexis Bibcode: 2014AAS...22421205S Altcode: We present a 2.5D MHD simulation of a magnetic flux rope (FR) propagating in the heliosphere and investigate the cause of the observed sharp plasma β transition. Specifically, we consider a strong internal magnetic field and an explosive fast start, such that the plasma β is significantly lower in the FR than the sheath region that is formed ahead. This leads to an unusual FR morphology in the first stage of propagation, while the more traditional view (e.g. from space weather simulations like Enlil) of a `pancake' shaped FR is observed as it approaches 1AU. We investigate how an equipartition line, defined by a magnetic Weber number, surrounding a core region of a propagating FR can demarcate a boundary layer where there is a sharp transition in the plasma β. The substructure affects the distribution of toroidal flux, with the majority of the flux remaining in a small core region which maintains a quasi-cylindrical structure. Quantitatively, we investigate a locus of points where the kinetic energy density of the relative inflow field is equal to the energy density of the transverse magnetic field (i.e. effective tension force). The simulation provides compelling evidence that at all heliocentric distances the distribution of toroidal magnetic flux away from the FR axis is not linear; with 80% of the toroidal flux occurring within 40% of the distance from the FR axis. Thus our simulation displays evidence that the competing ideas of a pancaking structure observed remotely can coexist with a quasi-cylindrical magnetic structure seen in situ Title: Earth-directed ICME magnetic field configuration Authors: Nieves-Chinchilla, Teresa; Vourlidas, A.; Szabo, A.; Savani, N.; Hidalgo, A. M. Bibcode: 2014shin.confE...8N Altcode: It is well known that the geoeffectiveness of interplanetary coronal mass ejections (ICMEs) depends on their magnetic field configuration. However, it remains unclear how the ICME interactions with the solar wind or other solar transient structures affect their magnetic configuration through, say, distortion of their cross-section, or deformation of their front. Obviously, precise space weather forecasting is depended on precise understanding of the evolution of the ICME internal magnetic topology. Title: Independent CMEs from a Single Solar Active Region - The Case of the Super-Eruptive NOAA AR11429 Authors: Chintzoglou, Georgios; Patsourakos, Spiros; Vourlidas, Angelos Bibcode: 2014AAS...22432328C Altcode: In this investigation we study AR 11429, the origin of the twin super-fast CME eruptions of 07-Mar-2012. This AR fulfills all the requirements for the 'perfect storm'; namely, Hale's law incompatibility and a delta-magnetic configuration. In fact, during its limb-to-limb transit, AR 11429 spawned several eruptions which caused geomagnetic storms, including the biggest in Cycle 24 so far. Magnetic Flux Ropes (MFRs) are twisted magnetic structures in the corona, best seen in ~10MK hot plasma emission and are often considered as the culprit causing such super-eruptions. However, their 'dormant' existence in the solar atmosphere (i.e. prior to eruptions), is a matter of strong debate. Aided by multi-wavelength and multi-spacecraft observations (SDO/HMI & AIA, HINODE/SOT/SP, STEREO B/EUVI) and by using a Non-Linear Force-Free (NLFFF) model for the coronal magnetic field, our work shows two separate, weakly-twisted magnetic flux systems which suggest the existence of possible pre-eruption MFRs. Title: Three-Dimensional Evolution of Flux-Rope CMEs and Its Relation to the Local Orientation of the Heliospheric Current Sheet Authors: Isavnin, A.; Vourlidas, A.; Kilpua, E. K. J. Bibcode: 2014SoPh..289.2141I Altcode: 2013arXiv1312.0458I; 2014SoPh..tmp...16I Flux ropes ejected from the Sun may change their geometrical orientation during their evolution, which directly affects their geoeffectiveness. Therefore, it is crucial to understand how solar flux ropes evolve in the heliosphere to improve our space-weather forecasting tools. We present a follow-up study of the concepts described by Isavnin, Vourlidas, and Kilpua (Solar Phys.284, 203, 2013). We analyze 14 coronal mass ejections (CMEs), with clear flux-rope signatures, observed during the decay of Solar Cycle 23 and rise of Solar Cycle 24. First, we estimate initial orientations of the flux ropes at the origin using extreme-ultraviolet observations of post-eruption arcades and/or eruptive prominences. Then we reconstruct multi-viewpoint coronagraph observations of the CMEs from ≈ 2 to 30 R⊙ with a three-dimensional geometric representation of a flux rope to determine their geometrical parameters. Finally, we propagate the flux ropes from ≈ 30 R⊙ to 1 AU through MHD-simulated background solar wind while using in-situ measurements at 1 AU of the associated magnetic cloud as a constraint for the propagation technique. This methodology allows us to estimate the flux-rope orientation all the way from the Sun to 1 AU. We find that while the flux-ropes' deflection occurs predominantly below 30 R⊙, a significant amount of deflection and rotation happens between 30 R⊙ and 1 AU. We compare the flux-rope orientation to the local orientation of the heliospheric current sheet (HCS). We find that slow flux ropes tend to align with the streams of slow solar wind in the inner heliosphere. During the solar-cycle minimum the slow solar-wind channel as well as the HCS usually occupy the area in the vicinity of the solar equatorial plane, which in the past led researchers to the hypothesis that flux ropes align with the HCS. Our results show that exceptions from this rule are explained by interaction with the Parker-spiraled background magnetic field, which dominates over the magnetic interaction with the HCS in the inner heliosphere at least during solar-minimum conditions. Title: Do Interacting Coronal Mass Ejections Play a Role in Solar Energetic Particle Events? Authors: Kahler, S. W.; Vourlidas, A. Bibcode: 2014ApJ...784...47K Altcode: Gradual solar energetic (E > 10 MeV) particle (SEP) events are produced in shocks driven by fast and wide coronal mass ejections (CMEs). With a set of western hemisphere 20 MeV SEP events, we test the possibility that SEP peak intensities, Ip, are enhanced by interactions of their associated CMEs with preceding CMEs (preCMEs) launched during the previous 12 hr. Among SEP events with no, 1, or 2 or more (2+) preCMEs, we find enhanced Ip for the groups with preCMEs, but no differences in TO+TR, the time from CME launch to SEP onset and the time from onset to SEP half-peak Ip. Neither the timings of the preCMEs relative to their associated CMEs nor the preCME widths W pre, speeds V pre, or numbers correlate with the SEP Ip values. The 20 MeV Ip of all the preCME groups correlate with the 2 MeV proton background intensities, consistent with a general correlation with possible seed particle populations. Furthermore, the fraction of CMEs with preCMEs also increases with the 2 MeV proton background intensities. This implies that the higher SEP Ip values with preCMEs may not be due primarily to CME interactions, such as the "twin-CME" scenario, but are explained by a general increase of both background seed particles and more frequent CMEs during times of higher solar activity. This explanation is not supported by our analysis of 2 MeV proton backgrounds in two earlier preCME studies of SEP events, so the relevance of CME interactions for larger SEP event intensities remains unclear. Title: Tracking the Evolution of a Coherent Magnetic Flux Rope Continuously from the Inner to the Outer Corona Authors: Cheng, X.; Ding, M. D.; Guo, Y.; Zhang, J.; Vourlidas, A.; Liu, Y. D.; Olmedo, O.; Sun, J. Q.; Li, C. Bibcode: 2014ApJ...780...28C Altcode: 2013arXiv1310.6782C The magnetic flux rope (MFR) is believed to be the underlying magnetic structure of coronal mass ejections (CMEs). However, it remains unclear how an MFR evolves into and forms the multi-component structure of a CME. In this paper, we perform a comprehensive study of an extreme-ultraviolet (EUV) MFR eruption on 2013 May 22 by tracking its morphological evolution, studying its kinematics, and quantifying its thermal property. As EUV brightenings begin, the MFR starts to rise slowly and shows helical threads winding around an axis. Meanwhile, cool filamentary materials descend spirally down to the chromosphere. These features provide direct observational evidence of intrinsically helical structure of the MFR. Through detailed kinematical analysis, we find that the MFR evolution has two distinct phases: a slow rise phase and an impulsive acceleration phase. We attribute the first phase to the magnetic reconnection within the quasi-separatrix layers surrounding the MFR, and the much more energetic second phase to the fast magnetic reconnection underneath the MFR. We suggest that the transition between these two phases is caused by the torus instability. Moreover, we identify that the MFR evolves smoothly into the outer corona and appears as a coherent structure within the white-light CME volume. The MFR in the outer corona was enveloped by bright fronts that originated from plasma pile-up in front of the expanding MFR. The fronts are also associated with the preceding sheath region followed by the outmost MFR-driven shock. Title: Coordinated science with the Solar Orbiter, Solar Probe Plus, Interhelioprobe and SPORT missions Authors: Maksimovic, Milan; Vourlidas, Angelos; Zimovets, Ivan; Velli, Marco; Zhukov, Andrei; Kuznetsov, Vladimir; Liu, Ying; Bale, Stuart; Ming, Xiong Bibcode: 2014cosp...40E1956M Altcode: The concurrent science operations of the ESA Solar Orbiter (SO), NASA Solar Probe Plus (SPP), Russian Interhelioprobe (IHP) and Chinese SPORT missions will offer a truly unique epoch in heliospheric science. While each mission will achieve its own important science objectives, taken together the four missions will be capable of doing the multi-point measurements required to address many problems in Heliophysics such as the coronal origin of the solar wind plasma and magnetic field or the way the Solar transients drive the heliospheric variability. In this presentation, we discuss the capabilities of the four missions and the Science synergy that will be realized by concurrent operations Title: The STEREO Encounter with the Tail of Comet Elenin and Expectations for ISON Authors: Galvin, A. B.; Kucharek, H.; Klecker, B.; Simunac, K.; Farrugia, C. J.; Wimmer-Schweingruber, R. F.; Berger, L.; Drews, C.; Vourlidas, A. Bibcode: 2013AGUFM.P31A1789G Altcode: The longest encounter to date of a space probe with a comet occurred in late July through mid August 2011 when the STEREO B (STB) observatory was immersed in the plasma environment of comet C/2010 X1 (Elenin). Closest approach was reached on July 31 at a distance of 7.4 million kilometers, with the nominal radial tail alignment occurring on August 12. Continuous observations of cometary ions are available for over three weeks. These ions were created over a broad range of solar wind conditions, including slow and fast solar wind, stream interaction regions, and an interplanetary coronal mass ejection. In the mass-per-charge range of water-group ions, the STB/PLASTIC instrument found that the major ion constituent was O+, with significant contributions from O+2 and C+. In the mass-per-charge range 23-36 amu/e there was a clear contribution by molecular ions. The composition is tracked on a daily basis and shows variations. There are also temporal variations in the speed distribution profiles. An abrupt decrease in the water-group ion intensity coincided with the passage of an interplanetary coronal mass ejection (ICME). STB/SECCHI imaged this same ICME as it interacted with the comet, observing a comet tail disconnection event. An opportunity for another comet tail passage by STEREO will occur with comet ISON in late November 2013. This comet's orbital plane is not near the ecliptic, hence this encounter, if it occurs, will be a shorter duration. Using the tools developed for the Elenin encounter, we will search for the ISON signatures in the in-situ data set and present any preliminary results available. Title: Inner Heliospheric Evolution of a "Stealth" CME Derived from Multi-view Imaging and Multipoint in Situ observations. I. Propagation to 1 AU Authors: Nieves-Chinchilla, T.; Vourlidas, A.; Stenborg, G.; Savani, N. P.; Koval, A.; Szabo, A.; Jian, L. K. Bibcode: 2013ApJ...779...55N Altcode: 2013arXiv1311.6895N Coronal mass ejections (CMEs) are the main driver of space weather. Therefore, a precise forecasting of their likely geo-effectiveness relies on an accurate tracking of their morphological and kinematical evolution throughout the interplanetary medium. However, single viewpoint observations require many assumptions to model the development of the features of CMEs. The most common hypotheses were those of radial propagation and self-similar expansion. The use of different viewpoints shows that, at least for some cases, those assumptions are no longer valid. From radial propagation, typical attributes that can now be confirmed to exist are over-expansion and/or rotation along the propagation axis. Understanding the 3D development and evolution of the CME features will help to establish the connection between remote and in situ observations, and hence help forecast space weather. We present an analysis of the morphological and kinematical evolution of a STEREO-B-directed CME on 2009 August 25-27. By means of a comprehensive analysis of remote imaging observations provided by the SOHO, STEREO, and SDO missions, and in situ measurements recorded by Wind, ACE, and MESSENGER, we prove in this paper that the event exhibits signatures of deflection, which are usually associated with changes in the direction of propagation and/or also with rotation. The interaction with other magnetic obstacles could act as a catalyst of deflection or rotation effects. We also propose a method to investigate the change of the CME tilt from the analysis of height-time direct measurements. If this method is validated in further work, it may have important implications for space weather studies because it will allow for inference of the interplanetary counterpart of the CME's orientation. Title: A Plasma β Transition within a Propagating Flux Rope Authors: Savani, N. P.; Vourlidas, A.; Shiota, D.; Linton, M. G.; Kusano, K.; Lugaz, N.; Rouillard, A. P. Bibcode: 2013ApJ...779..142S Altcode: 2013arXiv1310.4747S We present a 2.5 dimensional magnetohydrodynamic simulation of a magnetic flux rope (FR) propagating in the heliosphere and investigate the cause of the observed sharp plasma β transition. Specifically, we consider a strong internal magnetic field and an explosive fast start, such that the plasma β is significantly lower in the FR than in the sheath region that is formed ahead. This leads to an unusual FR morphology in the first stage of propagation, while the more traditional view (e.g., from space weather simulations like Enlil) of a pancake-shaped FR is observed as it approaches 1 AU. We investigate how an equipartition line, defined by a magnetic Weber number, surrounding a core region of a propagating FR, can demarcate a boundary layer where there is a sharp transition in the plasma β. The substructure affects the distribution of toroidal flux, with the majority of the flux remaining in a small core region that maintains a quasi-cylindrical structure. We quantitatively investigate a locus of points where the kinetic energy density of the relative inflow field is equal to the energy density of the transverse magnetic field (i.e., effective tension force). The simulation provides compelling evidence that at all heliocentric distances the distribution of toroidal magnetic flux away from the FR axis is not linear, with 80% of the toroidal flux occurring within 40% of the distance from the FR axis. Thus, our simulation displays evidence that the competing ideas of a pancaking structure observed remotely can coexist with a quasi-cylindrical magnetic structure seen in situ. Title: Quantitative comparison of methods for predicting the arrival of coronal mass ejections at Earth based on multiview imaging Authors: Colaninno, R. C.; Vourlidas, A.; Wu, C. C. Bibcode: 2013JGRA..118.6866C Altcode: 2013arXiv1310.6680C We investigate the performance of six methods for predicting the coronal mass ejection (CME) time of arrival (ToA) and velocity at Earth using a sample of nine Earth-impacting CMEs between March 2010 and June 2011. The CMEs were tracked continuously from the Sun to near Earth in multiviewpoint imaging data from STEREO Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) and SOHO Large Angle and Spectroscopic Coronagraph (LASCO). We use the Graduate Cylindrical Shell model to estimate the three-dimensional direction and height of the CMEs in every image out to ∼200R⊙. We fit the derived three-dimensional (deprojected) height and time (HT) data with six different methods to extrapolate the CME ToA and velocity at Earth. We compare the fitting results with the in situ data from the Wind spacecraft. We find that a simple linear fit above a height of 50R⊙ gives the ToA with an error ±6h for seven (78%) of the CMEs. For the full sample, we are able to predict the ToA to within ±13h. These results are a half day improvement over past CME arrival time methods that only used SOHO LASCO data. We conclude that heliographic height-time measurements of the CME front made away from the Sun-Earth line and beyond the coronagraphic field of view are sufficient for reasonably accurate predictions of their ToA. Title: Solar Eruptive Events (SEE) 2020 Mission Concept Authors: Lin, R. P.; Caspi, A.; Krucker, S.; Hudson, H.; Hurford, G.; Bandler, S.; Christe, S.; Davila, J.; Dennis, B.; Holman, G.; Milligan, R.; Shih, A. Y.; Kahler, S.; Kontar, E.; Wiedenbeck, M.; Cirtain, J.; Doschek, G.; Share, G. H.; Vourlidas, A.; Raymond, J.; Smith, D. M.; McConnell, M.; Emslie, G. Bibcode: 2013arXiv1311.5243L Altcode: Major solar eruptive events (SEEs), consisting of both a large flare and a near simultaneous large fast coronal mass ejection (CME), are the most powerful explosions and also the most powerful and energetic particle accelerators in the solar system, producing solar energetic particles (SEPs) up to tens of GeV for ions and hundreds of MeV for electrons. The intense fluxes of escaping SEPs are a major hazard for humans in space and for spacecraft. Furthermore, the solar plasma ejected at high speed in the fast CME completely restructures the interplanetary medium (IPM) - major SEEs therefore produce the most extreme space weather in geospace, the interplanetary medium, and at other planets. Thus, understanding the flare/CME energy release process(es) and the related particle acceleration processes are major goals in Heliophysics. To make the next major breakthroughs, we propose a new mission concept, SEE 2020, a single spacecraft with a complement of advanced new instruments that focus directly on the coronal energy release and particle acceleration sites, and provide the detailed diagnostics of the magnetic fields, plasmas, mass motions, and energetic particles required to understand the fundamental physical processes involved. Title: Origins of Rolling, Twisting, and Non-radial Propagation of Eruptive Solar Events Authors: Panasenco, Olga; Martin, Sara F.; Velli, Marco; Vourlidas, Angelos Bibcode: 2013SoPh..287..391P Altcode: 2012arXiv1211.1376P; 2012SoPh..tmp..321P We demonstrate that major asymmetries in erupting filaments and CMEs, namely major twists and non-radial motions are typically related to the larger-scale ambient environment around eruptive events. Our analysis of prominence eruptions observed by the STEREO, SDO, and SOHO spacecraft shows that prominence spines retain, during the initial phases, the thin ribbon-like topology they had prior to the eruption. This topology allows bending, rolling, and twisting during the early phase of the eruption, but not before. The combined ascent and initial bending of the filament ribbon is non-radial in the same general direction as for the enveloping CME. However, the non-radial motion of the filament is greater than that of the CME. In considering the global magnetic environment around CMEs, as approximated by the Potential Field Source Surface (PFSS) model, we find that the non-radial propagation of both erupting filaments and associated CMEs is correlated with the presence of nearby coronal holes, which deflect the erupting plasma and embedded fields. In addition, CME and filament motions, respectively, are guided towards weaker field regions, namely null points existing at different heights in the overlying configuration. Due to the presence of the coronal hole, the large-scale forces acting on the CME may be asymmetric. We find that the CME propagates usually non-radially in the direction of least resistance, which is always away from the coronal hole. We demonstrate these results using both low- and high-latitude examples. Title: Study of a Coronal Mass Ejection with SOHO/UVCS and STEREO data Authors: Susino, Roberto; Bemporad, Alessandro; Dolei, Sergio; Vourlidas, Angelos Bibcode: 2013AdSpR..52..957S Altcode: We study the 3-D kinematics of a Coronal Mass Ejection (CME) using data acquired by the LASCO C2 and UVCS instruments on board SOHO, and the COR1 coronagraphs and EUVI telescopes on board STEREO. The event, which occurred on May 20, 2007, was a partial-halo CME associated with a prominence eruption. This is the first CME studied with UVCS data that occurred in the STEREO era. The longitudinal angle between the STEREO spacecrafts was ∼7.7° at that time, and this allowed us to reconstruct via triangulation technique the 3-D trajectory of the erupting prominence observed by STEREO/EUVI. Information on the 3-D expansion of the CME provided by STEREO/COR1 data have been combined with spectroscopic observations by SOHO/UVCS. First results presented here show that line-of-sight velocities derived from spectroscopic data are not fully in agreement with those previously derived via triangulation technique, thus pointing out possible limitations of this technique. Title: Shock formation characteristics in the low corona from type II radio bursts Authors: Kouloumvakos, A.; Preka-Papadema, P.; Vourlidas, A.; Moussas, X.; Hillaris, A.; Tsitsipis, P.; Kontogeorgos, A. Bibcode: 2013hell.confS..19K Altcode: In this analysis we have identified the formation of coronal shock waves from 2007 to 2011, using as proxies the type II radio bursts from radio spectrograph ARTEMIS-IV and RSTN. For the 42 events we have identified, we combined data from STEREO, SOHO/LASCO και SDO with the characteristics of the composite radio spectra to investigate the properties of the type II formation with the associated flares and CMEs. From the timings between the flare, the CME onset, the HXR peak and the type II start, we grouped the type IIs into separate categories. We found that in most of the cases the type II radio burst starts at the flare maximum phase and particularly in 60% of the cases at the HXR maximum. All the characteristics of the type IIs obtained from their spectrum (duration, df, df/dt). We compared the computed velocities of the type IIs, using deferent density models, with the observed speeds of the CMEs from STEREO and SOHO/LASCO. Finally, from the composite radio spectra we associated the type II with the occurrence of other transient radio emissions such as, radio bursts type III or IV. Title: 'Hurricane Season' in the Inner Heliosphere: Observations of Coronal Mass Authors: Vourlidas, A. Bibcode: 2013hell.conf....2V Altcode: The current solar cycle, albeit low in sunspot numbers, is not lacking in coronal explosive activity. The solar corona has produced several spectacular Coronal Mass Ejections (CMEs) directed at Earth and other planets. In addition, this is the first time in human history that we are able to image continuously the full 360 degree corona and the full inner heliosphere from the Sun to Earth, and beyond. In addition, a host of inner heliospheric spacecraft can directly probe the quiescent and transient solar wind at several locations around Mercury, Venus, Earth, and Mars. These unprecedented observational capabilities offer us a unique opportunity to study the solar maximum activity and in particular CMEs and their impact on Earth and the other planets. The new field of Interplanetary Space Weather is being born. In this talk, I review our progress (sometimes) and befuddlement (more often) towards understanding the evolution of CMEs in the inner heliosphere. I discuss how this knowledge is shaping Space Weather efforts around the world, including a comprehensive approach from a large group of Greek solar and space physicists under the THALIS aegis. I will also present ideas for future missions and instrumentation to improve our Space Weather predictive capabilities. Title: Sun-to-Earth Analysis of a Major Geoeffective Solar Eruption within the Framework of the Authors: Patsourakos, S.; Vlahos, L.; Georgoulis, M.; Tziotziou, K.; Nindos, A.; Podladchikova, O.; Vourlidas, A.; Anastasiadis, A.; Sandberg, I.; Tsinganos, K.; Daglis, I.; Hillaris, A.; Preka-Papadema, P.; Sarris, M.; Sarris, T. Bibcode: 2013hell.conf...10P Altcode: Transient expulsions of gigantic clouds of solar coronal plasma into the interplanetary space in the form of Coronal Mass Ejections (CMEs) and sudden, intense flashes of electromagnetic radiation, solar flares, are well-established drivers of the variable Space Weather. Given the innate, intricate links and connections between the solar drivers and their geomagnetic effects, synergistic efforts assembling all pieces of the puzzle along the Sun-Earth line are required to advance our understanding of the physics of Space Weather. This is precisely the focal point of the Hellenic National Space Weather Research Network (HNSWRN) under the THALIS Programme. Within the HNSWRN framework, we present here the first results from a coordinated multi-instrument case study of a major solar eruption (X5.4 and X1.3 flares associated with two ultra-fast (>2000 km/s) CMEs) which were launched early on 7 March 2012 and triggered an intense geomagnetic storm (min Dst =-147 nT) approximately two days afterwards. Several elements of the associated phenomena, such as the flare and CME, EUV wave, WL shock, proton and electron event, interplanetary type II radio burst, ICME and magnetic cloud and their spatiotemporal relationships and connections are studied all way from Sun to Earth. To this end, we make use of satellite data from a flotilla of solar, heliospheric and magnetospheric missions and monitors (e.g., SDO, STEREO, WIND, ACE, Herschel, Planck and INTEGRAL). We also present our first steps toward formulating a cohesive physical scenario to explain the string of the observables and to assess the various physical mechanisms than enabled and gave rise to the significant geoeffectiveness of the eruption. Title: Analysis of the Deflection of CMEs by Coronal Magnetic Fields Authors: Liewer, Paulett C.; Panasenco, O.; Vourlidas, A. Bibcode: 2013SPD....4410103L Altcode: Understanding coronal influences on the direction of propagation of CMEs is important for space weather prediction. It is well known that CMEs often propagate non-radially, e.g., they do not move out radially from the location of the solar source (see, e.g., Cremades and Bothmer, A&A, 2004; Panasenco et al., Sol. Phys. 2013). There is evidence that most CMEs exit the corona in the minimum field region surrounding the coronal/heliospheric current sheet (HCS). If this is the case, then the degree of deflection should reflect the distance of the source region from the current sheet region. Here we study the observed deflection in latitude of four CMEs using STEREO/SECCHI’s EUV and white light observations to trace the deflection. A potential-field source surface (PFSS) model (Schrijver & DeRosa, Sol. Phys. 2003) is used to give information on the magnetic forces acting on the CME at different heights in the lower corona. This model, as well as the PFSS model results at the GONG website (http://gong.nso.edu/data/magmap/archive.html) and the coronal observations from STEREO, are used to try to determine the location of the HCS. For the events studied, we find cases when the deflection is gradual (occurring between the surface at several solar radii) and cases where the deflection is immediate (within ~1.5 solar radii). There are many cases in the literature where CMEs originating at high latitude are deflected towards the ecliptic and eventually impact Earth. Several of the CMEs we analyzed were later detected in situ at ~1 AU and we compare the near-Sun trajectory information to the trajectory information determine from the in situ information. Title: A Fractionated Space Weather Base at L5 using CubeSats and Solar Sails Authors: Liewer, Paulett C.; Klesh, A.; Lo, M.; Murphy, N.; Staehle, R. L.; Vourlidas, A.; Cutler, J. W.; Lightsey, G. Bibcode: 2013SPD....44..151L Altcode: The Sun-Earth L5 Lagrange point is an ideal location for an operational space weather mission to provide early warning of Earth-directed solar storms (CMEs, shocks and associated solar energetic particles) so the effects on power grids, spacecraft and communications systems can be mitigated. Such missions have been proposed using conventional spacecraft and chemical propulsion at costs of hundreds of millions of dollars. Here we describe a mission that can accomplish the goals at a much lower cost by dividing the payload among a cluster of interplanetary CubeSats that reach orbits around L5 using solar sails. The ascendancy of CubeSats has brought renewed interest in solar sail propulsion because sail area scales directly with spacecraft mass. The concept presented here draws heavily on a NIAC study (Staehle et al., AIAA, 2012) that developed a 6U CubeSat architecture for interplanetary missions. This study allocated 2U for a solar sail; the sail system was based on the Planetary Society’s LightSail-1TM architecture. At a recent workshop on small satellites, hosted by the Keck Institute for Space Studies, a concept was developed for a fractionated Space Weather Base (SWB) at L5. In this concept, a loose formation of CubeSats, each ~6U in size and each carrying a portion of the science payload, can accomplish, at a much reduced cost, many of the goals of a conventional single-spacecraft L5 mission, as described in the 2013 NRC Solar and Space Physics Decadal report. Each of the small ~6U interplanetary CubeSats reaches an orbit around L5 using its own solar sail of approximately 64 m2 which fits in ~2U. Key to the mission is that only one of the CubeSats carries a high-gain antenna and other hardware necessary for sending high-rate science data to Earth. The other CubeSats, in addition to carrying one or two science instruments, carry a much smaller communication system to send the science data to the communication hub and low-rate engineering data to Earth. The SWB-L5 mission can later be expanded incrementally to add new instruments and new objectives by sending additional small spacecraft to the L5 base. The mission described below represents a potential beginning for a permanent space warning system at L5. Title: SDO Observations of Solar Jets Authors: Moschou, S. P.; Tsinganos, K.; Vourlidas, A.; Archontis, V. Bibcode: 2013SoPh..284..427M Altcode: 2012SoPh..tmp..310M We present an analysis of high cadence observations of solar jets observed in the Extreme Ultraviolet (EUV), at 304 Å, with the Atmospheric Imaging Assembly instrument aboard the Solar Dynamics Observatory (SDO). The jets in our sample lie very close to the solar limb to minimize projection effects. Two of the events show clear helical patterns during ejection. We also find that some of the jets are recurrent and that most of them cannot overcome solar gravity. Title: Solar energetic particles and their variability from the sun and beyond Authors: Mewaldt, R. A.; Cohen, C. M. S.; Mason, G. M.; von Rosenvinge, T. T.; Leske, R. A.; Luhmann, J. G.; Odstrcil, D.; Vourlidas, A. Bibcode: 2013AIPC.1539..116M Altcode: With the onset of solar cycle 24 activity STEREO and near-Earth spacecraft are now measuring many multi-spacecraft solar particle events. We present examples of time-intensity distributions, energy spectra, fits to longitude distributions, a combined imaging/in-situ study, and MHD modeling of one event. Implications of these new results are discussed. Title: A plasma beta transition within a propagating CME leading to a magnetic substructure Authors: Savani, Neel P.; Vourlidas, A.; Shiota, D.; Linton, M.; Kusano, K.; Lugaz, N.; Rouillard, A. P. Bibcode: 2013shin.confE.149S Altcode: We present a study of how a sharp transition in the plasma beta within a simulated flux rope (FR) affects the distribution of toriodal flux within the obstacle. Specifically, we consider a 2.5D MHD simulation of a magnetic FR with a strong internal magnetic field and an explosive fast start. Qualitatively the overall effects show that the sharp boundary of the low-to-high plasma beta within the outer segment of a flux rope leads to layers of magnetic flux 'peeling' off the main body. This leads to an unusual flux rope morphology in the first stage of propagation, while the more traditional view of a 'pancake' shaped FR is observed as it approaches 1AU. However the simulation provides compelling evidence that at all heliocentric distances the distribution of magnetic flux away from the FR axis is not linear; with 80% of the flux occurring within 40% of the distance from the FR axis. Thus our simulation shows that the competing ideas of a pancaking structure observed remotely can coexist with a quasi-cylindrical magnetic structure seen in situ. Title: A Comparison of the Intensities and Energies of Gradual Solar Energetic Particle Events with the Dynamical Properties of Associated Coronal Mass Ejections Authors: Kahler, S. W.; Vourlidas, A. Bibcode: 2013ApJ...769..143K Altcode: Gradual solar energetic particle (SEP) events observed at 1 AU are produced by shocks driven by coronal mass ejections (CMEs). Characterizations of the remotely imaged CMEs and of their associated SEP events observed in situ can be used to increase our ability to forecast SEP events and to understand better the physical connections between the two phenomena. We carry out a statistical comparison of the peak intensities Ip20, of 120 western-hemisphere 20 MeV SEP events with those of their associated CMEs observed by the Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph over the past solar cycle. For a subset of 96 events observed with the EPACT instrument on the Wind spacecraft we also compare the SEP 2 MeV peak intensities Ip2, power-law energy spectral exponents γ, total SEP energies Esep, and 2 MeV nuc-1 H/He ratios with CME properties. New analyses of white-light CME images enable us to improve calculations of the CME masses and potential energies and then to determine two values of their kinetic energies based on frontal V (fr) and center-of-mass V (cm) speeds. Despite considerable scatter in the SEP and CME data, the large dynamical ranges of both the SEP and CME parameters allow us to determine statistical trends in the comparisons of the logs of the parameters. Ip2, Ip20, and Esep are significantly correlated with CME kinetic energies, masses, and speeds, while γ trends lower (harder). Those correlations are higher with V (fr) than with V (cm) parameters, indicating a less significant role for the body of the CME than for the CME front in SEP production. The high ratios (>=10%) of Esep to CME energies found by Mewaldt et al. are confirmed, and the fits are consistent with a linear relationship between the two energies. The 2 MeV nuc-1 H/He ratios decrease with increasing CME speeds, which may be an effect of shock geometry. We discuss several factors that limit the estimates of both the SEP and CME energies. Title: The arrival of coronal mass ejections at Earth Authors: Colaninno, Robin C.; Vourlidas, A.; Wu, C. C. Bibcode: 2013shin.confE.148C Altcode: We analyze nine Earth-impacting CMEs which we track continuously from the the Sun to near Earth in imaging data. We use the Graduate Cylindrical Shell (GCS) model to find the three-dimensional position of the CMEs in all the imaging data. We fit the height and time data derived from the GCS model with six different method to extrapolate the CME arrival time and velocity at Earth. We compare the results of our fit methods with the in situ data from the WIND spacecraft. We find that assuming a constant velocity after a height of 50 Rsun gives the best predict the arrival times with an error +-13 hours. For seven of the CMEs, we are able to predict the arrival time to within +-6 hours. This is a significant improvement over using only LASCO images to predict CME arrival times. However, we are still unable to reliably predict the velocity of the CME when it arrives at Earth. Modeling the kinematics of a CME is important for exploring the forces on the CME and interaction with the solar wind. Title: Simulation of the Coronal Mass Ejection on 2011 March 7: from Chromosphere to 1 AU Authors: Jin, Meng; Manchester, Ward; van der Holst, Bart; Oran, Rona; Sokolov, Igor; Toth, Gabor; Gombosi, Tamas I.; Vourlidas, Angelos; Liu, Yang; Sun, Xudong Bibcode: 2013shin.confE...4J Altcode: On 2011 March 7, a fast CME (> 2000 km/s) occurred in NOAA 11164. This event is also associated with a Solar Energetic Particle (SEP) event. In this study, we present the magnetohydrodynamics simulation results of this event by using the newly developed Alfven Wave SOlar Model (AWSOM) in Space Weather Modeling Framework (SWMF). The background solar wind starts from chromosphere with heat conduction and radiative cooling. The solar wind is driven by Alfven-wave pressure and heated by Alfven-wave dissipation. The magnetic field of the inner boundary is specified with a synoptic magnetogram from SDO/HMI. We initiate the CME by using the Gibson-Low flux rope model. In order to produce physically correct CME structures and CME-driven shocks, the electron and proton temperatures are separated so that the electron heat conduction is explicitly treated in conjunction with proton shock heating. We simulate the CME propagation to 1 AU. Comprehensive validation work is done by using the remote as well as the in-situ observation from SOHO, SDO, STEREOA/B, ACE, and WIND. Our results show that the new model can reproduce most of the observed features near the Sun and in the heliosphere. The CME-driven shock is well reproduced, which is important for modeling the SEP event with diffusive shock acceleration. We also try to compare the differences and similarities between this event and previous simulated extreme events (e.g., the 2003 Halloween CMEs). Title: The Height Evolution of the "True" Coronal Mass Ejection Mass derived from STEREO COR1 and COR2 Observations Authors: Bein, B. M.; Temmer, M.; Vourlidas, A.; Veronig, A. M.; Utz, D. Bibcode: 2013ApJ...768...31B Altcode: 2013arXiv1303.3372B Using combined STEREO-A and STEREO-B EUVI, COR1, and COR2 data, we derive deprojected coronal mass ejection (CME) kinematics and CME "true" mass evolutions for a sample of 25 events that occurred during 2007 December to 2011 April. We develop a fitting function to describe the CME mass evolution with height. The function considers both the effect of the coronagraph occulter, at the beginning of the CME evolution, and an actual mass increase. The latter becomes important at about 10-15 R ⊙ and is assumed to mostly contribute up to 20 R ⊙. The mass increase ranges from 2% to 6% per R ⊙ and is positively correlated to the total CME mass. Due to the combination of COR1 and COR2 mass measurements, we are able to estimate the "true" mass value for very low coronal heights (<3 R ⊙). Based on the deprojected CME kinematics and initial ejected masses, we derive the kinetic energies and propelling forces acting on the CME in the low corona (<3 R ⊙). The derived CME kinetic energies range between 1.0-66 × 1023 J, and the forces range between 2.2-510 × 1014 N. Title: Tracking the momentum flux of a CME and quantifying its influence on geomagnetically induced currents at Earth Authors: Savani, N. P.; Vourlidas, A.; Pulkkinen, A.; Nieves-Chinchilla, T.; Lavraud, B.; Owens, M. J. Bibcode: 2013SpWea..11..245S Altcode: 2013arXiv1303.2574S We investigate a coronal mass ejection (CME) propagating toward Earth on 29 March 2011. This event is specifically chosen for its predominately northward directed magnetic field, so that the influence from the momentum flux onto Earth can be isolated. We focus our study on understanding how a small Earth-directed segment propagates. Mass images are created from the white-light cameras onboard STEREO which are also converted into mass height-time maps (mass J-maps). The mass tracks on these J-maps correspond to the sheath region between the CME and its associated shock front as detected by in situ measurements at L1. A time series of mass measurements from the STEREO COR-2A instrument is made along the Earth propagation direction. Qualitatively, this mass time series shows a remarkable resemblance to the L1 in situ density series. The in situ measurements are used as inputs into a three-dimensional (3-D) magnetospheric space weather simulation from the Community Coordinated Modeling Center. These simulations display a sudden compression of the magnetosphere from the large momentum flux at the leading edge of the CME, and predictions are made for the time derivative of the magnetic field (dB/dt) on the ground. The predicted dB/dt values were then compared with the observations from specific equatorially located ground stations and showed notable similarity. This study of the momentum of a CME from the Sun down to its influence on magnetic ground stations on Earth is presented as a preliminary proof of concept, such that future attempts may try to use remote sensing to create density and velocity time series as inputs to magnetospheric simulations. Title: Three-Dimensional Evolution of Erupted Flux Ropes from the Sun (2 - 20 R ⊙) to 1 AU Authors: Isavnin, A.; Vourlidas, A.; Kilpua, E. K. J. Bibcode: 2013SoPh..284..203I Altcode: 2012arXiv1211.2108I Studying the evolution of magnetic clouds entrained in coronal mass ejections using in-situ data is a difficult task, since only a limited number of observational points is available at large heliocentric distances. Remote sensing observations can, however, provide important information for events close to the Sun. In this work we estimate the flux rope orientation first in the close vicinity of the Sun (2 - 20 R⊙) using forward modeling of STEREO/SECCHI and SOHO/LASCO coronagraph images of coronal mass ejections and then in situ using Grad-Shafranov reconstruction of the magnetic cloud. Thus, we are able to measure changes in the orientation of the erupted flux ropes as they propagate from the Sun to 1 AU. We present both techniques and use them to study 15 magnetic clouds observed during the minimum following Solar Cycle 23 and the rise of Solar Cycle 24. This is the first multievent study to compare the three-dimensional parameters of CMEs from imaging and in-situ reconstructions. The results of our analysis confirm earlier studies showing that the flux ropes tend to deflect towards the solar equatorial plane. We also find evidence of rotation on their travel from the Sun to 1 AU. In contrast to past studies, our method allows one to deduce the evolution of the three-dimensional orientation of individual flux ropes rather than on a statistical basis. Title: Tracking the momentum flux of a CME and quantifying its influence on geomagnetically induced currents at Earth Authors: Savani, N. P.; Vourlidas, A.; Pulkkinen, A.; Nieves-Chinchilla, T.; Lavraud, B.; Owens, M. J. Bibcode: 2013AGUSMSH21B..01S Altcode: We investigate a CME propagating towards Earth on 29 March 2011. This event is specifically chosen for its predominately northward directed magnetic field, so that the influence from the momentum flux onto Earth can be isolated. We focus our study on understanding how a small Earth-directed segment propagates. Mass images are created from the white-light cameras onboard STEREO which are also converted into mass height-time maps (mass J-maps). The mass tracks on these J-maps correspond to the sheath region between the CME and its associated shock front as detected by in situ measurements at L1. A time-series of mass measurements from the STEREO COR-2A instrument are made along the Earth propagation direction. Qualitatively, this mass time-series shows a remarkable resemblance to the L1 in situ density series. The in situ measurements are used as inputs into a 3D magnetospheric space weather simulation from CCMC. These simulations display a sudden compression of the magnetosphere from the large momentum flux at the leading edge of the CME and predictions are made for the time-derivative of the magnetic field (dB/dt) on the ground. The predicted dB/dt were then compared with observations from specific equatorially-located ground stations and show notable similarity. This study of the momentum of a CME from the Sun down to its influence on magnetic ground stations on Earth is presented as preliminary proof of concept, such that future attempts may try to use remote sensing to create density and velocity time-series as inputs to magnetospheric simulations. Title: Observational Study of the Tridimensional Trajectory of Small White-Light Transients in the Inner Solar Corona Authors: Lopez-Portela, C.; Blanco-Cano, X.; Stenborg, G.; Vourlidas, A. Bibcode: 2013AGUSMSH23A..02L Altcode: The physical mechanisms responsible for the low corona origin and subsequent interplanetary development of the small scale white-light transients, known as blobs, is relevant to the formation and acceleration mechanisms of the slow solar wind (Sheeley et al., 1997). Since they are considered to be reliable tracers of the slow solar wind, a statistical kinematical characterization of these faint features should provide to the understanding of its origins and acceleration. The vantage observing points provided by the SECCHI and LASCO imagers aboard the STEREO and SOHO missions, respectively, allows us to get a good estimation of their trajectory in the 3D space and hence perform a detailed analysis of their unprojected kinematical parameters. To address this issue, we have surveyed the SOHO/LASCO C2 and C3, and the STEREO/SECCHI COR 1 and COR 2 databases for the year 2007 through 2010 (i.e., a period comprising the declining phase of the extended past solar minimum and the ascending phase of cycle 24) and selected about 100 blob-like features. The selection of events was facilitated by the scarce presence of coronal mass ejection events during this period, and it was limited to ±30° from the Sun's equator. The restricted latitudinal range is inspired by the work of Wang et al. (1998), who proposed that blobs are liberated from the cusp of helmet steamers. Two methods have been considered for the determination of the 3D kinematical parameters: (1) the tie-pointing and triangulation technique (Thompson W.T., 2008) and (2) the Height-Time analysis as developed by Mierla et al. (2008). In this work, we report on the set of transients studied by both techniques, discuss the limitations encountered on the determination of the 3D trajectories, and explore their significance on understanding the physical mechanisms behind the generation/propagation of the slow solar wind. Title: CME - Solar Wind interaction using remote and in-situ observations Authors: Nieves-Chinchilla, T.; Stenborg, G.; Vourlidas, A.; Savani, N. P.; Hidalgo, M. A.; Vena, L.; Szabo, A.; Colaninno, R. C. Bibcode: 2013AGUSMSH23B..05N Altcode: Coronal mass ejections (CMEs) are the main drivers of Space Weather. Accurate forecasting of their likely geo-effectiveness requires accurate tracking of their morphological and kinematical evolution throughout the interplanetary medium. However, single view-point observations depend on strong assumptions to model the development of the CME; the most common hypotheses are those of radial propagation and self-similar expansion. The use of different view-points show that, at least for some cases, those assumptions may not be valid. Analyses of remote sensing and in-situ data show signatures of strong deflection, over-expansion and/or large deformation. These behaviors could hide effects as rotation, deviation from radial propagation, or interaction with other magnetic obstacles. Understanding the 3D development and evolution of CME features is therefore of utmost importance to help establish the connection between remote and in-situ observations, and hence improve forecasting of Space Weather. In this work, we present the analysis of a set of selected events exhibiting clear signatures of deflection. With the help of remote imaging observations provided by the SOHO, STEREO and SDO missions, and in-situ measurements recorded by Wind, ACE, and Messenger. We show that such signatures are evidence of hidden effects such as rotation, changes in the direction of propagation, and/or interaction with other magnetic obstacles. Title: How Many CMEs Have Flux Ropes? Deciphering the Signatures of Shocks, Flux Ropes, and Prominences in Coronagraph Observations of CMEs Authors: Vourlidas, A.; Lynch, B. J.; Howard, R. A.; Li, Y. Bibcode: 2013SoPh..284..179V Altcode: 2012arXiv1207.1599V We intend to provide a comprehensive answer to the question on whether all Coronal Mass Ejections (CMEs) have flux rope structure. To achieve this, we present a synthesis of the LASCO CME observations over the last 16 years, assisted by 3D MHD simulations of the breakout model, EUV and coronagraphic observations from STEREO and SDO, and statistics from a revised LASCO CME database. We argue that the bright loop often seen as the CME leading edge is the result of pileup at the boundary of the erupting flux rope irrespective of whether a cavity or, more generally, a three-part CME can be identified. Based on our previous work on white light shock detection and supported by the MHD simulations, we identify a new type of morphology, the `two-front' morphology. It consists of a faint front followed by diffuse emission and the bright loop-like CME leading edge. We show that the faint front is caused by density compression at a wave (or possibly shock) front driven by the CME. We also present highly detailed multi-wavelength EUV observations that clarify the relative positioning of the prominence at the bottom of a coronal cavity with a clear flux rope structure. Finally, we visually check the full LASCO CME database for flux rope structures. In the process, we classify the events into two clear flux rope classes (`three-part', and `Loop'), jets and outflows (no clear structure). We find that at least 40 % of the observed CMEs have clear flux rope structures and that ∼ 29 % of the database entries are either misidentifications or inadequately measured and should be discarded from statistical analyses. We propose a new definition for flux rope CMEs (FR-CMEs) as a coherent magnetic, twist-carrying coronal structure with angular width of at least 40∘ and able to reach beyond 10 R⊙ which erupts on a time scale of a few minutes to several hours. We conclude that flux ropes are a common occurrence in CMEs and pose a challenge for future studies to identify CMEs that are clearly not FR-CMEs. Title: On the relationship between interplanetary coronal mass ejections and magnetic clouds Authors: Kilpua, Emilia; Isavnin, Alexey; Vourlidas, Angelos; Koskinen, Hannu; Rodriguez, Luciano Bibcode: 2013EGUGA..15.2827K Altcode: The relationship of magnetic clouds (MCs) to interplanetary coronal mass ejections (ICMEs) is still an open issue in space research. The view that all ICMEs would originate as magnetic flux ropes has received increasing attention, although near the orbit of the Earth only about one-third of ICMEs show clear MC signatures and often the MC occupies only a portion of the ICME. We have performed a systematic comparison of the cases where ICME and MC signatures coincided and where ICME signatures extended significantly beyond the MC boundaries. We found clear differences in the ICME properties (eg., speed, magnetic field magnitude), in the ambient solar wind structure, and in the solar cycle dependence for these two event types. We show that the MC and the regions of ICME-related plasma in front and behind the MC have all distinct characteristics enforcing the conception that they have intrinsically different origin or evolve differently. Erosion of magnetic flux in front of the ICME may also reconfigure the initial three-part CME seen in white-light images to a more complex ICME, but the geometrical effect (i.e. the encounter through the CME leg and/or far from the flux rope center) has little contribution to the observed mismathch in the MC and ICME boundary times. We will also discuss ramifications to CME and space weather research. Title: Probing the origin of solar energetic particles by combining solar and heliospheric imagery with in-situ measurements from the STEREO spacecraft (Arne Richter Award for Outstanding Young Scientists Lecture) Authors: Rouillard, Alexis P.; Tylka, Allan; Vourlidas, Angelos; Ng, Chee K. Bibcode: 2013EGUGA..1513908R Altcode: The Solar-Terrestrial Relations Observatory (STEREO), launched in 2006, is equipped with cameras that are observing the Sun and heliosphere from two vantage points. The orbital configuration of the spacecraft reached in 2011-2012 provides an unprecedented opportunity to track the expansion of Coronal Mass Ejections and their associated pressure waves in 3-D. We will present a series of analyses that combine ultraviolet and white-light images obtained by STEREO and the Solar Dynamics Observatory (SDO) to track, in the lower corona, the spatial and temporal evolution of pressure waves associated with the onset of CMEs. We use in-situ measurements of the onset of solar energetic particle events (SEPs) to determine their release time near the Sun. We concentrate on the proton-rich events detected by the near-Earth spacecraft and the STEREOs during 2011 and 2012. We use a simple model of the distribution of interplanerary magnetic field lines to determine the footpoint locations of field lines connecting the lower corona to the points of in-situ measurements. We (1) determine the height and spatial extent of the pressure waves at the SEP release times, (2) compare the longitudinal extent of SEP events with the extent of the pressure waves, (3) compare the kinematic properties of pressure waves launched over widely separated longitudes. We discuss the successes and challenges faced when interpreting these observations in terms of the acceleration of particles at coronal shocks. Title: Three-dimensional evolution of ejected flux ropes from the Sun to 1 AU Authors: Isavnin, Alexey; Vourlidas, Angelos; Kilpua, Emilia K. J. Bibcode: 2013EGUGA..15.3239I Altcode: Studying the evolution of magnetic clouds entrained in coronal mass ejections using in-situ data is a difficult task since only a limited number of observational points is available at large heliocentric distances. Remote sensing observations can, however, provide important information for events close to the Sun. In this work we estimate the flux rope orientation first by studying the associated prominences and/or post-eruptive arcades using STEREO/EUVI and SOHO/EIT observations, then in the close vicinity of the Sun using forward modeling of STEREO/SECCHI and SOHO/LASCO coronagraph images of coronal mass ejections and, finally, in-situ using Grad-Shafranov reconstruction of the magnetic cloud at 1 AU. We show that it is possible to reconstruct the three-dimensional orientation and geometry of the flux rope in each of these three stages of its evolution. Thus, we are able to measure changes in the orientation of the erupted flux ropes as they propagate from the Sun to 1 AU. In contrast to past studies, our method allows one to deduce the evolution of the three-dimensional orientation of individual flux ropes rather than on a statistical basis. We study 15 magnetic clouds observed during the minimum following Solar Cycle 23 and the rise of Solar Cycle 24. The results of our analysis confirm earlier studies showing that the flux ropes tend to deflect towards the solar equatorial plane. We also find evidence of rotation on their travel from the Sun to 1 AU. We further compare the orientations of the studied flux ropes with the local orientation of the heliospheric current sheet using global MHD simulations of the solar corona. Title: Tracking the momentum flux of a CME and quantifying its influence on geomagnetically induced currents at Earth Authors: Savani, Neel; Vourlidas, Angelos; Pullkinen, Antti Bibcode: 2013EGUGA..15.2314S Altcode: We investigate a CME propagating towards Earth on 29 March 2011. This event is specifically chosen for its predominately northward directed magnetic field, so that the influence from the momentum flux onto Earth can be isolated. We focus our study on understanding how a small Earth-directed segment propagates. Mass images are created from the white-light cameras onboard STEREO which are also converted into mass height-time maps (mass J-maps). The mass tracks on these J-maps correspond to the sheath region between the CME and its associated shock front as detected by in situ measurements at L1. A time-series of mass measurements from the STEREO COR-2A instrument are made along the Earth propagation direction. Qualitatively, this mass time-series shows a remarkable resemblance to the L1 in situ density series. The in situ measurements are used as inputs into a 3D magnetospheric space weather simulation from CCMC. These simulations display a sudden compression of the magnetosphere from the large momentum flux at the leading edge of the CME and predictions are made for the time-derivative of the magnetic field (dB/dt) on the ground. The predicted dB/dt were then compared with observations from specific equatorially-located ground stations and show notable similarity. This study of the momentum of a CME from the Sun down to its influence on magnetic ground stations on Earth is presented as preliminary proof of concept, such that future attempts may try to use remote sensing to create density and velocity time-series as inputs to magnetospheric simulations. Title: Derivation of the Magnetic Field in a Coronal Mass Ejection Core via Multi-frequency Radio Imaging Authors: Tun, Samuel D.; Vourlidas, A. Bibcode: 2013ApJ...766..130T Altcode: The magnetic field within the core of a coronal mass ejection (CME) on 2010 August 14 is derived from analysis of multi-wavelength radio imaging data. This CME's core was found to be the source of a moving type IV radio burst, whose emission is here determined to arise from the gyrosynchrotron process. The CME core's true trajectory, electron density, and line-of-sight depth are derived from stereoscopic observations, constraining these parameters in the radio emission models. We find that the CME carries a substantial amount of mildly relativistic electrons (E < 100 keV) in a strong magnetic field (B < 15 G), and that the spectra at lower heights are preferentially suppressed at lower frequencies through absorption from thermal electrons. We discuss the results in light of previous moving type IV burst studies, and outline a plan for the eventual use of radio methods for CME magnetic field diagnostics. Title: CME propagation analysis using remote and in-situ observations Authors: Nieves-Chinchilla, Teresa; Stenborg, Guillermo; Vourlidas, Angelos; Savani, Neel P.; Hidalgo, Miguel A.; Vena, Luis A.; Szabo, Adam; Colaninno, Robin C. Bibcode: 2013enss.confE..50N Altcode: Coronal mass ejections (CMEs) are the main drivers of Space Weather. Accurate forecasting of their likely geo-effectiveness requires accurate tracking of their morphological and kinematical evolution throughout the interplanetary medium. However, single view-point observations depend on strong assumptions to model the development of the CME; the most common hypotheses are those of radial propagation and self-similar expansion. The use of different view-points show that, at least for some cases, those assumptions may not be valid. Analyses of remote sensing and in-situ data show signatures of strong deflection, over-expansion and/or large deformation. These behaviors could hide effects as rotation, deviation from radial propagation, or interaction with other magnetic obstacles. Understanding the 3D development and evolution of CME features is therefore of utmost importance to help establish the connection between remote and in-situ observations, and hence improve forecasting of Space Weather. In this work, we present the analysis of a set of selected events exhibiting clear signatures of deflection. With the help of remote imaging observations provided by the SOHO, STEREO and SDO missions, and in-situ measurements recorded by Wind, ACE, and Messenger. We show that such signatures are evidence of hidden effects such as rotation, changes in the direction of propagation, and/or interaction with other magnetic obstacles. Title: First direct EUV observation and multi-temperature analysis of a coherent, wave-like propagating disturbance along pseudo-open field lines above a sunspot Authors: Stenborg, Guillermo; Stekel, Tardelli; Vourlidas, Angelos; Howard, Russell Bibcode: 2013enss.confE..55S Altcode: We report the first direct observation (along with a comprehensive kinematical characterization) of a wave-like front recorded in several SDO AIA channels. The front propagates coherently along a bundle of pseudo-open field lines with origin on an active region sunspot. Wavelet-processing of AIA images makes the wave-like disturbance clearly discernible with the naked eye. The disturbance propagates with an average plane-of-sky phase velocity of 50 km/sec in the 131 Å, 171 Å, 193 Å, 211 Å, 304 Å and 335 Å channels, exhibiting a 3 min periodicity in all cases. Its origin could be tracked down to a higher-than-average intensity point inside the umbra of the corresponding spot (i.e., an umbral dot) observed in the 1600 Å and 1700 Å AIA channels. The intensity of the source oscillates in phase with the wave-like phenomenon observed in the other channels. We speculate on the magneto-acoustic nature of the wave. Title: Direct Evidence for a Fast Coronal Mass Ejection Driven by the Prior Formation and Subsequent Destabilization of a Magnetic Flux Rope Authors: Patsourakos, S.; Vourlidas, A.; Stenborg, G. Bibcode: 2013ApJ...764..125P Altcode: 2012arXiv1211.7211P Magnetic flux ropes play a central role in the physics of coronal mass ejections (CMEs). Although a flux-rope topology is inferred for the majority of coronagraphic observations of CMEs, a heated debate rages on whether the flux ropes pre-exist or whether they are formed on-the-fly during the eruption. Here, we present a detailed analysis of extreme-ultraviolet observations of the formation of a flux rope during a confined flare followed about 7 hr later by the ejection of the flux rope and an eruptive flare. The two flares occurred during 2012 July 18 and 19. The second event unleashed a fast (>1000 km s-1) CME. We present the first direct evidence of a fast CME driven by the prior formation and destabilization of a coronal magnetic flux rope formed during the confined flare on July 18. Title: Multi-Spacecraft Observations of the Longitudinal Properties of Solar Energetic Particle Events Authors: Mewaldt, R. A.; Cohen, C. M.; Mason, G. M.; von Rosenvinge, T. T.; Gomez-Herrero, R.; Vourlidas, A.; Wiedenbeck, M. E. Bibcode: 2012AGUFMSH23B..02M Altcode: During the recent rise in solar activity, the twin STEREO spacecraft, in combination with near-Earth assets (e.g., ACE, GOES, RHESSI, SDO, SOHO, and Wind) have provided ~360° coverage of solar energetic particle (SEP) events, coronal mass ejections (CMEs), shocks, and other aspects of solar eruptions. This combination has provided an unprecedented opportunity to observe how the properties of SEP events vary with longitude. Initial results indicate that particles are distributed in longitude more easily than was earlier appreciated. Indeed, most recent large SEP events associated with CME-driven shocks are observed by both STEREOs and ACE, even as these spacecraft are separated by >100° in longitude. This talk will discuss longitudinal, intensity, composition, and spectral variations of large SEP events and compare them with models and previous studies. Small 3He-rich flares associated with flares and coronal jets are also found to be distributed more broadly in longitude than reported in single-point studies. Recent observations, issues, and proposed explanations for SEP longitudinal variations will be reviewed. Title: Kinematics of Earth Impacting Coronal Mass Ejections Authors: Colaninno, R. C.; Vourlidas, A. Bibcode: 2012AGUFMSH31A2210C Altcode: With the data from the STEREO mission, we are able to continuously monitor Coronal Mass Ejections (CMEs) as they progress from the Sun to Earth. However, even with continuous monitoring with remote sensing observations, we are still unable to accurately predict the arrival or terrestrial impact of a CME. In this study, we analyze nine CMEs from the Sun to Earth as observed in both the remote sensing and in situ data sets. In this study, we track nine CMEs from the Sun to 70% - 98% of the distance to Earth with the remote sensing data. We use the Graduate Cyclical Shell (GCS) model to estimate the position of each CME as it is observed in the inner heliosphere. From the derived kinematics, we compare the predicted arrival times and impact velocities with the in situ data. We consider different method for fitting the kinematics and the modeled geometry of the CME to improve the predicted arrival time. Title: The relation between the properties of pressure variations in the lower corona and solar energetic particle events Authors: Rouillard, A. P.; Vourlidas, A.; Tylka, A. J.; Cohen, C. M.; Mewaldt, R. A.; Mason, G. M.; Thernisien, A. F. Bibcode: 2012AGUFMSH24A..07R Altcode: We combine ultraviolet and white-light images obtained by the Solar Dynamics Observatory (SDO) and the Solar-Terrestrial Relations Observatory (STEREO) to track, in the lower corona, the spatial and temporal evolution of pressure waves associated with the onset of Coronal Mass Ejections (CMEs). We use in-situ measurements of the onset of solar energetic particle events (SEPs) to determine their release time near the Sun. We concentrate on the proton-rich events detected by the near-Earth spacecraft and the STEREOs during 2011 and 2012. We use a simple model of the distribution of interplanerary magnetic field lines to determine the foopoint locations of field lines connecting the lower corona to the points of in-situ measurements. We (1) determine the height and spatial extent of the pressure waves at the SEP release times, (2) compare the longitudinal extent of SEP events with the extent of the pressure waves, (3) compare the kinematic properties of pressure waves launched over widely separated longitudes. We discuss the successes and challenges faced when interpreting these observations in terms of the acceleration of particles at coronal shocks. Title: Super-elastic collision of large-scale magnetized plasmoids in the heliosphere Authors: Shen, Chenglong; Wang, Yuming; Wang, Shui; Liu, Ying; Liu, Rui; Vourlidas, Angelos; Miao, Bin; Ye, Pinzhong; Liu, Jiajia; Zhou, Zhenjun Bibcode: 2012NatPh...8..923S Altcode: 2014arXiv1412.7375S A super-elastic collision is an unusual process in which some mechanism causes the kinetic energy of the system to increase. Most studies have focused on solid-like objects, and have rarely considered gases or liquids, as the collision of these is primarily a mixing process. However, magnetized plasmoids are different from ordinary gases--as cross-field diffusion is effectively prohibited--but it remains unclear how they behave during a collision. Here we present a comprehensive picture of a unique collision between two coronal mass ejections in the heliosphere, which are the largest magnetized plasmoids erupting from the Sun. Our analysis reveals that these two magnetized plasmoids collided as if they were solid-like objects, with a likelihood of 73% that the collision was super-elastic. The total kinetic energy of the plasmoid system increased by about 6.6% through the collision, significantly influencing its dynamics. Title: Super-elastic Collision between Two Coronal Mass Ejections in the Heliosphere Authors: Wang, Y.; Shen, C.; Wang, S.; Liu, Y.; Liu, R.; Vourlidas, A.; Miao, B.; Liu, J.; Zhou, Z. Bibcode: 2012AGUFMSH21C..02W Altcode: Super-elastic collision is an abnormal collisional process, in which some particular mechanisms cause the kinetic energy of the system increasing. Most studies in this aspect focus on solid-like objects, but they rarely consider gases or liquids, as the collision of the latter is primarily a mixing process. With cross-field diffusion being effectively prohibited, magnetized plasmoids are different from ordinary gases. But it remains unclear how they act during a collision. Here we present the global picture of a unique collision between two coronal mass ejections in the heliosphere, which are the largest magnetized plasmoids erupting from the Sun. Our analysis for the first time reveals that these two magnetized plasmoids collided like solid-like objects with a 75% likelihood of being super-elastic. Their total kinetic energy surprisingly increased by about 6.9% through the collision, which significantly influenced the dynamics of the plasmoids. Title: A Comparison of Solar Energetic Particle Events with the Properties of Coronal Mass Ejections Authors: Kahler, S. W.; Vourlidas, A. Bibcode: 2012AGUFMSH23B..07K Altcode: Gradual solar energetic particle (SEP) events observed at 1 AU are produced by shocks driven by coronal mass ejections (CMEs). Our limited characterizations of the remotely imaged CMEs and of their associated SEP events observed in situ must be improved to increase our ability to forecast SEP events and to understand better the physical connections between the two phenomena. We carry out a statistical comparison of properties of 115 SEP events with those of their associated CMEs observed over the past solar cycle. Improved measurements of white-light CME images enable us to improve calculations of the masses and energies of CMEs using both leading edge and center- of-mass kinematics. These values are used in statistical comparisons with the peak 20-MeV intensities, the energy power-law spectral indices, the 2-MeV/nuc H/He ratios, and calculated total energies of SEP events observed on the Wind spacecraft. The large dynamical ranges of the SEP parameters allow us to look for statistical trends in the data that could give us physical insights into the physics of SEP production as well as possible SEP prediction tools. Title: Combining remote and in-situ observations to learn about CME evolution Authors: Nieves-Chinchilla, T.; Stenborg, G.; Vourlidas, A.; Colaninno, R. C.; Szabo, A.; Hidalgo, M. A.; Lepping, R. P.; Collinson, G. A.; Boardsen, S. A.; Anderson, B. J.; Korth, H.; Barabash, S.; Zhang, T.; Frahm, R. A.; Coates, A. J.; Shane, N. Bibcode: 2012AGUFMSH21C..04N Altcode: Multi-spacecraft observations of CME/ICMEs are critical sources of information to learn about the CME initiation, propagation, and evolution from the Sun through the heliosphere. However, the investigation has been undertaken from two, quite separate points of view, namely remote sensing and in-situ observations. In recent years, the availability of heliospheric imaging has provided a big impetus to link the events as observed from these two perspectives. However, a comprehensive and coordinated analysis of the multi-view point data, using different techniques and models, is still far of being completely understood. In this work, we demonstrate the discrepancy between these two points of view using a thorough analysis of imaging and in-situ observations at many inner heliospheric locations. We will show that the measurements of the distortion of the ICMEs is strongly affected by projection effects and that in-situ reconstructions of the CME structure are highly dependent on the selection of the magnetic field boundary. Therefore, both the cross section distortion and expansion, and, therefore, the CME evolution, are still unclear. We use a combination of remote (SOHO, STEREO, SDO) and in-situ (Wind, ACE, VEX, MESSENGER) observations to show the potential this approach has to shed light into the dynamical interaction of CMEs with the solar wind during their propagation and development through the interplanetary medium. Title: Simulate the Coronal Mass Ejection on 2011 March 7 from Chromosphere to 1 AU Authors: Jin, M.; Manchester, W. B.; van der Holst, B.; Oran, R.; Sokolov, I.; Toth, G.; Gombosi, T. I.; Vourlidas, A.; Liu, Y.; Sun, X. Bibcode: 2012AGUFMSH33E..04J Altcode: On 2011 March 7, a fast CME (> 2000 km/s) occurred in NOAA 11164. This event is also associated with a Solar Energetic Particle (SEP) event. In this study, we present the magnetohydrodynamics simulation results of this event. We initiate the CME by using the Titov-Demoulin flux rope model. The background solar wind starts from chromosphere with heat conduction and radiative cooling. The solar wind is driven by Alfven-wave pressure and heated by Alfven-wave dissipation. The magnetic field of the inner boundary is specified with a synoptic magnetogram from SDO/HMI. In order to produce the physically correct CME structures and CME-driven shocks, the electron and proton temperatures are separated so that the electron heat conduction is explicitly treated in conjunction with proton shock heating. We simulate the CME propagation to 1 AU. A comprehensive validation work is done by using the remote as well as the in-situ observation from SOHO, STEREOA/B, ACE, and WIND. Our result shows that the new model can reproduce most of the observed features near the Sun and in the heliosphere. The CME-driven shock is well reproduced, which is important for modeling the SEP event with diffusive shock acceleration. Title: Space weather effects of Cycle 24 SEP events Authors: Cohen, C. M.; Mewaldt, R. A.; Mason, G. M.; Vourlidas, A. Bibcode: 2012AGUFMSH44B..03C Altcode: When coronal mass ejections (CMEs) are fast and massive enough they can generate interplanetary shocks that accelerate particles to tens or hundreds of MeV/nucleon. These solar energetic particle (SEP) events are a space weather hazard to astronauts and sensitive space-based equipment. If the CME is directed towards Earth and impacts the magnetosphere it can trigger a geomagnetic storm, resulting in a variety of detrimental effects on communication systems and power grids. Although to date, solar cycle 24 has not produced many large-fluence SEP events nor many geoeffective CMEs, we will compare the activity experienced so far to the most significant events of cycle 23. Possible implications for the remainder of the cycle will also be discussed. Title: A Space Weather Mission to the Earth's 5th Lagrangian Point (L5) Authors: Howard, R. A.; Vourlidas, A.; Ko, Y.; Biesecker, D. A.; Krucker, S.; Murphy, N.; Bogdan, T. J.; St Cyr, O. C.; Davila, J. M.; Doschek, G. A.; Gopalswamy, N.; Korendyke, C. M.; Laming, J. M.; Liewer, P. C.; Lin, R. P.; Plunkett, S. P.; Socker, D. G.; Tomczyk, S.; Webb, D. F. Bibcode: 2012AGUFMSA13D..07H Altcode: The highly successful STEREO mission, launched by NASA in 2006, consisted of two spacecraft in heliocentric orbit, one leading and one trailing the Earth and each separating from Earth at the rate of about 22.5 degrees per year. Thus the two spacecraft have been probing different probe/Sun/Earth angles. The utility of having remote sensing and in-situ instrumentation away from the Sun-Earth line was well demonstrated by STEREO. Here we propose the concept of a mission at the 5th Lagrangian "point" in the Earth/Sun system, located behind Earth about 60 degrees to the East of the Sun-Earth line. Such a mission would enable many aspects affecting space weather to be well determined and thus improving the prediction of the conditions of the solar wind as it impinges on geospace. For example, Coronal Mass Ejections can tracked for a significant distance toward Earth, new active regions can be observed before they become visible to the Earth observer, the solar wind can be measured before it rotates to Earth. The advantages of such a mission will be discussed in this presentation. Title: Exploring Small Spatial Scales in the Transition Region and Solar Corona with the Very High Angular Resolution Imaging Spectrometer (VERIS) Authors: Chua, D. H.; Korendyke, C. M.; Vourlidas, A.; Brown, C. M.; Tun-Beltran, S.; Klimchuk, J. A.; Landi, E.; Seely, J.; Davila, J. M.; Hagood, R.; Roberts, D.; Shepler, E.; Feldman, R.; Moser, J.; Shea, J. Bibcode: 2012AGUFMSH33A2217C Altcode: Theoretical and experimental investigations of the transition region and coronal loops point to the importance of processes occurring on small spatial scales in governing the strong dynamics and impulsive energy release in these regions. As a consequence, high spatial, temporal, and temperature resolution over a broad temperature range, and accuracy in velocity and density determinations are all critical observational parameters. Current instruments lack one or more of these properties. These observational deficiencies have created a wide array of opposing descriptions of coronal loop heating and questions such as whether or not the plasma within coronal loops is multi-thermal or isothermal. High spectral and spatial resolution spectroscopic data are absolutely required to resolve these controversies and to advance our understanding of the dynamics within the solar atmosphere. We will achieve this with the Very High Angular Resolution Imaging Spectrometer (VERIS) sounding rocket payload. VERIS consists of an off-axis paraboloid telescope feeding a very high angular resolution, extreme ultraviolet (EUV) imaging spectrometer that will provide the first ever, simultaneous sub-arcsecond (0.16 arcsecond/pixel) spectra in bright lines needed to study plasma structures in the transition region, quiet corona, and active region core. It will do so with a spectral resolution of >5000 to allow Doppler velocity determinations to better than 3 km/s. VERIS uses a novel two-element, normal incidence optical design with highly reflective, broad wavelength coverage EUV coatings to access a spectral range with broad temperature coverage (0.03-15 MK) and density-sensitive line ratios. Combined with Hinode Solar Optical Telescope (SOT) and ground based observatories, VERIS will deliver simultaneous observations of the entire solar atmosphere from the photosphere to the multi-million degree corona at sub-arcsecond resolution for the first time ever, allowing us to understand the missing link between chromospheric structures and the corona. VERIS will be launched from White Sands Missile Range in early 2013. This paper presents a progress report on the VERIS payload and a summary of observations planned to further our understanding of the fine-scale structure of individual coronal loops and the heating mechanisms operating within them. Title: Preface Authors: Fleck, Bernhard; Heber, Bernd; Vourlidas, Angelos; van Driel-Gesztelyi, Lidia; Mandrini, Cristina H.; Leibacher, John Bibcode: 2012SoPh..281....1F Altcode: 2012SoPh..tmp..223F No abstract at ADS Title: Magnetic Topology of Active Regions and Coronal Holes: Implications for Coronal Outflows and the Solar Wind Authors: van Driel-Gesztelyi, L.; Culhane, J. L.; Baker, D.; Démoulin, P.; Mandrini, C. H.; DeRosa, M. L.; Rouillard, A. P.; Opitz, A.; Stenborg, G.; Vourlidas, A.; Brooks, D. H. Bibcode: 2012SoPh..281..237V Altcode: 2012SoPh..tmp..228V During 2 - 18 January 2008 a pair of low-latitude opposite-polarity coronal holes (CHs) were observed on the Sun with two active regions (ARs) and the heliospheric plasma sheet located between them. We use the Hinode/EUV Imaging Spectrometer (EIS) to locate AR-related outflows and measure their velocities. Solar-Terrestrial Relations Observatory (STEREO) imaging is also employed, as are the Advanced Composition Explorer (ACE) in-situ observations, to assess the resulting impacts on the solar wind (SW) properties. Magnetic-field extrapolations of the two ARs confirm that AR plasma outflows observed with EIS are co-spatial with quasi-separatrix layer locations, including the separatrix of a null point. Global potential-field source-surface modeling indicates that field lines in the vicinity of the null point extend up to the source surface, enabling a part of the EIS plasma upflows access to the SW. We find that similar upflow properties are also observed within closed-field regions that do not reach the source surface. We conclude that some of plasma upflows observed with EIS remain confined along closed coronal loops, but that a fraction of the plasma may be released into the slow SW. This suggests that ARs bordering coronal holes can contribute to the slow SW. Analyzing the in-situ data, we propose that the type of slow SW present depends on whether the AR is fully or partially enclosed by an overlying streamer. Title: Global Energetics of Thirty-eight Large Solar Eruptive Events Authors: Emslie, A. G.; Dennis, B. R.; Shih, A. Y.; Chamberlin, P. C.; Mewaldt, R. A.; Moore, C. S.; Share, G. H.; Vourlidas, A.; Welsch, B. T. Bibcode: 2012ApJ...759...71E Altcode: 2012arXiv1209.2654E We have evaluated the energetics of 38 solar eruptive events observed by a variety of spacecraft instruments between 2002 February and 2006 December, as accurately as the observations allow. The measured energetic components include: (1) the radiated energy in the Geostationary Operational Environmental Satellite 1-8 Å band, (2) the total energy radiated from the soft X-ray (SXR) emitting plasma, (3) the peak energy in the SXR-emitting plasma, (4) the bolometric radiated energy over the full duration of the event, (5) the energy in flare-accelerated electrons above 20 keV and in flare-accelerated ions above 1 MeV, (6) the kinetic and potential energies of the coronal mass ejection (CME), (7) the energy in solar energetic particles (SEPs) observed in interplanetary space, and (8) the amount of free (non-potential) magnetic energy estimated to be available in the pertinent active region. Major conclusions include: (1) the energy radiated by the SXR-emitting plasma exceeds, by about half an order of magnitude, the peak energy content of the thermal plasma that produces this radiation; (2) the energy content in flare-accelerated electrons and ions is sufficient to supply the bolometric energy radiated across all wavelengths throughout the event; (3) the energy contents of flare-accelerated electrons and ions are comparable; (4) the energy in SEPs is typically a few percent of the CME kinetic energy (measured in the rest frame of the solar wind); and (5) the available magnetic energy is sufficient to power the CME, the flare-accelerated particles, and the hot thermal plasma. Title: A Study of the Heliocentric Dependence of Shock Standoff Distance and Geometry using 2.5D Magnetohydrodynamic Simulations of Coronal Mass Ejection Driven Shocks Authors: Savani, N. P.; Shiota, D.; Kusano, K.; Vourlidas, A.; Lugaz, N. Bibcode: 2012ApJ...759..103S Altcode: 2012arXiv1209.1990S We perform four numerical magnetohydrodynamic simulations in 2.5 dimensions (2.5D) of fast coronal mass ejections (CMEs) and their associated shock fronts between 10 Rs and 300 Rs. We investigate the relative change in the shock standoff distance, Δ, as a fraction of the CME radial half-width, D OB (i.e., Δ/D OB). Previous hydrodynamic studies have related the shock standoff distance for Earth's magnetosphere to the density compression ratio (DR; ρ u/ρ d) measured across the bow shock. The DR coefficient, k dr, which is the proportionality constant between the relative standoff distance (Δ/D OB) and the compression ratio, was semi-empirically estimated as 1.1. For CMEs, we show that this value varies linearly as a function of heliocentric distance and changes significantly for different radii of curvature of the CME's leading edge. We find that a value of 0.8 ± 0.1 is more appropriate for small heliocentric distances (<30 Rs) which corresponds to the spherical geometry of a magnetosphere presented by Seiff. As the CME propagates its cross section becomes more oblate and the k dr value increases linearly with heliocentric distance, such that k dr = 1.1 is most appropriate at a heliocentric distance of about 80 Rs. For terrestrial distances (215 Rs) we estimate k dr = 1.8 ± 0.3, which also indicates that the CME cross-sectional structure is generally more oblate than that of Earth's magnetosphere. These alterations to the proportionality coefficients may serve to improve investigations into the estimates of the magnetic field in the corona upstream of a CME as well as the aspect ratio of CMEs as measured in situ. Title: Three-Dimensional Properties of Coronal Mass Ejections from STEREO/SECCHI Observations Authors: Bosman, E.; Bothmer, V.; Nisticò, G.; Vourlidas, A.; Howard, R. A.; Davies, J. A. Bibcode: 2012SoPh..281..167B Altcode: 2012SoPh..tmp..234B We identify 565 coronal mass ejections (CMEs) between January 2007 and December 2010 in observations from the twin STEREO/SECCHI/COR2 coronagraphs aboard the STEREO mission. Our list is in full agreement with the corresponding SOHO/LASCO CME Catalog (http://cdaw.gsfc.nasa.gov/CME_list/) for events with angular widths of 45∘ and up. The monthly event rates behave similarly to sunspot rates showing a three- to fourfold rise between September 2009 and March 2010. We select 51 events with well-defined white-light structure and model them as three-dimensional (3D) flux ropes using a forward-modeling technique developed by Thernisien, Howard and Vourlidas (Astrophys. J. 652, 763 - 773, 2006). We derive their 3D properties and identify their source regions. We find that the majority of the CME flux ropes (82 %) lie within 30∘ of the solar equator. Also, 82 % of the events are displaced from their source region, to a lower latitude, by 25∘ or less. These findings provide strong support for the deflection of CMEs towards the solar equator reported in earlier observations, e.g. by Cremades and Bothmer (Astron. Astrophys.422, 307 - 322, 2004). Title: On the Nature and Genesis of EUV Waves: A Synthesis of Observations from SOHO, STEREO, SDO, and Hinode (Invited Review) Authors: Patsourakos, Spiros; Vourlidas, Angelos Bibcode: 2012SoPh..281..187P Altcode: 2012SoPh..tmp...93P; 2012arXiv1203.1135P A major, albeit serendipitous, discovery of the SOlar and Heliospheric Observatory mission was the observation by the Extreme Ultraviolet Telescope (EIT) of large-scale extreme ultraviolet (EUV) intensity fronts propagating over a significant fraction of the Sun's surface. These so-called EIT or EUV waves are associated with eruptive phenomena and have been studied intensely. However, their wave nature has been challenged by non-wave (or pseudo-wave) interpretations and the subject remains under debate. A string of recent solar missions has provided a wealth of detailed EUV observations of these waves bringing us closer to resolving the question of their nature. With this review, we gather the current state-of-the-art knowledge in the field and synthesize it into a picture of an EUV wave driven by the lateral expansion of the CME. This picture can account for both wave and pseudo-wave interpretations of the observations, thus resolving the controversy over the nature of EUV waves to a large degree but not completely. We close with a discussion on several remaining open questions in the field of EUV waves research. Title: Uncovering the Birth of a Coronal Mass Ejection from Two-Viewpoint SECCHI Observations Authors: Vourlidas, A.; Syntelis, P.; Tsinganos, K. Bibcode: 2012SoPh..280..509V Altcode: 2012arXiv1201.0162V; 2012SoPh..tmp...27V We investigate the initiation and formation of Coronal Mass Ejections (CMEs) via a detailed two-viewpoint analysis of low corona observations of a relatively fast CME acquired by the SECCHI instruments aboard the STEREO mission. The event which occurred on 2 January 2008, was chosen because of several unique characteristics. It shows upward motions for at least four hours before the flare peak. Its speed and acceleration profiles exhibit a number of inflections which seem to have a direct counterpart in the GOES light curves. We detect and measure, in 3D, loops that collapse toward the erupting channel while the CME is increasing in size and accelerates. We suggest that these collapsing loops are our first evidence of magnetic evacuation behind the forming CME flux rope. We report the detection of a hot structure which becomes the core of the white light CME. We observe and measure unidirectional flows along the erupting filament channel which may be associated with the eruption process. Finally, we compare these observations to the predictions from the standard flare-CME model and find a very satisfactory agreement. We conclude that the standard flare-CME concept is a reliable representation of the initial stages of CMEs and that multi-viewpoint, high cadence EUV observations can be extremely useful in understanding the formation of CMEs. Title: Intercomparison of the LASCO-C2, SECCHI-COR1, SECCHI-COR2, and Mk4 Coronagraphs Authors: Frazin, Richard A.; Vásquez, Alberto M.; Thompson, William T.; Hewett, Russell J.; Lamy, Philippe; Llebaria, Antoine; Vourlidas, Angelos; Burkepile, Joan Bibcode: 2012SoPh..280..273F Altcode: 2012SoPh..tmp..140F In order to assess the reliability and consistency of white-light coronagraph measurements, we report on quantitative comparisons between polarized brightness [pB] and total brightness [B] images taken by the following white-light coronagraphs: LASCO-C2 on SOHO, SECCHI-COR1 and -COR2 on STEREO, and the ground-based MLSO-Mk4. The data for this comparison were taken on 16 April 2007, when both STEREO spacecraft were within 3.1∘ of Earth's heliographic longitude, affording essentially the same view of the Sun for all of the instruments. Due to the difficulties of estimating stray-light backgrounds in COR1 and COR2, only Mk4 and C2 produce reliable coronal-hole values (but not at overlapping heights), and these cannot be validated without rocket flights or ground-based eclipse measurements. Generally, the agreement between all of the instruments' pB values is within the uncertainties in bright streamer structures, implying that measurements of bright CMEs also should be trustworthy. Dominant sources of uncertainty and stray light are discussed, as is the design of future coronagraphs from the perspective of the experiences with these instruments. Title: Secondary Waves and/or the "Reflection" from and "Transmission" through a Coronal Hole of an Extreme Ultraviolet Wave Associated with the 2011 February 15 X2.2 Flare Observed with SDO/AIA and STEREO/EUVI Authors: Olmedo, Oscar; Vourlidas, Angelos; Zhang, Jie; Cheng, Xin Bibcode: 2012ApJ...756..143O Altcode: 2012arXiv1206.6137O For the first time, the kinematic evolution of a coronal wave over the entire solar surface is studied. Full Sun maps can be made by combining images from the Solar Terrestrial Relations Observatory satellites, Ahead and Behind, and the Solar Dynamics Observatory, thanks to the wide angular separation between them. We study the propagation of a coronal wave, also known as the "Extreme Ultraviolet Imaging Telescope" wave, and its interaction with a coronal hole (CH) resulting in secondary waves and/or reflection and transmission. We explore the possibility of the wave obeying the law of reflection. In a detailed example, we find that a loop arcade at the CH boundary cascades and oscillates as a result of the extreme ultraviolet (EUV) wave passage and triggers a wave directed eastward that appears to have reflected. We find that the speed of this wave decelerates to an asymptotic value, which is less than half of the primary EUV wave speed. Thanks to the full Sun coverage we are able to determine that part of the primary wave is transmitted through the CH. This is the first observation of its kind. The kinematic measurements of the reflected and transmitted wave tracks are consistent with a fast-mode magnetohydrodynamic wave interpretation. Eventually, all wave tracks decelerate and disappear at a distance. A possible scenario of the whole process is that the wave is initially driven by the expanding coronal mass ejection and subsequently decouples from the driver and then propagates at the local fast-mode speed. Title: Erratum: "Initiation and Development of the White-light and Radio Coronal Mass Ejection on 2001 April 15" (2012, ApJ, 750, 147) Authors: Démoulin, P.; Vourlidas, A.; Pick, M.; Bouteille, A. Bibcode: 2012ApJ...754..156D Altcode: No abstract at ADS Title: Science Highlights from the First Three Years of CME Observations from STEREO/SECCHI Authors: Vourlidas, A. Bibcode: 2012ASPC..454..367V Altcode: Since early 2007, the SECCHI experiment aboard the STEREO mission has been observing the Sun and the heliosphere from two varying vantage points using EUV disk imagers, coronagraphs and heliospheric imagers. Despite the prolonged solar minimum, the unprecedented coverage of solar eruptions from the low corona to beyond 1 AU is providing many new and fundamental insights into the physics of CME formation, initiation and propagation. Here, I highlight a few key results and outline possible scientific synergies between the STEREO and the Hinode payloads. Title: Magnetic topology, coronal outflows, and the solar wind Authors: Mandrini, Cristina H.; Culhane, J. Leonard; Vourlidas, Angelos; Demoulin, Pascal; Stenborg, Guillermo; Opitz, Andrea; Rouillard, Alexis; Van Driel-Gesztelyi, Lidia; Baker, Deborah; DeRosa, Marc; Brooks, David Bibcode: 2012cosp...39.1173M Altcode: 2012cosp.meet.1173M During 2-18 January 2008 a pair of low-latitude opposite polarity coronal holes were observed on the Sun flanked by two ARs with the heliospheric plasma sheet between them. Hinode/EUV Imaging Telescope (EIS) is used to locate AR-related outflows and measure their velocities. The Advanced Composition Explorer (ACE) in-situ observations are employed to assess the resulting impacts on the interplanetary solar wind (SW). Magnetic field extrapolations of the two ARs confirm that AR plasma outflows observed with EIS are co-spatial with quasi-separatrix layer locations, including the separatrix of a null point. Global potential field source-surface modeling indicates that field lines in the vicinity of the null point extend up to the source-surface, enabling a part of the EIS plasma upflows access to the SW. Similar upflow magnitude is also observed within closed field regions. Though part of the plasma upflows observed with EIS remain confined along closed coronal loops, a subset of them are indeed able to make their imprint in the slow SW, making ARs bordering coronal holes a slow SW contributor. Title: Future Remote-Sensing Observations of CMEs from out of the Ecliptic Authors: Lugaz, Noé; Roussev, Ilia; Liewer, Paulett; Vourlidas, Angelos; Downs, Cooper Bibcode: 2012cosp...39.1116L Altcode: 2012cosp.meet.1116L In the past four decades, Coronal Mass Ejections (CMEs) have been observed remotely with coronagraphs primarily from Earth or L1. More recently, using SMEI and STEREO/SECCHI, CMEs are now routinely observed to larger distances (up to 1 AU and beyond) and from directions away from the Sun-Earth line. We will review some of the new techniques, which have been devised to analyze these observations and discuss how they might be adapted to observations from out-of-ecliptic. We will also present simulated white-light and extreme-ultraviolet (EUV) images of CMEs as they would appear from different orbits above the ecliptic. Taking advantage of the fact that, in MHD simulations, the plasma parameters are known in at each time-step in the full 3-D volume, we will discuss how multiple viewpoints might help reveal the 3-D nature of CMEs and associated phenomena. Title: The Longitudinal Properties of a Solar Energetic Particle Event Investigated Using Modern Solar Imaging Authors: Rouillard, A. P.; Sheeley, N. R.; Tylka, A.; Vourlidas, A.; Ng, C. K.; Rakowski, C.; Cohen, C. M. S.; Mewaldt, R. A.; Mason, G. M.; Reames, D.; Savani, N. P.; StCyr, O. C.; Szabo, A. Bibcode: 2012ApJ...752...44R Altcode: We use combined high-cadence, high-resolution, and multi-point imaging by the Solar-Terrestrial Relations Observatory (STEREO) and the Solar and Heliospheric Observatory to investigate the hour-long eruption of a fast and wide coronal mass ejection (CME) on 2011 March 21 when the twin STEREO spacecraft were located beyond the solar limbs. We analyze the relation between the eruption of the CME, the evolution of an Extreme Ultraviolet (EUV) wave, and the onset of a solar energetic particle (SEP) event measured in situ by the STEREO and near-Earth orbiting spacecraft. Combined ultraviolet and white-light images of the lower corona reveal that in an initial CME lateral "expansion phase," the EUV disturbance tracks the laterally expanding flanks of the CME, both moving parallel to the solar surface with speeds of ~450 km s-1. When the lateral expansion of the ejecta ceases, the EUV disturbance carries on propagating parallel to the solar surface but devolves rapidly into a less coherent structure. Multi-point tracking of the CME leading edge and the effects of the launched compression waves (e.g., pushed streamers) give anti-sunward speeds that initially exceed 900 km s-1 at all measured position angles. We combine our analysis of ultraviolet and white-light images with a comprehensive study of the velocity dispersion of energetic particles measured in situ by particle detectors located at STEREO-A (STA) and first Lagrange point (L1), to demonstrate that the delayed solar particle release times at STA and L1 are consistent with the time required (30-40 minutes) for the CME to perturb the corona over a wide range of longitudes. This study finds an association between the longitudinal extent of the perturbed corona (in EUV and white light) and the longitudinal extent of the SEP event in the heliosphere. Title: Uncloaking Structures and Dynamic Phenomena on EUV images via a multi-resolution based image-processing technique Authors: Stenborg, Guillermo Adrian; Vourlidas, Angelos; Howard, Russell Bibcode: 2012shin.confE.213S Altcode: Groundbreaking observations of the low solar corona at extreme ultraviolet (EUV) wavelengths have been provided by the EIT instrument on board SOHO for more than 15 years. At the beginning of 2007, the EUVI instruments on board the twin STEREO spacecraft opened doors and commenced to image the EUV low corona with an improved cadence and spatial resolution from two vantage points off the Sun-Earth line. Since February 2010, the AIA instrument on board the Solar Dynamics Observatory observes the low EUVI corona at a 10 sec cadence in 8 wavelengths. Despite the increasing quality of the EUV observations, they have not been fully exploited. A customized wavelet-based image cleaning and enhancing technique that exploits the multi-scale nature of the observed solar features has been developed (Stenborg et al., 2008) to maximize the scientific return of the EIT observations. We have now adapted it to work with STEREO/EUVI and SDO/AIA images. Its application has already helped unveil phenomena only theorized before, as well as revealed phenomena that have not found a satisfactory explanation yet. In this presentation, we make a brief survey of the new products, and recent related discoveries, in particular with regard to its relevance to the prominence/cavity/CME expansion paradigm. Title: Remote and in situ observations of an unusual Earth-directed coronal mass ejection from multiple viewpoints Authors: Nieves-Chinchilla, T.; Colaninno, R.; Vourlidas, A.; Szabo, A.; Lepping, R. P.; Boardsen, S. A.; Anderson, B. J.; Korth, H. Bibcode: 2012JGRA..117.6106N Altcode: 2012JGRA..11706106N During June 16-21, 2010, an Earth-directed coronal mass ejection (CME) event was observed by instruments onboard STEREO, SOHO, MESSENGER and Wind. This event was the first direct detection of a rotating CME in the middle and outer corona. Here, we carry out a comprehensive analysis of the evolution of the CME in the interplanetary medium comparing in situ and remote observations, with analytical models and three-dimensional reconstructions. In particular, we investigate the parallel and perpendicular cross section expansion of the CME from the corona through the heliosphere up to 1 AU. We use height-time measurements and the Gradual Cylindrical Shell (GCS) technique to model the imaging observations, remove the projection effects, and derive the 3-dimensional extent of the event. Then, we compare the results with in situ analytical Magnetic Cloud (MC) models, and with geometrical predictions from past works. We find that the parallel (along the propagation plane) cross section expansion agrees well with the in situ model and with the Bothmer and Schwenn (1998) empirical relationship based on in situ observations between 0.3 and 1 AU. Our results effectively extend this empirical relationship to about 5 solar radii. The expansion of the perpendicular diameter agrees very well with the in situ results at MESSENGER (∼0.5 AU) but not at 1 AU. We also find a slightly different, from Bothmer and Schwenn (1998), empirical relationship for the perpendicular expansion. More importantly, we find no evidence that the CME undergoes a significant latitudinal over-expansion as it is commonly assumed. Instead, we find evidence that effects due to CME rotation and expansion can be easily confused in the images leading to a severe overestimation of the proper 3D size of the event. Finally, we find that the reconstructions of the CME morphology from the in situ observations at 1 AU are in agreement with the remote sensing observations but they show a big discrepancy at MESSENGER. We attribute this discrepancy to the ambiguity of selecting the proper boundaries due to the lack of accompanying plasma measurements. Title: The influence of CME momentum onto the Earth's Magnetosphere Authors: Savani, Neel P.; Vourlidas, A. Bibcode: 2012shin.confE..12S Altcode: Recent observations have been able to track the white light structures of CMEs from remote observations of the corona out to planetary bodies, where comparative studies with in situ measurements have been made. The majority of these studies have focused on achieving consistent results for parameters such as the arrival time, propagation direction and the orientation of a possible magnetic flux rope topology. In this study we focus on estimating mass and momentum of the CME for both the structure in its entirety and for the narrow slit which travels over Earth. We track the mass profile of the CME through the Heliospheric Imagers onboard STEREO and monitor the resulting in situ measurements at L1. We test the hypothesis that the sudden increase in momentum of the solar wind instigates a geomagnetic disturbance and affects the initial phase of the magnetic activity indices. Title: Three-dimensional evolution of erupted flux ropes from the Sun to 1AU Authors: Isavnin, Alexey; Vourlidas, Angelos; Kilpua, Emilia K. J. Bibcode: 2012shin.confE..83I Altcode: Studying the evolution of magnetic clouds entrained in by coronal mass ejections using in-situ data is a difficult task since only a limited number of observational points is at hand. In this work we estimate the flux rope orientation first in the close vicinity of the Sun (2-20Rs) using forward modeling of STEREO/SECCHI and SOHO/LASCO coronagraph images of coronal mass ejections and then in situ using Grad-Shafranov reconstruction of the magnetic cloud. Thus, we are able to measure changes in the orientation of individual erupted flux ropes as they propagated from the Sun to 1AU. We use this method to study 15 magnetic clouds observed during the minimum following the Solar Cycle 23 and the rise of the Solar Cycle 24. Our analysis of these selected events shows that flux ropes tend to deflect towards the solar equatorial plane on their travel from the Sun to 1AU and also experience rotation. Title: Study of the coronal thermal response to an EUV wave Authors: Olmedo, Oscar A.; Vourlidas, Angelos; Stenborg, Guillermo Bibcode: 2012shin.confE.102O Altcode: In this work we use observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory to study, in high-temporal cadence, the temperature response of the corona to the passage of EUV waves. We use the flux ratios of the six AIA EUV channels and DEM to study how the temperature of the disturbed plasma evolves with time. During our investigation we found that there is an appreciable amount of stray light scatter, particularly in the 131 and 94 Angstrom AIA channels, due to the flare associated with the EUV wave. We explore several methods in an attempt to suppress this scatter. Title: Are There Connections in Eruptive Events Across Time and Space? Authors: Vourlidas, Angelos Bibcode: 2012shin.confE.158V Altcode: Coronal Mass Ejections (CMEs) from different source regions occur sometimes in close temporal proximity. Repeated eruptive flares occur sometimes at the same location in an active region. Are these eruptions related somehow? Can eruptions 'communicate' across large distances or in across time or are they simply chance occurrences? In this talk, I will discuss how observations of 'sympathetic' CMEs and 'homologous' flares relate to the questions above. Title: Initiation and Development of the White-light and Radio Coronal Mass Ejection on 2001 April 15 Authors: Démoulin, P.; Vourlidas, A.; Pick, M.; Bouteille, A. Bibcode: 2012ApJ...750..147D Altcode: The 2001 April 15 event was one of the largest of the last solar cycle. A former study established that this event was associated with a coronal mass ejection (CME) observed both at white light and radio frequencies. This radio CME is illuminated by synchrotron emission from relativistic electrons. In this paper, we investigate the relation of the radio CME to its extreme-ultraviolet (EUV) and white-light counterpart and reach four main conclusions. (1) The radio CME corresponds to the white-light flux rope cavity. (2) The presence of a reconnecting current sheet behind the erupting flux rope is framed, both from below and above, by bursty radio sources. This reconnection is the source of relativistic radiating electrons which are injected down along the reconnected coronal arches and up along the flux rope border forming the radio CME. (3) Radio imaging reveals an important lateral overexpansion in the low corona; this overexpansion is at the origin of compression regions where type II and III bursts are imaged. (4) Already in the initiation phase, radio images reveal large-scale interactions of the source active region (AR) with its surroundings, including another AR and open magnetic fields. Thus, these complementary radio, EUV, and white-light data validate the flux rope eruption model of CMEs. Title: A decade of coronagraphic and spectroscopic studies of CME-driven shocks Authors: Vourlidas, Angelos; Bemporad, Alessandro Bibcode: 2012AIPC.1436..279V Altcode: 2012arXiv1207.1603V Shocks driven by Coronal Mass Ejections (CMEs) are primary agents of space weather. They can accelerate particles to high energies and can compress the magnetosphere thus setting in motion geomagnetic storms. For many years, these shocks were studied only in-situ when they crossed over spacecraft or remotely through their radio emission spectra. Neither of these two methods provides information on the spatial structure of the shock nor on its relationship to its driver, the CME. In the last decade, we have been able to not only image shocks with coronagraphs but also measure their properties remotely through the use of spectroscopic and image analysis methods. Thanks to instrumentation on STEREO and SOHO we can now image shocks (and waves) from the low corona, through the inner heliosphere, to Earth. Here, we review the progress made in imaging and analyzing CME-driven shocks and show that joint coronagraphic and spectrscopic observations are our best means to understand shock physics close to the Sun. Title: High spatial resolution VAULT H-Lyα observations and multiwavelength analysis of an active region filament Authors: Vial, J. -C.; Olivier, K.; Philippon, A. A.; Vourlidas, A.; Yurchyshyn, V. Bibcode: 2012A&A...541A.108V Altcode: Context. The search for the fine structure of prominences has received considerable new attention thanks to the Swedish Solar Telescope (SST) Hα pictures that provide an unsurpassed spatial resolution. Recently, it has been shown that the filaments' coronal environment, at least for quiescent filaments, is perturbed by either cool absorbing material (in the EUV) or an "emissivity blocking" (actually a lack of transition region and coronal material).
Aims: The aim is to assess the fine structure in an active region filament and to determine the nature of the EUV absorption or lack of emission phenomena, using the very optically thick line H-Lyα, formed at a temperature higher than Hα.
Methods: We performed a multiwavelength study where high-resolution imaging in the H-Lyα line (VAULT) was analysed and compared with observations of an active region filament in Hα (BBSO) and EUV lines (EIT and TRACE).
Results: As for the SST data, small-scale structures were detected at a typical scale of about one to two arcseconds with, for some cuts, an indication of fine scales down to 0.4 arcsec in the optically thick H-Lyα line. The filament intensity relative to the intensity of the (active) region it is embedded in is about 0.2 in H-Lyα. This ratio (Lymanα ratio intensity or "LRI") is the lowest value compared to other lines, e.g. Hα. The filament environment was also investigated and evidence of an UV extension was found. The comparison of spatial cuts in different lines across the filament shows evidence of strong absorption, and consequently of cool plasma on one side of the filament, but not on the other (that side is obscured by the filament itself).
Conclusions: The absence of very fine structure in H-Lyα compared to Hα is explained by the formation temperature of the H-Lyα line (~20 000 K), where the transition regions of the thin threads begin to merge. From the detection of H-Lyα absorption on the observable side of the filament side, we derive the presence of absorbing (cool) material and possibly also of emissivity blocking (or coronal void). This poses the question whether these absorption effects are typical of active region filaments.

Appendix A is available in electronic form at http://www.aanda.org Title: Global Energetics of Large Solar Eruptive Events Authors: Dennis, Brian R.; Emslie, A. G.; Chamberlin, P. C.; Mewaldt, R. A.; Moore, C. S.; Share, G. H.; Shih, A. Y.; Vourlidas, A.; Welsch, B. Bibcode: 2012AAS...22041002D Altcode: We have evaluated the energetics of the larger solar eruptive events recorded with a variety of spacecraft instruments between February 2002 and December 2006. All of the energetically important components of the flares and of the accompanying coronal mass ejections and solar energetic particles have been evaluated as accurately as the observations allow. These components include the following: (1) the total energy in the high temperature plasma determined from the RHESSI thermal X-ray observations; (2) the total energies in accelerated electrons above 20 keV and ions above 1 MeV from RHESSI hard X-ray and gamma-ray observations, respectively; (3) the potential and kinetic energies of the CME from SOHO/LASCO observations; (4) the solar energetic particle (SEP) energy estimates from in situ measurements on ACE, GOES, and SOHO; (5) the total radiated energy from the SORCE/TSI measurements where available, and otherwise from the Flare Irradiance Spectral Model (FISM). The results are assimilated and discussed relative to the probable amount of nonpotential magnetic energy estimated to be available in the flaring active regions from MDI line-of-sight magnetograms. Title: Observation of “Transmission” of an EUV Wave Through a Coronal Hole Authors: Olmedo, Oscar; Vourlidas, A.; Zhang, J.; Cheng, X. Bibcode: 2012AAS...22052120O Altcode: We present for the first time what appears to be the “transmission” of an EUV wave through a coronal hole. Though this effect had not previously been observed, numerical simulations indicate that EUV waves can cross coronal holes. The EUV wave event studied in this work occurred on 2011 February 15 and was associated with an X class flare. It is seen that the part of the wave that crosses the coronal hole appears to accelerate relative to the part over the quiet Sun. This observation is fully consistent with the behavior of a fast-mode wave since the fast-mode speed will be higher in a coronal hole (due to its reduced plasma density) than in the quiet Sun at a given height. These observations are hard to reconcile with a pure pseudo-wave interpretation of EUV waves. Our findings indicate that we accept either all EUV waves as fast-mode waves or the hybrid interpretation of EUV waves where the coronal mass ejections outer envelope, observed as a pseudo-wave, triggers a fast-mode wave seen later on in the event. In the latter scenario the EUV wave should look to propagate continuously as the coronal mass ejection leaves behind a fast-mode wave in its wake. And it is this fast-mode wave that crosses the coronal hole. Title: The Current Status of Research on Coronal Mass Ejections Authors: Vourlidas, Angelos Bibcode: 2012AAS...22030401V Altcode: Coronal Mass Ejections (CMEs) are the main drivers of Space Weather and have been the focus of intense research since the mid-1990's. Since 2007, CMEs have even been studied stereoscopically by the STEREO mission. We now have observations spanning more than one solar cycle, 3D information, simultaneous remote and in-situ observations, a wide wavelength coverage, and quite sophisticated MHD simulations. In this talk, I will review our current status of knowledge on the CME phenomenon with an emphasis on the open issues on the geoeffectiveness of these events. Title: CME mass evolution derived from stereoscopic observations of STEREO/SECCHI instruments COR1 and COR2 Authors: Bein, B.; Temmer, M.; Vourlidas, A.; Veronig, A. Bibcode: 2012EGUGA..14.7174B Altcode: The STEREO mission consists of two nearly identical spacecraft STEREO-A and STEREO-B, which observe simultaneously the Sun from two different vantage points. We use observations from both coronagraphs, COR1 and COR2 of the SECCHI instrument suite aboard STEREO-A and STEREO-B, to derive the CME mass evolution for a height range from 1.4 to 15 RSun. Due to the fact that we have observations from two different vantage points, we measure not only the projected mass but can estimate the 'true' CME mass evolution with height. We developed a fit function, which considers the mass increase based on the geometry of the instrument (mass hidden behind the occulter) and a possible 'real' mass increase with height. The fit parameters are compared with characteristic CME quantities. Title: Type II Radio Emission from Shock Formation In The Low Corona on 13-Jun-2010: Combined Observations from the ARTEMIS-IV Radiospectrograph and SDO/AIA Authors: Kouloumvakos, A.; Vourlidas, A.; Preka-Papadema, P.; Hillaris, A.; Caroubalos, C.; Moussas, X.; Tsitsipis, P.; Kontogeorgos, A. Bibcode: 2012hell.confQ..12K Altcode: High cadence observations in the low corona from AIA imagers combined with radiospectrograph high-resolution recordings give a new perspective of shock formation in the low corona. Using ARTEMIS-IV observations of drifting type-II metric radio emission and ultra-high resolution observations from the AIA imagers we present direct observation of shock formation in the EUV and its association to the accompanying type-II during the 13-Jun-2010 Event. We will show that, in this case, the coronal expansion driven by the formation of the CME ejecta is responsible for both EUV and radio emissions. Title: STEREO and SDO observations of several solar jets Authors: Tsinganos, K.; Moschou, S.; Vourlidas, A. Bibcode: 2012hell.conf...13T Altcode: We present an analysis of recent observations of several solar jets observed at the solar limb with STEREO A/B and the Solar Dynamics Observatory (SDO). We construct fitted height-time diagrams at all wavelengths and calculate the temporal evolution of the jet speed and acceleration. The first case is a large solar jet observed on 06/30/2010, simultaneously by STEREO & SDO in the north solar pole, at many wavelengths, from 171 to 304 Angstroms. It has a precursor and lasts in total for about 60 minutes, while the main jet reaches a height of 0.3 Ro and a maximum speed of about 250 km/sec. The second sample contains a set of four solar limb jets observed 5 days earlier than the previous one, i.e., 06/25/2010. All jets are observed with SDO while two of them are simultaneously observed with STEREO. Two jets have a precursor and last from 60 - 120 minutes, reaching heights of less than 0.2 Ro. Finally, we analyse a jet observed by STEREO on 11/12/2008 in 174, 195, 284 and 304 Angstroms. The jet reaches a height of 0.25 Ro and a maximum speed of about 150 km/sec. Magnetograms during the jet appearances show the corresponding magnetic topologies. The velocities involved are smaller than the escape speed from the sun at each radius. The results are preliminarily discussed in relation to possible jet formation mechanisms. Title: New Views of the Solar Corona from STEREO and SDO Authors: Vourlidas, A. Bibcode: 2012hell.conf....6V Altcode: In the last few years, we have been treated to an unusual visual feast of solar observations of the corona in EUV wavelengths. The observations from the two vantage points of STEREO/SECCHI are now capturing the entire solar atmosphere simultaneously in four wavelengths. The SDO/AIA images provide us with arcsecond resolution images of the full visible disk in ten wavelengths. All these data are captured with cadences of a few seconds to a few minutes. In this talk, I review some intriguing results from our first attempts to deal with these observations which touch upon the problems of coronal mass ejection initiation and solar wind generation. I will also discuss data processing techniques that may help us recover even more information from the images. The talk will contain a generous portion of beautiful EUV images and movies of the solar corona. Title: Constraining a Model for EUV Wave Formation with SDO and STEREO Quadrature Observations Authors: Patsourakos, S.; Vourlidas, A.; Olmedo, O. Bibcode: 2012hell.conf....7P Altcode: The generation mechanism(s) of large-scale propagating intensity fronts seen in the EUV, often called EUV waves, in association with impulsive Coronal Mass Ejection (CMEs) is currently a matter of debate. The strong lateral expansion which some impulsive CMEs undergo during their early phases, when they are observed in the inner corona by EUV imagers, is one possible mechanism for the generation of EUV waves. One impulsive CME - EUV wave pair was observed during 15 February 2011 in quadrature by SDO and STEREO. The source active region was close to disk center as seen by SDO and at the limb as seen by STEREO. This configuration allowed us to determine the kinematics of the EUV wave and of the early EUV CME by AIA/SDO and EUVI/STEREO respectively. The detailed kinematics of the early EUV CME (height and radius evolution of the erupting flux) were then used to constrain a simple model of EUV wave formation, invoking the erupting flux as the wave driver. The ground tracks of the EUV wave as predicted by this data-driven model were then compared with those of the observed wave. Title: On the initiation of Coronal Mass Ejections observed by STEREO/EUVI Authors: Syntelis, P.; Tsinganos, K.; Vourlidas, A.; Gontikakis, C. Bibcode: 2012hell.confR..14S Altcode: This study examines different stages of a Coronal Mass Ejection's (CME) initiation in NOAA Active Region (AR) 10980, observed on January 2, 2008 by STEREO's Extreme UltraViolet Imager (EUVI). We identify a first phase consisting of an upward motion, which at 1.58R? reaches the velocity of 70 (4) km/s. Those measurements are extrapolated to later time frames to examine whether this initial acceleration drives the CME's propagation later on. We also identify an ascending new flux-rope beneath the CME. During the CME's rise, there are indications that some adjacent loops incline to the main CME body. At the later phase of the initiation, some moving blob-like structures appear along the CME flanks. Propagation speeds of these blobs are measured. These blobs could be indications that a siphon flow exists along the CME. Title: Investigation of the Formation and Separation of an Extreme-ultraviolet Wave from the Expansion of a Coronal Mass Ejection Authors: Cheng, X.; Zhang, J.; Olmedo, O.; Vourlidas, A.; Ding, M. D.; Liu, Y. Bibcode: 2012ApJ...745L...5C Altcode: 2011arXiv1112.4540C We address the nature of EUV waves through direct observations of the formation of a diffuse wave driven by the expansion of a coronal mass ejection (CME) and its subsequent separation from the CME front. The wave and the CME on 2011 June 7 were well observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. Following the solar eruption onset, marked by the beginning of the rapid increasing of the CME velocity and the X-ray flux of accompanying flare, the CME exhibits a strong lateral expansion. During this impulsive expansion phase, the expansion speed of the CME bubble increases from 100 km s-1 to 450 km s-1 in only six minutes. An important finding is that a diffuse wave front starts to separate from the front of the expanding bubble shortly after the lateral expansion slows down. Also a type II burst is formed near the time of the separation. After the separation, two distinct fronts propagate with different kinematic properties. The diffuse front travels across the entire solar disk, while the sharp front rises up, forming the CME ejecta with the diffuse front ahead of it. These observations suggest that the previously termed EUV wave is a composite phenomenon and driven by the CME expansion. While the CME expansion is accelerating, the wave front is cospatial with the CME front, thus the two fronts are indiscernible. Following the end of the acceleration phase, the wave moves away from the CME front with a gradually increasing distance between them. Title: CMEs in the the Interplanetary Medium : analysis from the Sun to 1 AU Authors: Colaninno, R. C.; Vourlidas, A.; Nieves-Chinchilla, T. Bibcode: 2011AGUFMSH23A1946C Altcode: For many years, white light coronagraphs have provided information on the near Sun evolution of coronal mass ejections (CMEs). More recently, the Heliospheric Imager (HI) instruments aboard the STEREO mission are providing crucial remote sensing information on the interplanetary evolution of these events. Data from in situ instruments complete the overall characterization of interplanetary CMEs. In this work, we present an analysis of a CME from near the Sun to 1 AU using combined data from multiple spacecraft. We compare the propagation and evolution as observed in remote sensing data with in situ observations and derived parameters. Title: Uncovering the Wave Nature of the EIT Wave for the 2010 January 17 Event through Its Correlation to the Background Magnetosonic Speed Authors: Zhao, X. H.; Wu, S. T.; Wang, A. H.; Vourlidas, A.; Feng, X. S.; Jiang, C. W. Bibcode: 2011ApJ...742..131Z Altcode: An EIT wave, which typically appears as a diffuse brightening that propagates across the solar disk, is one of the major discoveries of the Extreme ultraviolet Imaging Telescope on board the Solar and Heliospheric Observatory. However, the physical nature of the so-called EIT wave continues to be debated. In order to understand the relationship between an EIT wave and its associated coronal wave front, we investigate the morphology and kinematics of the coronal mass ejection (CME)-EIT wave event that occurred on 2010 January 17. Using the observations of the SECCHI EUVI, COR1, and COR2 instruments on board the Solar Terrestrial Relations Observation-B, we track the shape and movements of the CME fronts along different radial directions to a distance of about 15 solar radii (Rs ); for the EIT wave, we determine the propagation of the wave front on the solar surface along different propagating paths. The relation between the EIT wave speed, the CME speed, and the local fast-mode characteristic speed is also investigated. Our results demonstrate that the propagation of the CME front is much faster than that of the EIT wave on the solar surface, and that both the CME front and the EIT wave propagate faster than the fast-mode speed in their local environments. Specifically, we show a significant positive correlation between the EIT wave speed and the local fast-mode wave speed in the propagation paths of the EIT wave. Our findings support that the EIT wave under study is a fast-mode magnetohydrodynamic wave. Title: Measurement of the Fast-Mode Wave Speed Using Full Sun Map observations of Coronal Wave Events Authors: Olmedo, O. A.; Vourlidas, A.; Zhang, J.; Cheng, X. Bibcode: 2011AGUFMSH12A..06O Altcode: In this study we use observations from AIA on SDO, and EUVI on STEREO to study the propagation of coronal "waves" over the entire solar surface by constructing full Sun maps from all three telescopes. By tracing paths that originate at the active region and reflect from the coronal hole boundary we are able to predict the trajectory that "wave" will take upon reflection. We compare the events that took place on 13 and 15 February 2011, from the same active region, and find that the reflected waves have comparable speeds (~280-300 km/s), yet had different incident speeds (~400 vs. ~600 km/s respectively). We interpret the reflected wave as propagating at the fast-mode wave speed. Finally, the high-cadence AIA observations allow us to examine the temporal evolution of the wave in great detail. We compare the evolution of the intensity/thermal response of the several wavelength observations. Title: A comparative study of the evolving morphology of 2.5-D simulated CMEs to Earth's magnetosphere Authors: Savani, N. P.; Shiota, D.; Kusano, K.; Lugaz, N.; Vourlidas, A. Bibcode: 2011AGUFMSH22A..03S Altcode: Our understanding of the evolving morphology of coronal mass ejections (CMEs) has advanced significantly after remote-sensing observations became available from the wide fields-of-view from STEREO/SECCHI. However, the most practical way to relate the shock parameters up and downstream to the CME morphology remains with the numerical MHD models. We present 2.5-D numerical investigations of fast CMEs and its associated shock between 10Rs and 250Rs. We display the axis-symmetric results of the CMEs from different speeds and magnetic field strength along the axis of the flux rope structure. We discuss the relationship between the Mach number and density ratio over the shock to the aspect ratio of CMEs. The sheath distance and the size of the CME perpendicular to the spacecraft direction of travel are related to those values estimated from Earth's magnetosphere. Title: The longitudinal properties of solar energetic particle events investigated using modern solar imaging. Authors: Rouillard, A. P.; Sheeley, N. R.; Tylka, A. J.; Vourlidas, A.; Ng, C. K.; Mason, G. M.; Cohen, C. M. Bibcode: 2011AGUFMSH33D..03R Altcode: On 2011 March 21, the Solar-Terrestrial Relations Observatory (STEREO) imaged the launch (at ~02:10UT) and outward propagation of a fast (>1300 km s-1) and wide (latitudinal extent greater than 90 degrees) coronal mass ejection (CME) which emerged W135 degrees (behind the west-limb as viewed from near-Earth spacecraft). Protons with energies exceeding 90 MeV were first detected by the STEREO-Ahead (STA) spacecraft and a few minutes later by near-Earth orbiting spacecraft. Velocity dispersion analyses of energetic electrons, protons and heavier ions, put the solar particle release (SPR) times along magnetic field lines connected to STA at ~02:30UT and along magnetic field lines connected to near-Earth spacecraft at ~ 03:00UT. The spatial evolution of a pressure wave and its associated shock forming around the CME could be tracked using (critical) high-cadence and high-resolution STA (extreme ultraviolet and white-light) images. We demonstrate that the delay between the SEP onset at STA and Earth is consistent with the time required for the pressure wave to propagate from the launch-site of the CME to the base of coronal streamers that are magnetically connected to near-Earth spacecraft. By considering measured shock speeds and inferred shock geometries along different longitudes and by deriving spectra of energetic protons, this study also presents some interpretation of the longitudinal variability of the SEP event in terms of the evolution of the compression wave. Time permitting, we will also summarise the results of similar analyses carried out for the other energetic CME events in 2010 and 2011. Title: Plasma Outflows Within Polar Coronal Plumes Authors: Raouafi, N.; Stenborg, G.; Vourlidas, A. Bibcode: 2011AGUFMSH13B1959R Altcode: Plasma outflow velocities within polar coronal plumes and their contribution to the fast solar wind are a matter of controversy. We investigate the plasma dynamics within plumes through the analysis of high cadence and spatial resolution observations from the Solar Dynamic Observatory (SDO) jointly with STEREO and Hinode data. This analysis allows us to address the source of heating and plasma acceleration inside polar plumes and therefore obtain constraint on the contribution of plumes to the fast solar wind. Our results provide important constraints of theoretical model dealing with the formation and evolution of polar coronal plumes. Title: The role of CMEs in the lateral spread of electron events in the inner heliosphere Authors: Nieves-Chinchilla, T.; Gómez-Herrero, R.; Colaninno, R. C.; Vourlidas, A.; Szabo, A. Bibcode: 2011AGUFMSH31B2001N Altcode: This work focuses on the study of the role played by solar wind transient events in the longitudinal spread of particles during some SEP events. We have selected SEP events observed simultaneously by STEREO and/or ACE/Wind that show an increase in the flux of nearly relativistic electrons. We combine in situ and remote sensing analysis to identify the 3D morphology, position, and kinematics of CMEs that could facilitate the lateral spread. Title: Observations of the White Light Corona from Solar Orbiter and Solar Probe Plus Authors: Howard, R. A.; Thernisien, A. F.; Vourlidas, A.; Plunkett, S. P.; Korendyke, C. M.; Sheeley, N. R.; Morrill, J. S.; Socker, D. G.; Linton, M. G.; Liewer, P. C.; De Jong, E. M.; Velli, M. M.; Mikic, Z.; Bothmer, V.; Lamy, P. L. Bibcode: 2011AGUFMSH43F..06H Altcode: The SoloHI instrument on Solar Orbiter and the WISPR instrument on Solar Probe+ will make white light coronagraphic images of the corona as the two spacecraft orbit the Sun. The minimum perihelia for Solar Orbiter is about 60 Rsun and for SP+ is 9.5 Rsun. The wide field of view of the WISPR instrument (about 105 degrees radially) corresponds to viewing the corona from 2.2 Rsun to 20 Rsun. Thus the entire Thomson hemisphere is contained within the telescope's field and we need to think of the instrument as being a traditional remote sensing instrument and then transitioning to a local in-situ instrument. The local behavior derives from the fact that the maximum Thomson scattering will favor the electron plasma close to the spacecraft - exactly what the in-situ instruments will be sampling. SoloHI and WISPR will also observe scattered light from dust in the inner heliosphere, which will be an entirely new spatial regime for dust observations from a coronagraph, which we assume to arise from dust in the general neighborhood of about half way between the observer and the Sun. As the dust grains approach the Sun, they evaporate and do not contribute to the scattering. A dust free zone has been postulated to exist somewhere inside of 5 Rsun where all dust is evaporated, but this has never been observed. The radial position where the evaporation occurs will depend on the precise molecular composition of the individual grains. The orbital plane of Solar Orbiter will gradually increase up to about 35 degrees, enabling a very different view through the zodiacal dust cloud to test the models generated from in-ecliptic observations. In this paper we will explore some of the issues associated with the observation of the dust and will present a simple model to explore the sensitivity of the instrument to observe such evaporations. Title: Deriving the Physical Parameters of a Solar Ejection with an Isotropic Magnetohydrodynamic Evolutionary Model Authors: Berdichevsky, Daniel B.; Stenborg, Guillermo; Vourlidas, Angelos Bibcode: 2011ApJ...741...47B Altcode: The time-space evolution of a ~50° wide coronal mass ejection (CME) on 2007 May 21 is followed remotely with the Solar Terrestrial Relations Observatory heliospheric imager HI-1, and measured in situ near Venus by the MESSENGER and Venus-Express spacecraft. The paper compares the observations of the CME structure with a simple, analytical magnetohydrodynamic force-free solution. It corresponds to a self-similar evolution, which gives a consistent picture of the main spatial-temporal features for both remote and in situ observations. Our main findings are (1) the self-similar evolution allows us to map the CME bright front into about 1/3 of the whole interplanetary counterpart of the coronal mass ejection (ICME, i.e., corresponding to the in situ observed passage of the plasma and magnetic field structure), in good quantitative agreement with the imaging measurements, (2) the cavity following the CME front maps into the rest of the ICME structure, 80% or more of which is consistent with a force free, cylindrically shaped flux rope, and (3) time and space conditions constrain the translational speed of the FR center to 301 km s-1, and the expansion speed of the FR core to 26 km s-1. A careful determination of the ICME cross-section and volume allows us to calculate the mass of the CME bright region (4.3 ± 1.1 1014 g) from the in situ measurements of the proton number density, which we assume to be uniform inside the bright region, of excellent agreement with the value estimated from the SECCHI HI-1 observations for the same structure. We provide model estimates for several global parameters including FR helicity (~2 × 1026 Weber2). Title: A study of coronal mass ejections and the subsurface structure at their source regions Authors: Baldner, C.; Chen, J.; Vourlidas, A. Bibcode: 2011sdmi.confE.104B Altcode: Coronal mass ejection (CME) is one of the most violent phenomena in the solar atmosphere. One of the possible sources to cause such violent eruption could be the magnetic flux and energy from below the photosphere, However, due to the large difference in scales, the subsurface and the atmosphere of the Sun have often been studied separately. In this study, our objective is to combine the studies in both fields in the hope to connect the subsurface magnetic fields to the dynamics in the atmosphere. We selected a system of three active regions, AR10987, AR10988 and AR10989, for this study. These three active regions were located approximately at a same latitude and almost equally separated. Two CMEs were detected from this group during our observation period. We compared the CMEs with different CME models both qualitatively and quantitatively. The best-matched model was then used to deduce the possible driving mechanism of the CMEs. For the study of the subsurface structure, we employed the techniques of local helioseismology to obtain both the thermal and magnetic structural properties. I will discuss our results in this presentation. Title: Recent Advances in Heliophysics from Space-Based Observations Authors: Vourlidas, A. Bibcode: 2011Ippa....2...37V Altcode: The Sun is the only star we can observe in detail and on the other hand, solar variability drives the heliosphere and influences the environment around our planet. Over the last 10-15 years, a large number of space missions have been providing a smorgasbord of observations from the photosphere to the outer reaches of the heliosphere. As a consequence, solar and space physics are being integrated into a joint research field, called heliophysics, and are tackling the mysteries of the Sun and the heliosphere with great success. In this short review, I discuss a few of those exciting advances in an attempt to capture the spirit of progress that permeates the field. Due to space restrictions, I left out many major results which may be addressed in future articles. Title: Forward Modeling of a CME Driven Shock : When is a Halo CME not a CME? Authors: Colaninno, Robin C.; Olmedo, Oscar; Thernisien, Arnaud; Vourlidas, Angelos Bibcode: 2011shin.confE...2C Altcode: In this work, we use the a forward modeling technique to model both a CME and the resulting CME driven shock observed on 24 February 2011. We incorporate coronagraph data from STEREO-SECCHI and SOHO LASCO to fit the forward model. The 24 February 2011 CME and shock were directed towards the STEREO-B spacecraft. From SOHO-LASCO, we can see the CME driving the shock edge on. However, in both the STEREO-A and B fields of view, the CME is hidden behind the occulter. The shock was also measured in-situ at STEREO-B. If this event had been seen from only the STEREO-A and B points of view, it might have been identified as a weak halo CME or incorrectly associated with a secondary slow CME. The implications of this event for space weather predications are discussed. Title: Interpreting the Properties of Solar Energetic Particle Events by Using Combined Imaging and Modeling of Interplanetary Shocks Authors: Rouillard, A. P.; Odstřcil, D.; Sheeley, N. R.; Tylka, A.; Vourlidas, A.; Mason, G.; Wu, C. -C.; Savani, N. P.; Wood, B. E.; Ng, C. K.; Stenborg, G.; Szabo, A.; St. Cyr, O. C. Bibcode: 2011ApJ...735....7R Altcode: Images of the solar corona obtained by the Solar-Terrestrial Relations Observatory (STEREO) provide high-cadence, high-resolution observations of a compression wave forming ahead of a fast (940 km s-1) coronal mass ejection (CME) that erupted at ~9:00 UT on 2010 April 03. The passage of this wave at 1 AU is detected in situ by the Advanced Composition Explorer and Wind spacecraft at 08:00 UT on April 05 as a shock followed by a turbulent and heated sheath. These unprecedented and complementary observations of a shock-sheath region from the Sun to 1 AU are used to investigate the onset of a Solar Energetic Particle (SEP) event measured at the first Lagrange point (L1) and at STEREO-Behind (STB). The spatial extent, radial coordinates, and speed of the ejection are measured from STEREO observations and used as inputs to a numerical simulation of the CME propagation in the background solar wind. The simulated magnetic and plasma properties of the shock and sheath region at L1 agree very well with the in situ measurements. These simulation results reveal that L1 and STB are magnetically connected to the western and eastern edges of the driven shock, respectively. They also show that the 12 hr delay between the eruption time of the ejection and the SEP onset at L1 corresponds to the time required for the bow shock to reach the magnetic field lines connected with L1. The simulated shock compression ratio increases along these magnetic field lines until the maximum flux of high-energy particles is observed. Title: The Reflection of Coronal Waves from Coronal Holes Seen in Full Sun Synoptic Maps Authors: Olmedo, Oscar; Olmedo, Oscar; Vourlidas, Angelos; Zhang, Jie; Cheng, Xin Bibcode: 2011shin.confE..76O Altcode: We demonstrate the wave nature of Title: The First Observation of a Rapidly Rotating Coronal Mass Ejection in the Middle Corona Authors: Vourlidas, A.; Colaninno, R.; Nieves-Chinchilla, T.; Stenborg, G. Bibcode: 2011ApJ...733L..23V Altcode: In this Letter, we present the first direct detection of a rotating coronal mass ejection (CME) in the middle corona (5-15 R sun). The CME rotation rate is 60° day-1, which is the highest rate reported yet. The Earth-directed event was observed by the STEREO/SECCHI and SOHO/LASCO instruments. We are able to derive the three-dimensional morphology and orientation of the CME flux rope by applying a forward-fitting model to simultaneous observations from three vantage points (SECCHI-A, -B, LASCO). Surprisingly, we find that even such rapidly rotating CME does not result in significant projection effects (variable angular width) in any single coronagraph view. This finding may explain the prevalent view of constant angular width for CMEs above 5 R sun and the lack of detections of rotating CMEs in the past. Finally, the CME is a "stealth" CME with very weak low corona signatures as viewed from Earth. It originated from a quiet-Sun neutral line. We tentatively attribute the fast rotation to a possible disconnection of one of the CME footpoints early in the eruption. We discuss the implications of such rotations to space weather prediction. Title: CME reconstruction: Pre-STEREO and STEREO era Authors: Thernisien, A.; Vourlidas, A.; Howard, R. A. Bibcode: 2011JASTP..73.1156T Altcode: Since the first observations of coronal mass ejections (CMEs) in 1970s, their three-dimensional (3D) morphology has been a key ingredient for understanding their origin and evolution. The determination of their 3D structure using a single viewpoint, however posed a challenge because only their 2D projection on the sky plane is observed. The operation of the STEREO mission with its unique capability of imaging the inner heliosphere from two viewpoints has greatly improved this situation. It is therefore timely to review the pre-STEREO efforts in 3D CME reconstruction and compare them with the first STEREO results in this area. Our paper focuses on the techniques relevant to the CME morphology: forward modeling, polarimetric, spectroscopic, direct inversion. We also discuss the limitations and considerations involved in each technique. Title: Euv Imaging Of Shock Formation In The Low Corona With Sdo/aia Authors: Vourlidas, Angelos; Patsourakos, S.; Kouloumvakos, T. Bibcode: 2011SPD....42.0907V Altcode: 2011BAAS..43S.0907V Shock generation in the low corona has long been inferred by spectral observations of drifting so-called type-II radio emission in the metric wavelengths. Type-IIs occur with coronal mass ejections (CMEs) and/or flares but not consistently. Therefore, the exact relationship has been difficult to pin down, mostly because of the lack of radio imaging capability and of the low cadence of EUV observations in the low corona during the flare/CME formation. The advent of ultra-high observations from the AIA imagers has changed all that. In this talk, we present several direct observations of shock formation in the EUV and their association to the accompanying type-IIs. We will show that the coronal expansion driven by the formation of the CME ejecta is responsible for both EUV and radio emissions. Title: Viewing The Entire Sun With STEREO And SDO Authors: Thompson, William T.; Gurman, J. B.; Kucera, T. A.; Howard, R. A.; Vourlidas, A.; Wuelser, J.; Pesnell, D. Bibcode: 2011SPD....42.1835T Altcode: 2011BAAS..43S.1835T On 6 February 2011, the two Solar Terrestrial Relations Observatory (STEREO) spacecraft were at 180 degrees separation. This allowed the first-ever simultaneous view of the entire Sun. Combining the STEREO data with corresponding images from the Solar Dynamics Observatory (SDO) allows this full-Sun view to continue for the next eight years. We show how the data from the three viewpoints are combined into a single heliographic map. Processing of the STEREO beacon telemetry allows these full-Sun views to be created in near-real-time, allowing tracking of solar activity even on the far side of the Sun. This is a valuable space-weather tool, not only for anticipating activity before it rotates onto the Earth-view, but also for deep space missions in other parts of the solar system. Scientific use of the data includes the ability to continuously track the entire lifecycle of active regions, filaments, coronal holes, and other solar features. There is also a significant public outreach component to this activity. The STEREO Science Center produces products from the three viewpoints used in iPhone/iPad and Android applications, as well as time sequences for spherical projection systems used in museums, such as Science-on-a-Sphere and Magic Planet. Title: New Results Revealed By Enhanced Extreme-Ultraviolet Images Authors: Stenborg, Guillermo A.; Vourlidas, A.; Howard, R. Bibcode: 2011SPD....42.1809S Altcode: 2011BAAS..43S.1809S Groundbreaking observations of the low solar corona at extreme ultraviolet (EUV) wavelengths have been provided by the EIT instrument on board SOHO for more than 15 years. At the beginning of 2007, the EUVI instruments onboard the twin STEREO S/C opened doors and commenced to image the EUV low corona with a better cadence and better spatial resolution from two vantage points off the Sun-Earth line. And now, since February 2010 the AIA instrument on board the Solar Dynamics Observatory observes the low EUVI corona at a 10 sec cadence in 8 wavelengths. Despite the increasing quality of the EUV observations, they have not been fully exploited. A customized wavelet-based image cleaning and enhancing technique that exploits the multi-scale nature of the observed solar features has been developed (Stenborg et al., 2008) to maximize the scientific return of the EIT observations. We have now adapted it to work with STEREO/EUVI and SDO/AIA images. Its application has already helped unveil phenomena only theorized before, as well as revealed phenomena that have not found a satisfactory explanation yet. In this presentation, a brief survey of the new products and recent discoveries will be shown. Title: Solar Eruptive Events (SEE) Mission for the Next Solar Maximum Authors: Lin, Robert P.; Krucker, S.; Caspi, A.; Hurford, G.; Dennis, B.; Holman, G.; Christe, S.; Shih, A. Y.; Bandler, S.; Davila, J.; Milligan, R.; Kahler, S.; Weidenbeck, M.; Doschek, G.; Vourlidas, A.; Share, G.; Raymond, J.; McConnell, M.; Emslie, G. Bibcode: 2011SPD....42.2204L Altcode: 2011BAAS..43S.2204L Major solar eruptive events consisting of both a large flare and a near simultaneous large fast coronal mass ejection (CME), are the most powerful explosions and also the most powerful and energetic particle accelerators in the solar system, producing solar energetic particles (SEPs) up to tens of GeV for ions and 10s-100s of MeV for electrons. The intense fluxes of escaping SEPs are a major hazard for humans in space and for spacecraft. Furthermore, the solar plasma ejected at high speed in the fast CME completely restructures the interplanetary medium, producing the most extreme space weather in geospace, at other planets, and in the heliosphere. Thus, the understanding of the flare/CME energy release process and of the related particle acceleration processes in SEEs is a major goal in Heliophysics. Here we present a concept for a Solar Eruptive Events (SEE) mission, consisting of a comprehensive set of advanced new instruments on the single spacecraft in low Earth orbit, that focus directly on the coronal energy release and particle acceleration in flares and CMEs. SEE will provide new focussing hard X-ray imaging spectroscopy of energetic electrons in the flare acceleration region, new energetic neutral atom (ENA) imaging spectroscopy of SEPs being accelerated by the CME at altitudes above 2 solar radii, gamma-ray imaging spectroscopy of flare-accelerated energetic ions, plus detailed EUV/UV/Soft X-ray diagnostics of the plasmas density, temperature, and mass motions in the energy release and particle acceleration regions. Together with ground-based measurements of coronal magnetic fields from ATST, FASR, and COSMO, SEE will enable major breakthroughs in our understanding of the fundamental physical processes involved in major solar eruptive events. Title: Study of the Coronal Wave Event of February 15, 2011 Over the Entire Solar Surface. Authors: Olmedo, Oscar; Vourlidas, A.; Zhang, J.; Cheng, X. Bibcode: 2011SPD....42.1834O Altcode: 2011BAAS..43S.1834O We investigate the coronal wave associated with the February 15, 2011 X-class flare. The flare occurred at 1:44 UT in active region NOAA 11158. We use observations from the Atmospheric Imaging Assembly (AIA) aboard Solar Dynamics Observatory, and the Extreme Ultraviolet Image (EUVI) aboard the Solar Terrestrial Relations Observatory to study the propagation of the coronal wave over the entire solar surface with the help of full Sun synoptic maps. The high-cadence AIA observations allow us to examine the temporal evolution of the wave in great detail. Our investigation focuses on two aspects: (i) The apparent transmission and reflection of the wave through a coronal hole, and (ii) the thermal response in the corona during the coronal wave passage. Title: Erratum: "Comprehensive Analysis of Coronal Mass Ejection Mass and Energy Properties Over a Full Solar Cycle" (2010, ApJ, 722, 1522) Authors: Vourlidas, A.; Howard, R. A.; Esfandiari, E.; Patsourakos, S.; Yashiro, S.; Michalek, G. Bibcode: 2011ApJ...730...59V Altcode: No abstract at ADS Title: A novel technique to measure intensity fluctuations in EUV images and to detect coronal sound waves nearby active regions Authors: Stenborg, G.; Marsch, E.; Vourlidas, A.; Howard, R.; Baldwin, K. Bibcode: 2011A&A...526A..58S Altcode: Context. In the past years, evidence for the existence of outward-moving (Doppler blue-shifted) plasma and slow-mode magneto-acoustic propagating waves in various magnetic field structures (loops in particular) in the solar corona has been found in ultraviolet images and spectra. Yet their origin and possible connection to and importance for the mass and energy supply to the corona and solar wind is still unclear. There has been increasing interest in this problem thanks to the high-resolution observations available from the extreme ultraviolet (EUV) imagers on the Solar TErrestrial RElationships Observatory (STEREO) and the EUV spectrometer on the Hinode mission.
Aims: Flows and waves exist in the corona, and their signatures appear in EUV imaging observations but are extremely difficult to analyse quantitatively because of their weak intensity. Hence, such information is currently available mostly from spectroscopic observations that are restricted in their spatial and temporal coverage. To understand the nature and origin of these fluctuations, imaging observations are essential. Here, we present measurements of the speed of intensity fluctuations observed along apparently open field lines with the Extreme UltraViolet Imagers (EUVI) onboard the STEREO mission. One aim of our paper is to demonstrate that we can make reliable kinematic measurements from these EUV images, thereby complementing and extending the spectroscopic measurements and opening up the full corona for such an analysis. Another aim is to examine the assumptions that lead to flow versus wave interpretation for these fluctuations.
Methods: We have developed a novel image-processing method by fusing well established techniques for the kinematic analysis of coronal mass ejections (CME) with standard wavelet analysis. The power of our method lies with its ability to recover weak intensity fluctuations along individual magnetic structures at any orientation , anywhere within the full solar disk , and using standard synoptic observing sequences (cadence <3 min) without the need for special observation plans.
Results: Using information from both EUVI imagers, we obtained wave phase speeds with values on the order of 60-90 km s-1, compatible with those obtained by other previous measurements. Moreover, we studied the periodicity of the observed fluctuations and established a predominance of a 16-min period, and other periods that seem to be multiples of an underlying 8-min period.
Conclusions: The validation of our analysis technique opens up new possibilities for the study of coronal flows and waves, by extending it to the full disk and to a larger number of coronal structures than has been possible previously. It opens up a new scientific capability for the EUV observations from the recently launched Solar Dynamics Observatory. Here we clearly establish the ubiquitous existence of sound waves which continuously propagate along apparently open magnetic field lines.

Movies 1 and 2 (Figs. 12 and 13) are only available in electronic form at http://www.aanda.org Title: Evidence for a current sheet forming in the wake of a coronal mass ejection from multi-viewpoint coronagraph observations Authors: Patsourakos, S.; Vourlidas, A. Bibcode: 2011A&A...525A..27P Altcode: 2010arXiv1010.0323P Context. Ray-like features observed by coronagraphs in the wake of coronal mass ejections (CMEs) are sometimes interpreted as the white light counterparts of current sheets (CSs) produced by the eruption. The 3D geometry of these ray-like features is largely unknown and its knowledge should clarify their association to the CS and place constraints on CME physics and coronal conditions.
Aims: If these rays are related to field relaxation behind CMEs, therefore representing current sheets, then they should be aligned to the CME axis. With this study we test these important implications for the first time.
Methods: An example of such a post-CME ray was observed by various coronagraphs, including these of the Sun Earth Connection Coronal and Heliospheric investigation (SECCHI) onboard the Solar Terrestrial Relations Observatory (STEREO) twin spacecraft and the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). The ray was observed in the aftermath of a CME which occurred on 9 April 2008. The twin STEREO spacecraft were separated by about 48° on that day. This significant separation combined with a third “eye” view supplied by LASCO allow for a truly multi-viewpoint observation of the ray and of the CME. We applied 3D forward geometrical modeling to the CME and to the ray as simultaneously viewed by SECCHI-A and B and by SECCHI-A and LASCO, respectively.
Results: We found that the ray can be approximated by a rectangular slab, nearly aligned with the CME axis, and much smaller than the CME in both terms of thickness and depth (≈0.05 and 0.15 R⊙ respectively). The ray electron density and temperature were substantially higher than their values in the ambient corona. We found that the ray and CME are significantly displaced from the associated post-CME flaring loops.
Conclusions: The properties and location of the ray are fully consistent with the expectations of the standard CME theories for post-CME current sheets. Therefore, our multi-viewpoint observations supply strong evidence that the observed post-CME ray is indeed related to a post-CME current sheet.

Movies are only available in electronic form at http://www.aanda.org Title: The Wide Field Imager for Solar PRobe (WISPR) Authors: Plunkett, S. P.; Howard, R. A.; Vourlidas, A.; Korendyke, C. M.; Socker, D. G.; Morrill, J. S.; Sheeley, N. R.; Linton, M.; Liewer, P. C.; de Jong, E. M.; Mikic, Z. Bibcode: 2010AGUFMSH11B1622P Altcode: The Wide Field Imager for Solar PRobe (WISPR) will image the Thomson-scattered light from the coronal plasma in the inner corona, with unprecedented spatial resolution, cadence, and sensitivity. WISPR follows on the SECCHI Heliospheric Imager (HI) aboard the STEREO mission, and addresses all four key objectives in the Solar Probe Plus: Report of the STDT (2008): (1) Determine the structure and dynamics of the magnetic fields at the sources of the fast and slow solar wind, (2) Trace the flow of energy that heats the solar corona and accelerates the SW, (3) explore the mechanisms that accelerate and transport energetic particles, (4) explore dusty plasma phenomena and their influence on the solar wind and energetic particle formation. Situated in the ram direction of the Solar Probe Plus (SPP) spacecraft (S/C), WISPR will have the unique ability to image the coronal structures when they are close to the Sun, as they approach, and as they pass over the spacecraft. As a remote sensor, WISPR will connect the structures close to the Sun to the spacecraft and provide important spatial and temporal information; measuring, for example, the properties of the structures generating the shocks and SEPs that will be measured in a few minutes at the S/C. Since the S/C is embedded in the corona, WISPR and the in situ instruments will measure for the first time the same plasma. Also as the SPP transits through the corona, the rapidly-varying viewpoint and high spatial resolution of WISPR will enable tomographic imaging of the corona, and lead to higher fidelity and finer scale 3D reconstructions than are possible with the STEREO mission or single-view rotational tomography. The wide field of view will include at times other inner heliospheric probes (e.g. Solar Orbiter) and will image the outflowing wind that is impinging on that probe. In addition to this standard imaging mode, WISPR opens a new capability for imaging instruments, the measurement of pressure turbulence by employing a high cadence mode (~1 sec) to image a small region in the corona. For the first time, the slopes of the power spectral density from images can be compared directly to the density and magnetic field fluctuations seen in situ as a function of coronal spatial structure and heliocentric distance. In addition, the 1 sec cadence can be generated anywhere within the WISPR field, enabling the study of the transition of the solar wind injected at the tops of the helmet streamers to inertial dissipation scales. Title: The Genesis of an Impulsive CME observed by AIA on SDO Authors: Patsourakos, S.; Vourlidas, A.; Stenborg, G. Bibcode: 2010AGUFMSH14A..03P Altcode: Understanding the first moments in the life-time of Coronal Mass Ejections (CMEs), i.e. their genesis, represents possibly the key to unlock the physical processes responsible for their initiation. After this critical interval, which could last as little as few minutes for the most impulsive events, differences between various CME models become minimal. The recent launch of the SDO mission and the availability of high-quality EUV imaging from AIA in particular, opened a new avenue into CME initiation investigations with its unprecedented image cadence and multi-wavelength simultaneous coverage. We here report on AIA observations of an impulsive CME-flare-EUV wave event which took place during 13 June 2010. All the important dynamics (e.g., rise phase of the flare, impulsive acceleration of the CME) had a duration of only 10 minutes making this event a perfect showcase event for AIA. Taking advantage of the unique aspects of AIA data (12 sec cadence and 7 different EUV channels) we present a detailed analysis of this event which includes: (1) its kinematic behavior (acceleration profile); (2) radial and expansion speeds; (3) relationships between (1) and (2) with the flare energy release; (4) multi-temperature evolution of the early CME. All the above supply new strong constraints for the physics of impulsive CMEs. Title: The Genesis of an Impulsive Coronal Mass Ejection Observed at Ultra-high Cadence by AIA on SDO Authors: Patsourakos, S.; Vourlidas, A.; Stenborg, G. Bibcode: 2010ApJ...724L.188P Altcode: 2010arXiv1010.5234P The study of fast, eruptive events in the low solar corona is one of the science objectives of the Atmospheric Imaging Assembly (AIA) imagers on the recently launched Solar Dynamics Observatory (SDO), which take full disk images in 10 wavelengths with arcsecond resolution and 12 s cadence. We study with AIA the formation of an impulsive coronal mass ejection (CME) which occurred on 2010 June 13 and was associated with an M1.0 class flare. Specifically, we analyze the formation of the CME EUV bubble and its initial dynamics and thermal evolution in the low corona using AIA images in three wavelengths (171 Å, 193 Å, and 211 Å). We derive the first ultra-high cadence measurements of the temporal evolution of the CME bubble aspect ratio (=bubble height/bubble radius). Our main result is that the CME formation undergoes three phases: it starts with a slow self-similar expansion followed by a fast but short-lived (~70 s) period of strong lateral overexpansion which essentially creates the CME. Then the CME undergoes another phase of self-similar expansion until it exits the AIA field of view. During the studied interval, the CME height-time profile shows a strong, short-lived, acceleration followed by deceleration. The lateral overexpansion phase coincides with the deceleration phase. The impulsive flare heating and CME acceleration are closely coupled. However, the lateral overexpansion of the CME occurs during the declining phase and is therefore not linked to flare reconnection. In addition, the multi-thermal analysis of the bubble does not show significant evidence of temperature change. Title: Temporal evolution and spatial variation of the solar wind from multi-spacecraft measurements Authors: Opitz, A.; Wurz, P.; Fedorov, A.; Sauvaud, J.; Luhmann, J. G.; Riley, P.; Szego, K.; Russell, C. T.; Galvin, A. B.; Rouillard, A. P.; Vourlidas, A.; van Driel-Gesztelyi, L. Bibcode: 2010AGUFMSH33C..07O Altcode: We study the temporal evolution and the spatial variation of the solar wind on different scales. The analyzed multi-spacecraft (STEREO, VEX, SOHO, MEX, and other spacecraft) measurements were obtained between 2007 and 2010 during solar minimum in the inner heliosphere. We derived the temporal and spatial variability of the different solar wind parameters (proton bulk velocity, electron core density, etc). These results support prediction of the solar wind parameters for different heliospheric positions and help to derive its validity range. In order to explain occasional deviations from the nominal solar wind evolution we use imaging data and modeling results. Title: Causes, Occurrences, and Consequences of Extreme Solar Particle Events (Invited) Authors: Mewaldt, R. A.; Cohen, C. M.; Mason, G. M.; Vourlidas, A. Bibcode: 2010AGUFMSH52A..01M Altcode: This talk will discuss the conditions that result in extreme solar energetic particle (SEP) events, their frequency of occurrence, and some of their consequences. It will argued that the largest SEP events are accelerated by shocks driven by fast coronal mass ejections (CMEs), and that they require CMEs with kinetic energies exceeding 1032 ergs that encounter an abundant population of suprathermal seed particles. The occurrence frequency of extreme SEP events will be investigated using in-situ, ground-based, and polar ice-core data. Finally, we discuss some of the potential consequences of extreme SEP events for humans and hardware in space. Title: Kinematic Characterization Of In/out Pairs As Seen In Secchi Authors: Baldwin, K. L.; Vourlidas, A.; Zhang, J.; Linton, M. Bibcode: 2010AGUFMSH23B1853B Altcode: This study investigates the kinematic properties of the “in/out pair” coronal features seen in Thompson scattered, white-light coronagraph images. Frequently, the pairs occur as the after-math of solar coronal mass ejections appearing at first as a pin hole tear along the streamer axis. The tear appears consistently at around 5 solar radii. Due to the timing and location of these events, it is likely that the pairs are indicators of magnetic reconnection at the trailing edge of CMEs. Using the SECCHI COR1/COR2 instruments in combination with the LASCO C2 data, we are able to calculate the 3D location as well as the true speed of the pairs using elongation-time map (so-called JMAP) capabilities. The inflow portion of the pairs are seen in both SECCHI and LASCO coronagraphs and travel at approximately 100 km/s. While, the outflow portion take the shape of the outflow of the preceding storm and travel faster than 200 km/s. The images used in this analysis were processed using a running difference technique. Previous images subtraction highlights the proper motions of the intensity enhancements, while removing background effects. These results may shed light on the processes of magnetic reconnection following solar storms. Title: Importance of Heliospheric Evolution to Understand CME Geo-effectiveness Authors: Lugaz, N.; Roussev, I. I.; Vourlidas, A.; Gombosi, T. I. Bibcode: 2010AGUFMSH51C1695L Altcode: The properties of coronal mass ejections (CMEs) as they leave the corona (around 5-15 Rsun), are an important indication of their potential geo-effectiveness. It is, for example, the case for their speed, direction and orientation. However, during the heliosopheric propagation, these properties can change dramatically. Here, we present cases, when a CME expected geo-effectivness is significantly modified during its propagation and when the speed, direction and orientation of a CME at 1 AU can not simply be predicted directly from the properties in the corona. We focus on 3-D MHD simulations of CMEs as well as the analysis of heliospheric observations by STEREO/SECCHI. We present instances of shock-shock interaction, shock-CME interaction as well as cases when a CME is deflected in the heliosphere. Title: Simulations of Overexpanding CME Cavities Authors: Kliem, B.; Forbes, T.; Vourlidas, A.; Patsourakos, S. Bibcode: 2010AGUFMSH51A1661K Altcode: Coronal mass ejection (CME) cavities seen in white-light coronagraphs expand nearly self similarly in the outer corona and inner solar wind. Little is known about their initial expansion in the inner corona. A two-phase evolution, consisting of an initial overexpansion up to a heliocentric front height of about 1.5 solar radii, followed by nearly self-similar expansion, was recently discovered in STEREO/SECCHI observations of a fast CME (Patsourakos et al. 2010). The overexpansion is expressed as a decrease of the cavity aspect ratio (center height by radius) by at least a factor of 2 during the rise phase of the main CME acceleration. We present MHD simulations of erupting flux ropes that show the initial overexpansion of a cavity in line with the observed evolution. The contributions of ideal-MHD expansion and of magnetic reconnection to the growth of the flux rope and cavity in the simulations will be quantified to identify the primary cause of the overexpansion. This assesses the diagnostic potential of the overexpansion for the change of flux rope current and the role of magnetic reconnection in the early evolution of CMEs. Title: Interpreting SDO/AIA observations of EUV waves, a comprehensive analysis with direct comparison to global MHD simulations Authors: Downs, C.; Roussev, I. I.; Vourlidas, A.; van der Holst, B.; Lugaz, N. Bibcode: 2010AGUFMSH11A1614D Altcode: In this work we present an analysis of two EUV waves observed by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) in the context of thermodynamic MHD simulations of the global Solar Corona. Due to the extreme advances in cadence, resolution, and bandpass coverage in the EUV regime, the AIA instrument offers an unprecedented ability to observe the dynamics of large scale coronal wave-like transients known as EUV waves. However, the complexity of the corona, coupled with line-of-sight (LOS) projection of structures, can often make the physical nature of EUV waves difficult to interpret directly. To provide a comprehensive physical analysis and further compliment observational insight, we employ a global MHD model that captures the thermodynamic structure of the low corona for the conditions of a given solar rotation (the LC component of the SWMF). This provides a self-consistent framework to characterize both the pre-event conditions as well as the time-dependent dynamics of the eruption itself using a CME eruption model. A key feature of this model is the ability to synthesize the multi-filter response of the SDO/AIA instrument directly from model data, which allows for direct interpretation of AIA observations with full knowledge of the 3D magnetic and thermodynamic structures in the simulations. We focus on the interpretation of the stark thermodynamic signatures in the multi-filter AIA data within the propagating EUV wave front (unambiguous now due to the high uniform cadence of the AIA band-passes) and address the non-linear interaction of the EUV wave front with neighboring regions in the ambient corona. Title: Kinematic analysis and comparison of the CME and its related EIT wave for January 10, 2010 event Authors: Zhao, X.; Wu, S.; Wang, A.; Vourlidas, A. Bibcode: 2010AGUFMSH23B1844Z Altcode: EIT wave, typically appearing as a diffuse brightening propagating across the Sun, is one of the major discoveries of the Extreme ultraviolet Imaging Telescope (EIT) on SOHO. But the physical nature of the so-called EIT wave is strongly debated. In order to understand the relationship between the EIT wave and its related Coronal mass ejection (CME), we investigate the morphology and kinematics of the CME-EIT wave event happened on January 10, 2010. Using the observations of SECCHI/EUVI, SECCHI/COR1 and SECCHI/COR2 onboard the STEREO-B, we track the shape and movements of the CME fronts along different radial directions to the distance of about 15 solar radii; While for the EIT wave, we determine the propagation of the wave front on the solar surface along different propagation directions. Our tracking results demonstrate that the CME front propagation is much faster than the propagation of the EIT wave on the surface. While this CME exhibits deceleration during its moving out, the EIT wave propagates at nearly constant speed. We also compare their propagation speeds to the characteristic speeds, and find out that both the CME and the EIT wave propagate beyond and with the fast-mode speed. Title: White Light and Radio Emission of CME-Shocks: their Evolution in the Interplanetary Medium Authors: Ontiveros, V.; Corona-Romero, P.; Gonzalez-Esparza, A.; Aguilar-Rodriguez, E.; Vourlidas, A. Bibcode: 2010AGUFMSH23B1845O Altcode: We analysed fast Coronal Mass Ejections (CMEs) driving shocks close to the solar surface and their evolution in the interplanetary (IP) medium. For each event we derived the CME kinematics and the shock strength from coronograph images, and the shock speeds in the IP medium from their type II radio burst emissions. We studied these events with an analytical model to illuminate their IP evolution. Title: The Birth of Coronal Mass Ejections As Seen by STEREO and SDO Authors: Vourlidas, A.; Patsourakos, S. Bibcode: 2010AGUFMSH21C..07V Altcode: Despite observations of thousands of coronal mass ejections (CMEs), the details of their formation still elude us. Impulsive CMEs, in particular, originate low in the corona, and form within 10-15 mins while accelerating rapidly. This region of the corona is regularly observed by EUV imagers but the rapid CME evolution requires high cadence and relatively large fields of view. Thanks to the operation of the STEREO and SDO missions, we are currently in a unique position to address the problem of CME formation. The two missions provide almost simultaneous observations from three viewpoints with 3 EUV imagers. The EUV instruments observe in the same (or similar) channels and have highly complimentary cadences and fields of view. In this paper, we discuss a coherent picture of the birth of CMEs based on a study of the first few-minute evolution of several impulsive CMEs. These CMEs seem to first undergo an non-linear expansion followed by a self-similar phase. We discuss the implication for CME initiation models. Title: Imaging the Solar Wind with SoloHI Authors: Howard, R. A.; Vourlidas, A.; Plunkett, S. P.; Korendyke, C. M.; McMullin, D. R.; Liewer, P. C.; Velli, M. M.; Solohi Bibcode: 2010AGUFMSH11B1627H Altcode: Imaging outflows in the corona have been observed with the SOHO/LASCO instrument, since 1996. With the launch of the STEREO mission in 2006, these outflows can be followed into the heliosphere, with the SECCHI/Heliospheric Imager. For the Solar Orbiter mission, we have proposed an instrument called the Solar Orbiter Heliospheric Imager (SoloHI) to be able to image the solar wind and the density fluctuations in the wind and thus provide the link between the in-situ and remote sensing measurements. The nature of the Thomson scattering process integrates along a particular look direction but the scattering is a maximum on the Thomson sphere - the locus of points that form a right angle between the look direction and the solar vector. The experience from SECCHI/HI shows that the density fluctuations are easily visible and can be tracked back into the low corona, enabling a coupling between the solar wind plasma crossing the spacecraft and the source region in the corona. However, the SECCHI/HI observations have low cadence and long integration times. As a new observing mode for SoloHI, we have implemented a capability to readout a subset of the image at a time cadence of about 1 second. Thus small scale fluctuations can be observed in addition to the large scale fluctuations observed from SECCHI/HI. This will enable us to determine the spectral index of the density fluctuations over an unprecedented range of heights (from 5 to 135 Rsun) to compare with the in-situ determinations of the spectral index. This may indicate whether the fluctuations are generated close to the sun and convected out by the solar wind or are generated within the solar wind. Title: Capturing the Three-Dimensional Motion of the 16 June 2010 CME in the STEREO-SECCHI Observations using Scene Flow Authors: Colaninno, R. C.; Vourlidas, A. Bibcode: 2010AGUFMSH23B1856C Altcode: The motion of coronal mass ejections (CMEs) in the heliosphere is governed by the complex interactions of the magnetic field and gas pressure both internal and external to the CME. The two-viewpoint observations of the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument suite abroad the Solar TErrestrial RElations Observatory (STEREO) mission is a unique resource for studying these forces throughout the heliosphere. To access the fullest potential of these data, we first need to apply advanced image analysis tools to deal with the three-dimensional data. Here, we present the application of the computer vision technique of scene flow on the CME observed by SECCHI on 10 June 2010. Scene flow methods estimate the three-dimensional motion of points in the field of view using multiple camera sequences. We use a scene flow algorithm to estimate the three-dimensional velocity at every point on a surface of the 10 June 2010 CME. We discuss how these technique can be used in future research. Title: Reconstructing CMEs with Coordinated Imaging and In Situ Observations: Global Structure, Kinematics, and Implications for Space Weather Forecasting Authors: Liu, Y.; Thernisien, A. F.; Luhmann, J. G.; Vourlidas, A.; Davies, J. A.; Lin, R. P.; Bale, S. Bibcode: 2010AGUFMSH23B1861L Altcode: We reconstruct the global structure and kinematics of coronal mass ejections (CMEs) using coordinated imaging and in situ observations from multiple vantage points. A forward modeling technique, which assumes a rope-like morphology for CMEs, is used to determine the global structure (including orientation and propagation direction) from coronagraph observations. We reconstruct the corresponding structure from in situ measurements at 1 AU with the Grad-Shafranov (GS) method, which gives the flux-rope orientation, cross section and a rough knowledge of the propagation direction. CME kinematics (propagation direction and radial distance) during the transit from the Sun to 1 AU are studied with a geometric triangulation technique, which provides an unambiguous association between solar observations and in situ signatures; a track fitting approach is invoked when data are available from only one spacecraft. We show how the results obtained from imaging and in situ data can be compared by applying these methods to some events, especially Earth-directed ones. This merged imaging and in situ study shows important consequences and implications for CME research as well as space weather forecasting: (1) CME propagation directions can be determined to a relatively good precision as shown by the consistency between different methods; (2) the geometric triangulation technique shows a promising capability to link solar observations with corresponding in situ signatures at 1 AU and to predict CME arrival at the Earth; (3) the flux rope within CMEs, which has the most hazardous southward magnetic field, cannot be imaged at large distances due to expansion; (4) the flux-rope orientation derived from in situ measurements at 1 AU may have a large deviation from that determined by coronagraph image modeling; (5) we find, for the first time, that CMEs undergo a westward migration with respect to the Sun-Earth line at their acceleration phase, which we suggest as a universal feature produced by the magnetic field connecting the Sun and ejecta. Importance of having dedicated spacecraft at L4 and L5, which are well situated for the triangulation concept, is also discussed based on the results. Title: Connecting CME expansion from Sun to 1 AU Authors: Nieves-Chinchilla, T.; Colaninno, R. C.; Vourlidas, A.; Szabo, A.; Vinas, A. F.; Davila, J. M. Bibcode: 2010AGUFMSH23B1841N Altcode: EUV disk imagers and white light coronagraphs have provided for many years information on the early formation and evolution of coronal mass ejections (CMEs). More recently, the novel heliospheric imaging instruments aboard the STEREO mission are providing crucial remote sensing information on the interplanetary evolution of these events while in situ instruments complete the overall characterization of the interplanetary CMEs. In this work, we present an analysis of CMEs from the Sun to the interplanetary medium using combined data from SDO, SOHO, STEREO, WIND, and ACE spacecraft. From the remote sensing analysis, the most notable feature of a CME observed in the SECCHI suite of instruments field of view is its elliptic cross section. However, most of the models for in situ modeling impose the circular cross-section geometry. In this work, we link the remote sensing observations with the in situ data through an analytical in situ model which incorporates the distortion in the cross-section. In this study, different aspects such as the ambient solar wind, magnetic field configurations, plasma parameters, etc, have been taken into account in order to cover the widest spectrum of possible scenarios. Title: Examining Periodic Solar-Wind Density Structures Observed in the SECCHI Heliospheric Imagers Authors: Viall, Nicholeen M.; Spence, Harlan E.; Vourlidas, Angelos; Howard, Russell Bibcode: 2010SoPh..267..175V Altcode: 2010arXiv1009.5885V; 2010SoPh..tmp..174V We present an analysis of small-scale, periodic, solar-wind density enhancements (length scales as small as ≈ 1000 Mm) observed in images from the Heliospheric Imager (HI) aboard STEREO-A. We discuss their possible relationship to periodic fluctuations of the proton density that have been identified at 1 AU using in-situ plasma measurements. Specifically, Viall, Kepko, and Spence (J. Geophys. Res.113, A07101, 2008) examined 11 years of in-situ solar-wind density measurements at 1 AU and demonstrated that not only turbulent structures, but also nonturbulent, periodic density structures exist in the solar wind with scale sizes of hundreds to one thousand Mm. In a subsequent paper, Viall, Spence, and Kasper (Geophys. Res. Lett.36, L23102, 2009) analyzed the α-to-proton solar-wind abundance ratio measured during one such event of periodic density structures, demonstrating that the plasma behavior was highly suggestive that either temporally or spatially varying coronal source plasma created those density structures. Large periodic density structures observed at 1 AU, which were generated in the corona, can be observable in coronal and heliospheric white-light images if they possess sufficiently high density contrast. Indeed, we identify such periodic density structures as they enter the HI field of view and follow them as they advect with the solar wind through the images. The smaller, periodic density structures that we identify in the images are comparable in size to the larger structures analyzed in-situ at 1 AU, yielding further evidence that periodic density enhancements are a consequence of coronal activity as the solar wind is formed. Title: A Catalog of Halo Coronal Mass Ejections from SOHO Authors: Gopalswamy, N.; Yashiro, S.; Michalek, G.; Xie, H.; Mäkelä, P.; Vourlidas, A.; Howard, R. A. Bibcode: 2010SunGe...5....7G Altcode: Coronal mass ejections (CMEs) that appear to surround the occulting disk of the observing coronagraph are known as halo CMEs. Halos constitute a subset of energetic CMEs that have important heliospheric consequences. Here we describe an on-line catalog that contains all the halo CMEs that were identified in the images obtained by the Solar and Heliospheric Observatory (SOHO) mission's Large Angle and Spectrometric Coronagraph (LASCO) since 1996. Until the end of 2007, some 396 halo CMEs were recorded. For each halo CME, we identify the solar source (heliographic coordinates), the soft X-ray flare importance, and the flare onset time. From the sky-plane speed measurements and the solar source information we obtain the space speed of CMEs using a cone model. In addition to the description of the catalog (http://cdaw.gsfc.nasa.gov/CME_list/HALO/halo.html), we summarize the statistical properties of the halo CMEs. We confirm that halo CMEs are twice faster than ordinary CMEs and are associated with major flares on the average. We also compared the annual rate of halo CMEs with that obtained by automatic detection methods and found that most of these methods have difficulty in identifying full halo CMEs. Title: Toward understanding the early stages of an impulsively accelerated coronal mass ejection. SECCHI observations Authors: Patsourakos, S.; Vourlidas, A.; Kliem, B. Bibcode: 2010A&A...522A.100P Altcode: 2010arXiv1008.1171P Context. The expanding magnetic flux in coronal mass ejections (CMEs) often forms a cavity. Studies of CME cavities have so far been limited to the pre-event configuration to evolved CMEs at great heights, and to two-dimensional imaging data.
Aims: Quantitative analysis of three-dimensional cavity evolution at CME onset can reveal information that is relevant to the genesis of the eruption.
Methods: A spherical model was simultaneously fit to Solar Terrestrial Relations Observatory (STEREO) Extreme Ultraviolet Imager (EUVI) and Inner Coronagraph (COR1) data of an impulsively accelerated CME on 25 March 2008, which displays a well-defined extreme ultraviolet (EUV) and white-light cavity of nearly circular shape already at low heights h ≈ 0.2 R_⊙. The center height h(t) and radial expansion r(t) of the cavity were obtained in the whole height range of the main acceleration. We interpret them as the axis height and as a quantity proportional to the minor radius of a flux rope.
Results: The three-dimensional expansion of the CME exhibits two phases in the course of its main upward acceleration. From the first h and r data points, taken shortly after the onset of the main acceleration, the erupting flux shows an overexpansion compared to its rise, as expressed by the decrease in the aspect ratio from κ = h/r ≈ 3 to κ ≈ (1.5-2). This phase is approximately coincident with the impulsive rise in the acceleration and is followed by a phase of very gradual change in the aspect ratio (a nearly self-similar expansion) toward κ ~ 2.5 at h ~ 10 R_⊙. The initial overexpansion of the CME cavity can be caused by flux conservation around a rising flux rope of decreasing axial current and by the addition of flux to a growing, or by even newly formed, flux rope by magnetic reconnection. Further analysis will be required to decide which of these contributions is dominant. The data also suggest that the horizontal component of the impulsive cavity expansion (parallel to the solar surface) triggers the associated EUV wave, which subsequently detaches from the CME volume. Title: Reconstructing Coronal Mass Ejections with Coordinated Imaging and in Situ Observations: Global Structure, Kinematics, and Implications for Space Weather Forecasting Authors: Liu, Ying; Thernisien, Arnaud; Luhmann, Janet G.; Vourlidas, Angelos; Davies, Jackie A.; Lin, Robert P.; Bale, Stuart D. Bibcode: 2010ApJ...722.1762L Altcode: 2010arXiv1009.1414L We reconstruct the global structure and kinematics of coronal mass ejections (CMEs) using coordinated imaging and in situ observations from multiple vantage points. A forward modeling technique, which assumes a rope-like morphology for CMEs, is used to determine the global structure (including orientation and propagation direction) from coronagraph observations. We reconstruct the corresponding structure from in situ measurements at 1 AU with the Grad-Shafranov method, which gives the flux-rope orientation, cross section, and a rough knowledge of the propagation direction. CME kinematics (propagation direction and radial distance) during the transit from the Sun to 1 AU are studied with a geometric triangulation technique, which provides an unambiguous association between solar observations and in situ signatures; a track fitting approach is invoked when data are available from only one spacecraft. We show how the results obtained from imaging and in situ data can be compared by applying these methods to the 2007 November 14-16 and 2008 December 12 CMEs. This merged imaging and in situ study shows important consequences and implications for CME research as well as space weather forecasting: (1) CME propagation directions can be determined to a relatively good precision as shown by the consistency between different methods; (2) the geometric triangulation technique shows a promising capability to link solar observations with corresponding in situ signatures at 1 AU and to predict CME arrival at the Earth; (3) the flux rope within CMEs, which has the most hazardous southward magnetic field, cannot be imaged at large distances due to expansion; (4) the flux-rope orientation derived from in situ measurements at 1 AU may have a large deviation from that determined by coronagraph image modeling; and (5) we find, for the first time, that CMEs undergo a westward migration with respect to the Sun-Earth line at their acceleration phase, which we suggest is a universal feature produced by the magnetic field connecting the Sun and ejecta. The importance of having dedicated spacecraft at L4 and L5, which are well situated for the triangulation concept, is also discussed based on the results. Title: Comprehensive Analysis of Coronal Mass Ejection Mass and Energy Properties Over a Full Solar Cycle Authors: Vourlidas, A.; Howard, R. A.; Esfandiari, E.; Patsourakos, S.; Yashiro, S.; Michalek, G. Bibcode: 2010ApJ...722.1522V Altcode: 2010arXiv1008.3737V The LASCO coronagraphs, in continuous operation since 1995, have observed the evolution of the solar corona and coronal mass ejections (CMEs) over a full solar cycle with high-quality images and regular cadence. This is the first time that such a data set becomes available and constitutes a unique resource for the study of CMEs. In this paper, we present a comprehensive investigation of the solar cycle dependence on the CME mass and energy over a full solar cycle (1996-2009) including the first in-depth discussion of the mass and energy analysis methods and their associated errors. Our analysis provides several results worthy of further studies. It demonstrates the possible existence of two event classes: "normal" CMEs reaching constant mass for >10 R sun and "pseudo"-CMEs which disappear in the C3 field of view. It shows that the mass and energy properties of CME reach constant levels and therefore should be measured only above ~10 R sun. The mass density (g/R 2 sun) of CMEs varies relatively little (< order of magnitude) suggesting that the majority of the mass originates from a small range in coronal heights. We find a sudden reduction in the CME mass in mid-2003 which may be related to a change in the electron content of the large-scale corona and we uncover the presence of a 6 month periodicity in the ejected mass from 2003 onward. Title: Sun to 1 AU propagation and evolution of a slow streamer-blowout coronal mass ejection Authors: Lynch, B. J.; Li, Y.; Thernisien, A. F. R.; Robbrecht, E.; Fisher, G. H.; Luhmann, J. G.; Vourlidas, A. Bibcode: 2010JGRA..115.7106L Altcode: 2010JGRA..11507106L We present a comprehensive analysis of the evolution of the classic, slow streamer-blowout CME of 1 June 2008 observed by the STEREO twin spacecraft to infer relevant properties of the pre-eruption source region which includes a substantial portion of the coronal helmet streamer belt. The CME was directed ∼40° East of the Sun-Earth line and the Heliospheric Imager observations are consistent with the CME propagating essentially radially to 1 AU. The elongation-time J-map constructed from the STEREO-A HI images tracks the arrival of two density peaks that bound the magnetic flux rope ICME seen at STEREO-B on 6 June 2008. From the STEREO-A elongation-time plots we measure the ICME flux rope radial size Rc(t) and find it well approximated by the constant expansion value Vexp = 24.5 km/s obtained from the STEREO-B declining velocity profile within the magnetic cloud. The flux rope spatial orientation, determined by forward modeling fits to the STEREO COR2 and HI1 data, approaches the observed 1 AU flux rope orientation and suggests large-scale rotation during propagation, as predicted by recent numerical simulations. We compare the ICME flux content to the PFSS model coronal field for Carrington Rotation 2070 and find sufficient streamer belt flux to account for the observed ICME poloidal/twist flux if reconnection during CME initiation process is responsible for the conversion of overlying field into the flux rope twist component in the standard fashion. However, the PFSS model field cannot account for the ICME toroidal/axial flux component. We estimate the field strength of the pre-eruption sheared/axial component in the low corona and the timescales required to accumulate this energized pre-eruption configuration via differential rotation and flux cancelation by supergranular diffusion at the polarity inversion line. We show that both mechanisms are capable of generating the desired shear component over time periods of roughly 1-2 months. We discuss the implications for slow streamer-blowout CMEs arising as a natural consequence of the corona's re-adjustment to the long term evolutionary driving of the photospheric fields. Title: MHD Simulation of the 2008 December 12 CME: Comparison with STEREO Observations Authors: Jin, Meng; Manchester, Ward; van der Holst, Bart; Frazin, Richard; Gombosi, Tamas; Vourlidas, Angelos; Liu, Ying; Vasquez, Alberto Bibcode: 2010shin.confE.147J Altcode: We model the 2008 December 12 coronal mass ejection (CME) from its active region origin and follow its propagation to 1AU. This CME is ideal for study for it erupted from near disk center producing a magnetic cloud that passed the Earth 5 days later as observed by Wind. The resulting ICME passed between the STEREO spacecraft and was well observed by COR1 and COR2 coronagraphs as well as the HI1 and HI2 imagers. We compare our numerical model to these extensive observations to understand and verify the three-dimensional (3-D) structure of the ejected plasma. We employ a new advanced two-temperature model of the solar wind, which combines improved thermodynamics along with the treatment of Afven waves. The model address both field-aligned electron and ion heat conduction with collisional coupling between the two species. Alfven waves heat the ions, which then transfer their energy to electrons, which transport the energy far into the corona. We use numerous observations to specify boundary conditions for the numerical model, including MDI synoptic magnetograms and 3-D tomographic reconstructions of coronal temperature and density based on STEREO EUVI data. Title: Reconstructing CMEs with Coordinated Imaging and In Situ Observations: Global Structure, Kinematics, and Implications for Space Weather Forecasting Authors: Liu, Ying; Thernisien, Arnaud; Luhmann, Janet G.; Vourlidas, Angelos; Davies, Jackie A.; Lin, Robert P.; Bale, Stuart D. Bibcode: 2010shin.confE.136L Altcode: We reconstruct the global structure and kinematics of coronal mass ejections (CMEs) using coordinated imaging and in situ observations. We will first briefly review and discuss various techniques with which to convert elongation measurements to radial distances, a challenge in determining CME kinematics. We will then discuss what CME properties we can compare between white light observations and in situ measurements, and show how to determine the properties and make the comparison. Both case studies (including the 2008 December 12 and 2010 April 3 events) and a statistical analysis will be presented. Consequences and implications for CME research and space weather forecasting resulting from this merged imaging and in situ study will be discussed based on the results. Title: Comparing Techniques to Derive the Direction of Propagation of CMEs Authors: Lugaz, Noe; Roussev, I. I.; Vourlidas, A. Bibcode: 2010shin.confE.137L Altcode: Using data from SECCHI and the HIs, it is possible to derive the direction of propagation of CMEs in addition to their speed with a variety of methods. When the 2 STEREO spacecraft separation is optimal, it is possible to derive the CME direction using simultaneous observations from the twin spacecraft and also, using observations from only one spacecraft with fitting methods. This makes it possible to compare and validate different analyses techniques. Here, we propose a new fitting method and compare the results from these two methods with those from two stereoscopic methods. We address one possible source of errors of fitting methods: the assumption of radial propagation. Using stereoscopic methods, we find that at least 7 of 12 studied CMEs had small or negligible heliospheric deflection. Title: Kinematic Characterization of In/Out Pairs as seen in SECCHI Images Authors: Baldwin, Katherine; Vourlidas, Angelos; Linton, Mark; Howard, Russell; Stenborg, Guillermo Bibcode: 2010shin.confE.148B Altcode: This study investigates the kinematic properties of the 'in/out pair' coronal features seen in Thompson scattered, white-light coronagraph images. Frequently, the pairs occur as the aftermath of solar coronal mass ejections appearing at first as a pin hole tear along the streamer axis. The tear appears consistently at around 5 solar radii. Due to the timing and location of these events, it is likely that the pairs are indicators of magnetic reconnection at the trailing edge of CMEs. Using the SECCHI COR1/COR2 instruments in combination with the LASCO C2 data, we are able to calculate the 3D location as well as the true speed of the pairs using elongation-time map (so-called JMAP) capabilities. The inflow portion of the pairs are seen in both SECCHI and LASCO coronagraphs and travel at approximately 100 km/s. While, the outflow portion take the shape of the outflow of the preceding storm and travel faster than 200 km/s. The images used in this analysis were processed using a running difference technique. Previous images subtraction highlights the proper motions of the intensity enhancements, while removing background effects. These results may shed light on the processes of magnetic reconnection following solar storms. Title: Determining the Azimuthal Properties of Coronal Mass Ejections from Multi-Spacecraft Remote-Sensing Observations with STEREO SECCHI Authors: Lugaz, N.; Hernandez-Charpak, J. N.; Roussev, I. I.; Davis, C. J.; Vourlidas, A.; Davies, J. A. Bibcode: 2010ApJ...715..493L Altcode: 2010arXiv1004.0945L We discuss how simultaneous observations by multiple heliospheric imagers (HIs) can provide some important information about the azimuthal properties of coronal mass ejections (CMEs) in the heliosphere. We propose two simple models of CME geometry that can be used to derive information about the azimuthal deflection and the azimuthal expansion of CMEs from SECCHI/HI observations. We apply these two models to four CMEs well observed by both STEREO spacecraft during the year 2008. We find that in three cases, the joint STEREO-A and B observations are consistent with CMEs moving radially outward. In some cases, we are able to derive the azimuthal cross section of the CME fronts, and we are able to measure the deviation from self-similar evolution. The results from this analysis show the importance of having multiple satellites dedicated to space weather forecasting, for example, in orbits at the Lagrangian L4 and L5 points. Title: Examining Periodic Solar Wind Density Structures in SECCHI HI1A Authors: Viall, Nicholeen; Vourlidas, A.; Spence, H.; Howard, R. Bibcode: 2010AAS...21630303V Altcode: We present an analysis of small-scale periodic solar wind density enhancements observed in SECCHI HI1. We discuss their possible relationship to periodic fluctuations of the proton density observed in-situ with the Wind SWE data. Viall et al. [2008] used 11 years of solar wind density measurements at 1 AU and demonstrated that in addition to turbulent fluctuations, non-turbulent periodic density structures with length scales of tens to hundreds of megameters exist in the solar wind. Event studies of the periodic density structures reveal instances in which the density structures have alpha/proton abundance ratio changes associated with the density structures. Specifically, the alpha density varies with the same periodicity as the protons, but in antiphase. For those events, this strongly suggests either time varying or spatially varying coronal source plasma that created the density structures. If such periodic density structures observed at 1 AU are generated in the corona, then they may be observable in SECCHI HI1 data. We identify periodic density structures as they convect with the solar wind into the field of view of SECCHI HI and follow the train of structures as a function of time. The periodic density structures we analyze are comparable in size to the larger structures identified in-situ at 1 AU.

This research was supported through NASA Grant No. NNG05GK65G and an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Oak Ridge Associated Universities through a contract with NASA. Title: Kinematic Characterization Of In/out Pairs As Seen In Secchi Authors: Baldwin, Katherine; Vourlidas, A.; Linton, M. Bibcode: 2010AAS...21640625B Altcode: This study investigates the kinematic properties of the "in/out pair” coronal features seen in Thompson scattered, white-light coronagraph images. Frequently, the pairs occur as the after-math of solar coronal mass ejections appearing at first as a pin hole tear along the streamer axis. The tear appears consistently at around 5 solar radii. Due to the timing and location of these events, it is likely that the pairs are indicators of magnetic reconnection at the trailing edge of CMEs. Using the SECCHI COR1/COR2 instruments in combination with the LASCO C2 data, we are able to calculate the 3D location as well as the true speed of the pairs using elongation-time map (so-called JMAP) capabilities. The inflow portion of the pairs are seen in both SECCHI and LASCO coronagraphs and travel at approximately 100 km/s. While, the outflow portion take the shape of the outflow of the preceding storm and travel faster than 200 km/s. The images used in this analysis were processed using a running difference technique. Previous images subtraction highlights the proper motions of the intensity enhancements, while removing background effects. These results may shed light on the processes of magnetic reconnection following solar storms. Title: Tracking of Coronal White-Light Events by Texture Authors: Goussies, N.; Stenborg, G.; Vourlidas, A.; Howard, R. Bibcode: 2010SoPh..262..481G Altcode: 2010SoPh..tmp....8G The extraction of the kinematic properties of coronal mass ejections (CMEs) from white-light coronagraph images involves a significant degree of user interaction: defining the edge of the event, separating the core from the front or from nearby unrelated structures, etc. To contribute towards a less subjective and more quantitative definition, and therefore better kinematic characterization of such events, we have developed a novel image-processing technique based on the concept of "texture of the event". The texture is defined by the so-called gray-level co-occurrence matrix, and the technique consists of a supervised segmentation algorithm to isolate a particular region of interest based upon its similarity with a pre-specified model. Once the event is visually defined early in its evolution, it is possible to automatically track the event by applying the segmentation algorithm to the corresponding time series of coronagraph images. In this paper we describe the technique, present some examples, and show how the coronal background, the core of the event, and even the associated shock (if one exists) can be identified for different kind of CMEs detected by the LASCO and SECCHI coronagraphs. Title: Intermittent release of transients in the slow solar wind: 1. Remote sensing observations Authors: Rouillard, A. P.; Davies, J. A.; Lavraud, B.; Forsyth, R. J.; Savani, N. P.; Bewsher, D.; Brown, D. S.; Sheeley, N. R.; Davis, C. J.; Harrison, R. A.; Howard, R. A.; Vourlidas, A.; Lockwood, M.; Crothers, S. R.; Eyles, C. J. Bibcode: 2010JGRA..115.4103R Altcode: 2010JGRA..11504103R The Heliospheric Imager (HI) instruments on board the STEREO spacecraft are used to analyze the solar wind during August and September 2007. We show how HI can be used to image the streamer belt and, in particular, the variability of the slow solar wind which originates inside and in the vicinity of the streamer belt. Intermittent mass flows are observed in HI difference images, streaming out along the extension of helmet streamers. These flows can appear very differently in images: plasma distributed on twisted flux ropes, V-shaped structures, or “blobs.” The variety of these transient features may highlight the richness of phenomena that could occur near helmet streamers: emergence of flux ropes, reconnection of magnetic field lines at the tip of helmet streamers, or disconnection of open magnetic field lines. The plasma released with these transient events forms part of the solar wind in the higher corona; HI observations show that these transients are frequently entrained by corotating interaction regions (CIRs), leading to the formation of larger, brighter plasma structures in HI images. This entrainment is used to estimate the trajectory of these plasma ejecta. In doing so, we demonstrate that successive transients can be entrained by the same CIR in the high corona if they emanate from the same corotating source. Some parts of the streamers are more effective sources of transients than others. Surprisingly, evidence is given for the outflow of a recurring twisted magnetic structure, suggesting that the emergence of flux ropes can be recurrent. Title: Geometric Triangulation of Imaging Observations to Track Coronal Mass Ejections Continuously Out to 1 AU Authors: Liu, Ying; Davies, Jackie A.; Luhmann, Janet G.; Vourlidas, Angelos; Bale, Stuart D.; Lin, Robert P. Bibcode: 2010ApJ...710L..82L Altcode: 2010arXiv1001.1352L We describe a geometric triangulation technique, based on time-elongation maps constructed from imaging observations, to track coronal mass ejections (CMEs) continuously in the heliosphere and predict their impact on the Earth. Taking advantage of stereoscopic imaging observations from the Solar Terrestrial Relations Observatory, this technique can determine the propagation direction and radial distance of CMEs from their birth in the corona all the way to 1 AU. The efficacy of the method is demonstrated by its application to the 2008 December 12 CME, which manifests as a magnetic cloud (MC) from in situ measurements at the Earth. The predicted arrival time and radial velocity at the Earth are well confirmed by the in situ observations around the MC. Our method reveals non-radial motions and velocity changes of the CME over large distances in the heliosphere. It also associates the flux-rope structure measured in situ with the dark cavity of the CME in imaging observations. Implementation of the technique, which is expected to be a routine possibility in the future, may indicate a substantial advance in CME studies as well as space weather forecasting. Title: Extreme Ultraviolet Observations and Analysis of Micro-Eruptions and Their Associated Coronal Waves Authors: Podladchikova, O.; Vourlidas, A.; Van der Linden, R. A. M.; Wülser, J. -P.; Patsourakos, S. Bibcode: 2010ApJ...709..369P Altcode: The Solar Terrestrial Relations Observatory EUV telescopes have uncovered small-scale eruptive events, tentatively referred to as "mini-CMEs" because they exhibit morphologies similar to large-scale coronal mass ejections (CMEs). Coronal waves and widespread diffuse dimmings followed by the expansion of the coronal waves are the most brightly manifestations of large-scale CMEs. The high temporal and spatial resolution of the EUV data allows us to detect and analyze these eruptive events, to resolve their fine structure, and to show that the observed "mini-waves" have a strong similarity to the large-scale "EIT' waves. Here, we analyze a micro-event observed on 2007 October 17 by the Sun Earth Connection Coronal and Heliospheric Investigation EUV Imager (EUVI) in 171 Å (Fe IX) with a 2.5 minute cadence. The mini-CME differs from its large-scale counterparts by having smaller geometrical size, a shorter lifetime, and reduced intensity of coronal wave and dimmings. The small-scale coronal wave develops from micro-flaring sites and propagate up to a distance of 40,000 km in a wide angular sector of the quiet Sun over 20 minutes. The area of the small-scale dimming is two orders of magnitude smaller than for large-scale events. The average speed of the small-scale coronal wave studied is 14 km s-1. Our observations give strong indications that small-scale EUV coronal waves associated with the micro-eruptions propagate in the form of slow mode waves almost perpendicular to the background magnetic field. Title: MHD Simulation of the 2008 December 12 CME: Comparison with STEREO Observations Authors: Manchester, Ward, IV; van der Holst, Bart; Frazin, Richard; Gombosi, Tamas; Vourlidas, Angelos; Liu, Ying; Vásquez, Alberto Bibcode: 2010cosp...38.1857M Altcode: 2010cosp.meet.1857M We model the 2008 December 12 coronal mass ejection (CME) from its active region origin and follow its propagation to 1AU. This CME is ideal for study for it erupted from near disk center producing a magnetic cloud that passed the Earth 5 days later as observed by Wind. The resulting ICME passed between the STEREO spacecraft and was well observed by COR1 and COR2 coronagraphs as well as the HI1 and HI2 imagers. We compare our numerical model to these extensive observations to understand and verify the three-dimensional (3-D) structure of the ejected plasma. We employ a new advanced two-temperature model of the solar wind, which combines improved thermodynamics along with the treatment of Afven waves. The model address both field-aligned electron and ion heat conduction with collisional coupling between the two species. Alfven waves heat the ions, which then transfer their energy to electrons, which transport the energy far into the corona. We use numerous observations to specify boundary conditions for the numerical model, including MDI synoptic magnetograms and 3-D tomographic reconstructions of coronal temperature and density based on STEREO EUVI data. Title: The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations Authors: Vourlidas, A.; Sanchez Andrade-Nuño, B.; Landi, E.; Patsourakos, S.; Teriaca, L.; Schühle, U.; Korendyke, C. M.; Nestoras, I. Bibcode: 2010SoPh..261...53V Altcode: 2009arXiv0912.2272V The Very high Angular resolution ULtraviolet Telescope (VAULT) is a sounding rocket payload built to study the crucial interface between the solar chromosphere and the corona by observing the strongest line in the solar spectrum, the Ly α line at 1216 Å. In two flights, VAULT succeeded in obtaining the first ever subarcsecond ( 0.5\hbox{$^''$} ) images of this region with high sensitivity and cadence. Detailed analyses of those observations contributed significantly to new ideas about the nature of the transition region. Here, we present a broad overview of the Ly α atmosphere as revealed by the VAULT observations and bring together past results and new analyses from the second VAULT flight to create a synthesis of our current knowledge of the high-resolution Ly α Sun. We hope that this work will serve as a good reference for the design of upcoming Ly α telescopes and observing plans. Title: Coronal sound waves on open magnetic field lines originating near solar active regions Authors: Stenborg, Guillermo; Marsch, Eckart; Vourlidas, Angelos; Howard, Russell; Baldwin, Katherine Bibcode: 2010cosp...38.1814S Altcode: 2010cosp.meet.1814S In the past years, evidence for the existence of outward-moving plasma and slow-mode magne-toacoustic waves propagating in various magnetic field structures (loops in particular) in the solar corona has been found, yet their origin and possible connection with the mass and energy supply to the corona and solar wind is still unclear. These results were obtained by the high-resolution observations available from the extreme ultraviolet (EUV) imagers on the STEREO and Hinode missions, and from data obtained by the ultraviolet spectrometer on Hinode. Here, we present the first measurements of intensity fluctuations observed by the Extreme Ultra-Violet Imagers (EUVI) onboard the Solar TErrestrial RElationships Observatory (STEREO) mission along apparently open field lines near solar active regions. We demonstrate that one can make reliable kinematic measurements (speed, acceleration) from these EUV images, thereby complementing and extending the spectroscopic measurements. We have developed a series of image-processing steps to recover the weak intensity fluctuations along individual magnetic structures, de-projected them and produced distance-time maps. They can be analysed by use of well established techniques adapted from the kinematic analysis of Coronal Mass Ejection (CME), and by standard methods of wavelet analysis. We obtained wave phase speeds with values on the order of 100 km/s. We also studied the periodicity of the observed fluctuations and established a predominance of a 16-minutes period, as well as other periods being multi-ples of the 8-minutes period that appears to be the basic value. Thus we clearly established the ubiquitous existence of sound waves which seem to emanate continuously on open coronal fields. Title: Evidence for extended acceleration of solar flare ions from 1-8 MeV solar neutrons detected with the MESSENGER Neutron Spectrometer Authors: Feldman, William C.; Lawrence, David J.; Goldsten, John O.; Gold, Robert E.; Baker, Daniel N.; Haggerty, Dennis K.; Ho, George C.; Krucker, SäM.; Lin, Robert P.; Mewaldt, Richard A.; Murphy, Ronald J.; Nittler, Larry R.; Rhodes, Edgar A.; Slavin, James A.; Solomon, Sean C.; Starr, Richard D.; Vilas, Faith; Vourlidas, Angelos Bibcode: 2010JGRA..115.1102F Altcode: 2010JGRA..11501102F Neutrons produced on the Sun during the M2 flare on 31 December 2007 were observed at 0.48 AU by the MESSENGER Neutron Spectrometer. These observations are the first detection of solar neutrons inside 1 AU. This flare contained multiple acceleration episodes as seen in type III radio bursts. After these bursts ended, both the energetic particle and neutron fluxes decayed smoothly to background with an e-folding decay time of 2.84 h, spanning a 9 h time period. This time is considerably longer than the mean lifetime of a neutron, which indicates that either the observed neutrons were generated in the spacecraft by solar energetic particle protons, or they originated on the Sun. If most of the neutrons came from the Sun, as our simulations of neutron production on the spacecraft show, they must have been continuously produced. A likely explanation of their long duration is that energetic ions were accelerated over an extended time period onto closed magnetic arcades above the corona and then slowly pitch angle-scattered by coronal turbulence into their chromospheric loss cones. Because of their relatively low energy loss in the Neutron Spectrometer (0.5-7.5 MeV), most of these neutrons beta decay to energetic protons and electrons close to the Sun, thereby forming an extended seed population available for further acceleration by subsequent shocks driven by coronal mass ejections in interplanetary space. Title: Heatwaves on the Sun Authors: Robbrecht, Eva; Wang, Yi-Ming; Vourlidas, Angelos; Patsourakos, Spiros Bibcode: 2010cosp...38.1791R Altcode: 2010cosp.meet.1791R Dimmings have been observed for several years now, but their interpretation is still problematic. A dimming is an observational effect of diminished brightness with respect to pre-event images, which is usually interpreted as a density depletion. But not all dimmings are what they appear to be. In this paper we report on an unusual "dimming wave" which is not a density depletion but rather a heat wave. Thanks to the stereoscopic view from the SECCHI/EUVI imagers we are able not only to uncover the nature of the wave, but also to understand its three dimensional evolution and its relationship to a quiet sun CME. Title: Kinematic characterization of In/Out pairs as seen in SECCHI images Authors: Baldwin, Katherine; Vourlidas, Angelos Bibcode: 2010cosp...38.1864B Altcode: 2010cosp.meet.1864B This study investigates the kinematic properties of the "in/out pair" coronal features seen in Thompson scattered, white-light coronagraph images. Frequently, the pairs occur as the after-math of solar coronal mass ejections appearing at first as a pin hole tear along the streamer axis. The tear appears consistently at around 5 solar radii. Due to the timing and location of these events, it is likely that the pairs are indicators of magnetic reconnection at the trailing edge of CMEs. Using the SECCHI COR1/COR2 instruments in combination with the LASCO C2 data, we are able to calculate the 3D location as well as the true speed of the pairs using elongation-time map (so-called JMAP) capabilities. The inflow portion of the pairs are seen in both SECCHI and LASCO coronagraphs and travel at approximately 100 km/s. While, the outflow portion take the shape of the outflow of the preceding storm and travel faster than 200 km/s. The images used in this analysis were processed using a running difference technique. Previous images subtraction highlights the proper motions of the intensity enhance-ments, while removing background effects. These results may shed light on the processes of magnetic reconnection following solar storms. Title: MHD Modeling of CMEs and CIRs and Comparison with White Light Observations from STEREO/SECCHI Authors: Lugaz, Noé; Roussev, Ilia; Vourlidas, Angelos; Manchester, Ward, IV; Gombosi, Tamas Bibcode: 2010cosp...38.1869L Altcode: 2010cosp.meet.1869L Interplanetary coronal mass ejections (iCMEs) have complex magnetic and density structures, the result of their interaction with the structured solar wind, in particular with corotating interaction regions (CIRs), and also with previous eruptions. iCMEs and CIRs are been pri-marily measured in situ and studied via numerical simulations in the previous three decades, but, in the past five years, they have also been revealed through remote-sensing observations by heliospheric imagers. To understand and analyze these observations often requires the use of numerical modeling. Numerical simulations can be used to determine the origin of a complex ejecta observed near Earth or to analyze the origin, speed and extent of density structures observed remotely. In this talk, we review recent efforts to use numerical simulations of CMEs and CIRs for the analysis of line-of-sight images produced by STEREO/SECCHI in order to in-vestigate the density structure, energetics and kinematics of iCMEs in interplanetary space. We also discuss how numerical simulations can be used to test different methods for the derivation of iCME properties from remote observations and to predict and explain observational effects. In particular, we use a series of numerical simulations to test and compare some of the methods used to determine CME position, speed and direction from white-light observations. Finally, we show how numerical simulations are an essential tool for understanding the properties of iCMEs and for maximizing the return of heliospheric missions such as STEREO. Title: On the 3-D reconstruction of Coronal Mass Ejections using coronagraph data Authors: Mierla, M.; Inhester, B.; Antunes, A.; Boursier, Y.; Byrne, J. P.; Colaninno, R.; Davila, J.; de Koning, C. A.; Gallagher, P. T.; Gissot, S.; Howard, R. A.; Howard, T. A.; Kramar, M.; Lamy, P.; Liewer, P. C.; Maloney, S.; Marqué, C.; McAteer, R. T. J.; Moran, T.; Rodriguez, L.; Srivastava, N.; St. Cyr, O. C.; Stenborg, G.; Temmer, M.; Thernisien, A.; Vourlidas, A.; West, M. J.; Wood, B. E.; Zhukov, A. N. Bibcode: 2010AnGeo..28..203M Altcode: Coronal Mass ejections (CMEs) are enormous eruptions of magnetized plasma expelled from the Sun into the interplanetary space, over the course of hours to days. They can create major disturbances in the interplanetary medium and trigger severe magnetic storms when they collide with the Earth's magnetosphere. It is important to know their real speed, propagation direction and 3-D configuration in order to accurately predict their arrival time at the Earth. Using data from the SECCHI coronagraphs onboard the STEREO mission, which was launched in October 2006, we can infer the propagation direction and the 3-D structure of such events. In this review, we first describe different techniques that were used to model the 3-D configuration of CMEs in the coronagraph field of view (up to 15 R⊙). Then, we apply these techniques to different CMEs observed by various coronagraphs. A comparison of results obtained from the application of different reconstruction algorithms is presented and discussed. Title: The Evolution Of The Brightness Of The White Light Corona Over A Solar Cycle Authors: Howard, R. A.; Battams, K.; Vourlidas, A.; Morrill, J. S.; Stenborg, G. Bibcode: 2009AGUFMSH13C..04H Altcode: The LASCO C2 and C3 coronagraphs on the SOHO mission have been operating almost continuously since 1996. This long period covers two solar minima and one maximum. It has been reported that the solar wind magnetic field and pressure is abnormally low. We have asked whether there is any difference in the brightness, which is directly related to the electron content. We have generated plots of the total intensity for the entire 13 year period. Comparison over this long period is possible due to the excellent, absolute calibration of the coronagraphs using star transits. We find a solar cycle dependence of about 20%. However, we do not see a significant decrease of the current minimum compared to the previous one. Rather, the total intensity (summed over all position angles) is ~5% higher this minimum than previously due to a slightly broader streamer “belt” now than previously. In contrast, CMEs are about 2x less massive at the current minimum than the previous one. The CME average mass dramatically decreased from 2002 to 2004 by a factor of 5. This CME decrease corresponded to the average CME width becoming narrower. We note that the intensity structure of the current minimum did not achieve the simple structure of the previous minimum. Title: Kinematical characterization of intensity fluctuations observed in STEREO EUVI images: 1. On-disk case Authors: Baldwin, K. L.; Stenborg, G.; Vourlidas, A.; Howard, R. A. Bibcode: 2009AGUFMSH41B1650B Altcode: Enhanced, wavelet processed STEREO/EUVI images reveal intermittent intensity fluctuations traveling outwards along apparently-open field lines nearby active region coronal holes. The phenomenon has been observed and quantified using data from instruments on other missions. However, much debate still exists in the solar community about the physical cause and exact quantitative nature of the fluctuations. The STEREO/EUVI continuous coverage, full-disk imaging allows for the first time a more comprehensive study. In particular, we found that the phenomenon persists for as long as the topological configuration of the source region remains constant. In order to shed light on an understanding of the nature of the fluctuations, we have devised a method to determine the kinematical parameters of these apparent outflows. In this work, we introduce the method, report on the average plane-of-sky speed found for a set of selected dates, infer the true velocity by taking advantage of the STEREO two-point view, and discuss the possible scenarios that can explain the phenomenon. Title: Dependence of CME Propagation on Parameters of the Ejecta and Ambient Solar Wind Authors: Li, Y.; Lynch, B. J.; Luhmann, J. G.; Krauss-Varban, D.; Thernisien, A.; Vourlidas, A.; MacNeice, P. J. Bibcode: 2009AGUFMSH41A1632L Altcode: CME propagation through the heliosphere has been one of the most uncertain problems, due to its complex nature and sparse observations in the vast space. CME travel time, speed and trajectory have been often unpredictable, because they may be modified going through ambient solar wind streams and IMF structure. All of these parameters are important for understanding CMEs and their space weather consequences. Direct observations of CME propagation through to 1AU have only become a reality since the recent STEREO Heliospheric Imager (HI) observations. Based on a few strategically selected CMEs that vary in parameter space and situated in different solar wind/IMF conditions, we perform several CCMC ENLIL with cone model simulations to study the propagation. Comparisons between modeling results including CME driven shock properties, travel time, 3D trajectory, and distortion of the ejecta (limited to the model approximation) will be made. Comparisons are also made between modeling, HI imaging results, and observed in-situ parameters when available. Title: Geometric Triangulation of Imaging Observations to Track CMEs Continuously Out to 1 AU (Invited) Authors: Liu, Y.; Davies, J.; Luhmann, J. G.; Lin, R. P.; Bale, S.; Vourlidas, A. Bibcode: 2009AGUFMSH43A..04L Altcode: We describe a geometric triangulation technique, based on time-elongation maps constructed from imaging observations, to track coronal mass ejections (CMEs) continuously in the heliosphere and predict their impact on the Earth. Taking advantage of stereoscopic imaging observations from STEREO, this technique can precisely determine the propagation direction and radial distance of CMEs from their birth in the corona all the way to 1 AU. The efficacy of the method is demonstrated by its application to the 2008 December 12 CME, which manifests as a magnetic cloud (MC) from in situ measurements at the Earth. The predicted arrival time and radial velocity at the Earth are well confirmed by the in situ observations around the MC. Implementation of the technique, which is expected to be a routine possibility in the future, indicates a substantial advance in CME studies as well as space weather forecasting. Title: STEREO observations of interplanetary coronal mass ejections and prominence deflection during solar minimum period Authors: Kilpua, E. K. J.; Pomoell, J.; Vourlidas, A.; Vainio, R.; Luhmann, J.; Li, Y.; Schroeder, P.; Galvin, A. B.; Simunac, K. Bibcode: 2009AnGeo..27.4491K Altcode: In this paper we study the occurrence rate and solar origin of interplanetary coronal mass ejections (ICMEs) using data from the two Solar TErrestrial RElation Observatory (STEREO) and the Wind spacecraft. We perform a statistical survey of ICMEs during the late declining phase of solar cycle 23. Observations by multiple, well-separated spacecraft show that even at the time of extremely weak solar activity a considerable number of ICMEs were present in the interplanetary medium. Soon after the beginning of the STEREO science mission in January 2007 the number of ICMEs declined to less than one ICME per month, but in late 2008 the ICME rate clearly increased at each spacecraft although no apparent increase in the number of coronal mass ejections (CMEs) occurred. We suggest that the near-ecliptic ICME rate can increase due to CMEs that have been guided towards the equator from their high-latitude source regions by the magnetic fields in the polar coronal holes.

We consider two case studies to highlight the effects of the polar magnetic fields and CME deflection taking advantage of STEREO observations when the two spacecraft were in the quadrature configuration (i.e. separated by about 90 degrees). We study in detail the solar and interplanetary consequences of two CMEs that both originated from high-latitude source regions on 2 November 2008. The first CME was slow (radial speed 298 km/s) and associated with a huge polar crown prominence eruption. The CME was guided by polar coronal hole fields to the equator and it produced a clear flux rope ICME in the near-ecliptic solar wind. The second CME (radial speed 438 km/s) originated from an active region 11007 at latitude 35° N. This CME propagated clearly north of the first CME and no interplanetary consequences were identified. The two case studies suggest that slow and elongated CMEs have difficulties overcoming the straining effect of the overlying field and as a consequence they are guided by the polar coronal fields and cause in-situ effects close to the ecliptic plane. The 3-D propagation directions and CME widths obtained by using the forward modelling technique were consistent with the solar and in-situ observations. Title: Examining Solar Wind Number Density Structures Observed in SECCHI HI 1 Authors: Viall, N. M.; Spence, H. E.; Vourlidas, A.; Howard, R. A. Bibcode: 2009AGUFMSH13B1516V Altcode: We present an analysis of small-scale periodic solar wind density enhancements observed in SECCHI HI 1. We discuss their possible relationship to periodic fluctuations of the proton density observed in-situ with the Wind SWE data. Viall et al. [2008] used 11 years of solar wind density measurements at 1 AU and demonstrated that in addition to turbulent fluctuations, non-turbulent, periodic density structures exist in the solar wind. In the slow wind, periodic density structures occurred most often with radial length-scales of approximately 73, 120, 136 and 180 Mm. In the fast wind, periodic density structures occurred most often with radial length-scales of approximately 187, 270 and 400 Mm. Event studies of the periodic density structures reveal instances in which the density structures have alpha/proton abundance ratio changes associated with the density structures. Specifically, the alpha density varies with the same periodicity as the protons, but in antiphase. For those events, this strongly suggests either time varying or spatially varying coronal source plasma that created the density structures. If such periodic density structures observed at 1 AU are generated in the corona, then they may be observable in SECCHI HI1 data. For instance, larger scale plasmoids have been observed in the corona [e.g. Sheeley et al., 2009] and it is plausible that smaller, periodic structures may exist as well. We identify periodic density structures as they convect with the solar wind into the field of view of SECCHI HI and follow the train of structures as a function of time. The periodic density structures we analyze are comparable in size to the larger structures identified in-situ at 1 AU. Title: Determining CME azimuthal properties from stereoscopic heliospheric observations Authors: Lugaz, N.; Hernandez, J. N.; Roussev, I. I.; Vourlidas, A. Bibcode: 2009AGUFMSH41A1636L Altcode: We discuss how remote-sensing observations by multiple white-light imagers can provide some information about the azimuthal deflection and azimuthal expansion of Coronal Mass Ejections (CMEs) as they propagate in the heliosphere. Our analysis focuses on one CME which was well observed by the SECCHI/HIs onboard STEREO-A and B on April 26-28, 2008. By considering two simple models of CME geometry and using simultaneous observations from the two different viewpoints, we show that the observations can be best understood by modeling the CME as a propagating sphere of expanding radius on a fixed radial trajectory. Preliminary analysis shows that the CME expansion is self-similar from 0.2 AU until 0.5 AU and slows down afterwards. An alternative explanation of the observations is a deflection towards the east of a bubble CME. While observational effects may play a role, the results from these two models are corroborated by the non-detection of the CME at L1, where a CME hit was expected based on its initial width and direction. Title: Kinematical characterization of intensity fluctuations observed in STEREO EUVI images: II. Off-disk case Authors: Stenborg, G. A.; Baldwin, K.; Vourlidas, A.; Howard, R. A. Bibcode: 2009AGUFMSH41B1651S Altcode: Coherent quasi-periodic perturbations in brightness along polar plumes have been found with the Extreme ultraviolet Imager Telescope (EIT) onboard the SOlar and Heliospheric Observatory (SOHO). Unfortunately, without the use of high cadence EIT campaigns from SOHO, a systematic study of such phenomenon was not feasible due to the high temporal resolution required for this analysis. The advent of the Solar TErrestrial RElationships Observatory (STEREO) mission with its higher spatial and temporal resolution imagers resolved this issue. The twin Extreme UltraViolet Imagers (EUVI) aboard STEREO allowed for simultaneous, high cadence views of the plume structures from two view points. In our enhanced, wavelet processed STEREO/EUVI images, we have found persistent and quasi-steady intensity fluctuations apparently traveling outward above polar coronal holes. The projected plane-of-sky linear speed ranges from 70 to 150 km/sec for these above-the-limb fluctuations. Additionally, some cases exhibit an acceleration pattern very close to the limb. In this work, we introduce the method developed to systematically measure the kinematical parameters of the phenomenon, we compute several parameters for pre-selected dates, and we discuss the existence of an apparent quasi-periodic pattern observed in the Height-Time maps. Finally, we relate our quantitative findings to previous works. Title: Sun to 1 AU Propagation of a Slow Streamer-Blowout Coronal Mass Ejection Authors: Lynch, B. J.; Li, Y.; Thernisien, A. F.; Robbrecht, E.; Luhmann, J. G.; Vourlidas, A. Bibcode: 2009AGUFMSH41A1635L Altcode: We present the time history and evolution of the 3-dimensional size, shape, and orientation of the slow, classic streamer blowout CME of 2008 Jun 01 by combining STEREO-A remote imaging of its interplanetary propagation with in situ STEREO-B plasma and field measurements at 1~AU. The STEREO-A HI coverage allows unambigious identification of the CME white light front-cavity structure and the resulting ICME flux rope boundaries in running difference images. The elongation-time tracks predict the arrival of the ICME at STEREO-B on 2008 June 06 remarkably well. Starting from the simplest in situ flux rope model for the coherent magnetic cloud field structure, we utilize the unprecedented coverage of the coronal and heliospheric imaging observations to obtain important corrections for the ICME flux rope geometry. MHD modeling results obtained from the NASA Community Coordinated Modeling Center for the ambient heliopsheric solar wind stream structure and a simple CME-like density-pulse propagation are used to verify the overall propagation direction and characterize some of the observed evolutionary properties. The ICME radial expansion, i.e. the time evolution of the flux rope radius Rc(t) from the STEREO-A elongation-time plots, is well approximated by the standard treatment of constant radial expansion Vexp = 24.5 km/s measured from the in situ bulk velocity profile. The 3-dimensional spatial orientation of the ICME flux rope determined by forward modeling in the inner heliosphere shows excellent agreement with the observed 1~AU flux rope orientation and evidence for large scale rotation of the ICME flux rope during its propagation, as predicted by recent numerical simulations. In addition, measurements of the CME's latitudinal angular width allows us to improve the estimate the actual flux rope cross-sectional area and measurements of the CME's longitudinal extent allows us to estimate a more realistic CME ``loop length". These geometric quantities are used to improve the estimates of the ICME in situ toroidal and poloidal magnetic fluxes, ΦT and ΦP. The in situ flux values are then compared to the magnetic fluxes inferred from this event's source region, which includes a substantial portion of the large scale coronal helmet streamer belt. We conlude by discussing our results in the context of both CME initiation and the physical mechanism(s) that energize the pre-eruption configuration. Support for this work was provided by NASA HGI NNX08AJ04G. Title: Geoeffective CME-driven Shocks: Comparison Between Imaging Data and in-situ Observations Authors: Ontiveros, V.; Gonzalez-Esparza, A.; Vourlidas, A. Bibcode: 2009AGUFMSH41A1630O Altcode: Fast Coronal Mass Ejections (CMEs) drive shock waves that can be recognized in the coronagraph images. Properties of the shock and the CME, such as density compression ratio, mass, kinetic energy, and the direction of propagation, can be measured from these images. The aim of this study is: (1) to compare these properties with in-situ measurements of the large scale Shock-Sheath-CME structure in the interplanetary medium, and (2) to track back to the Sun geoeffective parameters of the CME-shock, that have been recognized as the main cause of moderate and intense geomagnetic storms. Title: A Review of Coronagraphic Observations of Shocks Driven by Coronal Mass Ejections Authors: Vourlidas, Angelos; Ontiveros, Veronica Bibcode: 2009AIPC.1183..139V Altcode: 2009arXiv0908.1996V The existence of shocks driven by Coronal Mass Ejections (CMEs) has always been assumed based on the superalfvenic speeds for some of these events and on indirect evidence such as radio bursts and distant streamer deflections. However, the direct signature of the plasma enhancement at the shock front has escaped detection until recently. Since 2003, work on LASCO observations has shown that CME-driven shocks can be detected by white light coronagraph observations from a few solar radii to at least 20 Rsun. Shock properties, such as the density compression ratio and their direction can be extracted from the data. We review this work here and demonstrate how to recognize the various shock morphologies in the images. We also discuss how the two-viewpoint coronagraph observations from the STEREO mission allow the reconstruction of the 3D envelope of the shock revealing some interesting properties of the shocks (e.g., anisotropic expansion). Title: First Measurements of the Mass of Coronal Mass Ejections from the EUV Dimming Observed with STEREO EUVI A+B Spacecraft Authors: Aschwanden, Markus J.; Nitta, Nariaki V.; Wuelser, Jean-Pierre; Lemen, James R.; Sandman, Anne; Vourlidas, Angelos; Colaninno, Robin C. Bibcode: 2009ApJ...706..376A Altcode: The masses of coronal mass ejections (CMEs) have traditionally been determined from white-light coronagraphs (based on Thomson scattering of electrons), as well as from extreme ultraviolet (EUV) dimming observed with one spacecraft. Here we develop an improved method of measuring CME masses based on EUV dimming observed with the dual STEREO/EUVI spacecraft in multiple temperature filters that includes three-dimensional volume and density modeling in the dimming region and background corona. As a test, we investigate eight CME events with previous mass determinations from STEREO/COR2, of which six cases are reliably detected with the Extreme Ultraviolet Imager (EUVI) using our automated multi-wavelength detection code. We find CME masses in the range of m CME = (2-7) × 1015 g. The agreement between the two EUVI/A and B spacecraft is mA /mB = 1.3 ± 0.6 and the consistency with white-light measurements by COR2 is m EUVI/m COR2 = 1.1 ± 0.3. The consistency between EUVI and COR2 implies no significant mass backflows (or inflows) at r < 4 R sun and adequate temperature coverage for the bulk of the CME mass in the range of T ≈ 0.5-3.0 MK. The temporal evolution of the EUV dimming allows us to also model the evolution of the CME density ne (t), volume V(t), height-time h(t), and propagation speed v(t) in terms of an adiabatically expanding self-similar geometry. We determine e-folding EUV dimming times of tD = 1.3 ± 1.4 hr. We test the adiabatic expansion model in terms of the predicted detection delay (Δt ≈ 0.7 hr) between EUVI and COR2 for the fastest CME event (2008 March 25) and find good agreement with the observed delay (Δt ≈ 0.8 hr). Title: The Impact of Geometry on Observations of CME Brightness and Propagation Authors: Morrill, J. S.; Howard, R. A.; Vourlidas, A.; Webb, D. F.; Kunkel, V. Bibcode: 2009SoPh..259..179M Altcode: Coronal mass ejections (CMEs) have a significant impact on space weather and geomagnetic storms and so have been the subject of numerous studies. Most CME observations have been made while these events are near the Sun (e.g., SOHO/LASCO). Recent data from the Coriolis/SMEI and STEREO/SECCHI-HI instruments have imaged CMEs farther into the heliosphere. Analyses of CME observations near the Sun measure the properties of these events by assuming that the emission is in the plane of the sky and hence the speed and mass are lower limits to the true values. However, this assumption cannot be used to analyze optical observations of CMEs far from the Sun, such as observations from SMEI and SECCHI-HI, since the CME source is likely to be far from the limb. In this paper we consider the geometry of observations made by LASCO, SMEI, and SECCHI. We also present results that estimate both CME speed and trajectory by fitting the CME elongations observed by these instruments. Using a constant CME speed does not generally produce profiles that fit observations at both large and small elongation, simultaneously. We include the results of a simple empirical model that alters the CME speed to an estimated value of the solar wind speed to simulate the effect of drag on the propagating CME. This change in speed improves the fit between the model and observations over a broad range of elongations. Title: What Is the Nature of EUV Waves? First STEREO 3D Observations and Comparison with Theoretical Models Authors: Patsourakos, S.; Vourlidas, A.; Wang, Y. M.; Stenborg, G.; Thernisien, A. Bibcode: 2009SoPh..259...49P Altcode: 2009arXiv0905.2189P One of the major discoveries of the Extreme ultraviolet Imaging Telescope (EIT) on SOHO was the intensity enhancements propagating over a large fraction of the solar surface. The physical origin(s) of the so-called EIT waves is still strongly debated with either wave (primarily fast-mode MHD waves) or nonwave (pseudo-wave) interpretations. The difficulty in understanding the nature of EUV waves lies in the limitations of the EIT observations that have been used almost exclusively for their study. They suffer from low cadence and single temperature and viewpoint coverage. These limitations are largely overcome by the SECCHI/EUVI observations onboard the STEREO mission. The EUVI telescopes provide high-cadence, simultaneous multitemperature coverage and two well-separated viewpoints. We present here the first detailed analysis of an EUV wave observed by the EUVI disk imagers on 7 December 2007 when the STEREO spacecraft separation was ≈ 45°. Both a small flare and a coronal mass ejection (CME) were associated with the wave. We also offer the first comprehensive comparison of the various wave interpretations against the observations. Our major findings are as follows: (1) High-cadence (2.5-minute) 171 Å images showed a strong association between expanding loops and the wave onset and significant differences in the wave appearance between the two STEREO viewpoints during its early stages; these differences largely disappeared later; (2) the wave appears at the active region periphery when an abrupt disappearance of the expanding loops occurs within an interval of 2.5 minutes; (3) almost simultaneous images at different temperatures showed that the wave was most visible in the 1 - 2 MK range and almost invisible in chromospheric/transition region temperatures; (4) triangulations of the wave indicate it was rather low lying (≈ 90 Mm above the surface); (5) forward-fitting of the corresponding CME as seen by the COR1 coronagraphs showed that the projection of the best-fit model on the solar surface was inconsistent with the location and size of the co-temporal EUV wave; and (6) simulations of a fast-mode wave were found in good agreement with the overall shape and location of the observed wave. Our findings give significant support for a fast-mode interpretation of EUV waves and indicate that they are probably triggered by the rapid expansion of the loops associated with the CME. Title: Deriving the radial distances of wide coronal mass ejections from elongation measurements in the heliosphere - application to CME-CME interaction Authors: Lugaz, N.; Vourlidas, A.; Roussev, I. I. Bibcode: 2009AnGeo..27.3479L Altcode: 2009arXiv0909.0534L We present general considerations regarding the derivation of the radial distances of coronal mass ejections (CMEs) from elongation angle measurements such as those provided by SECCHI and SMEI, focusing on measurements in the Heliospheric Imager 2 (HI-2) field of view (i.e. past 0.3 AU). This study is based on a three-dimensional (3-D) magneto-hydrodynamics (MHD) simulation of two CMEs observed by SECCHI on 24-27 January 2007. Having a 3-D simulation with synthetic HI images, we are able to compare the two basic methods used to derive CME positions from elongation angles, the so-called "Point-P" and "Fixed-φ" approximations. We confirm, following similar works, that both methods, while valid in the most inner heliosphere, yield increasingly large errors in HI-2 field of view for fast and wide CMEs. Using a simple model of a CME as an expanding self-similar sphere, we derive an analytical relationship between elongation angles and radial distances for wide CMEs. This relationship is simply the harmonic mean of the "Point-P" and "Fixed-φ" approximations and it is aimed at complementing 3-D fitting of CMEs by cone models or flux rope shapes. It proves better at getting the kinematics of the simulated CME right when we compare the results of our line-of-sights to the MHD simulation. Based on this approximation, we re-analyze the J-maps (time-elongation maps) in 26-27 January 2007 and present the first observational evidence that the merging of CMEs is associated with a momentum exchange from the faster ejection to the slower one due to the propagation of the shock wave associated with the fast eruption through the slow eruption. Title: No Trace Left Behind: STEREO Observation of a Coronal Mass Ejection Without Low Coronal Signatures Authors: Robbrecht, Eva; Patsourakos, Spiros; Vourlidas, Angelos Bibcode: 2009ApJ...701..283R Altcode: 2009arXiv0905.2583R The availability of high-quality synoptic observations of the extreme-ultraviolet (EUV) and visible corona during the SOHO mission has advanced our understanding of the low corona manifestations of coronal mass ejections (CMEs). The EUV imager/white light coronagraph connection has been proven so powerful, it is routinely assumed that if no EUV signatures are present when a CME is observed by a coronagraph, then the event must originate behind the visible limb. This assumption carries strong implications for space weather forecasting but has not been put to the test. This paper presents the first detailed analysis of a frontside, large-scale CME that has no obvious counterparts in the low corona as observed in EUV and Hα wavelengths. The event was observed by the SECCHI instruments onboard the STEREO mission. The COR2A coronagraph observed a slow flux-rope-type CME, while an extremely faint partial halo was observed in COR2B. The event evolved very slowly and is typical of the streamer-blowout CME class. EUVI A 171 Å images show a concave feature above the east limb, relatively stable for about two days before the eruption, when it rises into the coronagraphic fields and develops into the core of the CME. None of the typical low corona signatures of a CME (flaring, EUV dimming, filament eruption, waves) were observed in the EUVI B images, which we attribute to the unusually large height from which the flux rope lifted off. This interpretation is supported by the CME mass measurements and estimates of the expected EUV dimming intensity. Only thanks to the availability of the two viewpoints we were able to identify the likely source region. The event originated along a neutral line over the quiet-Sun. No active regions were present anywhere on the visible (from STEREO B) face of the disk. Leaving no trace behind on the solar disk, this observation shows unambiguously that a CME eruption does not need to have clear on-disk signatures. Also it sheds light on the question of "mystery" geomagnetic storms, storms without clear solar origin (formerly called problem storms). We discuss the implications for space weather monitoring. Preliminary inspection of STEREO data indicates that events like this are not uncommon, particularly during the ongoing period of deep solar minimum. Title: CME-driven shocks: Formation and deformation Authors: Liu, Ying; Luhmann, J. G.; Lin, R. P.; Bale, S. D.; Richardson, J. D.; Manchester, W. B.; Kasper, J. C.; Vourlidas, A. Bibcode: 2009shin.confE.123L Altcode: We discuss the formation and deformation of CME-driven shocks by combining high-cadence imaging observations of the corona and coordinated in situ measurements. Various shock signatures in the corona, including remote deflection of coronal structures, a weak edge ahead of the CME front in white light and coronal metric type II bursts, are used to investigate the distance and time of shock formation, a puzzle lasting for several decades. Early CME kinematics obtained from high-cadence observations are compared with a certain range of Alfven speeds determined from band splitting of type II bursts and motion of plasma blobs in the post-CME plasma sheet. CMEs and their preceding shocks can also be deformed by coronal structures that act like density/field obstacles as well as solar wind speed gradient when the solar wind momentum dominates the magnetic force. The curvature of CMEs/shocks resulting from this distortion is studied in terms of the elevation angle of their normals and plasma deflection flows in CME sheaths and is compared with global MHD simulations. Multi-spacecraft measurements of specific events coordinated by MHD propagation of the solar wind are also examined in order to probe the global structure of CME-driven shocks. Title: Origins of Solar Minimum CMEs with ICMEs Authors: Li, Yan; Luhmann, J. G.; Lynch, B. J.; Toy, V.; Thernisien, A.; Vourlidas, A.; Kilpua, E.; Jian, L. Bibcode: 2009shin.confE.167L Altcode: We study a group of approximately one dozen CMEs occurred during the current solar minimum in order to understand their associations (or lack of) with coronal activity (e.g., flares, prominences/filaments). These CMEs are the sources of all the significant ICMEs that were detected by spacecraft at 1AU between Jan 2007 and Sept 2008. They make up only a small fraction of the total CME population in various catalogs in this time span. Most CMEs in this group are slow eruptions and have no association with flares. For some of these CMEs, we cannot identify any associated solar activity on the disk. What gave rise to this group of solar minimum CMEs and what can we learn from them? Title: Examining Solar Wind Number Density Structures Observed in SECCHI HI 1 Authors: Viall, Nicholeen Mary; Spence, Harlan E.; Vourlidas, Angelos; Howard, Russ Bibcode: 2009shin.confE.133V Altcode: We explore small-scale quasi-periodic solar wind density fluctuations observed in SECCHI HI 1. We discuss their possible relationship to periodic fluctuations of the proton density observed in-situ with the Wind SWE data. Viall et al. [2008] used 11 years of solar wind density measurements at 1 AU and demonstrated that in addition to turbulent fluctuations, non-turbulent, periodic density structures exist in the solar wind. In the slow wind, periodic density structures occurred most often with radial length-scales of approximately 73, 120, 136 and 180 Mm. In the fast wind, periodic density structures occurred most often with radial length-scales of approximately 187, 270 and 400 Mm. Event studies of the periodic density structures reveal instances in which the density structure has alpha/proton abundance ratio changes associated with the density structures. Specifically, the alpha density varies with the same periodicity as the protons, but in antiphase. This strongly suggests either time varying or spatially varying coronal source plasma that created the density structures. If such periodic density structures observed at 1AU are generated in the corona, then they may be observable in SECCHI HI1 data. For instance, larger scale plasmoids have been observed in the corona [e.g. Sheeley et al., 2009] and it is plausible that smaller, quasi-periodic structures may exist as well. We identify quasi-periodic density structures in the SECCHI HI1 images that are comparable in size to those identified in-situ at 1AU. Title: Tracking CMEs/shocks and predicting their arrival time at the Earth Authors: Liu, Ying; Luhmann, J. G.; Lin, R. P.; Bale, S. D.; Davies, J. A.; Thernisien, A.; Vourlidas, A. Bibcode: 2009shin.confE..59L Altcode: Coronal mass ejections (CMEs) have been recognized as primary drivers of interplanetary disturbances. Of central importance in space weather forecasting is to track CMEs and their preceding shocks from the Sun continuously out to 1 AU. We will discuss and evaluate three different strategies for this purpose, specifically (1) frequency drift of type II bursts to track CME-driven shocks; (2) MHD propagation of observed solar wind disturbances; and (3) geometric triangulation of white-light features observed by wide-angle coronagraphs and heliospheric imagers from vantage points off the Sun-Earth line. Event studies together with implications for instrumentation will be presented to demonstrate the capabilities with which the impact of a solar storm on the Earth can be predicted with small ambiguities. Title: Kinematics of CMEs observed in SECCHI HI: Fast solar wind acceleration of CMEs? Authors: Colaninno, Robin Crescenza; Vourlidas, Angelos Bibcode: 2009shin.confE.166C Altcode: The SECCHI HI instruments allow us to observe CMEs from 15 solar radii to 1 AU. In these data, we often see a fast lateral expansion of the CME. This lateral expansion causes a pancaking effect where the angular extent of the CME becomes much larger than its radial extent. A possible cause of this pancaking is an interaction of the CME with the fast solar wind. By fitting a geometric surface to the two viewpoints of STEREO data, we are able to infer the shape and direction of the CME at low coronal heights. By using the HI data and extrapolating the directional information from the geometric model, we can estimate the position of the CME as it moves in the solar wind. Here we will combine this data with Predictive Science's heliospheric models to discover if CMEs are interacting with the fast solar wind. Title: On Magnetic Donuts and Croissants: The Structure of the Slow Solar Wind as Revealed from the SECCHI Telescopes on STEREO Authors: Vourlidas, Angelos Bibcode: 2009shin.confE.132V Altcode: The SECCHI telescopes aboard the STEREO mission have been providing continuous imaging of the corona and inner heliosphere since 2007. The observations have already provided important clues about the magnetic, croissant-like, nature of CMEs. However, the extended solar minimum allows us an opportunity to observe the quiescent solar wind as well. I review the status of solar wind analysis based on the SECCHI observations some of which show that donut-like structures are propagating in the wind. I also discuss the role of such observations in discriminating among the various theories for the solar wind generation. Title: "Extreme Ultraviolet Waves" are Waves: First Quadrature Observations of an Extreme Ultraviolet Wave from STEREO Authors: Patsourakos, Spiros; Vourlidas, Angelos Bibcode: 2009ApJ...700L.182P Altcode: 2009arXiv0905.2164P The nature of coronal mass ejection (CME)-associated low corona propagating disturbances, "extreme ultraviolet (EUV) waves," has been controversial since their discovery by EIT on SOHO. The low-cadence, single-viewpoint EUV images and the lack of simultaneous inner corona white-light observations have hindered the resolution of the debate on whether they are true waves or just projections of the expanding CME. The operation of the twin EUV imagers and inner corona coronagraphs aboard STEREO has improved the situation dramatically. During early 2009, the STEREO Ahead (STA) and Behind (STB) spacecrafts observed the Sun in quadrature having a ≈90° angular separation. An EUV wave and CME erupted from active region 11012, on February 13, when the region was exactly at the limb for STA and hence at disk center for STB. The STEREO observations capture the development of a CME and its accompanying EUV wave not only with high cadence but also in quadrature. The resulting unprecedented data set allowed us to separate the CME structures from the EUV wave signatures and to determine without doubt the true nature of the wave. It is a fast-mode MHD wave after all. Title: Dynamic Lyα jets Authors: Koza, J.; Rutten, R. J.; Vourlidas, A. Bibcode: 2009A&A...499..917K Altcode: 2008arXiv0807.4889K Context: The solar chromosphere and transition region are highly structured and complex regimes. A recent breakthrough has been the identification of dynamic fibrils observed in Hα as caused by field-aligned magnetoacoustic shocks.
Aims: We seek to find whether such dynamic fibrils are also observed in Lyα.
Methods: We used a brief sequence of four high-resolution Lyα images of the solar limb taken by the Very high Angular resolution ULtraviolet Telescope (VAULT), which displays many extending and retracting Lyα jets. We measured their top trajectories and fitted parabolas to the 30 best-defined ones.
Results: Most jet tops move supersonically. Half of them decelerate, sometimes superballistically, the others accelerate. This bifurcation may arise from incomplete sampling of recurrent jets.
Conclusions: The similarities between dynamic Lyα jets and Hα fibrils suggest that the magnetoacoustic shocks causing dynamic Hα fibrils also affect dynamic Lyα jets. Title: Morphology and density structure of post-CME current sheets Authors: Vršnak, B.; Poletto, G.; Vujić, E.; Vourlidas, A.; Ko, Y. -K.; Raymond, J. C.; Ciaravella, A.; Žic, T.; Webb, D. F.; Bemporad, A.; Landini, F.; Schettino, G.; Jacobs, C.; Suess, S. T. Bibcode: 2009A&A...499..905V Altcode: 2009arXiv0902.3705V Context: Eruption of a coronal mass ejection (CME) drags and “opens” the coronal magnetic field, presumably leading to the formation of a large-scale current sheet and field relaxation by magnetic reconnection.
Aims: We analyze the physical characteristics of ray-like coronal features formed in the aftermath of CMEs, to confirm whether interpreting this phenomenon in terms of a reconnecting current sheet is consistent with observations.
Methods: The study focuses on measurements of the ray width, density excess, and coronal velocity field as a function of the radial distance.
Results: The morphology of the rays implies that they are produced by Petschek-like reconnection in the large-scale current sheet formed in the wake of CME. The hypothesis is supported by the flow pattern, often showing outflows along the ray, and sometimes also inflows into the ray. The inferred inflow velocities range from 3 to 30 km s-1, and are consistent with the narrow opening-angle of rays, which add up to a few degrees. The density of rays is an order of magnitude higher than in the ambient corona. The density-excess measurements are compared with the results of the analytical model in which the Petschek-like reconnection geometry is applied to the vertical current sheet, taking into account the decrease in the external coronal density and magnetic field with height.
Conclusions: The model results are consistent with the observations, revealing that the main cause of the density excess in rays is a transport of the dense plasma from lower to higher heights by the reconnection outflow. Title: Coronal Mass Ejections and Global Coronal Magnetic Field Reconfiguration Authors: Liu, Ying; Luhmann, Janet G.; Lin, Robert P.; Bale, Stuart D.; Vourlidas, Angelos; Petrie, Gordon J. D. Bibcode: 2009ApJ...698L..51L Altcode: We investigate the role of coronal mass ejections (CMEs) in the global coronal magnetic field reconfiguration, a debate that has lasted for about two decades. Key evidence of the coronal field restructuring during the 2007 December 31 CME is provided by combining imaging observations from widely separated spacecraft with the potential-field source-surface (PFSS) model, thanks to the extraordinarily quiet Sun at the present solar minimum. The helmet streamer, previously disrupted by the CME, re-forms but is displaced southward permanently; the preexisting heliospheric plasma sheet (HPS) is also disrupted as evidenced by the concave-outward shape of the CME. The south polar coronal hole shrinks considerably. Plasma blobs moving outward along the newly formed HPS suggest the occurrence of magnetic reconnection between the fields blown open by the CME and the ambient adjacent open fields. A streamer-like structure is also observed in the wake of the CME and interpreted as a plasma sheet where the thin post-CME current sheet is embedded. These results are important for understanding the coronal field evolution over a solar cycle as well as the complete picture of CME initiation and propagation. Title: First Determination of the True Mass of Coronal Mass Ejections: A Novel Approach to Using the Two STEREO Viewpoints Authors: Colaninno, Robin C.; Vourlidas, Angelos Bibcode: 2009ApJ...698..852C Altcode: 2009arXiv0903.4344C The twin Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) COR2 coronagraphs of the Solar Terrestrial Relations Observatory (STEREO) provide images of the solar corona from two viewpoints in the solar system. Since their launch in late 2006, the STEREO Ahead (A) and Behind (B) spacecraft have been slowly separating from Earth at a rate of 22fdg5 per year. By the end of 2007, the two spacecraft were separated by more than 40° from each other. At that time, we began to see large-scale differences in the morphology and total intensity between coronal mass ejections (CMEs) observed with SECCHI-COR2 on STEREO-A and B. Due to the effects of the Thomson scattering geometry, the intensity of an observed CME is dependent on the angle it makes with the observed plane of the sky. From the intensity images, we can calculate the integrated line-of-sight electron density and mass. We demonstrate that it is possible to simultaneously derive the direction and true total mass of the CME if we make the simple assumption that the same mass should be observed in COR2-A and B. Title: The Polarimetric Performance of the SECCHI/COR2 Coronagraphs on the Stereo Mission Authors: Baldwin, Katherine; Vourlidas, A. Bibcode: 2009SPD....40.1805B Altcode: The COR2 coronagraphs have been observing the corona in polarized light since January 2007. The COR2 observations are used widely for estimates of the density and 3D structure of the corona and for the localization of coronal mass ejections. The characterization of the polarimetric performance of the instrument is very important for these analyses but also for observations involving the total brightness only. This is because the polarizer is placed permanently in the optical train of the telescope and therefore affects every COR2 image. In this paper, we give a report on our polarization calibrations, including instrumental polarization and provide estimates for the expected accuracy of COR2 polarimetric analysis on the estimation of coronal density and the localization of structures. Title: Study of the 2007 April 20 CME-Comet Interaction Event with an MHD Model Authors: Jia, Y. D.; Russell, C. T.; Jian, L. K.; Manchester, W. B.; Cohen, O.; Vourlidas, A.; Hansen, K. C.; Combi, M. R.; Gombosi, T. I. Bibcode: 2009ApJ...696L..56J Altcode: 2009arXiv0903.4942J This study examines the tail disconnection event on 2007 April 20 on comet 2P/Encke, caused by a coronal mass ejection (CME) at a heliocentric distance of 0.34 AU. During their interaction, both the CME and the comet are visible with high temporal and spatial resolution by the STEREO-A spacecraft. Previously, only current sheets or shocks have been accepted as possible reasons for comet tail disconnections, so it is puzzling that the CME caused this event. The MHD simulation presented in this work reproduces the interaction process and demonstrates how the CME triggered a tail disconnection in the April 20 event. It is found that the CME disturbs the comet with a combination of a 180° sudden rotation of the interplanetary magnetic field (IMF), followed by a 90° gradual rotation. Such an interpretation applies our understanding of solar wind-comet interactions to determine the in situ IMF orientation of the CME encountering Encke. Title: Two Years of the STEREO Heliospheric Imagers. Invited Review Authors: Harrison, Richard A.; Davies, Jackie A.; Rouillard, Alexis P.; Davis, Christopher J.; Eyles, Christopher J.; Bewsher, Danielle; Crothers, Steve R.; Howard, Russell A.; Sheeley, Neil R.; Vourlidas, Angelos; Webb, David F.; Brown, Daniel S.; Dorrian, Gareth D. Bibcode: 2009SoPh..256..219H Altcode: Imaging of the heliosphere is a burgeoning area of research. As a result, it is awash with new results, using novel applications, and is demonstrating great potential for future research in a wide range of topical areas. The STEREO (Solar TErrestrial RElations Observatory) Heliospheric Imager (HI) instruments are at the heart of this new development, building on the pioneering observations of the SMEI (Solar Mass Ejection Imager) instrument aboard the Coriolis spacecraft. Other earlier heliospheric imaging systems have included ground-based interplanetary scintillation (IPS) facilities and the photometers on the Helios spacecraft. With the HI instruments, we now have routine wide-angle imaging of the inner heliosphere, from vantage points outside the Sun-Earth line. HI has been used to investigate the development of coronal mass ejections (CMEs) as they pass through the heliosphere to 1 AU and beyond. Synoptic mapping has also allowed us to see graphic illustrations of the nature of mass outflow as a function of distance from the Sun - in particular, stressing the complexity of the near-Sun solar wind. The instruments have also been used to image co-rotating interaction regions (CIRs), to study the interaction of comets with the solar wind and CMEs, and to witness the impact of CMEs and CIRs on planets. The very nature of this area of research - which brings together aspects of solar physics, space-environment physics, and solar-terrestrial physics - means that the research papers are spread among a wide range of journals from different disciplines. Thus, in this special issue, it is timely and appropriate to provide a review of the results of the first two years of the HI investigations. Title: Forward Modeling of Coronal Mass Ejections Using STEREO/SECCHI Data Authors: Thernisien, A.; Vourlidas, A.; Howard, R. A. Bibcode: 2009SoPh..256..111T Altcode: We describe a forward modeling method developed to study the coronal mass ejections observed with STEREO/SECCHI. We present a survey of 26 CMEs modeled with this method. We selected most of the bright events observed since November 2007 to August 2008, after when the separation was greater than 40° degrees, thus showing noticeable differences between the two views. From these stereoscopic observations and using a geometric model of a flux rope, we are able to determine the three-dimensional direction of propagation, the three-dimensional velocity and acceleration of the CME front, and in most of the cases the flux rope orientation and length. We define a merit function that allows us to partially automate the fit, as well as perform a sensitivity analysis on the model parameters. We find a precision on the longitude and latitude to be of a maximum of ±17° and ±4°, respectively, for a 10% decrease of the merit function but a precision on the flux rope orientation and length to be almost one order of magnitude larger, showing that these parameters are more difficult to estimate using only coronagraph data. Finally, comparison with independent measurements shows a good agreement with the direction and speed we estimated. Title: Solar - Terrestrial Simulation in the STEREO Era: The 24 - 25 January 2007 Eruptions Authors: Lugaz, N.; Vourlidas, A.; Roussev, I. I.; Morgan, H. Bibcode: 2009SoPh..256..269L Altcode: 2009arXiv0902.2004L The SECCHI instruments aboard the recently launched STEREO spacecraft enable for the first time the continuous tracking of coronal mass ejections (CMEs) from the Sun to 1 AU. We analyze line-of-sight observations of the 24 - 25 January 2007 CMEs and fill the 20-hour gap in SECCHI coverage in 25 January by performing a numerical simulation using a three-dimensional magneto-hydrodynamic (MHD) code, the Space Weather Modeling Framework (SWMF). We show how the observations reflect the interaction of the two successive CMEs with each other and with the structured solar wind. We make a detailed comparison between the observations and synthetic images from our model, including time-elongation maps for several position angles. Having numerical simulations to disentangle observational from physical effects, we are able to study the three-dimensional nature of the ejections and their evolution in the inner heliosphere. This study reflects the start of a new era where, on one hand, models of CME propagation and interaction can be fully tested by using heliospheric observations and, on the other hand, observations can be better interpreted by using global numerical models. Title: The Sub-arcsecond Structure Of The Upper Chromosphere: Results From The 2nd Flight Of The Nrl Vault Sounding Rocket Payload Authors: Sanchez-Andrade Nuno, Bruno; Vourlidas, A.; Korendyke, C. Bibcode: 2009SPD....40.2901S Altcode: The Very high Angular resolution ULtraviolet Telescope (VAULT) is an Lya spectroheliograph flown on a sounding rocket. The payload is capable of obtaining Lya filtergrams with a spatial resolution of around 0.33'' ( 200 km) over an extended field of view (535'' x 235'') . The instrument is tuned to the Ly-a line because it forms at the boundary of the upper chromosphere low corona. On its last flight, on 14 June 2002, VAULT observed an area around NOAA AR 9997 & 9998 with a rich variety of features: quiet Sun network, limb spicules, filaments, prominences and plage.

The observing campaign incorporated a wide variety of ground-based and space-borne instruments. The level 0.9 VAULT data is open and available from http://wwwsolar.nrl.navy.mil/rockets/vault .We have recently releseased SolarSoft-compatible software for easy access and processing of the data.

This contribution showcases the data capabilities and availability. We present contrast-enhanced images by means of wavelet image processing. The images reveal in extraordinary detail the dynamics of the smallest solar scales (200-300 km). We observe flows along thin threads on the prominence, exploding events on the plage and even in the quiet sun regions. Title: No trace left behind: STEREO Observation of a Coronal Mass Ejection Lacking Low Coronal Signatures Authors: Vourlidas, Angelos; Robbrecht, E.; Patsourakos, S. Bibcode: 2009SPD....40.2104V Altcode: The availability of high quality synoptic observations of the EUV and visible corona during the SOHO mission has advanced our understanding of the low corona manifestations of CMEs. The EUV imager/White light coronagraph connection has been proven so powerful, it is routinely assumed that if no EUV signatures are present when a CME is observed by a coronagraph, then the event must originate behind the visible limb. This assumption carries strong implications for space weather forecasting but has not been put to the test. This paper presents the first detailed analysis of a frontside, large-scale CME that has no obvious counterparts in the low corona. The event was observed by the SECCHI instruments on the STEREO mission. The COR2A coronagraph observed the event as a typical flux-rope type CME, while an extremely faint partial halo was observed in COR2B. The event evolved very slowly and is typical of the streamer-blowout CME class. EUVI-A 171A images show a concave feature above the east limb, relatively stable for about two days before the eruption, when it rises into the coronagraphic fields and develops into the core of the CME. None of the typical low corona signatures of a CME (flaring, EUV dimming, filament eruption, waves) were observed. Thanks to the two STEREO viewpoints we were able to identify the likely source region. The event originated along a quiet sun neutral line. No active regions were present anywhere on the visible face of the disk. Leaving no trace behind, this observation shows unambiguously that a CME eruption does not need to have clear on-disk signatures. Also it sheds light on the question of `mystery' geomagnetic storms; storms without clear solar origin. Preliminary inspection of STEREO data indicates that events like this are not uncommon, particularly during the ongoing period of deep solar minimum. Title: Quadrature STEREO Observations Determine the Nature of EUV Waves Authors: Kliem, Bernhard; Patsourakos, S.; Vourlidas, A.; Ontiveros, V. Bibcode: 2009SPD....40.2603K Altcode: One of the major discoveries of EIT on SOHO was the observation of large-scale EUV intensity disturbances which travel over significant fractions of the solar disk. These `EUV waves' are associated with CME onsets and can be either an MHD wave triggered by the eruption or the footprints of the associated CME, which currently is a subject of intense debate. EUV waves are better observed when their source region is close to disk center, whereas CME onsets and CMEs in general are better observed off-limb. Therefore, simultaneous multi-viewpoint observations of EUV waves are best suited to clarify the nature of these transients and to determine their true relationship with CMEs.

We present here the first quadrature STEREO observations of an EUV wave. The wave was observed on 2009 February 13 by both satellites, which were at a separation of 90 degrees. The wave originated from an erupting active region near disk center as seen from SC B and propagated over almost the entire visible solar disk. For SC A the active region was at the east limb and showed a small erupting bubble, expanding impulsively in both radial and lateral directions and inducing deflections of nearby and remote coronal structures. We present high cadence EUVI and COR1 measurements of both the wave (SC B), and the expanding EUV bubble (SC A), and of the resulting white-light CME (SC A; COR1). These would allow to quantify for the first time the true sizes and expansion characteristics of both the EUV wave and the associated CME.

Finally, we search for wave-associated features in 3D MHD simulations of CME onsets based on ideal MHD instabilities. These are compared with the STEREO observations. Title: Reconstruction of CME-Driven Shocks Using STEREO Observations Authors: Vourlidas, A.; Ontiveros, Veronica; Riley, P. Bibcode: 2009SPD....40.2212V Altcode: Recent work has shown that CME-driven shocks can easily be detected by white light coronagraph observations from a few solar radii above the surface to at least 20 Rs. However, the shock emission suffers from the same projection effects at the CME emission making precise measurements of the shock properties difficult and prone to assumptions. The two viewpoint observations from the SECCHI/COR2 coronagraphs aboard the STEREO mission offer an unprecedented opportunity to reconstruct the 3D envelope of the shock using the same procedures applied to the successful reconstruction of the CME itself. Due to the low solar activity over the last years, there have been only a handful of white lght shock candidates observed with SECCHI. We examine the most prominent one, associated with the eruption on December 31, 2007. We find that the shock does not evolve isotropically but it is influenced by the large scale coronal magnetic field configuration. To study this interaction in more detail, we employ a sophisticated thermodynamic model of the corona to derive a 3d distribution of the Alfvén speed around the eruption site. We find that we can account for the coronagraph observations only if the shape of the shock closely matches that of the surrounding magnetic field. Title: First Measurements of the Mass of Coronal Mass Ejections from the EUV Dimming Observed with Stereo EUVI A and B Spacecraft Authors: Aschwanden, Markus J.; Nitta, N. V.; Wuelser, J.; Lemen, J. R.; Sandman, A.; Vourlidas, A.; Colaninno, R. C. Bibcode: 2009SPD....40.2116A Altcode: The masses of Coronal Mass Ejections (CMEs) have traditionally been determined from white-light coronagraphs, based on the Thomson scattering of electrons. Here we develop a new method of measuring CME masses from the EUV dimming seen with EUV imaging telescopes in multiple temperature filters. As a test we compare the CME masses measured by STEREO/EUVI A and B with those previously determined by STEREO/COR2, for a set of 8 CME events of which we detected 7 with EUVI and determined the masses in 6 cases. We find CME masses in the range of m = (2-7) x 10(15) g. The agreement between the two EUVI/A and B spacecraft is mA/mB =1.3 +/- 0.6 and the consistency with white-light measurements by COR2 is mEUVI/mCOR2 = 1.1 +/- 0.3. The consistency between EUVI and COR2 implies no significant mass backflows (or inflows) at r < 4 R and adequate temperature coverage for the bulk of the CME mass in the range of T = 0.5-3.0 MK. The temporal evolution of the EUV dimming allows us also to model the evolution of the CME density, volume, height-time, and propagation speed in terms of an adiabatically expanding self-similar geometry. We test this model with the predicted detection delay between EUVI and COR2 for the 2008-Mar-25 event. Title: Large-scale Structures Caused by Interacting Coronal Mass Ejections: Their Formation and Detection as Revealed by MHD Simulations Authors: Lugaz, N.; Roussev, I. I.; Vourlidas, A. Bibcode: 2009EGUGA..11.6510L Altcode: The interaction of successive coronal mass ejections (CMEs) on their way to Earth (and other planets) has been a leading cause of large-scale and long-lived structures resulting in intense geo-magnetic storms during past solar cycles. Associated with the interaction, the merging of shock waves, which creates denser sheaths and the compression of the magnetic field in ejecta are expected to result in unusal responses of the magnetosphere. Here, we present results of magneto-hydrodynamic simulations of geo-effective events from the years 2000 and 2001 with the Space Weather Modeling Framework (SWMF). Our focus is on the propagation and interaction of successive CMEs from the Sun to the Earth and the understanding of the mechanisms which may result in larger and more geo-effective structures. We will also present simulations showing how the Heliospheric Imagers onboard STEREO will help predicting complex ejecta during solar cycle 24. Title: The SOHO/LASCO CME Catalog Authors: Gopalswamy, N.; Yashiro, S.; Michalek, G.; Stenborg, G.; Vourlidas, A.; Freeland, S.; Howard, R. Bibcode: 2009EM&P..104..295G Altcode: 2009EM&P..tmp....8G Coronal mass ejections (CMEs) are routinely identified in the images of the solar corona obtained by the Solar and Heliospheric Observatory (SOHO) mission’s Large Angle and Spectrometric Coronagraph (LASCO) since 1996. The identified CMEs are measured and their basic attributes are cataloged in a data base known as the SOHO/LASCO CME Catalog. The Catalog also contains digital data, movies, and plots for each CME, so detailed scientific investigations can be performed on CMEs and the related phenomena such as flares, radio bursts, solar energetic particle events, and geomagnetic storms. This paper provides a brief description of the Catalog and summarizes the statistical properties of CMEs obtained using the Catalog. Data products relevant to space weather research and some CME issues that can be addressed using the Catalog are discussed. The URL of the Catalog is: <ExternalRef> <RefSource>http://cdaw.gsfc.nasa.gov/CME_list</RefSource> <RefTarget Address="http://cdaw.gsfc.nasa.gov/CME_list" TargetType="URL"/> </ExternalRef>. Title: Driving Currents for Flux Rope Coronal Mass Ejections Authors: Subramanian, Prasad; Vourlidas, Angelos Bibcode: 2009ApJ...693.1219S Altcode: 2008arXiv0810.4210S We present a method for measuring electrical currents enclosed by flux rope structures that are ejected within solar coronal mass ejections (CMEs). Such currents are responsible for providing the Lorentz self-force that propels CMEs. Our estimates for the driving current are based on measurements of the propelling force obtained using data from the LASCO coronagraphs aboard the SOHO satellite. We find that upper limits on the currents enclosed by CMEs are typically around 1010 A. We estimate that the magnetic flux enclosed by the CMEs in the LASCO field of view is a few times 1021 Mx. Title: POLAR investigation of the Sun—POLARIS Authors: Appourchaux, T.; Liewer, P.; Watt, M.; Alexander, D.; Andretta, V.; Auchère, F.; D'Arrigo, P.; Ayon, J.; Corbard, T.; Fineschi, S.; Finsterle, W.; Floyd, L.; Garbe, G.; Gizon, L.; Hassler, D.; Harra, L.; Kosovichev, A.; Leibacher, J.; Leipold, M.; Murphy, N.; Maksimovic, M.; Martinez-Pillet, V.; Matthews, B. S. A.; Mewaldt, R.; Moses, D.; Newmark, J.; Régnier, S.; Schmutz, W.; Socker, D.; Spadaro, D.; Stuttard, M.; Trosseille, C.; Ulrich, R.; Velli, M.; Vourlidas, A.; Wimmer-Schweingruber, C. R.; Zurbuchen, T. Bibcode: 2009ExA....23.1079A Altcode: 2008ExA...tmp...40A; 2008arXiv0805.4389A The POLAR Investigation of the Sun (POLARIS) mission uses a combination of a gravity assist and solar sail propulsion to place a spacecraft in a 0.48 AU circular orbit around the Sun with an inclination of 75° with respect to solar equator. This challenging orbit is made possible by the challenging development of solar sail propulsion. This first extended view of the high-latitude regions of the Sun will enable crucial observations not possible from the ecliptic viewpoint or from Solar Orbiter. While Solar Orbiter would give the first glimpse of the high latitude magnetic field and flows to probe the solar dynamo, it does not have sufficient viewing of the polar regions to achieve POLARIS’s primary objective: determining the relation between the magnetism and dynamics of the Sun’s polar regions and the solar cycle. Title: Quantitative Measurements of Coronal Mass Ejection-Driven Shocks from LASCO Observations Authors: Ontiveros, Veronica; Vourlidas, Angelos Bibcode: 2009ApJ...693..267O Altcode: 2008arXiv0811.3743O In this paper, we demonstrate that coronal mass ejection (CME)-driven shocks can be detected in white light coronagraph images and in which properties such as the density compression ratio and shock direction can be measured. Also, their propagation direction can be deduced via simple modeling. We focused on CMEs during the ascending phase of solar cycle 23 when the large-scale morphology of the corona was simple. We selected events which were good candidates to drive a shock due to their high speeds (V > 1500 km s-1). The final list includes 15 CMEs. For each event, we calibrated the LASCO data, constructed excess mass images, and searched for indications of faint and relatively sharp fronts ahead of the bright CME front. We found such signatures in 86% (13/15) of the events and measured the upstream/downstream densities to estimate the shock strength. Our values are in agreement with theoretical expectations and show good correlations with the CME kinetic energy and momentum. Finally, we used a simple forward modeling technique to estimate the three-dimensional shape and orientation of the white light shock features. We found excellent agreement with the observed density profiles and the locations of the CME source regions. Our results strongly suggest that the observed brightness enhancements result from density enhancements due to a bow-shock structure driven by the CME. Title: Multispacecraft Observations of Magnetic Clouds and Their Solar Origins between 19 and 23 May 2007 Authors: Kilpua, E. K. J.; Liewer, P. C.; Farrugia, C.; Luhmann, J. G.; Möstl, C.; Li, Y.; Liu, Y.; Lynch, B. J.; Russell, C. T.; Vourlidas, A.; Acuna, M. H.; Galvin, A. B.; Larson, D.; Sauvaud, J. A. Bibcode: 2009SoPh..254..325K Altcode: 2008SoPh..tmp..194K We analyze a series of complex interplanetary events and their solar origins that occurred between 19 and 23 May 2007 using observations by the STEREO and Wind satellites. The analyses demonstrate the new opportunities offered by the STEREO multispacecraft configuration for diagnosing the structure of in situ events and relating them to their solar sources. The investigated period was characterized by two high-speed solar wind streams and magnetic clouds observed in the vicinity of the sector boundary. The observing satellites were separated by a longitudinal distance comparable to the typical radial extent of magnetic clouds at 1 AU (fraction of an AU), and, indeed, clear differences were evident in the records from these spacecraft. Two partial-halo coronal mass ejections (CMEs) were launched from the same active region less than a day apart, the first on 19 May and the second on 20 May 2007. The clear signatures of the magnetic cloud associated with the first CME were observed by STEREO B and Wind while only STEREO A recorded clear signatures of the magnetic cloud associated with the latter CME. Both magnetic clouds appeared to have interacted strongly with the ambient solar wind and the data showed evidence that they were a part of the coronal streamer belt. Wind and STEREO B also recorded a shocklike disturbance propagating inside a magnetic cloud that compressed the field and plasma at the cloud's trailing portion. The results illustrate how distant multisatellite observations can reveal the complex structure of the extension of the coronal streamer into interplanetary space even during the solar activity minimum. Title: The CME-ICME Connection and Interplanetary Structure During Solar Minimum Authors: Li, Y.; Lynch, B. J.; Luhmann, J. G.; Kilpua, E.; Toy, V.; Vourlidas, A.; Russell, C. T.; Galvin, A. B. Bibcode: 2008AGUFMSH13B1542L Altcode: When an interplanetary transient (ICME) exhibits a large angle and smooth rotation in the IMF vector, it is classified as a magnetic cloud (MC) and commonly interpreted as the signature of a magnetic flux rope. On the average bout a third of ICME ejecta are MCs, although the fraction seems to be larger during the quiet phase of the solar cycle. Non-flux rope ICMEs are likely (1) distorted during the transit through heliosphere, (2) observed at an unfavorable crossing angle if the ICME structure has spatial variation, (3) or are simply have a more complex internal structure. Five Magnetic Clouds (MC) have been found from a total of nine ICMEs observed during 2007 January 01 to 2008 August 31, when the separation of STEREO A (STA) and B (STB) spacecraft varied between 0.05 to 70.35 degrees heliolongitude. We investigate the four best MCs using observations from three spacecraft (STA, STB and ACE). The first MC seems to have been detected by all three spacecraft (STA and STB 40.4 degrees apart), while the latter three were detected by only one of the STEREO spacecraft and sometimes by ACE. From the inferred flux rope orientation at each crossing and the spatial variation of the ICME properties, we interpret how each MC flux rope was situated relative to the spacecraft, and its connection to the Sun from corresponding coronal and heliospheric modeling results. Each of the MCs can be associated at low confidence (in contrary to expectations for solar minimum time) with a CME observed by coronagraphs on board STEREO and/or SOHO. All potential parent CMEs were very slow in the 200 km/s range (plane-of-sky), but the speeds of the MCs were between ~390 and ~480 km/s, indicating acceleration in the heliosphere. Solar disk activities are minor around the four CMEs, with no GOES x-ray flares, and two possibly associated filament eruptions. Some CME structures appear to form in the coronagraph field of view rather than rising from below. Several low/mid- latitude coronal holes and a highly warped coronal streamer arcade and source surface neutral line dominate the coronal structure during the period of the study. Previous studies have shown that the MC fluxrope orientation may be aligned with the large-scale coronal streamer arcades. Estimated MC orientations are discussed and compared with events during the previous solar minimum, which exhibited a more dipolar coronal structure. This work was supported, in part, by NASA NNG06GE51G, NNX08AJ04G, and NAS5-03131. Title: Multipoint Analysis of Meso-scale Structures in the Ambient Solar Wind: STEREO-A, -B, and L1 Observations Authors: Spence, H. E.; Viall, N. M.; Vourlidas, A.; Howard, R. A.; Simunac, K.; Kistler, L. M.; Galvin, A. B.; Kasper, J. C.; Lazarus, A. J. Bibcode: 2008AGUFMSH12A..06S Altcode: We explore sources of apparent time-dependence of meso-scale structures (those lasting two to three days and less) in the ambient solar wind through analysis of measurements from STEREO-A, -B, and L1 spacecraft (WIND, ACE, and SOHO). In early 2008, stable corotating interaction regions and high-speed streams provided excellent boundaries and features for co-registering the large-scale, corotating solar wind observed by several heliospheric spacecraft separated in solar orbital phase near 1 AU. During this period, STEREO-B (located 23 degrees behind the Earth in heliographic longitude) first observed the large-scale corotating stream structures, followed by the WIND, ACE, and SOHO spacecraft at Earth, then finally by STEREO-A (located 22 degrees ahead of the Earth in heliographic longitude). Conspicuous similarities in the macro-scale solar wind flow dominate the comparison between spacecraft observations and permit us to time-adjust the observed flow features reasonably well by assuming a simple corotating solar wind source. While the co-registered, large-scale solar wind structure agrees well, mesoscale flow features can exhibit large measured differences at the various spacecraft. We focus on one such interesting feature which exhibits apparent time dependence. Though this few-day-long, significant flow speed event is observed by the PLASTIC experiments on both STEREO-A and STEREO-B, it is not seen at the L1 spacecraft which the STEREO spacecraft bracket in space and time. We explore potential sources of the apparent time dependence of this meso-scale feature. Latitudinal differences in the multipoint measurements is one source that could account for the apparent mesoscale flow structure variability. We also explore explicit time variation of the solar wind's source, by analyzing relevant coronal holes observed simultaneously by the STEREO spacecraft imagers. This event and analysis underscores that multipoint heliospheric observations and analysis reveals the existence of mesoscale structure in the solar wind and can be used to constrain its possible source(s). Title: STEREO ICMEs and their Solar Source Regions Near Solar Minimum Authors: Toy, V.; Li, Y.; Luhmann, J. G.; Schroeder, P.; Vourlidas, A.; Jian, L. K.; Russell, C. T.; Galvin, A. B.; Simunac, K.; Acuna, M.; Sauvaud, J. A.; Skoug, R.; Petrie, G. Bibcode: 2008AGUFMSH23A1620T Altcode: Although the quiet activity period surrounding the current solar minimum has prevailed since the launch of STEREO in October 2006, there have been at least 9 clear in-situ detections of ICMEs (Interplanetary Coronal Mass Ejections) by one or more spacecraft during the time the imagers were also operating. These observations provide unusually complete data sets for evaluating helio-longitude extent of the ICMEs and for identifying the probable solar cause(s) of the events. In this poster we present information on these ICMEs from the IMPACT and PLASTIC and ACE in-situ investigations, together with solar images from STEREO and SOHO that seem to capture the causative activity at the Sun. We find that even though the Sun was very quiet in '07-'08, with few active regions visible in GONG and SOHO magnetograms, there were numerous CME candidates that erupted through the near-equatorial helmet streamers. Most events could be identified with EUV disk activity as well as a coronagraph CME, even if the associated active region was very small or weak. Old cycle active regions, new and decayed, continued to maintain a warp in the large-scale helmet streamer belt that was a frequent site of the eruptions. However, the warp in the streamer belt may simply indicate that the active region(s) present is(are) sufficiently strong to affect the large scale quiet coronal field structure. Overall we see no gross differences between the solar activity and ICME causes during this and the previous solar activity minimum, when the Streamer belt was less warped due to the existence of stronger solar polar fields. Title: Comparison of MHD Simulations of CME Evolution and Structure with Coronagraph Observations Authors: Manchester, W. B.; Vourlidas, A.; Jai, Y.; Lugaz, N.; Roussev, I.; Gombosi, T.; Opher, M. Bibcode: 2008AGUFMSH11A..07M Altcode: Coronal mass ejections (CMEs) expel significant amounts of plasma into interplanetary space producing large-scale variations in density that are manifest in coronagraph images. A limitation of these images is that they present two-dimensional projections of three-dimensional structures that are challenging to interpret. The circumstances are even more complex when CMEs are observed at large elongation and the location of preferential scattering is significantly curved. To address the interpretation of such coronagraph images, we examine the Thomson-scattered white-light appearance of 3D MHD simulations of CMEs to identify and reproduce features observed by LASCO and SECCHI coronagraphs. We find close quantitative comparison with LASCO observations and produce shapes at large elongations as seen by SECCHI. We find evidence of shock propagation, magnetic clouds, CME pancaking, and complex time evolution as CMEs propagate at large elongation past the Thomson sphere. A key point is to determine how the 3-D structure of CMEs is affected by propagation through a structured solar wind. Title: Interactions of Multiple CMEs with Complex Interplanetary Medium as Revealed by STEREO Authors: Lugaz, N.; Vourlidas, A.; Roussev, I. I. Bibcode: 2008AGUFMSH13B1553L Altcode: Since the launch of STEREO in November 2006, continuous white-light observations of solar transients on their way to the Earth have been made possible. STEREO/SECCHI observations have also revealed the complexity and dynamic structure of the interplanetary medium. In this talk, we will discuss the significance of 3-D numerical simulations in the interpretation of observations taken by SECCHI. Our focus will be on a series of two ejections on January, 24-25, 2007, which have been simulated with the Space Weather Modeling Framework (SWMF). We will discuss the appearance of coronal mass ejections (CMEs) and dense streams in the Heliospheric Imagers' field-of-view. Detailed comparisons between the real and simulated time-elongation plots will be presented. We will also discuss how observations of CME-CME interaction can be distinguished from the interaction of CMEs with dense streams in the solar wind using the simulations. Title: STEREO Observations of a post-CME Current Sheet Authors: Patsourakos, S.; Vourlidas, A.; Stenborg, G. Bibcode: 2008AGUFMSH13B1552P Altcode: Ray-like features in the wake of Coronal Mass Ejections (CMEs) are often interpreted as current sheets produced by the eruption. The 3D geometry of such post-CME current sheets is largely unknown and its knowledge should place important constraints on CME physics and coronal conditions. An example of a post-CME current sheet was observed on April 9th 2008, in the aftermath of the 'cartwheel' CME, which was observed by Hinode, SoHO, STEREO and TRACE. The CME and the corresponding current sheet were well-observed by both STEREO spacecraft, which were separated by about 48 degrees the day of the event. We present here an analysis of the 3D morphology of the current sheet using data from the COR1 and COR2 coronagraphs from both STEREO spacecraft. We will attempt various forward models (e.g., slabs, cylinders) of the current sheet as seen by the COR1 and COR2 coronagraphs from both STEREO spacecraft. This will characterize the 3D geometry of the current sheet and more precisely its shape and its real width and length. Our forward modeling will also supply the radial variation of the density along the current sheet. This information will supply some estimates of the temperature and magnetic field distributions in and out the current sheet respectively. Title: First STEREO observation of a quiet sun CME Authors: Robbrecht, E.; Patsourakos, S.; Vourlidas, A. Bibcode: 2008AGUFMSH13B1560R Altcode: Streamer-blowouts form a particular class of CMEs characterized by a slow rise and swelling of the streamer that can last for days. While they are more massive than the average CME, their slow development complicates their association with features/activity in the low corona and hampers studies on their initiation mechanism(s). This paper reports on the first observation from 2 viewpoints of a streamer blowout CME. The event was observed by the SECCHI/COR2 A instrument as a typical flux-rope type CME, while a very faint partial halo was observed in COR2-B. The CME erupted from the east limb in the COR2 A field of view. EUVI-171 A images show a bright feature above the limb, traveling from the southern hemisphere towards the equator after which it slowly rises into the coronagraphic fields of view developing into the flux-rope structure CME. At the time of eruption the separation between the two STEREO spacecraft is sufficiently large (54 deg) to observe the source region face-on in STEREO-B. However, inspection of EUVI B data didn't reveal any particular source region, other than the quiet sun. No flaring activity could be related to the eruption. This observation shows unambiguously that a CME eruption does not necessarily have clear on-disk signature. Also it sheds light on the long-standing question of the necessity of having a flare for producing a CME. This result supplies strong constraints for CME initiation models. This type of observation could not have been achieved without the multi-viewpoint observations by STEREO. Title: Propagation and Decoupling of ICMEs and interplanetary shocks Authors: Gonzalez-Esparza, A.; Aguilar-Rodriguez, E.; Ontiveros-Hernandez, V.; Corona-Romero, P.; Vourlidas, A. Bibcode: 2008AGUFMSH13B1558G Altcode: The tracking of a solar storm from the Sun to 1~AU is one of the crucial issues for space weather forecasting. We use white light, remote radio and in-situ measurements to study the propagation of ICME/shock events. We compare these observations with two simple 1-D HD models: analytical and numerical, which focus on the transferring of momentum from the CME to the shock. The aim of the study is to understand how a fast CME/shock decelerates in the interplanetary medium. Title: Evidence for the Magnetic Trapping of Solar-Flare Ions from 1-8-MeV Solar Neutrons Detected with the MESSENGER Neutron Spectrometer Authors: Feldman, W. C.; Lawrence, D. J.; Goldsten, J. O.; Gold, R. E.; Baker, D. N.; Haggerty, D. K.; Krucker, S.; Lin, R. P.; Murphy, R. J.; Nittler, L. R.; Slavin, J. A.; Solomon, S. C.; Starr, R. D.; Vilas, F.; Vourlidas, A. Bibcode: 2008AGUFM.U12A..02F Altcode: Neutrons produced on the Sun during the M2 flare on 31 December 2007 were observed throughout an approximately 10-hour period at 0.48 AU by the MESSENGER Neutron Spectrometer. This flare contained multiple acceleration episodes as seen in Type III radio bursts and fine structure in the energetic-particle environment at MESSENGER. After these bursts ended, both the energetic-particle and neutron fluxes decayed smoothly to background with an e-folding decay time of 2.84 hours. The fact that this time is considerably longer than the mean life of a neutron (886 s) indicates that neutrons at the Sun must have been continuously produced. A likely explanation is that a considerable fraction of the energetic ions accelerated during the flare remained trapped on closed magnetic arcades high in the corona and were slowly pitch-angle scattered by coronal turbulence into their chromospheric loss cones. Subsequent interactions with chromospheric ions generated neutrons that scatter to form a population of upward-going albedo neutrons. Title: Observations and analysis of the April 9, 2008 CME using STEREO, Hinode TRACE and SoHO data Authors: Reeves, K. K.; Patsourakos, S.; Stenborg, G.; Miralles, M.; Deluca, E.; Forbes, T.; Golub, L.; Kasper, J.; Landi, E.; McKenzie, D.; Narukage, N.; Raymond, J.; Savage, S.; Su, Y.; van Ballegooijen, A.; Vourlidas, A.; Webb, D. Bibcode: 2008AGUFMSH12A..04R Altcode: On April 9, 2008 a CME originating from an active region behind the limb was well-observed by STEREO, Hinode, TRACE and SoHO. Several interesting features connected to this eruption were observed. (1) The interaction of the CME with open field lines from a nearby coronal hole appeared to cause an abrupt change in the direction of the CME ejecta. (2) The prominence material was heated, as evidenced by a change from absorption to emission in the EUV wavelengths. (3) Because the active region was behind the limb, the X-Ray Telescope on Hinode was able to take long enough exposure times to observe a faint current- sheet like structure, and it was able to monitor the dynamics of the plasma surrounding this structure. This event is also being studied in the context of activity that occurred during the Whole Heliosphere Interval (WHI). Title: Mass Measurements of Coronal Mass Ejections Using the SECCHI-COR2 Coronagraphs Authors: Colaninno, R. C.; Vourlidas, A.; Thernisien, A. Bibcode: 2008AGUFMSH13B1549C Altcode: The twin Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) COR2 coronagraphs of the Solar Terrestrial Relations Observatory (STEREO) provide images of the solar corona from two view points in the solar system. Since their launch in late 2006, the STEREO Ahead (A) and Behind (B) spacecraft have been slowing separating from Earth at a rate of 22.5 degrees per year. By the end of 2007, the two spacecraft were separated by more than 40 degrees from each other. At this time, we began to see large- scale differences in the morphology and total intensity between coronal mass ejections (CMEs) observed with SECCHI-COR2 on STEREO-A and B. Because the CME emission is due to Thomson scattering, the intensity of an observed CME is dependent on the angle it makes with the observed plane-of-the-sky. From the intensity images, we can calculate the integrated line of sight electron density and mass. We demonstrate that is is possible to simultaneously derive the direction and true total mass of the CME if we make the simple assumption that the same mass should be observed in COR2-A and B. Title: Calibration Results for the COR2 Instrument Aboard the STEREO Satellite Authors: Baldwin, K.; Vourlidas, A. Bibcode: 2008AGUFMSH13B1532B Altcode: We report on the calibration status of the COR2 internally occulting coronagraphs aboard the Solar Terrestrial Relations Observatory (STEREO) satellites. The COR2 instruments are part of the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument package aboard STEREO. The field of view of the COR2 instruments extends from 2.5 to 15 solar radii and its linear spectral filter transmits from 650nm to 750nm. All pre-flight optical calibration efforts were preformed at the Naval Research Laboratory's Solar Coronagraph Optical Test Chamber (SCOTCH), including: a vignetting function, calculation of stray light effects and image quality. To verify the instrument performance in flight we have developed a star fitting routine to extract the intensity of various stars as they transverse the telescope's field of view. Using the pre- flight and in-flight results in combination with star positions and star counts, we derived calibration factors for the external/internal geometric and photometric calibration. Specifically, calibration efforts include pointing corrections, distortion and vignetting. Calibrations will be implemented to improve the accuracy of scientific calculations performed using the COR2 data set. Title: Three-dimensional MHD Simulation of the 2003 October 28 Coronal Mass Ejection: Comparison with LASCO Coronagraph Observations Authors: Manchester, Ward B., IV; Vourlidas, Angelos; Tóth, Gábor; Lugaz, Noé; Roussev, Ilia I.; Sokolov, Igor V.; Gombosi, Tamas I.; De Zeeuw, Darren L.; Opher, Merav Bibcode: 2008ApJ...684.1448M Altcode: 2008arXiv0805.3707M We numerically model the coronal mass ejection (CME) event of 2003 October 28 that erupted from AR 10486 and propagated to Earth in less than 20 hr, causing severe geomagnetic storms. The magnetohydrodynamic (MHD) model is formulated by first arriving at a steady state corona and solar wind employing synoptic magnetograms. We initiate two CMEs from the same active region, one approximately a day earlier that preconditions the solar wind for the much faster CME on the 28th. This second CME travels through the corona at a rate of over 2500 km s-1, driving a strong forward shock. We clearly identify this shock in an image produced by the Large Angle Spectrometric Coronagraph (LASCO) C3 and reproduce the shock and its appearance in synthetic white-light images from the simulation. We find excellent agreement with both the general morphology and the quantitative brightness of the model CME with LASCO observations. These results demonstrate that the CME shape is largely determined by its interaction with the ambient solar wind and may not be sensitive to the initiation process. We then show how the CME would appear as observed by wide-angle coronagraphs on board the Solar Terrestrial Relations Observatory (STEREO) spacecraft. We find complex time evolution of the white-light images as a result of the way in which the density structures pass through the Thomson sphere. The simulation is performed with the Space Weather Modeling Framework (SWMF). Title: The Brightness of Density Structures at Large Solar Elongation Angles: What Is Being Observed by STEREO SECCHI? Authors: Lugaz, N.; Vourlidas, A.; Roussev, I. I.; Jacobs, C.; Manchester, W. B., IV; Cohen, O. Bibcode: 2008ApJ...684L.111L Altcode: 2008arXiv0808.0198L We discuss features of coronal mass ejections (CMEs) that are specific to heliospheric observations at large elongation angles. Our analysis is focused on a series of two eruptions that occurred on 2007 January 24-25, which were tracked by the Heliospheric Imagers (HIs) on board STEREO. Using a three-dimensional (3D) magnetohydrodynamic simulation of these ejections with the Space Weather Modeling Framework (SWMF), we illustrate how the combination of the 3D nature of CMEs, solar rotation, and geometry associated with the Thomson sphere results in complex effects in the brightness observed by the HIs. Our results demonstrate that these effects make any in-depth analysis of CME observations without 3D simulations challenging. In particular, the association of bright features seen by the HIs with fronts of CME-driven shocks is far from trivial. In this Letter, we argue that, on 2007 January 26, the HIs observed not only two CMEs, but also a dense corotating stream compressed by the CME-driven shocks. Title: Dynamic Fibrils in Ly-alpha Authors: Koza, J.; Rutten, R. J.; Vourlidas, A.; Suetterlin, P. Bibcode: 2008ESPM...12.2.16K Altcode: We have detected dynamic fibrils (DFs) in Ly-alpha filtergrams taken with the rocket-borne Very high Angular resolution ULtraviolet Telescope (VAULT). Although the data consist of only a 1-min sequence of 4 images taken near the solar limb during the second VAULT flight, they enable us to identify and study the time evolution of over 50 DFs. Most show parabolic trajectories in their angular extent, with supersonic maximum velocities. The measured decelerations vary from sub-ballistic to super-ballistic. The similarities with DFs seen in Halpha suggest a common cause, possibly the presence of hot transition-region interfaces around cool oscillation-fed jets. Title: STEREO and RHESSI Observations of Electron Acceleration in a Partially Disk-Occulted Solar Flare Authors: Krucker, S.; Wuelser, J. -P.; Vourlidas, A.; Davila, J.; Thompson, W. T.; White, S.; Lin, R. P. Bibcode: 2008ESPM...12.2.84K Altcode: RHESSI hard X-ray observations of partially-disk occulted solar flares provide crucial information on faint coronal hard X-ray sources in the absence of generally much brighter emissions from footpoints of flare loops. Coronal hard X-ray sources can differ fundamentally from the classical footpoint sources of the flare impulsive phase and provide unique information about the supra-thermal electrons closest to the site in the corona where their acceleration is believed to occur. The different view-angles provided by the STEREO spacecraft allow us to put the partially occulted hard X-ray sources observed by RHESSI in context with the EUV flare ribbons and the EUV emission from CME observed by STEREO/EUVI.

In this presentation we report on the GOES C8 flare observed on December 31, 2007 peaking around 01:11UT. From Earth-view (RHESSI), the flare occurs about 12 degrees behind the eastern limb giving an occultation height of 16 Mm. From STEREO B, the flare ribbons are seen on the disk (about 10 degrees from the limb), while the flare is highly occulted (130 Mm) for STEREO A observations so that emissions related to the associated CME are seen. Despite the occultation, RHESSI observes strong non-thermal emissions up to 100 keV that entirely originate from the corona. Initially, the coronal hard X-ray emission is seen from above the EUV flare ribbons similar to what is reported in the Masuda flare. Later on, emissions from a radially extended (approximately 20 Mm) source is seen. The radial extension is in the same direction as the current sheet of the outward moving CME suggesting that the HXR emission might be a direct signature of electrons accelerated in the reconnection process. Title: Solar-terrestrial Simulations in the STEREO Era Authors: Lugaz, N.; Roussev, I.; Vourlidas, A. Bibcode: 2008ESPM...12..5.2L Altcode: Due to the scarcity of heliospheric observations, over the past decade global 3-D numerical simulations have become increasingly important in studying the propagation of coronal mass ejections (CMEs) from the Sun to the Earth. Since the launch of STEREO in November 2006, continuous white-light observations of solar transients on their way to the Earth in near-real time have become possible.

In this talk, we will discuss the significance of 3-D simulations in the interpretation of observations taken by the Heliospheric Imagers. We will focus on a series of two ejections in January, 24-25, 2007, which have been simulated with the Space Weather Modeling Framework (SWMF). We will present detailed comparisons between real and simulated time-elongation plots and discuss the appearance of CME-CME interaction in real and synthetic observations. Title: Physical parameters along the boundaries of a mid-latitude streamer and in its adjacent regions Authors: Susino, R.; Ventura, R.; Spadaro, D.; Vourlidas, A.; Landi, E. Bibcode: 2008A&A...488..303S Altcode: Context: Coronal streamers appear to be strictly associated with the generation of the slow solar wind, even if a firm identification of the sources of the particle flux within these structures is still an unresolved issue.
Aims: The purpose of this work is to contribute to a better knowledge of the physical characteristics of streamers and of their surroundings in a wide range of heliocentric distances and at both high radial and latitudinal resolutions.
Methods: The analysis is based on spectral observations of a narrow, mid-latitude streamer performed with UVCS/SOHO during one week in May 2004: H i Lyα and O vi resonance doublet line intensities and profiles were obtained at different heliocentric distances and latitudes. In addition, white-light polarized brightness images were taken in the same days of observation, through the LASCO/SOHO C2 coronagraph.
Results: The radial variations in electron density and temperature, H i and O vi kinetic temperatures, and outflow velocities were derived from the observed line intensities, profiles, and O vi line intensity ratios between 1.6 and 5.0 R_⊙, in two regions, 2-3 arcmin wide, located along the boundaries and in a narrow strip (5-10 arcmin) outside the streamer structure. Significantly high kinetic temperatures and outflow velocities were found in the out-of-streamer region above 3.0 R_⊙ for the O vi ions and, for the first time, H i atoms, compared to those obtained along the streamer boundaries. Moreover, the O vi kinetic temperatures and velocities turn out much higher than the H i ones at any heliocentric distance in all the observed regions. A higher anisotropy is also noticed for the O vi kinetic temperature in the region flanking the streamer.
Conclusions: The slow coronal wind is found to flow with significantly different speeds and kinetic temperatures along the boundaries of the streamer and in the out-of-streamer regions at all heights, above 3.0-3.5 R_⊙. This fact, consistent with previous studies, indicates that two components of slow wind probably form in the observed regions: one originates just above the streamer cusp and flows with velocities a little higher than 100 km s-1, while the other flows along the open magnetic field lines flanking the streamer with velocities slightly lower than the slow wind asymptotic heliospheric value of ~400 km s-1, around 5.0 R_⊙. Title: How Efficient are Coronal Mass Ejections at Accelerating Solar Energetic Particles? Authors: Mewaldt, R. A.; Cohen, C. M. S.; Giacalone, J.; Mason, G. M.; Chollet, E. E.; Desai, M. I.; Haggerty, D. K.; Looper, M. D.; Selesnick, R. S.; Vourlidas, A. Bibcode: 2008AIPC.1039..111M Altcode: The largest solar energetic particle (SEP) events are thought to be due to particle acceleration at a shock driven by a fast coronal mass ejection (CME). We investigate the efficiency of this process by comparing the total energy content of energetic particles with the kinetic energy of the associated CMEs. The energy content of 23 large SEP events from 1998 through 2003 is estimated based on data from ACE, GOES, and SAMPEX, and interpreted using the results of particle transport simulations and inferred longitude distributions. CME data for these events are obtained from SOHO. When compared to the estimated kinetic energy of the associated coronal mass ejections (CMEs), it is found that large SEP events can extract ~10% or more of the CME kinetic energy. The largest SEP events appear to require massive, very energetic CMEs. Title: The Solar Magnetic Field and Coronal Dynamics of the Eruption on 2007 May 19 Authors: Li, Y.; Lynch, B. J.; Stenborg, G.; Luhmann, J. G.; Huttunen, K. E. J.; Welsch, B. T.; Liewer, P. C.; Vourlidas, A. Bibcode: 2008ApJ...681L..37L Altcode: The solar eruption on 2007 May 19, from AR 10956 near solar disk center, consisted of a B9.5 flare (12:48 UT), a filament eruption, an EUV dimming, a coronal wave, and a multifront CME. The eruption was observed by the twin STEREO spacecraft at a separation angle of 8.5°. We report analysis of the source region photospheric magnetic field and its preeruption evolution using MDI magnetograms, the coronal magnetic field topology estimated via PFSS modeling, and the coronal dynamics of the eruption through STEREO EUVI wavelet-enhanced anaglyph movies. Despite its moderate magnitude and size, AR 10956 was a complex and highly nonpotential active region with a multipolar configuration, and hosted frequent flares, multiple filament eruptions, and CMEs. In the 2 days prior to the May 19 eruption, the total unsigned magnetic flux of the region decreased by ~17%. We interpret the photospheric magnetic field evolution, the coronal field topology, and the observed coronal dynamics in the context of current models of CME initiation and discuss the prospects for future MHD modeling inspired by these analyses. Title: STEREO SECCHI Stereoscopic Observations Constraining the Initiation of Polar Coronal Jets Authors: Patsourakos, S.; Pariat, E.; Vourlidas, A.; Antiochos, S. K.; Wuelser, J. P. Bibcode: 2008ApJ...680L..73P Altcode: 2008arXiv0804.4862P We report on the first stereoscopic observations of polar coronal jets made by the EUVI/SECCHI imagers on board the twin STEREO spacecraft. The significantly separated viewpoints (~11°) allowed us to infer the 3D dynamics and morphology of a well-defined EUV coronal jet for the first time. Triangulations of the jet's location in simultaneous image pairs led to the true 3D position and thereby its kinematics. Initially the jet ascends slowly at ≈10-20 km s-1 and then, after an apparent "jump" takes place, it accelerates impulsively to velocities exceeding 300 km s-1 with accelerations exceeding the solar gravity. Helical structure is the most important geometrical feature of the jet which shows evidence of untwisting. The jet structure appears strikingly different from each of the two STEREO viewpoints: face-on in one viewpoint and edge-on in the other. This provides conclusive evidence that the observed helical structure is real and does not result from possible projection effects of single-viewpoint observations. The clear demonstration of twisted structure in polar jets compares favorably with synthetic images from a recent MHD simulation of jets invoking magnetic untwisting as their driving mechanism. Therefore, the latter can be considered as a viable mechanism for the initiation of polar jets. Title: The Encounter of Comet Encke with a Coronal Mass Ejection: A Unique Cosmic Collision Authors: Vourlidas, A. Bibcode: 2008Ippa....2d..14V Altcode: No abstract at ADS Title: STEREO small ICME activity and the connection to the large-scale coronal structure during the solar activity minimum Authors: Huttunen, K. E.; Luhmann, J. G.; Gosling, J. T.; Li, Y.; Larson, D.; Schroeder, P.; Elliot, H.; Petrie, G.; Vourlidas, A.; Galvin, A. B.; Russell, C. T. Bibcode: 2008AGUSMSH21A..06H Altcode: We have investigated ICME activity during the solar activity minimum from March 2007 to December 2007 using observations from the STEREO and Wind spacecraft. During this period the angular separation of the twin STEREO satellites increased from about 1 to 44 degrees while Wind was located at the L1 point. At solar minimum the interplanetary medium is dominated by recurrent high-speed streams, but slow solar wind frequently includes ICME events. These slow ICMEs tend to have shorter durations and weaker magnetic fields than typical ICMEs at 1 AU. We will discuss the properties of these small ICMEs and their scale-sizes. In addition we will relate the ICMEs to the large-scale coronal structure using the GONG magnetogram synoptic maps. We also discuss the possible connection of these events to the transient outflows from coronal streamers identified originally by SOHO/LASCO and currently observed by the STEREO/SECCHI imagers. Title: Understanding the Initiation of Polar Coronal Jets with STEREO/SECCHI Stereoscopic Observations Authors: Vourlidas, A.; Patsourakos, S.; Pariat, E.; Antiochos, S. Bibcode: 2008AGUSMSH23A..02V Altcode: Polar coronal jets are collimated transient ejections of plasma occurring in polar coronal holes. The kinematics and mostly the 3D morphology of jets place strong constraints on the physical mechanism(s) responsible for their initiation, and were not accessible before the STEREO mission. We report on the first stereoscopic observations of polar coronal jets made by the EUVI/SECCHI imagers on-board the twin STEREO spacecraft at spacecraft separations of ~ 11° and ~ 45°. Triangulations of the jet locations in simultaneous image pairs led to the true 3D position and thereby their kinematics. The most important geometrical feature of the observed jets is helical structures showing evidence of untwisting. The jet structure appear strikingly different from each of the two STEREO viewpoints: face-on in the one viewpoint and edge-on in the other. This provides solid evidence that the observed helical structure is real and not resulting from possible projection effects of single viewpoint observations. The clear demonstration of twisted structure in polar jets compares favorably with synthetic images from a recent MHD simulation of jets invoking magnetic untwisting as their driving mechanism. Title: Initiation and Evolution of CMEs from Helmet Streamers Authors: Liu, Y.; Luhmann, J.; Odstrcil, D.; Li, Y.; Vourlidas, A.; Lin, R.; Bale, S. Bibcode: 2008AGUSMSH31A..04L Altcode: A traditional picture for CME eruptions is that the closed magnetic fields underneath a helmet streamer are destabilized to produce a CME. At the tip of the streamer belt is the heliospheric plasma sheet (HPS) which is characterized by slow, dense and cold solar wind. An important point, missed by early CME observations, is that CMEs disrupting the streamer belt and moving through the HPS would be distorted into a concave-outward shape by the interaction with the HPS. For the first time, the interaction between CMEs and the preexisting HPS is clearly imaged by SECCHI and LASCO from the Sun out to several tens of solar radii. The 31 December 2007 CME first appears as a bulge swelling from the base of a streamer and pushing EUV plumes aside, consistent with the traditional scenario for CME initiation; the CME then quickly becomes concave-outward owing to the interaction with the preexisting HPS. The streamer reforms after the CME but seems a little displaced. A similar picture is observed for the 5 September 2005 CME. The CME source regions are underneath the streamer belt as revealed by the PFSS modeled coronal fields; an MHD model using the observed photospheric magnetic fields as input gives a bi-modal ambient solar wind, consistent with the observed concave-outward shape. We also discuss deflection flows ahead of the CMEs and how CMEs regulate the global field configuration of the Sun based on the observations. These results are important for understanding the complete picture of CME initiation and propagation. Title: Stereoscopic Analysis of STEREO/EUVI Observations of May 19, 2007 Erupting Filament Authors: Liewer, P. C.; Dejong, E. M.; Hall, J. R.; Huttunen, K. J.; Howard, R. A.; Vourlidas, A.; Thompson, W. T. Bibcode: 2008AGUSMSH23A..04L Altcode: A filament eruption, associated with a B9.5 flare, was observed by the Solar TERrestrial Relations Observatory (STEREO) on May 19, 2007, beginning at about 13 UT in AR10956. Analysis of remote and in situ observations indicate that this event is the most probable source of an interplanetary magnetic cloud observed by the Wind and STEREO B spacecraft on 2007 May 21-22. Here, we use observations from the SECCHI/EUVI telescopes to analyze the behavior of the filament before and during the eruption and to study its relation to other solar signatures of the CME event. At this time, STEREO A and B were sufficiently separated to determine the three- dimensional structure of the filament using stereoscopy. The filament could be followed in SECCHI/EUVI 304 Angstrom stereoscopic data from about 12 hours before to about 2 hours after the eruption. Although the filament has episodes of activity during this period, no dramatic pre-eruption warning signal is seen. Other results from stereoscopic analysis of STEREO/ EUVI data will also be presented. Copyright 2008 California Institute of Technology. Government sponsorship acknowledged. Title: Physical Properties of a Coronal Streamer at 2.5 Solar Radii Authors: Uzzo, M.; Strachan, L.; Kohl, J.; Vourlidas, A. Bibcode: 2008AGUSMSH51B..03U Altcode: In this presentation the plasma properties of a streamer observed in April of 2007 at 2.5 solar radii are examined. The data comes from observations conducted by the Ultraviolet Coronagraph Spectrometer (UVCS) and the Large Angle Spectroscopic Coronagraph (LASCO) C2 instrument aboard the Solar and Heliospheric Observatory (SOHO). From the UV spectral profiles the proton and oxygen kinetic temperatures can be derived as a function of latitude across the streamer. The observed line intensities are used to calculate the photospheric normalized absolute elemental abundances for O, S, N and Fe. The abundances are analyzed with respect to the FIP effect and compared to in situ measurements at SOHO. An estimate for the electron density is determined from both the UV data and the polarized white light data from LASCO C2. Title: Imaging the Heliosphere at Solar Minimum: SECCHI Observations During the Whole Heliosphere Interval Authors: Plunkett, S. P.; Howard, R. A.; Vourlidas, A.; Stenborg, G. A.; Thompson, W. T. Bibcode: 2008AGUSMSH51A..07P Altcode: We present remotely sensed imaging observations of the inner heliosphere from the SECCHI experiment on the STEREO mission during the Whole Heliosphere Interval in March and April 2008. These observations reveal the large-scale structure and dynamics of the heliosphere near solar minimum, extending from the surface of the Sun to beyond 1 AU, from two vantage points in the ecliptic plane separated by about 50 degrees. Title: On the Origins of Coronal Mass Ejections during Solar Minimum using STEREO Observations Authors: Li, Y.; Luhmann, J. G.; Lynch, B. J.; Huttunen, E.; Toy, V.; Vourlidas, A.; Petrie, G. Bibcode: 2008AGUSMSH43A..08L Altcode: This study addresses the question of the origins of CMEs at the current solar minimum. It is a common consensus that it should be straight forward to track a CME from its source to 1AU during solar quiet times when the solar wind and IMF structure is less complex and fewer CMEs and other coronal activity occur. In reality, total of 1249 CMEs from January to October 2007 are reported on the LASCO CME catalog. Only ~23% (292) CMEs are wider than 30deg and ~2% (28) CMEs wider than 90deg from L1 view point. Most CMEs in the catalog are narrow or jet-like and are classified as poor events. Majority of the CMEs are slow with only one event over 1000km/s. But it has not been an easy task to relate a CME to its source during this period. Using an appropriate set of events and images from three viewing angles from STEREO A/B and SOHO at L1, we determine the sources of the CMEs and their locations on the Sun and in the large scale coronal field. Among other issues, we discuss the implications of our results to CME generation/origin, specifically, whether CMEs always originate from photospheric magnetic neutral lines? Whether some CMEs originate higher in the corona with no signature on the solar disk? Title: The Sun as the Source of Heliospheric "Space Weather": A CISM Integrated Model Perspective and STEREO Inspiration Authors: Luhmann, J. G.; Li, Y.; Lynch, B.; Lee, C. O.; Huttunen, E.; Liu, Y.; Toy, V.; Odstrcil, D.; Riley, P.; Linker, J.; Mikic, Z.; Arge, C.; Petrie, G.; Zhao, X.; Liu, Y.; Hoeksema, T.; Owens, M.; Galvin, A.; Simunac, K.; Howard, R.; Vourlidas, A.; Jian, L. K.; Russell, C. T. Bibcode: 2008AGUSMSH31C..01L Altcode: Models developed under the Center for Integrated Space weather Modeling (CISM) represent one effort that is underway to realistically simulate the Sun's physical controls over interplanetary conditions, or heliospheric "space weather", in three dimensions. This capability is critical for interpreting the latest observations from STEREO, whose goal is to enable connections to be made between what is observed in the heliosphere via distributed in-situ measurements and what is observed in the corona and heliosphere via imaging from separated 1 AU perspectives. The ways in which the CISM models are enabling the exploitation of STEREO and other observations toward increased understanding of the solar wind and coronal activity and its consequences are described. In particular, the models allow the identification of the sources of structures in the solar wind, and analyses of how the coronal context of the observed CMEs plays a key role in determining the ultimate terrestrial (and other planetary) response . Title: Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) Authors: Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.; Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Cook, J. W.; Hurley, A.; Davila, J. M.; Thompson, W. T.; St Cyr, O. C.; Mentzell, E.; Mehalick, K.; Lemen, J. R.; Wuelser, J. P.; Duncan, D. W.; Tarbell, T. D.; Wolfson, C. J.; Moore, A.; Harrison, R. A.; Waltham, N. R.; Lang, J.; Davis, C. J.; Eyles, C. J.; Mapson-Menard, H.; Simnett, G. M.; Halain, J. P.; Defise, J. M.; Mazy, E.; Rochus, P.; Mercier, R.; Ravet, M. F.; Delmotte, F.; Auchere, F.; Delaboudiniere, J. P.; Bothmer, V.; Deutsch, W.; Wang, D.; Rich, N.; Cooper, S.; Stephens, V.; Maahs, G.; Baugh, R.; McMullin, D.; Carter, T. Bibcode: 2008SSRv..136...67H Altcode: 2008SSRv..tmp...64H The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) is a five telescope package, which has been developed for the Solar Terrestrial Relation Observatory (STEREO) mission by the Naval Research Laboratory (USA), the Lockheed Solar and Astrophysics Laboratory (USA), the Goddard Space Flight Center (USA), the University of Birmingham (UK), the Rutherford Appleton Laboratory (UK), the Max Planck Institute for Solar System Research (Germany), the Centre Spatiale de Leige (Belgium), the Institut d’Optique (France) and the Institut d’Astrophysique Spatiale (France). SECCHI comprises five telescopes, which together image the solar corona from the solar disk to beyond 1 AU. These telescopes are: an extreme ultraviolet imager (EUVI: 1 1.7 R⊙), two traditional Lyot coronagraphs (COR1: 1.5 4 R⊙ and COR2: 2.5 15 R⊙) and two new designs of heliospheric imagers (HI-1: 15 84 R⊙ and HI-2: 66 318 R⊙). All the instruments use 2048×2048 pixel CCD arrays in a backside-in mode. The EUVI backside surface has been specially processed for EUV sensitivity, while the others have an anti-reflection coating applied. A multi-tasking operating system, running on a PowerPC CPU, receives commands from the spacecraft, controls the instrument operations, acquires the images and compresses them for downlink through the main science channel (at compression factors typically up to 20×) and also through a low bandwidth channel to be used for space weather forecasting (at compression factors up to 200×). An image compression factor of about 10× enable the collection of images at the rate of about one every 2 3 minutes. Identical instruments, except for different sizes of occulters, are included on the STEREO-A and STEREO-B spacecraft. Title: Heliospheric Images of the Solar Wind at Earth Authors: Sheeley, N. R., Jr.; Herbst, A. D.; Palatchi, C. A.; Wang, Y. -M.; Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.; Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Burlaga, L. F.; Davila, J. M.; Thompson, W. T.; St. Cyr, O. C.; Harrison, R. A.; Davis, C. J.; Eyles, C. J.; Halain, J. P.; Wang, D.; Rich, N. B.; Battams, K.; Esfandiari, E.; Stenborg, G. Bibcode: 2008ApJ...675..853S Altcode: During relatively quiet solar conditions throughout the spring and summer of 2007, the SECCHI HI2 white-light telescope on the STEREO B solar-orbiting spacecraft observed a succession of wave fronts sweeping past Earth. We have compared these heliospheric images with in situ plasma and magnetic field measurements obtained by near-Earth spacecraft, and we have found a near perfect association between the occurrence of these waves and the arrival of density enhancements at the leading edges of high-speed solar wind streams. Virtually all of the strong corotating interaction regions are accompanied by large-scale waves, and the low-density regions between them lack such waves. Because the Sun was dominated by long-lived coronal holes and recurrent solar wind streams during this interval, there is little doubt that we have been observing the compression regions that are formed at low latitude as solar rotation causes the high-speed wind from coronal holes to run into lower speed wind ahead of it. Title: SECCHI Observations of the Sun's Garden-Hose Density Spiral Authors: Sheeley, N. R., Jr.; Herbst, A. D.; Palatchi, C. A.; Wang, Y. -M.; Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.; Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Burlaga, L. F.; Davila, J. M.; Thompson, W. T.; St. Cyr, O. C.; Harrison, R. A.; Davis, C. J.; Eyles, C. J.; Halain, J. P.; Wang, D.; Rich, N. B.; Battams, K.; Esfandiari, E.; Stenborg, G. Bibcode: 2008ApJ...674L.109S Altcode: The SECCHI HI2 white-light imagers on the STEREO A and B spacecraft show systematically different proper motions of material moving outward from the Sun in front of high-speed solar wind streams from coronal holes. As a group of ejections enters the eastern (A) field of view, the elements at the rear of the group appear to overrun the elements at the front. (This is a projection effect and does not mean that the different elements actually merge.) The opposite is true in the western (B) field; the elements at the front of the group appear to run away from the elements at the rear. Elongation/time maps show this effect as a characteristic grouping of the tracks of motion into convergent patterns in the east and divergent patterns in the west, consistent with ejections from a single longitude on the rotating Sun. Evidently, we are observing segments of the "garden-hose" spiral made visible when fast wind from a low-latitude coronal hole compresses blobs of streamer material being shed at the leading edge of the hole. Title: A Fresh View of the Extreme-Ultraviolet Corona from the Application of a New Image-Processing Technique Authors: Stenborg, Guillermo; Vourlidas, Angelos; Howard, Russell A. Bibcode: 2008ApJ...674.1201S Altcode: The Extreme-ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) has provided (and continues to provide) the solar physics community with an unprecedented view of the extreme-ultraviolet (EUV) transition region and corona. In particular, it has observed EUV bright points, coronal holes, loops, and arcades, as well as dynamical events such as flares, EIT waves, and mass ejections. However, the multiscale nature of the observed solar features has not been fully exploited so far. In this paper, we introduce a technique to enhance the EUV features based on their multiscale nature, show a few examples of features not revealed with standard image-processing techniques (and therefore not previously noticed in the EIT data set), and make the solar physics community aware of the availability of the full EIT data set as processed with this novel technique. Title: Simulating the interaction of the 2007 April 19 CME with Comet Encke Authors: Manchester, Ward, IV; Gombosi, Tamas; Frazin, Richard; Vourlidas, Angelos; Toth, Gabor; Cohen, Ofer; Hansen, Kenneth; Sokolov, Igor; van der Holst, Bart Bibcode: 2008cosp...37.1896M Altcode: 2008cosp.meet.1896M We model the propagation of a coronal mass ejection (CME) that was observed with LASCO on April 19, 2007. The resulting ICME was observed with SECCHI (STEREO A) to impact comet Encke on April 20. We compare the results of our three-dimensional global MHD simulation of this event with both sets of coronagraph observations. In particular, we make synthetic Thomson-scattered white light images from the simulation to quantitatively compare to the coronagraph images made with LASCO and SECCHI. We then propagate the CME into interplanetary space where it interacts with comet Encke. We simulate the complex response of the cometary plasma to the CME impact. Title: Large solar energetic particle events of solar cycle 23 Authors: Mewaldt, R. A.; Chollet, Eileen; Cohen, Christina; Looper, Mark; Mason, Glenn; Vourlidas, Angelos; Giacalone, Joe; Haggerty, Dennis; Desai, Mihir; Selesnick, Richard Bibcode: 2008cosp...37.2020M Altcode: 2008cosp.meet.2020M We present the results of a survey of the largest solar energetic particle (SEP) events of Solar Cycle 23, based on data from ACE, GOES, SAMPEX, SOHO, and STEREO. The fluence spectra of the 25 largest proton events (as measured by >30 MeV protons) have been fit with common spectral shapes, and their spectral slopes and breaks determined. The spectral characteristics are compared with other signatures including Fe/O, He/H and total energy content, as well as selected solar and interplanetary parameters. Estimates of the total energy content of accelerated particles are made using the results of new particle transport simulations. When compared to the estimated kinetic energy of the associated CMEs it is found that SEPs frequently extract ∼10 per cent of the CME kinetic energy. Finally, we compare SEP fluences from solar cycle 23 to those measured during the past 50 years. Title: Stereoscopic Analysis of STEREO/EUVI Observations of May 19, 2007 Erupting Filament Authors: Liewer, Paulett; Luhmann, Janet G.; Huttunen, Emilia; Li, Yan; Howard, R. A.; Thompson, W. T.; Dejong, E. M.; Hall, J. R.; Falconer, D. A.; Vourlidas, Angelos Bibcode: 2008cosp...37.1778L Altcode: 2008cosp.meet.1778L A filament eruption, associated with a double coronal mass ejection (CME), was observed by the Solar TERrestrial Relations Observatory (STEREO) on May 19, 2007, beginning at about 13 UT in AR10956. Analysis of remote and in situ observations indicate that this event is the most probable source of an interplanetary magnetic cloud observed by the Wind and STEREO B spacecraft on 2007 May 21-22. Here, we use observations from the SECCHI/EUVI telescopes to analyze the behavior of the filament before and during the eruption and to study its relation to other solar signatures of the CME event. At this time, STEREO A and B were sufficiently separated to determine the three-dimensional structure of the filament using stereoscopy. The filament could be followed in SECCHI/EUVI 304 Angstrom stereoscopic data from about 12 hours before to about 2 hours after the eruption. Although the filament has episodes of activity during this period, no dramatic pre-eruption warning signal is seen. We also present an evaluation of a magnetogram-based CME-prediction measure for AR 10956 for the May 17-20, 2007 period and compare it with observed CME activity. Title: Solar Polar Imager: Observing Solar Activity from a New Perspective Authors: Liewer, P. C.; Ayon, J.; Alexander, D.; Kosovichev, A.; Mewaldt, R. A.; Socker, D. G.; Vourlidas, A. Bibcode: 2008nssv.book....1L Altcode: No abstract at ADS Title: Forward modeling reconstruction techniques applied to STEREO-SECCHI data Authors: Thernisien, A. F.; Howard, R. A.; Vourlidas, A. Bibcode: 2007AGUFMSH32A0778T Altcode: In past works, forward modeling techniques have been successfully used to study the morphology and the electron density of streamers and flux rope coronal mass ejections. Nevertheless, these studies have been done using SOHO-LASCO data. The STEREO mission, launched in October 2007, provide now 2 new points of view in addition to the one provided by SOHO. Besides the Lyot coronagraphs aboard the STEREO-SECCHI instrument package, the Heliospheric Imagers, also part of the SECCHI package, provide now a new and extended view of the corona, from 7 degrees elongation to almost 90 degrees. In this study, we will make use of the 3 points of view provided by these two missions to constrain better the three-dimensional reconstruction of CMEs, from few solar radii, up to Earth orbit. We will present the results concerning the morphology, dynamics and electron density obtained for different recent CME events. Title: How do CME-Shocks Look Like?: Study of Shock Geometry. Authors: Ontiveros, V.; Vourlidas, A. Bibcode: 2007AGUFMSH31A0223O Altcode: We use raytracing software to simulate white light coronagraph images of common 3D shock-like geometries, i.e. spherical and bow-shock type. We obtain the density profiles for different projections, shock thickness, and background and upstream densities. The results are compared to density profiles obtained from analyzing LASCO coronagraph images of CMEs that are good candidates to drive a shock due to their high velocities (V>1500 km/s). This work is funded by the LWS TR&T program. Title: Multipoint Analysis by STEREO and WIND of the Magnetic Cloud on May 21-23, 2007 Authors: Huttunen, K. E.; Luhmann, J. G.; Li, Y.; Lynch, B.; Liu, Y.; Schroeder, P.; Bale, S. D.; Lee, C. O.; Lin, R. P.; Vourlidas, A.; Farrugia, C.; Galvin, A. B.; Acuna, M. H.; Howard, R. A.; Kaiser, M.; Mewaldt, R. A.; Sauvaud, J.; Wiedenbeck, M. Bibcode: 2007AGUFMSH42A..03H Altcode: We will present multi-spacecraft observations by STEREO A and B and WIND of a magnetic cloud in the interplanetary space on May 21-23, 2007. At that time the angular separation between STEREO A and B was nearly 10 degrees. The differences in the observed magnetic field signatures at the locations of the spacecrafts suggest that they crossed the different parts of the magnetic cloud. STEREO B observed a very clear rotation of the magnetic field direction and presumably crossed the cloud close to the center whereas STEREO A likely traversed the leg of the magnetic cloud. Although the magnetic field maximum within this cloud was ~17 nT it did not produce significant geomagnetic response since the Z-component of the magnetic field was orientated northward. We will analyze the structure of the magnetic cloud at each spacecraft in order to deduce its larger-scale structure and orientation. In addition, we will study the solar source region of the magnetic cloud as well as the coronagraph and radio wave observations. Title: The source region magnetic conditions of solar eruption events observed by multi spacecraft Authors: Li, Y.; Lynch, B. J.; Welsch, B. T.; Stenborg, G. A.; Vourlidas, A.; Luhmann, J. G.; Fisher, G. H. Bibcode: 2007AGUFMSH32A0773L Altcode: The magnetic connectivity, topology and properties including magnetic flux changes, magnetic gradient and flow field from LCT of three active regions will be derived from photospheric magnetograms and synoptic maps to understand the initiation condition of eruptions/flares originated from the regions and the potential impact on the heliosphere and magnetosphere. The three active regions are AR10930 in December 2006 and AR10953 and AR10956 in May 2007. AR10930 and AR10956 are responsible for the two Magnetic Clouds observed by IMPACT on STEREO A/B during the first half year of the mission. The associated coronal CME/flare/filament activities will be studied using solar imaging data from SOHO, STEREO, BBSO and HINODE. We will analyze photospheric magnetograms and synoptic maps from MDI and GONG. Vector magnetic field observations from HINODE and SOLIS are currently being sought and if available will be value added information for initiation of the eruptions. PFSS model field line tracing based on the synoptic maps gives the magnetic topology and connectivity in the active region and the global large scale field. The large scale field results including regions with closed arcades and fields open to the interplanetary space give the context and relative location of the source region of the eruptions. Title: Modeling STEREO White-Light Observations of CMEs with 3D MHD Simulations Authors: Manchester, M. B.; Vourlidas, A.; Toth, G.; Lugaz, N.; Sokolov, I.; Gombosi, T.; de Zeeuw, D.; Opher, M. Bibcode: 2007AGUFMSH32A0785M Altcode: We model the Thomson-scattered white-light appearance of a variety of 3D MHD models of CMEs during solar minimum to reproduce large-scale features of SECCHI observations. We create a gallery of expected CME shapes at large elongations as seen by SECCHI. We examine evidence of shock propagation, magnetic clouds, CME pancaking, and complex time evolution as CMEs propagate at large elongation past the Thomson sphere. A key point is to determine how the structure of CMEs and CME-driven shocks are affected by interaction with the ambient solar wind. MHD models are performed with BATSRUS and SWMF, and formulated by first arriving at a steady state corona and solar wind employing synoptic magnetograms. We initiate CMEs from active regions low in the corona with magnetic flux ropes. Title: Using Global MHD Models to Interpret STEREO Observations Authors: Riley, P.; Mikic, Z.; Linker, J. A.; Odstrcil, D.; Luhmann, J. G.; Vourlidas, A. Bibcode: 2007AGUFMSH32A0788R Altcode: The STEREO mission presents a unique opportunity to combine both remote and in situ observations from multiple vantage points, and, in particular, to provide simultaneous limb and disk-centered observations. In spite of this wealth of data, the system remains remarkably under-sampled, and reconstructing 3-D structure from the observations remains a formidable task. In this presentation we use global MHD models, which reproduce the eruption and evolution of specific CME events through the corona and past the orbit of Earth, to explore the relationship between the various remote sensing and in situ observations that would be seen at the two STEREO spacecraft. These simulations were developed as part of our contribution to NASA's Living With a Star TR&T focused science topic on the relationship between ICMEs and their solar sources. Our model, which incorporates coronal heating, thermal conduction, and radiation, is capable of reproducing a wide variety of measurements, ranging from (polarized) brightness and emission images to in situ time series of magnetic and plasma parameters. Moreover, we can construct quantities that are either not directly observable, or can only be inferred locally, such as the Alfven speed, the location of the heliospheric current sheet, and the three-dimensional topology of the magnetic field. We believe that the combination of sophisticated modeling results and the exciting new measurements from the STEREO mission will allow us to address fundamental questions concerning the origin and evolution of CMEs, ultimately allowing us to develop predictive capabilities related to their potential to generate space weather effects. Title: A Catalog of Halo Coronal Mass Ejections from SOHO Authors: Gopalswamy, N.; Yashiro, S.; Michalek, G.; Xie, H.; Vourlidas, A.; Howard, R. A.; Schmidt, J. Bibcode: 2007AGUFMSH51A0262G Altcode: Halo coronal mass ejections (CMEs) have become one of the important subsets of CMEs, thanks to the extensive data accumulated by the Solar and Heliospheric Observatory (SOHO) mission. Halo CMEs are inherently more energetic on the average, so they are important for producing geomagnetic storms and solar energetic particle events (Gopalswamy et al., 2007). One of the key aspects halo CMEs is their source location, which decides whether the halo is symmetric or not. When the source is closer to the solar limb, the CMEs tend to become asymmetric halos or partial halos. Halos with their sources nearer to the limb are also the fastest (because of projection effects), but are less geoeffective due to the glancing blow they deliver to Earth's magnetosphere. Thus, providing source information to all halo CMEs in a separate catalog is useful information in selecting candidate geoeffective CMEs. The second important quantity of CMEs is the space speed, which decides the arrival time of CMEs at Earth. Since CMEs change their width during their early evolution, it is not easy to correct for the projection effects from the geometry of eruption. One way of correcting for projection effects is to use a cone model for CMEs. There are at least 3 published cone models, all of them seem to remove the projection effects reasonably well. The geometric parameters of the cone are determined using different methods in each model. Here we use the model by Xie et al. (2004), which has generally less restrictions, and hence can be applied to more number of halos. This paper provides a brief description of the catalog of halo CMEs, which resides at the CDAW Data Center, NASA Goddard Space Flight Center, Greenbelt, MD. The catalog enhances the existing data services at the CDAW Data Center, which participates in the Virtual Solar Observatory. Work supported by NASA's Virtual Observatories for Solar and Space Physics Data Program. References Gopalswamy et al., JGR, 112, A06112, doi:10.1029/2006JA012149, 2007 Xie et al. JGR, 109, A03109, doi: 10.1029/2003JA010226, 2004 Title: Towards a Better Understanding of CME Onsets with SECCHI on STEREO Authors: Patsourakos, S.; Vourlidas, A. Bibcode: 2007AGUFMSH32A0779P Altcode: Observations of the first minutes in the life of Coronal Mass Ejections (CMEs) represent the main key into identifying the physical mechanism(s) behind them. Previous observations of CME onsets were limited by factors such as low cadence, small field of view, single-temperature coverage, and lack of 3D information. These limitations are significantly mitigated by the availability of SECCHI observations onboard the STEREO mission. We analyze a series of high-cadence, multi-temperature observations of CME onsets taken with the EUVI/SECCHI imagers tied with high-cadence coronagraphic COR1/SECCHI observations. We discuss how our perception of well-known features pertinent to CME onsets such as dimmings, EIT waves and cavities is shaped by the unique characteristics of SECCHI observations, and of the 3D information available in STEREO obervations in particular. We finally discuss how the generic elements of our observations compare with the expectations of CME models in an attempt to place some constraints on them. Title: The Physical Properties of Coronal Streamers. II. Authors: Uzzo, M.; Strachan, L.; Vourlidas, A. Bibcode: 2007ApJ...671..912U Altcode: In this paper the plasma properties of three streamers observed in 2003 by the Ultraviolet Coronagraph Spectrometer (UVCS) are presented for five heights from 1.75 to 5.0 Rsolar. The kinetic temperatures for protons (Tk,p) and the O5+ ions (Tk,O) are derived as a function of height with preferential heating of O5+ over protons recorded. By examining how Tk,p varies with latitude at each height, an idea of the magnetic field morphology is found. At 1.75 Rsolar the elemental abundances (O, S, Ar, and Fe), electron temperature, and electron density are derived from the UV spectral data. All three streamers were quiescent with typical abundance values; however, no depleted cores were found. The first ionization potential (FIP) effect was detected for all three streamers with a bias of ~4. This is consistent with slow solar wind in situ measurements, thereby supporting the hypothetical connection between the two. All three streamers had a higher than expected electron temperature. The electron densities above 1.75 Rsolar are derived from the Large Angle Spectroscopic Coronagraph (LASCO) C2 polarized brightness data. Estimates for the O5+ outflow velocities are obtained using the O VI λ1032 over λ1037 intensity ratios and the estimated electron densities. All three streamers showed evidence of significant outflows at 4.0 and 5.0 Rsolar. Title: Heliospheric Streamers: Comparison Between Model Calculations and SECCHI Observations Authors: Howard, R. A.; Thernisien, A.; Vourlidas, A.; Morrill, J. S.; MacNiece, P. Bibcode: 2007AGUFMSH42A..04H Altcode: We have generated a time dependent 3-dimensional description of the electron density distribution out to 1 AU using the ENLIL model at the Community Coordinated Modeling Center (CCMC). Using this electron density description we have computed the brightness measurements that would be observed by coronagraphic instruments such as SECCHI using the Raytrace package. We compare the computed images with the actual SECCHI observations of streamers/heliospheric current sheet. Title: A New View of the Extreme Ultraviolet Corona from Wavelet-Processed EUV Images Authors: Stenborg, G. A.; Vourlidas, A.; Howard, R. A. Bibcode: 2007AGUFMSH14B..04S Altcode: Our knowledge of the structure and dynamics of the extreme ultraviolet solar corona has greatly increased over the last 11 years thanks to the observations from the Extreme-ultraviolet Imaging Telescope (EIT) aboard the SOHO spacecraft. The EIT images have revealed the early phases of coronal mass ejections (CMEs), discovered coronal waves associated with CMEs, recorded impressive post-CME loop systems and eruptive prominences, and detected reconnection at the base of coronal hole plumes, among other things. It would be natural to think that, by now, the EIT instrument has exhausted its discovery potential. We will demonstrate in this presentation that this is not the case. We have developed a wavelet-based image enhancement technique that exploits the multi-scale nature of the observed solar features, and treated the entire EIT database accordingly. The technique allowed us to remove the instrumental stray light background and enhance the fine coronal structures at the same time. The final images reveal such a wealth of structures and dynamics that they seem to have been obtained by a new instrument. The clarity of the enhanced images allows us to identify numerous and potentially interesting phenomena that were previously obscured by a background level that includes stray light and image noise. A few examples will be presented here, including application to the STEREO EUVI images. This presentation aims to bring the availability of this resource and its potential for significant discoveries to the attention of the solar physics community. Title: Direct Imaging of the Heliospheric Plasma Sheet from the SECCHI telescopes on the STEREO Mission Authors: Vourlidas, A.; Riley, P. Bibcode: 2007AGUFMSH21A0283V Altcode: We report the first ever direct imaging observations of the fine scale structure of the solar wind in the inner heliosphere. The observations were obtained by the Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument suite on the Solar Terrestrial Relations Observatory (STEREO) mission. The SECCHI telescopes can trace the coronal plasma from its origins at the solar corona to the Earth's neighborhood. Besides coronal mass ejections, the images also reveal the fine scale structure of the heliospheric plasma sheet during quiet periods. Here, we will show the evolution of these structures from the inner corona to the inner heliosphere. We will also include comparisons with large-scale MHD models of the heliosphere and discuss the importance of such observations for understanding the physics of the solar wind. Title: Physical parameters of a mid-latitude streamer during the declining phase of the solar cycle Authors: Spadaro, D.; Susino, R.; Ventura, R.; Vourlidas, A.; Landi, E. Bibcode: 2007A&A...475..707S Altcode: Context: Investigating the physical properties of solar coronal streamers is important for understanding their role in the global magnetic structure of the extended solar atmosphere, as well as in the generation of the slow solar wind.
Aims: We hope to contribute as completely as possible to the ongoing SOHO instruments campaign devoted to the study of the physical characteristics of coronal streamers at various heliocentric distances.
Methods: We analyzed ultraviolet H I Lyα and O VI resonance doublet lines observed by UVCS/SOHO in a narrow, mid-latitude streamer structure along different lines of sight during a week in May 2004 and made nearly simultaneous white-light polarized brightness measurements from the LASCO/SOHO C2 coronagraph.
Results: Electron densities and temperatures, H I and O VI kinetic temperatures, and outflow velocities were derived from the line intensities and widths, as well as from the O VI line intensity ratio in the 1.6-5 R⊙ range of heights, limited to the central region of the streamer. To our knowledge, the H I outflow velocities obtained in this work are the first ones determined inside a streamer structure. They are significantly lower than those of the O VI ions. This, together with the O VI kinetic temperatures that are much higher than the H I ones, suggest that the absorption of Alfvén waves at the ion cyclotron frequency might also occur inside streamers.
Conclusions: In comparison with other streamers described in the literature, the structure examined in this work generally exhibits lower electron density and neutral hydrogen kinetic temperature. Conversely, the O VI kinetic temperature and outflow velocity radial profiles are consistent with the results for the other examined streamers. Title: First Direct Observation of the Interaction between a Comet and a Coronal Mass Ejection Leading to a Complete Plasma Tail Disconnection Authors: Vourlidas, Angelos; Davis, Chris J.; Eyles, Chris J.; Crothers, Steve R.; Harrison, Richard A.; Howard, Russell A.; Moses, J. Daniel; Socker, Dennis G. Bibcode: 2007ApJ...668L..79V Altcode: This a discovery report of the first direct imaging of the interaction a comet with a coronal mass ejection (CME) in the inner heliosphere with high temporal and spatial resolution. The observations were obtained by the Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) Heliospheric Imager-1 (HI-1) aboard the STEREO mission. They reveal the extent of the plasma tail of comet 2P/Encke to unprecedented lengths and allow us to examine the mechanism behind a spectacular tail disconnection event. Our preliminary analysis suggests that the disconnection is driven by magnetic reconnection between the magnetic field entrained in the CME and the interplanetary field draped around the comet and not by pressure effects. Further analysis is required before we can conclude whether the reconnection occurs on the day side or on the tail side of the comet. However, the observations offer strong support to the idea that large-scale tail disconnections are magnetic in origin. The online movie reveals a wealth of interactions between solar wind structures and the plasma tail beyond the collision with the CME. Future analyses of this data set should provide critical insights on the structure of the inner heliosphere. Title: Erratum: ``Identification of a Peculiar Radio Source in the Aftermath of Large Coronal Mass Ejection Events'' (ApJ, 656, L105 [2007]) Authors: Vourlidas, Angelos; Pick, Monique; Hoang, Sang; Démoulin, Pascal Bibcode: 2007ApJ...665L.179V Altcode: In our recent Letter (A. Vourlidas et al. [ApJ, 656, L105 [2007]], hereafter Paper I), we determined the azimuth and elevation of our radio source with a direction-finding algorithm (Paper I, Fig. 4) assuming that the source emission dominates over the galactic background. This is generally true for type III emissions that are mainly used for these analyses. However, this condition does not necessarily hold for weaker emissions such as the broadband continuum source in our Letter. As the source intensity decreases to near the Galactic background level, the source direction shifts toward the direction of the Galactic center. It is therefore important to subtract the background before deriving source directions, which we did not do in Paper I. This correction has now been applied to the WIND WAVES data reported in Figure 4 of Paper I. As a result, there is no more significant drift in the source elevation or azimuth. The radio continuum source remains along the ecliptic plane as do other radio bursts observed in association with this coronal mass ejection (CME) event.

This correction does not significantly alter our proposed scenarios for the origin of the broadband source. The emission could still arise from electrons injected in nearby structures originating from interactions between the expanding CME and closed coronal loops or from the closing down of previously opened loops. Our velocity estimations are also unaffected by the corrections on the source location. They still suggest that the continuum propagates too slowly to be the CME shock. However, we must point out that M. J. Reiner, M. L. Kaiser, & J.-L. Bougeret (ApJ, 656, L105 [2007]) modeled this event as a type II source deriving an initial speed of 3000 km s-1, a strong deceleration of 41 ms-2 lasting for about 15 hr, followed by an almost constant propagation to the Earth. As the authors acknowledge in their paper, these parameters were obtained using a simple generic speed profile. Currently, there are no independent observations or theoretical predictions that show such a velocity profile for interplanetary CMEs. On the other hand, patchy, drifting structures that are typical signatures of interplanetary type II bursts are clearly seen in the radio spectrum after 14:30 UT but at a higher frequency than that of our continuum source. Similar patchy emissions are seen until a shock signature at Earth on September 24 at 21:00 UT. So a type II source is present in the spectrum.

Our initial intention with this work was to bring attention to the possibility that the conventional interpretation, as type II emission from a CME-driven shock, for low-frequency drifting continua might not hold true for all cases. We suggested in Paper I that the emission mechanism of this continuum could be gyrosynchrotron from nonthermal electrons. Recently, T. S. Bastian (ApJ, 665, 805 [2007]) proposed incoherent synchrotron emission from electrons entrained in the CME as an alternative explanation for such smooth type II-like sources. Therefore, we may be confronted with a new phenomenon, and we clearly need more studies to pin down the physical mechanism.

We are grateful to M. Reiner for pointing out the need for correction of our direction-finding results and for providing a preprint of M. J. Reiner, M. L. Kaiser, & J.-L. Bougeret (ApJ, 656, L105 [2007]). Title: The Quiet Sun Network at Subarcsecond Resolution: VAULT Observations and Radiative Transfer Modeling of Cool Loops Authors: Patsourakos, S.; Gouttebroze, P.; Vourlidas, A. Bibcode: 2007ApJ...664.1214P Altcode: One of the most enigmatic regions of the solar atmosphere is the transition region (TR), corresponding to plasmas with temperatures intermediate of the cool, few thousand K, chromosphere and the hot, few million K, corona. The traditional view is that the TR emission originates from a thin thermal interface in hot coronal structures, connecting their chromosphere with their corona. This paradigm fails badly for cool plasmas (~T<105 K), since it predicts emission orders of magnitude less than what it is observed. It was therefore proposed that the ``missing'' TR emission could originate from tiny, isolated from the hot corona, cool loops at TR temperatures. A major problem in investigating this proposal is the very small sizes of the hypothesized cool loops. Here, we report the first spatially resolved observations of subarcsecond-scale looplike structures seen in the Lyα line made by the Very High Angular Resolution Ultraviolet Telescope (VAULT). The subarcsecond (~0.3") resolution of VAULT allows us to directly view and resolve looplike structures in the quiet Sun network. We compare the observed intensities of these structures with simplified radiative transfer models of cool loops. The reasonable agreement between the models and the observations indicates that an explanation of the observed fine structure in terms of cool loops is plausible. Title: Progress Toward A Very High Angular Resolution Imaging Spectrometer (VERIS) Authors: Korendyke, Clarence M.; Vourlidas, A.; Landi, E.; Seely, J.; Klimchuck, J. Bibcode: 2007AAS...210.2604K Altcode: 2007BAAS...39Q.324K Recent imaging at arcsecond (TRACE) and sub-arcsecond (VAULT) spatial resolution clearly show that structures with fine spatial scales play a key role in the physics of the upper solar atmosphere. Both theoretical and observational considerations point to the importance of small spatial scales, impulsive energy release, strong dynamics, and extreme plasma nonuniformity. Fundamental questions regarding the nature, structure, properties and dynamics of loops and filamentary structures in the upper atmosphere have been raised.

To address these questions, we are developing a next generation, VEry high angular Resolution Imaging Spectrometer (VERIS) as a sounding rocket instrument. VERIS will obtain the necessary high spatial resolution, high fidelity measurements of plasma temperatures, densities and velocities. With broad simultaneous temperature coverage, the VERIS observations will directly address unresolved issues relating to interconnections of various temperature solar plasmas. VERIS will provide the first ever subarcsecond spectra of transition region and coronal structures. It will do so with a sufficient spectral resolution of to allow centroided Doppler velocity determinations to better than 3 km/s. VERIS uses a novel two element, normal incidence optical design with highly reflective EUV coatings to access a spectral range with broad temperature coverage (0.03-15 MK) and density-sensitive line ratios. Finally, in addition to the spectra, VERIS will simultaneously obtain spectrally pure slot images (10x150 arcsec) in the +/-1 grating orders, which can be combined to make instantaneous line-of-sight velocity maps with 8km/s accuracy over an unprecedented field of view.

The VERIS program is beginning the second year of its three year development cycle. All design activities and reviews are complete. Fabrication of all major components has begun. Brassboard electronics cards have been fabricated, assembled and tested. The paper presents the essential scientific characteristics of the instrument. Title: The Impact of Geometry on CME Observations Made by SEECHI Authors: Morrill, J.; Kunkel, V.; Halain, J. P.; Harrison, R. A.; Howard, R. A.; Moses, J. D.; Newmark, J.; Plunkett, S.; Socker, D.; Wang, D.; Vourlidas, A. Bibcode: 2007AGUSMSH41A..11M Altcode: Optical observations of Coronal Mass Ejections (CME's) during the past several decades have generally been confined to events observed near the sun. Although events originating from most regions of the sun can be observed, the assumption has often made that the CME is propagating in the plane-of-the-sky. This assumption is generally adequate to give lower limits of CME mass and speed. However, continuous observations of CME's are now being made from very near the solar surface to large distances from the sun by the SECCHI instrument on STEREO. When CME's are observed at great distances from the sun, plane-of-the-sky assumptions are not adequate for analysis of these events. In this presentation we will discuss some recent observations made by the SEECHI instruments and the impact of geometry on our interpretation of these events. Title: Energetics of solar coronal mass ejections Authors: Subramanian, P.; Vourlidas, A. Bibcode: 2007A&A...467..685S Altcode: 2007astro.ph..1160S Aims:We investigate whether solar coronal mass ejections are driven mainly by coupling to the ambient solar wind or through the release of internal magnetic energy.
Methods: We examine the energetics of 39 flux-rope like coronal mass ejections (CMEs) from the Sun using data in the distance range ~2-20 R⊙ from the Large Angle Spectroscopic Coronograph (LASCO) aboard the Solar and Heliospheric Observatory (SOHO). This comprises a complete sample of the best examples of flux-rope CMEs observed by LASCO in 1996-2001.
Results: We find that 69% of the CMEs in our sample experience a clearly identifiable driving power in the LASCO field of view. For those CMEs that are driven, we examine if they might be deriving most of their driving power by coupling to the solar wind. We do not find conclusive evidence in favor of this hypothesis. On the other hand, we find that their internal magnetic energy is a viable source of the required driving power. We have estimated upper and lower limits on the power that can possibly be provided by the internal magnetic field of a CME. We find that, on average, the lower limit to the available magnetic power is around 74% of what is required to drive the CMEs, while the upper limit can be as much as an order of magnitude larger. Title: The Sun To The Earth, A Panoramic View From SECCHI: Overview Authors: Moses, John Daniel; Newmark, J.; Howard, R. A.; Plunkett, S.; Socker, D.; Wang, D.; Vourlidas, A.; Halain, J.; Harrison, R. A.; Eyles, C. J.; Davila, J.; Lemen, J.; Wuelser, J. Bibcode: 2007AAS...21011904M Altcode: 2007BAAS...39..244M The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) is the remote sensing component of the STEREO mission to explore the source, initiation, and propagation through the heliosphere of Coronal Mass Ejections (CMEs). To achieve this goal, SECCHI must continuously observe CMEs from two different perspectives beginning with the pre-event coronal configuration and ending with the propagation of the event out of the inner heliosphere. Thus, each of the two STEREO observatories carries a suite of SECCHI telescopes with 5 different fields of view providing an uninterrupted view of coronal and Heliospheric phenomena from the solar chromosphere to 1 AU. This is the first panoramic view of the inner heliosphere dedicated to observing the spatial and temporal scales characteristic of CMEs at elongation angles from 0 to almost 90 degrees.

We present first results from the SECCHI imaging suite with emphasis on the unprecedented panoramic views of the heliosphere. We show direct observations of CMEs and the solar wind from initiation on the Sun throughout the inner heliosphere to 1 AU. The SECCHI suite performance exceeds that necessary to achieve the Level 1 STEREO science objectives. Thus, as the STEREO spacecraft separate to provide views from different directions we can anticipate breakthrough observations for issues currently unresolved by plane-of-sky projections through optically thin structures.

The most current information on SECCHI can be obtained from the STEREO mission website at http://stereo.gsfc.nasa.gov and the SECCHI website at http://secchi.nrl.navy.mil. The NRL participation in the STEREO mission is supported by NASA under S-13631-Y, and by the Office of Naval Research. Title: Chromospheric Science with the STEREO Mission Authors: Vourlidas, A. Bibcode: 2007ASPC..368..633V Altcode: The STEREO mission, launched in October 2006 comprises two spacecraft drifting at opposite directions from Earth. STEREO carries a suite of solar telescopes to provide, for the first time, stereoscopic views CMEs and of the corona including the cool, upper chromospheric line of He II at 304 Å. In my talk, I give an overview of the mission and its science objectives and discuss the areas where STEREO can provide important contributions to chromospheric science questions. Title: The SECCHI Experiment on the STEREO Mission Authors: Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.; Socker, D. G.; Wang, D.; Plunkett, S. P.; Baugh, R.; McMullin, D. R.; Davila, J. M.; Thompson, W. T.; Lemen, J. R.; Wuelser, J.; Harrison, R. A.; Waltham, N. R.; Davis, C. J.; Eyles, C. J.; Defise, J.; Halain, J.; Bothmer, V.; Delaboudiniere, J.; Auchere, F.; Mercier, R.; Ravet, M. F. Bibcode: 2007AGUSMSH33A..01H Altcode: The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO) mission is a suite of remote sensing instruments consisting of an extreme ultraviolet (EUV) imager, two white light coronagraphs, and two telescopes that comprise the heliospheric imager. SECCHI will observe coronal mass ejections (CMEs) from their birth at the sun, through the corona and into the heliosphere. A complete instrument suite is being carried on each of the two STEREO spacecraft, which will provide the first sampling of a CME from two vantage points. The spacecraft, launched 25 October 2006, are orbiting the Sun, one Ahead of the Earth and the other Behind, each separating from Earth at about 22 degrees per year. The varying separation means that we will have different observational capabilities as the spacecraft separate and therefore differing science goals. The primary science objectives all are focused on understanding the physics of the CME process their initiation, 3D morphology, propagation, interaction with the interplanetary medium and space weather effects. By observing the CME from multiple viewpoints with UV and coronagraphic telescopes and by combining these observations with radio and in-situ observations from the other instruments on STEREO as well as from other satellites and ground based observatories operating at the same time, answers to some of the outstanding questions will be obtained. We will show some of the initial results. Title: Seeing the Heliosphere with New Eyes: First Results from the SECCHI Experiment on STEREO Authors: Vourlidas, A. Bibcode: 2007AGUSMSH33A..02V Altcode: The STEREO mission was launched on October, 2006 with the main objective to study Coronal Mass Ejections (CMEs) from their initiation in the solar corona to their arrival at Earth using a suite of remote sensing and in-situ instruments on two, almost identical, spacecraft. The mission objectives are mainly addressed by the imaging experiment, named Sun-Earth Connection Coronal & Heliospheric Investigation (SECCHI), which comprises a suite of five telescopes; an EUVI full disk imager, two coronagraphs covering the range from 1.5 to 15 solar radii, and two heliospheric imagers observing along the Sun-Earth LINE from 15 solar radii to the Earth's orbit and beyond. It is the first time that such imaging capabilities are available and they will certainly lead to important advances in our understanding of the CME initiation, propagation, and its three-dimensional configuration. In this talk, we will showcase the observations and initial results from the first months of operations of the SECCHI telescopes. We will also discuss the instrument performance and synergies with existing observatories (e.g., SOHO). SECCHI was built by a consortium of US and European institutions under the direction of the Solar Physics Branch at the U.S. Naval Research Laboratory. Title: Forward Modeling Of Cme Events Applied To STEREO-SECCHI Data. Authors: Thernisien, Arnaud; Howard, R. A.; Vourlidas, A. Bibcode: 2007AAS...210.2807T Altcode: 2007BAAS...39R.136T We have implemented a simple flux rope CME model. With this purely geometric model, we were able to reproduce 30 different CME events observed with SOHO-LASCO. We were also able to determine locally the electron density profile in the CME leading edge. The STEREO mission, launched in October 2006, is made of two twin spacecrafts that observe the Sun from two points of view. In this presentation, I will describe how we applied our forward modeling technique to the simulation of CME events observed from 2 or 3 different points of view, by using STEREO-SECCHI data and also SOHO-LASCO. Title: Signatures of CMEs Shocks on LASCO Observations Authors: Ontiveros, V. Z.; Vourlidas, A. Bibcode: 2007AGUSMSH23A..03O Altcode: We report on our efforts to establish reliable markers of CME-driven shocks in white light coronograph images. For this study, we looked at events during the ascending phase of solar cycle 23 when the overall morphology of the white light corona is simple. We isolated events that will be good candidates to drive a shock due to their high velocities (V>1500 km/s). The list includes 15 CMEs. For each event we calibrated the LASCO images and searched for indications of faint sharp fronts ahead of the bright CME front. We report our findings of the analysis of the front morphology, the distant streamer deflections, and the mass and energetics of these events. This work is funded by the LWS TR&T program Title: The Physical Properties of Three Coronal Streamers from 2003 Authors: Uzzo, Michael; Strachan, L.; Vourlidas, A. Bibcode: 2007AAS...210.3002U Altcode: 2007BAAS...39..142U In this presentation we examine the plasma properties of three streamers observed in April, May and September of 2003 by two instruments, UVCS and LASCO, onboard the SOHO spacecraft. The properties are the electron density, electron temperature, elemental abundances, oxygen outflow velocity, proton kinetic temperature and oxygen kinetic temperature. These properties are then mapped onto the respective streamer with regards to height above the solar disk (1.75, 2.5, 3.0, 4.0 and 5.0 Ro) and latitude. The photospheric normalized absolute elemental abundances of O, Fe, Ar and S are derived at 1.75 Ro. The first ionization potential (FIP) bias measured within these streamers are compared to the results measured in situ within the slow solar wind. Title: Stereo Observations Of The Solar Corona Using The Secchi Experiment Authors: Plunkett, Simon P.; Howard, R. A.; Moses, J. D.; Vourlidas, A.; Socker, D.; Newmark, J.; Wang, D.; Baugh, R.; Davila, J.; Thompson, W.; St. Cyr, O. C.; Lemen, J.; Wuelser, J. P.; Harrison, R. A.; Waltham, N.; Davis, C. J.; Eyles, C. J.; Defise, J. M.; Halain, J. P.; Bothmer, V.; Delaboudiniere, J. P.; Auchere, F.; Mercier, R.; Ravet, M. F. Bibcode: 2007AAS...21011901P Altcode: 2007BAAS...39..243P The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO) mission is a suite of remote sensing instruments consisting of an extreme ultraviolet (EUV) imager, two white light coronagraphs, and two telescopes that comprise the heliospheric imager. The main objective of SECCHI is to observe coronal mass ejections (CMEs) from their birth at the sun, through the corona and into the heliosphere. A complete instrument suite is being carried on each of the two STEREO spacecraft, which will provide the first sampling of a CME from two vantage points as the spacecraft separate from each other at the rate of about 45 degrees per year. We will show examples of some of the data and some of the initial stereo results. Title: The Sun To The Earth, A Panoramic View From SECCHI: CME Observations Through The Inner Heliosphere Authors: Newmark, Jeffrey; Moses, J. D.; Howard, R. A.; Plunkett, S.; Socker, D.; Wang, D.; Vourlidas, A.; Halain, J. P.; Harrison, R. A.; Eyles, C. J.; Davila, J.; Lemen, J.; Wuelser, J. P. Bibcode: 2007AAS...21011905N Altcode: 2007BAAS...39..244N The STEREO SECCHI telescope suite is returning unprecedented viewsvof the Sun and inner heliosphere. The SECCHI instruments on each of the two STEREO spacecraft are observing Coronal Mass Ejections (CMEs) from their initiation, through the corona, and into interplanetary space beyond the Earth's orbit. We present a first analysis of a CME throughout the inner heliosphere. We focus on the propagation characteristics of the CME and the morphological properties of the CME as viewed from STEREO.

This first glimpse of a CME in the heliosphere clearly demonstrates the anticipated scientific returns that future STEREO observations (at larger angular separations) of CMEs in interplanetary space will provide.

The most current information can be obtained on the STEREO mission website at http://stereo.gsfc.nasa.gov and the SECCHI website at http://secchi.nrl.navy.mil. The NRL participation on SECCHI is supported by NASA under S-13631-Y, and by the Office of Naval Research. Title: Simulated CMEs and Predictions for STEREO Authors: Manchester, M. B.; Vourlidas, A.; Gombosi, T.; Sokolov, I. V.; Cohen, O.; Toth, G. Bibcode: 2007AGUSMSH41A..06M Altcode: We compare results of our global MHD simulations of CMEs propagating from Sun-to-Earth to observations made with STEREO. We model a number of events of varying degree of complexity, and model the observations that are made by the SECCHI coronagraph suite and in situ observations by IMPACT and PLASTIC. We make synthetic Thomson-scattered white light images from the simulations as they would appear to the COR1, COR2, and wide-angle coronagraphs HI1 and HI2. We identify shock structures in the coronagraph images and follow their evolution to Earth orbit. At large elongation, we find complex time evolution of the white- light images as a result of three-dimensional structures encountering large variations in scattering efficiency as they pass through the Thomson sphere. We then compare the modeled ICME plasma structures with observations from PLASTIC. We also model solar energetic particles and compare them with IMPACT observations. Title: Features and Properties of Coronal Mass Ejection/Flare Current Sheets Authors: Lin, J.; Li, J.; Forbes, T. G.; Ko, Y. -K.; Raymond, J. C.; Vourlidas, A. Bibcode: 2007ApJ...658L.123L Altcode: Solar eruptions occur when magnetic energy is suddenly converted into heat and kinetic energy by magnetic reconnection in a current sheet (CS). It is often assumed that CSs are too thin to be observable because the electric resistivity ηe in CSs is taken to be very small. In this work, we show the implications for the CS thickness d estimated from observations of three eruptions by the UVCS and the LASCO experiments on SOHO. We infer the effective ηe causing the rapid reconnection, which predicts much faster reconnection in a thick CS than that caused by the classical and anomalous resistivities. We find that in these events CSs are observable and have extremely large values of d and ηe, implying that large-scale turbulence is operating within CSs. We also discuss the properties of the so-called hyperresistivity caused by the tearing mode and the relation to our results. Title: Identification of a Peculiar Radio Source in the Aftermath of Large Coronal Mass Ejection Events Authors: Vourlidas, Angelos; Pick, Monique; Hoang, Sang; Démoulin, Pascal Bibcode: 2007ApJ...656L.105V Altcode: We report the discovery of a new radio feature associated with coronal mass ejection (CME) events. The feature is a low-frequency (<1 MHz), relatively wide (~300 kHz) continuum that appears just after the main phase of the eruptive event, lasts for several hours, and exhibits a slow negative frequency drift. So far, we have identified this radio signature in a handful of CME events and suspect it might be a common occurrence. The radio continuum starts almost simultaneously with the commonly observed decimetric type IV stationary continuum (also called flare continuum), but the two seem unrelated. The emission mechanism, whether plasma emission or gyroresonance, is unclear at the moment. On the basis of our preliminary analysis, we interpret this radio continuum as the lateral interaction of the CME with magnetic structures. Another possibility is that this continuum traces the reconfiguration of large-scale loop systems, such as streamers. In other words, it could be the large-scale counterpart of the post-CME arcades seen over active region neutral lines after big CME events. This Letter aims to bring attention to this feature and attract more research into its nature. Title: S ynergies With The Solar Orbiter Mission: Remote Sensing Studies Of The Corona And Coronal Transients Authors: Vourlidas, A. Bibcode: 2007ESASP.641E..14V Altcode: Currently, the Solar Orbiter (SolO) mission is planned to start its science observations around the next solar minimum (2018-2020) and extend to the maximum of cycle 25. Given the demanding deep space orbit and the restrictions on spacecraft resources, the mission will likely include a modest instrument payload designed to fully address a focused set of solar physics problems. Hopefully, SolO will not be the only solar mission op- erating at the time. The scientific return of the SolO mission will be greatly enhanced by joint observational programs with other instruments, both space-borne and gound- based ones. In this paper, I concentrate on obser- vations of the outer corona and of coronal mass ejections and discuss a few examples of synergistic science at the time of the SolO mission with an emphasis on the unique characteristics of the SolO orbit. Title: A Radio Burst and Its Associated CME on March 17, 2002 Authors: Yan, Y.; Pick, M.; Wang, M.; Krucker, S.; Vourlidas, A. Bibcode: 2006SoPh..239..277Y Altcode: 2006SoPh..tmp...78Y In this study, we present a detailed analysis, based on multiwavelength observations and magnetic field extrapolation, of a radio and X-ray event observed on March 17, 2002. This event was accompanied by a Coronal Mass Ejection (CME) observed by the Large-Angle Spectrometric Coronagraph (LASCO) aboard SOHO. During the main event, the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) mission observed a hard X-ray emission correlated in time with the development of a type III burst group. The CME development, the hard X-ray emission, and the type III burst group appear to be closely associated. The multifrequency Nançay Radioheliograph (NRH) shows that the type III bursts are produced at a distance from the active region that progressively increases with time. Their emitting sources are distributed along the western edge of the CME. We conclude the type III electron beams propagate in the interface region between the ascending CME and the neighboring open field lines. Due to the development of the CME, this region becomes progressively highly compressed. By measuring, at each frequency, the shift versus time of the type III positions, we estimate that the electron density in this compression region increased roughly by a factor of 10 over a few minutes. Another signature of this compression region is a narrow white light feature interpreted as a coronal shock driven by the CME lateral expansion. Title: Analysis of the Velocity Field of CMEs Using Optical Flow Methods Authors: Colaninno, Robin C.; Vourlidas, Angelos Bibcode: 2006ApJ...652.1747C Altcode: Optical flow is a powerful image processing tool for measuring motion in digital images. The optical flow algorithm provides an estimate of the velocity vector at every pixel from a pair of successive images. Here we present an application of this method to images of coronal mass ejections (CMEs). The technique is first tested and validated on a simulated CME. It is then applied to several CMEs observed with the LASCO C2 coronagraph to derive their velocity fields. The resulting velocity measurements allow us to visualize the evolution of the CME plasma and to separate the ``bulk'' velocity from the expansion velocity of a given CME. To our knowledge, this is the first time that such information has been extracted from CME observations. We discuss the limitations and accuracy of our optical flow method and propose further improvements. Title: Which CMEs are associated with Proton Events? Authors: Vourlidas, A.; Cane, H. V.; Richardson, I. Bibcode: 2006AGUFMSH41B..05V Altcode: We investigate the properties of CMEs associated with medium-sized proton events. We calibrated the LASCO C2 and C3 images for 69 events and looked for patterns in the CME morphology (e.g, CME shape, extent, speed) and the existence or not of a white light shock. The preliminary analysis seems to suggest that proton events are associated with a particular subset of CMEs. We report our results and our preliminary interpretations. Title: CME Brightness at Large Elongations: Application to LASCO and SMEI Observations Authors: Vourlidas, A.; Webb, D. F.; Morrill, J. S.; Jackson, B. V. Bibcode: 2006AGUFMSH32A..03V Altcode: The traditional analysis of the CME brightness relied on the assumption that all lines of sight through the CME were parallel due to the large distance between the observer and the event. However, this assumption is not correct when CME observations at large distances from the Sun are concerned. In a recent paper (Vourlidas & Howard 2006) we have outlined the proper geometry and presented a few theoretical predictions about the brightness evolution of CME launched at various angles relative to the Sun-observer line. In this talk, we use LASCO and SMEI observations of the same events to test our predictions and see how we can use our theoretical framework to interpret the observed CME structures. Title: The SECCHI Experiment on the STEREO Mission Authors: Howard, R. A.; Moses, D.; Vourlidas, A.; Newmark, J.; Socker, D. G.; Plunkett, S.; Wang, D.; Baugh, R.; McMullin, D.; Davila, J.; St. Cyr, C.; Thompson, W. T.; Lemen, J.; Wuelser, J.; Harrison, R. A.; Waltham, N. R.; Davis, C.; Eyles, C. J.; Defise, J.; Halain, J.; Bothmer, V.; Delaboudiniere, J.; Auchere, F.; Mercier, R.; Ravet, M. Bibcode: 2006AGUFMSM12A..02H Altcode: The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO) mission is a suite of remote sensing instruments consisting of an extreme ultraviolet (EUV) imager, two white light coronagraphs, and two telescopes that comprise the heliospheric imager. SECCHI will observe coronal mass ejections (CMEs) from their birth at the sun, through the corona and into the heliosphere. A complete instrument suite is being carried on each of the two STEREO spacecraft, which will provide the first sampling of a CME from two vantage points. The spacecraft will orbit the Sun, one Ahead of the Earth and the other Behind, each separating from Earth at about 22 degrees per year. The varying separation means that we will have different observational capabilities as the spacecraft separate and therefore differing science goals. The primary science objectives all are focused on understanding the physics of the CME process their initiation, 3D morphology, propagation, interaction with the interplanetary medium and space weather effects. By observing the CME from multiple viewpoints with UV and coronagraphic telescopes and by combining these observations with radio and in-situ observations from the other instruments on STEREO as well as from other satellites and ground based observatories operating at the same time, answers to some of the outstanding questions will be obtained. STEREO follows the very successful SOHO mission. SOHO's success was primarily due to the highly complementary nature of the instruments, but it was partly due to the very stable platform. The L1 orbit enables an extremely stable thermal environment and thus very stable pointing, as well as uninterrupted solar viewing. The STEREO will have both of these characteristics, but in addition will have multi-viewpoint viewing of CMEs, which will greatly enhance the many discoveries that SOHO data have produced. We have been developing techniques to interpret the observations from multiple viewpoints and to perform 3-dimensional deconvolution of the CME observations using forward modeling and inversion techniques. A continuous downlink of STEREO data will provide a low-resolution, real- time view from all of the instruments. The full data are downlinked once a day and will be available about 24 hours later. We will present some preliminary results from the instrument, which is expected to be launched in October/November, 2006 Title: Modeling of Flux Rope Coronal Mass Ejections Authors: Thernisien, A. F. R.; Howard, R. A.; Vourlidas, A. Bibcode: 2006ApJ...652..763T Altcode: We present a forward-modeling technique for flux rope-like CMEs using an empirically defined model of a flux rope, the graduated cylindrical shell (GCS). To compare it with white-light coronagraph observations, we assume an electron distribution through the GCS and derive synthetic images in total and polarized brightness for various projections of the model using a Thomson scattering ray-tracing program. We test our forward modeling technique on 34 LASCO CMEs analyzed by Cremades & Bothmer. We are able to reproduce the CME morphology and derive the electron density (at the CME front) of these events using multi-instrument observations (MDI, Hα, EIT, LASCO) under the assumption of self-similar expansion. This study suggests that a flux rope-like structure is a good description for these events. We also find that we need to invoke a deflection and/or rotation of the structure relative to the position and orientation of the source region in most cases. Finally, we demonstrate an original technique to fit the electron density of the CME leading edge. We find that, on average, the peak of the density at the CME front is 7.5 times that in the equatorial model of Saito et al., and can reach ~22 times the model in some cases. Title: Theoretical Investigation of the Onsets of Type II Radio Bursts during Solar Eruptions Authors: Lin, Jun; Mancuso, Salvatore; Vourlidas, Angelos Bibcode: 2006ApJ...649.1110L Altcode: On the basis of previous works, we investigated coronal mass ejection (CME) propagations and the consequent type II radio bursts invoked by the CME-driven shocks. The results indicate that the onset of type II bursts depends on the local Alfvén speed (or the magnetoacoustic wave speed in the non-force-free environment), which is governed by both the magnetic field and the plasma density. This determines that the type II burst cannot appear at any altitude. Instead, its onset positions can never be lower than a critical height for the given coronal environment, which consequently determines the start frequencies of the emission: for an eruption taking place in the magnetic configuration with a background field of 100 G, the onset of type II bursts should occur at around 0.5 Rsolar from the solar surface, and the corresponding start frequency of the fundamental component is about 150 MHz. This result is consistent with similar estimates based on observations that bring the corresponding frequency to a few hundred MHz. Our results further indicate that the onset of type II bursts depends on the rate of magnetic reconnection as well. When magnetic reconnection during the eruption is not fast enough, a type II burst may not occur at all even if the associated CME is fast (say, faster than 800 km s-1). This may account for the fast and radio-quiet CMEs. Related to these results, properties of the associated solar flares and type III radio bursts, especially those used as the precursors of the type II radio bursts, are also discussed. Title: The Flux-Rope Scaling of the Acceleration of Coronal Mass Ejections and Eruptive Prominences Authors: Chen, J.; Marqué, C.; Vourlidas, A.; Krall, J.; Schuck, P. W. Bibcode: 2006ApJ...649..452C Altcode: The new flux-rope scaling law of the acceleration of coronal mass ejections (CMEs) derived by Chen & Krall is quantitatively tested by comparing the theoretical prediction with the near-Sun acceleration profiles of 13 eruptive prominences (EPs) and four CMEs. A CME and associated EP are assumed to be organized by an underlying magnetic flux rope (MFR) with specific structural and geometrical relationships. The scaling law states that if the initial structure is a flux rope with a footpoint separation distance of Sf, then the height Zmax at which the acceleration measured at the centroid of the apex reaches maximum scales with Sf. The primary source of prominence data is the radio data from the archive of the Nobeyama Radio Observatory. A number of Hα events are also included. For CMEs, previously published events with good coverage of the initial acceleration are used. For each event, observed quantities are used to determine Sf and Zmax. It is shown that for the events included in the present study, Zmax scales with Sf in accordance with the scaling law. The result is consistent with the hypothesis that the preeruption magnetic structure underlying a CME and the associated EP is a flux rope driven by the toroidal Lorentz hoop force. The scaling law may constitute a quantitative observable discriminator of the preeruption magnetic geometry underlying CMEs/EPs and the driving force. Title: Detections of CME-Driven Shocks with LASCO Authors: Vourlidas, A. Bibcode: 2006ESASP.617E..23V Altcode: 2006soho...17E..23V No abstract at ADS Title: Physical Properties of a 2003 April Quiescent Streamer Authors: Uzzo, M.; Strachan, L.; Vourlidas, A.; Ko, Y. -K.; Raymond, J. C. Bibcode: 2006ApJ...645..720U Altcode: In 2003 April, the Ultraviolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory (SOHO) observed a quiescent streamer in an effort to derive the physical plasma parameters across the streamer and as a function of height (from 1.75 to 5.0 Rsolar). Values for the electron temperature, proton and O5+ kinetic temperatures, elemental abundances, and O5+ outflow velocity were derived. The presence of the first ionization potential (FIP) effect was also explored. These plasma parameters were compared to those derived for other previously reported active region and quiescent streamers. The photospheric normalized absolute elemental abundances for O, Si, S, Ar, and Fe were derived at 1.75 Rsolar. The remaining parameters were derived at five heights up to 5.0 Rsolar. To calculate the electron density above 2.2 Rsolar the polarized brightness data from another SOHO instrument, the Large Angle Spectroscopic Coronagraph (LASCO) C2 detector, was employed. The streamer was located above a complex filament structure and had a slightly higher electron temperature compared to what is typically found for quiescent streamers. This streamer did exhibit the customary FIP effect, but no abundance-depleted core typically found for such stable quiescent streamers was detected. The perpendicular kinetic temperature for the protons and the O5+ ions did not vary across the streamer. This differs from two other quiescent streamer comparison cases, in which the O5+ kinetic temperature did decrease at the core structure. The O5+ outflow velocities were similar to those observed in an equatorial streamer from solar minimum. Title: Forward Modeling Technique for the Reconstruction of the Solar Corona Authors: Thernisien, Arnaud; Howard, R. A.; Vourlidas, A. Bibcode: 2006SPD....37.0818T Altcode: 2006BAAS...38..233T We present a forward modeling technique for the reconstruction of structures such as streamers and CMEs observed with SOHO-LASCO. This technique relies on the computation of a synthetic image of brightness from an assumed electron density model. By iteratively comparing the reconstructed model and the data image, we are able to fit the parameters of the model, such as the position, the shape aspect parameters and the electron density.Streamers are observed as bright and quasi radial shapes. We show how it is possible to determine the electron density in these regions by modeling the streamer as a simple slab. We also show that we can reconstruct its three dimensional morphology using data 7 days apart.We present a model of flux rope CME that we were able to fit to 34 structured CME events observed on SOHO-LASCO. LASCO only provides the projection of the 3D CME structure, so many parameters of our model cannot be determined directly. We made use of information provided by multiple instrument (MDI, Halpha, EIT) in order to constrain our reconstruction, and also assumed self similar expansion (Cremades and Bothmer, A&A 2004).Finally, by combining the two models, streamer and CME, we present a case study of a streamer deflected by a CME during the eruption. We show how, by using our simulation software, we can change the observer point of view and look at the modeled event as if it was seen from Earth, and compare to a halo CME. Title: Analysis of the Velocity Field of CMEs Using Optical Flow Methods Authors: Colaninno, Robin C.; Vourlidas, A. Bibcode: 2006SPD....37.2404C Altcode: 2006BAAS...38..251C Optical flow is a powerful image processing tool for measuring motion in digital images. The optical flow algorithm estimates a velocity vector at every image pixel from a pair of successive images. Here we present the application of this method on images of coronal mass ejections (CMEs). The technique is first tested and validated on a simulated CME. Then it is applied to several CMEs observed with the LASCO-C2 coronagraph to derive their velocity fields. The resulting velocity measurements allow us to separate the 'bulk' velocity from the expansion velocity of a given CME. To our knowledge, this is the first time that such information has been extracted from CME observations. We discuss the limitations and accuracy of our optical flow method and propose further improvements. Title: Investigations of the Reconnecting Current Sheets in Solar Eruptions Authors: Lin, Jun; Li, J.; Forbes, T. G.; Ko, Y.; Raymond, J. C.; van Ballegooijen, A. A.; Vourlidas, A. Bibcode: 2006SPD....37.0826L Altcode: 2006BAAS...38..235L Observations and theories continuously provide evidence of formation and development of the reconnecting current sheets during major eruptions. Because the high electric conductivity and the force-free environment of the solar corona, the current sheet is usually confined in a small volume compared to the other structures involved in the eruption in order to allow the energy conversion or magnetic reconnection to take place at a plausible rate. The work investigating the sizes, especially thickness, of the current sheet developed by the eruption in reality was never conducted before since it is believed that the current sheet is too thin to be observable. It has often been stated that the thickness is limited either by the Lamor radius of particles, which is about tens of meters in the coronal environment, or by the mean-free-path of particles in the region where the interaction between particles and ion-acoustic waves occurs. In the latter case, the particle mean-free-path is a few kilometers. Here we use a set of unique observations provided by the UVCS and LASCO experiments on SOHO to determine the thickness, d, and furthermore the electric resistivity, etae, of the current sheets for three eruptive events. We find that d ranges from 1.0 x 104 km to 6.0 x 105 km, and etae from 1.0 x 105 ohm m to 4.0 x 106 ohm m. These values of etae are 12-14 orders of magnitude greater than the classical collisional resistivity, 4-6 orders of magnitude greater than estimates of anomalous resistivity, and even 1-3 orders greater than those often used for solar flares. The existence of such large values for d and etae suggests that large scale turbulent processes are operating within the current sheet. Understanding how a high level of turbulence can develop so rapidly is a challenging goal for future research. Title: On The CME Brightness At Large Elongations: Implications For Secchi Observations Authors: Vourlidas, Angelos; Howard, R. A. Bibcode: 2006SPD....37.2503V Altcode: 2006BAAS...38..252V The SECCHI instrument suite aboard the STEREO mission will allow us to follow a coronal mass ejection (CME) continuously from the Sun to Earth for the first time. The comparison of the CME emission among the various instruments is not as easy as one might think. This is because the telescopes record the Thomson scattered emission from the CME plasma which has a rather sensitive dependence on the geometry between the observer and the scattering material. Here, we will describe the proper treatment of the Thomson scattered emission, compare the CME brightness over a large range of elongation angles and discuss the implications for observations. Title: The Proper Treatment of Coronal Mass Ejection Brightness: A New Methodology and Implications for Observations Authors: Vourlidas, Angelos; Howard, Russell A. Bibcode: 2006ApJ...642.1216V Altcode: With the complement of coronagraphs and imagers in the SECCHI suite, we will follow a coronal mass ejection (CME) continuously from the Sun to Earth for the first time. The comparison, however, of the CME emission among the various instruments is not as easy as one might think. This is because the telescopes record the Thomson-scattered emission from the CME plasma, which has a rather sensitive dependence on the geometry between the observer and the scattering material. Here we describe the proper treatment of the Thomson-scattered emission, compare the CME brightness over a large range of elongation angles, and discuss the implications for existing and future white-light coronagraph observations. Title: Coronal Observations of CMEs. Report of Working Group A Authors: Schwenn, R.; Raymond, J. C.; Alexander, D.; Ciaravella, A.; Gopalswamy, N.; Howard, R.; Hudson, H.; Kaufmann, P.; Klassen, A.; Maia, D.; Munoz-Martinez, G.; Pick, M.; Reiner, M.; Srivastava, N.; Tripathi, D.; Vourlidas, A.; Wang, Y. -M.; Zhang, J. Bibcode: 2006SSRv..123..127S Altcode: 2006SSRv..tmp...58S CMEs have been observed for over 30 years with a wide variety of instruments. It is now possible to derive detailed and quantitative information on CME morphology, velocity, acceleration and mass. Flares associated with CMEs are observed in X-rays, and several different radio signatures are also seen. Optical and UV spectra of CMEs both on the disk and at the limb provide velocities along the line of sight and diagnostics for temperature, density and composition. From the vast quantity of data we attempt to synthesize the current state of knowledge of the properties of CMEs, along with some specific observed characteristics that illuminate the physical processes occurring during CME eruption. These include the common three-part structures of CMEs, which is generally attributed to compressed material at the leading edge, a low-density magnetic bubble and dense prominence gas. Signatures of shock waves are seen, but the location of these shocks relative to the other structures and the occurrence rate at the heights where Solar Energetic Particles are produced remains controversial. The relationships among CMEs, Moreton waves, EIT waves, and EUV dimming are also cloudy. The close connection between CMEs and flares suggests that magnetic reconnection plays an important role in CME eruption and evolution. We discuss the evidence for reconnection in current sheets from white-light, X-ray, radio and UV observations. Finally, we summarize the requirements for future instrumentation that might answer the outstanding questions and the opportunities that new space-based and ground-based observatories will provide in the future. Title: Multi-Wavelength Observations of CMEs and Associated Phenomena. Report of Working Group F Authors: Pick, M.; Forbes, T. G.; Mann, G.; Cane, H. V.; Chen, J.; Ciaravella, A.; Cremades, H.; Howard, R. A.; Hudson, H. S.; Klassen, A.; Klein, K. L.; Lee, M. A.; Linker, J. A.; Maia, D.; Mikic, Z.; Raymond, J. C.; Reiner, M. J.; Simnett, G. M.; Srivastava, N.; Tripathi, D.; Vainio, R.; Vourlidas, A.; Zhang, J.; Zurbuchen, T. H.; Sheeley, N. R.; Marqué, C. Bibcode: 2006SSRv..123..341P Altcode: 2006SSRv..tmp...60P This chapter reviews how our knowledge of CMEs and CME-associated phenomena has been improved, since the launch of the SOHO mission, thanks to multi-wavelength analysis. The combination of data obtained from space-based experiments and ground based instruments allows us to follow the space-time development of an event from the bottom of the corona to large distances in the interplanetary medium. Since CMEs originate in the low solar corona, understanding the physical processes that generate them is strongly dependant on coordinated multi-wavelength observations. CMEs display a large diversity in morphology and kinematic properties, but there is presently no statistical evidence that those properties may serve to group them into different classes. When a CME takes place, the coronal magnetic field undergoes restructuring. Much of the current research is focused on understanding how the corona sustains the stresses that allow the magnetic energy to build up and how, later on, this magnetic energy is released during eruptive flares and CMEs. Multi-wavelength observations have confirmed that reconnection plays a key role during the development of CMEs. Frequently, CMEs display a rather simple shape, exhibiting a well known three-part structure (bright leading edge, dark cavity and bright knot). These types of events have led to the proposal of the ‘`standard model’' of the development of a CME, a model which predicts the formation of current sheets. A few recent coronal observations provide some evidence for such sheets. Other more complex events correspond to multiple eruptions taking place on a time scale much shorter than the cadence of coronagraph instruments. They are often associated with large-scale dimming and coronal waves. The exact nature of these waves and the physical link between these different manifestations are not yet elucidated. We also discuss what kind of shocks are produced during a flare or a CME. Several questions remain unanswered. What is the nature of the shocks in the corona (blast-wave or piston-driven?) How they are related to Moreton waves seen in Hα? How they are related to interplanetary shocks? The last section discusses the origin of energetic electrons detected in the corona and in the interplanetary medium. “Complex type III-like events,”which are detected at hectometric wavelengths, high in the corona, and are associated with CMEs, appear to originate from electrons that have been accelerated lower in the corona and not at the bow shock of CMEs. Similarly, impulsive energetic electrons observed in the interplanetary medium are not the exclusive result of electron acceleration at the bow shocks of CMEs; rather they have a coronal origin. Title: Calibration of the Soho/Lasco C3 White Light Coronagraph Authors: Morrill, J. S.; Korendyke, C. M.; Brueckner, G. E.; Giovane, F.; Howard, R. A.; Koomen, M.; Moses, D.; Plunkett, S. P.; Vourlidas, A.; Esfandiari, E.; Rich, N.; Wang, D.; Thernisien, A. F.; Lamy, P.; Llebaria, A.; Biesecker, D.; Michels, D.; Gong, Q.; Andrews, M. Bibcode: 2006SoPh..233..331M Altcode: We present a detailed review of the calibration of the LASCO C3 coronagraph on the SOHO satellite. Most of the calibration has been in place since early in the mission and has been utilized to varying degrees as required by specific analysis efforts. However, using observational data from the nearly decade-long database of LASCO images, we have re-evaluated and improved many aspects of the calibration. This includes the photometric calibration, vignetting function, geometric distortion, stray light, and exposure and observation times. Using this comprehensive set of corrections we have generated and made available a set of calibrated coronal images along with a set of periodic background images to ease the accessibility and use of the LASCO database. Title: Sunspot Gyroresonance Emission at 17 GHz: A Statistical Study Authors: Vourlidas, Angelos; Gary, Dale E.; Shibasaki, Kiyoto Bibcode: 2006PASJ...58...11V Altcode: We investigate the sunspot gyroresonance emission at 17 GHz using the synoptic database of the Nobeyama Radioheliograph. Our statistical study is based on full disk observations obtained during the maximum of Cycle 22 (1992-94). We study the center-to-limb variation of the brightness and polarization of the sunspot radio emission and present some cases of polarization reversal. We find that the radio emission is most likely 3rd-harmonic gyroresonance emission arising from 2000 G fields in transition region, or low corona temperatures. Title: Properties of the Post-CME Current Sheets in Solar Eruptions Authors: Lin, J.; Li, J.; Forbes, T. G.; Ko, Y. -K.; Raymond, J. C.; van Ballegooijen, A. A.; Vourlidas, A. Bibcode: 2006cosp...36..198L Altcode: 2006cosp.meet..198L Solar eruptions constitute the most violent energy release process in the solar system They are are created when magnetic energy is suddenly converted into heat and kinetic energy by magnetic reconnection in a field reversal region or current sheet The effective electrical resistivity eta e of the sheet plasma plays a crucial role in energy conversion Here we present the results for the current sheet thickness d and eta e determined by analyzing a set of unique data for three eruptions observed by the UVCS and the LASCO experiments on SOHO Such a work was never conducted before since it is believed that the current sheet is too thin to be observable The extremely large values of d and eta e obtained in this work suggest that the current sheet in solar eruptions is observable in some circumstances and large-scale turbulence is operating within the current sheet This constitutes a challenging goal for future research on the magnetic energy conversion occurring in both space and laboratory Title: Multi-Wavelength Observations of CMEs and Associated Phenomena Authors: Pick, M.; Forbes, T. G.; Mann, G.; Cane, H. V.; Chen, J.; Ciaravella, A.; Cremades, H.; Howard, R. A.; Hudson, H. S.; Klassen, A.; Klein, K. L.; Lee, M. A.; Linker, J. A.; Maia, D.; Mikic, Z.; Raymond, J. C.; Reiner, M. J.; Simnett, G. M.; Srivastava, N.; Tripathi, D.; Vainio, R.; Vourlidas, A.; Zhang, J.; Zurbuchen, T. H.; Sheeley, N. R.; Marqué, C. Bibcode: 2006cme..book..341P Altcode: This chapter reviews how our knowledge of CMEs and CME-associated phenomena has been improved, since the launch of the SOHO mission, thanks to multi-wavelength analysis. The combination of data obtained from space-based experiments and ground based instruments allows us to follow the space-time development of an event from the bottom of the corona to large distances in the interplanetary medium. Since CMEs originate in the low solar corona, understanding the physical processes that generate them is strongly dependant on coordinated multi-wavelength observations. CMEs display a large diversity in morphology and kinematic properties, but there is presently no statistical evidence that those properties may serve to group them into different classes. When a CME takes place, the coronal magnetic field undergoes restructuring. Much of the current research is focused on understanding how the corona sustains the stresses that allow the magnetic energy to build up and how, later on, this magnetic energy is released during eruptive flares and CMEs. Multiwavelength observations have confirmed that reconnection plays a key role during the development of CMEs. Frequently, CMEs display a rather simple shape, exhibiting a well known three-part structure (bright leading edge, dark cavity and bright knot). These types of events have led to the proposal of the "standard model" of the development of a CME, a model which predicts the formation current sheets. A few recent coronal observations provide some evidence for such sheets. Other more complex events correspond to multiple eruptions taking place on a time scale much shorter than the cadence of coronagraph instruments. They are often associated with large-scale dimming and coronal waves. The exact nature of these waves and the physical link between these different manifestations are not yet elucidated. We also discuss what kind of shocks are produced during a flare or a CME. Several questions remain unanswered. What is the nature of the shocks in the corona (blast-wave or piston-driven?) How they are related to Moreton waves seen in Hα? How they are related to interplanetary shocks? The last section discusses the origin of energetic electrons detected in the corona and in the interplanetary medium. "Complex type III-like events," which are detected at hectometric wavelengths, high in the corona, and are associated with CMEs, appear to originate from electrons that have been accelerated lower in the corona and not at the bow shock of CMEs. Similarly, impulsive energetic electrons observed in the interplanetary medium are not the exclusive result of electron acceleration at the bow shocks of CMEs; rather they have a coronal origin. Title: Coronal Observations of CMEs Authors: Schwenn, R.; Raymond, J. C.; Alexander, D.; Ciaravella, A.; Gopalswamy, N.; Howard, R.; Hudson, H.; Kaufmann, P.; Klassen, A.; Maia, D.; Munoz-Martinez, G.; Pick, M.; Reiner, M.; Srivastava, N.; Tripathi, D.; Vourlidas, A.; Wang, Y. -M.; Zhang, J. Bibcode: 2006cme..book..127S Altcode: CMEs have been observed for over 30 years with a wide variety of instruments. It is now possible to derive detailed and quantitative information on CME morphology, velocity, acceleration and mass. Flares associated with CMEs are observed in X-rays, and several different radio signatures are also seen. Optical and UV spectra of CMEs both on the disk and at the limb provide velocities along the line of sight and diagnostics for temperature, density and composition. From the vast quantity of data we attempt to synthesize the current state of knowledge of the properties of CMEs, along with some specific observed characteristics that illuminate the physical processes occurring during CME eruption. These include the common three-part structures of CMEs, which is generally attributed to compressed material at the leading edge, a low-density magnetic bubble and dense prominence gas. Signatures of shock waves are seen, but the location of these shocks relative to the other structures and the occurrence rate at the heights where Solar Energetic Particles are produced remains controversial. The relationships among CMEs, Moreton waves, EIT waves, and EUV dimming are also cloudy. The close connection between CMEs and flares suggests that magnetic reconnection plays an important role in CME eruption and evolution. We discuss the evidence for reconnection in current sheets from white-light, X-ray, radio and UV observations. Finally, we summarize the requirements for future instrumentation that might answer the outstanding questions and the opportunities that new space-based and ground-based observatories will provide in the future. Title: The SECCHI Experiment on the STEREO Mission Authors: Howard, R.; Moses, D.; Vourlidas, A.; Davila, J.; Lemen, J.; Harrison, R.; Eyles, C.; Defise, J. -M.; Bothmer, V.; Ravet, M. -F.; Secchi Team Bibcode: 2006cosp...36..870H Altcode: 2006cosp.meet..870H The Sun Earth Connection Coronal and Heliospheric Investigation SECCHI on the NASA Solar Terrestrial Relations Observatory STEREO mission is a suite of remote sensing instruments consisting of an extreme ultraviolet EUV imager two white light coronagraphs and two telescopes that comprise the heliospheric imager SECCHI will observe coronal mass ejections CMEs from their birth at the sun through the corona and into the heliosphere A complete instrument suite is being carried on each of the two STEREO spacecraft which will provide the first sampling of a CME from two vantage points The spacecraft will orbit the Sun one Ahead of the Earth and the other Behind each separating from Earth at about 22 degrees per year The varying separation means that we will have different observational capabilities as the spacecraft separate and therefore differing science goals The primary science objectives all are focused on understanding the physics of the CME process - their initiation 3D morphology propagation interaction with the interplanetary medium and space weather effects By observing the CME from multiple viewpoints with UV and coronagraphic telescopes and by combining these observations with radio and in-situ observations from the other instruments on STEREO as well as from other satellites and ground based observatories operating at the same time answers to some of the outstanding questions will be obtained STEREO follows the very successful SOHO mission SOHO s success was primarily due to the highly complementary nature of the instruments but it was Title: A Review of White Light Streamers at the End of Cycle 23 Authors: Vourlidas, Angelos Bibcode: 2006IAUS..233..197V Altcode: This is a brief review of the quiescent large scale visible corona with an emphasis on the origin, structure and role of streamers in the solar wind. The review is mostly based on results from the last 10 years of the SOHO mission and the goal is to provide a coherent picture of what is known about streamers at the end of the current cycle. Title: A Flux-Rope Scaling of CME and Prominence Acceleration Authors: Marque, C.; Chen, J.; Vourlidas, A.; Krall, J.; Schuck, P. Bibcode: 2005AGUFMSH13A0293M Altcode: It has been known that coronal mass ejections (CMEs) and eruptive prominences (EPs) are closely associated with each other. A major question concerning CMEs and EPS is the magnetic geometry that underlies the eruptive plasma structures. It is now well established that many CMEs can be explained as erupting magnetic flux ropes. However, the coronal magnetic field cannot be directly measured at this time, and therefore the flux rope hypothesis has not been confirmed by magnetic field data. A second unresolved question is the structural relationship between the closely associated CMEs and EPs. Recently, it was theoretically found [1] that the height at which a CME or an EP attains maximum acceleration scales with the footpoint separation distance (S_f) of the underlying magnetic flux rope. This scaling law is characteristic of an erupting flux rope and is universal in that it depends only the flux rope geometry and the Lorentz force acting on the structure. It was shown to be well satisfied based on comparison with a small number of CMEs and EPs, indicating that the erupting structures in these events were initially flux ropes or evolved into flux ropes early enough. In the present paper, we present results of a study using a larger sample of events. In this study, we have analyzed CME events detected by LASCO, for which footpoints are determined by observational proxies such as magnetic neutral line length, and EPs seen in Hα and radio data, for which footpoint locations are observable. We find that CMEs and EPs in this large sample also satisfy the flux-rope scaling law. The results are consistent with the model structure with the bright CME rim at Z+2a and the prominence at Z-a, where Z is the height of the centroid and a is the minor radius of the flux rope, both defined at the apex of the flux rope.

1. Chen, J. and J. Krall, JGR, 108 (A11), 2003 Title: Testing the Predictions of the Catastrophe Model: Comparisons with Measurements of LASCO Flux Rope CMEs Authors: Vourlidas, A.; Lin, J. Bibcode: 2005AGUFMSH11C..05V Altcode: The search for the initiation mechanism of coronal mass ejections (CMEs)has led to two classes of models. Those that assume a preexisting magnetic flux rope and those that form such a flux rope during the eruption process. Which of these two classes comes closer to reality can only be found by comparing the model predictions to observed CME properties. Here, we concentrate on the predictions of a preexisting flux rope model (catastrophe model) in Lin et al (2004). Specifically, we compare the evolution of mass, speed and magnetic energy of the CME as predicted in the model to similar measurements/estimates of flux rope CMEs seen by the LASCO coronagraphs. We find interesting similarities between predictions and observations and we discuss the implications for improvements to the model. Ref: Lin, J. et al, ApJ, 602, 422, 2004 Title: Fast coronal mass ejection environments and the production of solar energetic particle events Authors: Kahler, S. W.; Vourlidas, A. Bibcode: 2005JGRA..11012S01K Altcode: The search continues for coronal environmental factors that determine whether a fast coronal mass ejection (CME) results in a solar energetic particle (SEP) event at 1 AU. From a plot of peak 20 MeV SEP intensities versus associated CME speeds we select for comparison two groups of fast, wide, western hemisphere CMEs observed with the LASCO coronagraph from 1998 to 2002. The SEP-rich CME group produced the largest observed SEP events, and the SEP-poor CME group produced the smallest or no observed SEP events. The major differences are that the SEP-rich CMEs are brighter and more likely to be streamer blowouts and to follow colocated CMEs within 12 or 24 hours. The SEP-poor CMEs are fainter and less likely to interact with streamers or to follow preceding colocated CMEs. Thus we confirm the recent result that the SEP event peak intensities are higher when the associated driver CMEs are preceded within a day by wide CMEs at the same locations. However, the enhanced brightness, and therefore mass, of the SEP-rich CMEs appears to be their most dominant characteristic and suggests that either large longitudinal and latitudinal extents or high densities are needed for fast CMEs to produce SEPs. Title: Relationships between CME brightness and in-situ plasma parameters observed at 1 AU Authors: Xie, H.; St. Cyr, C.; Lara, A.; Vourlidas, A. Bibcode: 2005AGUFMSH51C1225X Altcode: In this study, we investigate the relationships between the CME brightness observed by LASCO coronagraphs and the plasma density in the solar wind disturbance region, i.e, the interplanetary shock and the associated interplanetary CME (ICME) region. We derive the excess density and fluxes of mass, momentum and energy of a CME via the brightness of LASCO images, which is proportional to the plasma density of the CME, subtracting a background (a pre-event image) brighness. The excess density and fluxes of the solar wind disturbance was obtained by integrating the in-situ measured excess (above a ambient level) density, momentum, and energy over the duration of the disturbance. We find that there are good correlations between the excess density, and fluxes of mass, momentum and energy of CME in the corona and those in the ICME region. Also, we examine the effects of the CME interaction and thomson scattering on the correlation analysis results. Title: SEP Acceleration Efficiency of CMEs Authors: Howard, R. A.; Vourlidas, A.; Mewaldt, R. E. Bibcode: 2005AGUFMSH14A..02H Altcode: We investigate the efficiency of coronal mass ejections (CMEs) in accelerating solar energetic particles (SEPs) by comparing their respective kinetic energy budgets. Our SEP sample comprises a list of 20-30 well-observed events whose energy spectra are obtained by combining data from multiple in-situ instruments. The corresponding CMEs were observed with the LASCO coronagraphs. Calibrated images were used for the mass and velocity measurements. Because most of these events correspond to fast and extended CMEs, extra care was taken during the measurements to isolate the ejecta from other signatures usually associated with these type of events. The CME masses were corrected to the first order, for projection effects assuming radial propagation from the corresponding source regions. The implications for the acceleration efficiency of CMEs derived from the comparison between CME and SEP energies are discussed. Title: Modelling of CMES for the STEREO Mission Authors: Howard, R. A.; Thernisien, A. F.; Marque, Ch.; Vourlidas, A.; Patel, N. Bibcode: 2005ESASP.592..727H Altcode: 2005soho...16E.147H; 2005ESASP.592E.147H No abstract at ADS Title: Solar Polar Imager: Observing Solar Activity from a New Perspective Authors: Alexander, D.; Sandman, A.; Liewer, P.; Ayon, J.; Goldstein, B.; Murphy, N.; Velli, M.; Floyd, L.; Moses, D.; Socker, D.; Vourlidas, A.; Garbe, G.; Suess, S.; Hassler, D.; Kosovichev, A.; Mewaldt, R.; Neugebauer, M.; Ulrich, R.; Zurbuchen, T. Bibcode: 2005ESASP.592..663A Altcode: 2005soho...16E.131A; 2005ESASP.592E.131A No abstract at ADS Title: How Efficient are Coronal Mass Ejections at Accelerating Solar Energetic Particles? Authors: Mewaldt, R. A.; Cohen, C. M. S.; Mason, G. M.; Haggerty, D. K.; Looper, M. D.; Vourlidas, A.; Desai, M. I.; Giacalone, J.; Labrador, A. W.; Leske, R. A.; Mazur, J. E. Bibcode: 2005ESASP.592...67M Altcode: 2005soho...16E..10M; 2005ESASP.592E..10M No abstract at ADS Title: Coronal mass ejections and other extreme characteristics of the 2003 October-November solar eruptions Authors: Gopalswamy, N.; Yashiro, S.; Liu, Y.; Michalek, G.; Vourlidas, A.; Kaiser, M. L.; Howard, R. A. Bibcode: 2005JGRA..110.9S15G Altcode: 2005JGRA..11009S15G Fast coronal mass ejections (CMEs), X-class flares, solar energetic particle (SEP) events, and interplanetary shocks were abundantly observed during the episode of intense solar activity in late October and early November 2003. Most of the 80 CMEs originated from three active regions (NOAA ARs 484, 486, and 488). We compare the statistical properties of these CMEs with those of the general population of CMEs observed during cycle 23. We find that (1) the 2003 October-November CMEs were fast and wide on the average and hence were very energetic, (2) nearly 20 percent of the ultrafast CMEs (speed ≥2000 km s-1) of cycle 23 occurred during the October-November interval, including the fastest CME of the study period (∼2700 km s-1 on 4 November 2003 at 1954 UT), (3) the rate of full-halo CMEs was nearly four times the average rate during cycle 23, (4) at least sixteen shocks were observed near the Sun, while eight of them were intercepted by spacecraft along the Sun-Earth line, (5) the CMEs were highly geoeffective: the resulting geomagnetic storms were among the most intense of cycle 23, (6) the CMEs were associated with very large SEP events, including the largest event of cycle 23. These extreme properties were commensurate with the size and energy of the associated active regions. This study suggests that the speed of CMEs may not be much higher than ∼3000 km s-1, consistent with the free energy available in active regions. An important practical implication of such a speed limit is that the Sun-Earth travel times of CME-driven shocks may not be less than ∼0.5 day. Two of the shocks arrived at Earth in <24 hours, the first events in ∼30 years and only the 14th and 15th documented cases of such events since 1859. Title: Structure and Organization of the Upper Chromosphere Authors: Korendyke, C. M.; Landi, E.; Vourlidas, A. Bibcode: 2005AGUSMSH12A..05K Altcode: Over its past two flights, the VAULT sounding rocket instrument obtained a series of subarcsecond resolution images of the solar disk. These Lyman alpha images resolve and separate structures in the upper chromosphere. The observed plasmas are concentrated in larger diameter, optically thick loops. The images taken near the limb unambiguously identify the height of the upper chromosphere in the quiet sun. An unexpected level of evolution and activity is present in the "quiet sun" at small spatial scales. The third flight of the payload will investigate the interconnectivity of the observed structures with the photosphere. Title: On the Evolution of CME Mass Authors: Howard, R. A.; Vourlidas, A. Bibcode: 2005AGUSMSH53A..05H Altcode: Calculating the total mass of a CME is a standard technique that has been used for several decades and which SOHO/LASCO has refined and automated. The total mass of a CME is only that material that arises from below the occulting disk. It doesn't consider any mass that has been swept up from within the field of view and moved, since we always consider a "pre-event" coronal state. In this paper we turn to the question of swept up material and investigate the evolution in height of the volume density of the region at the CME front. Often the post-CME corona is "cleaned out", meaning that it is very dim compared to the pre-event and general background. We thus assume that the material has been swept up by the CME expansion through that volume. Can LASCO detect that swept up mass? To investigate this we have selected only events that have a clearly defined leading and trailing edge to the CME front, and which in an ideal sense are examples of the "three-part" CME. We calculated the mass of those LASCO events, which also gives the column electron density. We convert that electron content to a volume density in a narrow region at the center of the front, by approximating the shape as a small section of a sphere. This enables us to say that the depth along the line of sight is the same as the angular latitudinal span, which we take to be on the order of a few degrees. We find that the volume density in such events decreases with increasing height by a simple power law with an exponent of -3. This is exactly what would be expected for purely radial expansion and no pileup of material in the front. We will discuss why the pileup isn't observed by LASCO and where implications for the height origin of these CMEs. We will also discuss the implications for the upcoming STEREO mission. Title: Modeling of the Radio Metric Emission of the Quiet Sun Corona Using Potential Field Source Surface Extrapolations Authors: Marque, C.; Wang, Y.; Thernisien, A. F.; Howard, R. A.; Vourlidas, A. Bibcode: 2005AGUSMSH24A..05M Altcode: We present the result of a modeling of the Quiet Sun corona in the metric radio range (F~150-450 MHz). At these frequencies, the radio emission is dominated by non-thermal emissions (plasma emissions) due to populations of accelerated electrons, and, when the solar activity is low or moderate, by the thermal emission of the corona (bremsstrahlung). While this emission mechanism is well known, depending only on the electron density and temperature, the difficulties arise from the refraction that affects the radio waves propagating in the corona, which depends on the electron density distribution. In order to build a realistic description of the electron and temperature distribution in the corona for a given date, we have used Potential Field Source Surface extrapolations, based on synoptic maps of the photospheric magnetic field. The density and temperature distribution is based on scaling laws which depend on the field strength as well as the length of the loops. We use radio data from the Nancay Radioheliograph to constraint the free parameters of these scaling laws, and make qualitative and quantitative comparisons between the radio images and the simulations. Title: The Mass Properties of Coronal Mass Ejections: Evolution & Statistics Authors: Vourlidas, A.; Howard, R. Bibcode: 2005AGUSMSP44A..04V Altcode: A defining property of a Coronal Mass Ejection (CME) is naturally its mass. The LASCO observations of 1000s of CMEs over the last 8 years allow us to constrain statistically the "typical" CME mass but also to examine its evolution as a function of time during each event. Such work could not be done in the past due to the lower cadence and instrument sensitivity. Our analysis of the CME mass properties has revealed some interesting and maybe unexpected results. For example, close to half of the observed CMEs seem to blend into the background before reaching 30 Rs. In this paper, we will discuss our findings for the LASCO CME sample from 1996 to 2004. Title: Detection and Diagnostics of a Coronal Shock Wave Driven by a Partial-Halo Coronal Mass Ejection on 2000 June 28 Authors: Ciaravella, A.; Raymond, J. C.; Kahler, S. W.; Vourlidas, A.; Li, J. Bibcode: 2005ApJ...621.1121C Altcode: A fast partial-halo coronal mass ejection (CME) was observed on 2000 June 28 by instruments on the SOHO spacecraft. The CME leading edge and filamentary cold core were detected over the northwest limb at 2.32 Rsolar by the SOHO UV Coronagraph Spectrometer (UVCS). The broad profile of the O VI λ1032 line gives evidence of a shock front at the leading edge, supporting the identification of white-light CME sharp leading edges as fast-mode shocks. Line-of-sight speeds are as high as 1500 km s-1, comparable to the projected speed obtained from LASCO. Pumping of the O VI λ1032 by Lyβ (v=1810 km s-1) and of O VI λ1037 by O VI λ1032 (v=1648 km s-1) were detected, which provide diagnostics of outflow speed and density. The angle of the ejecta with the plane of the sky is obtained, combining the projected speed from LASCO with the line-of sight-speed, and varies between 7° and 46°. In the latter case the projected height of 2.32 Rsolar was at an actual heliocentric distance of 3.6 Rsolar. An associated solar energetic particle (SEP) event was observed at the L1 point following this CME. The abundance and charge-state data are consistent with a gradual shock-accelerated SEP event. A type II radio burst was observed at the same time the shock front was detected by UVCS. Title: Energetics of Coronal Mass Ejections Authors: Subramanian, Prasad; Vourlidas, Angelos Bibcode: 2005IAUS..226..314S Altcode: 2005astro.ph..2057S We examine the energetics of the best examples of flux-rope CMEs observed by LASCO in 1996-2001. We find that 69% of the CMEs in our sample experience a driving power in the LASCO field of view. For these CMEs which are driven, we examine if they might be deriving most of their driving energy by coupling to the solar wind. We do not find conclusive evidence to support this hypothesis. We adopt two different methods to estimate the energy that can possibly be released by the internal magnetic fields of the CMEs. We find that the internal magnetic fields are a viable source of driving power for these CMEs. Title: What Fraction of the Kinetic Energy of Coronal Mass Ejections goes into Accelerating Solar Energetic Particles? Authors: Mewaldt, R. A.; Cohen, C. M. S.; Mason, G. M.; Haggety, D. K.; Looper, M. D.; Vourlidas, A.; Desai, M. I.; Giacalone, J.; Labrador, A. W.; Leske, R. A.; Mazur, J. E. Bibcode: 2005ICRC....1..129M Altcode: 2005ICRC...29a.129M No abstract at ADS Title: Error Estimates in the Measurements of Mass and Energy in White Light CMEs Authors: Vourlidas, Angelos Bibcode: 2005IAUS..226...76V Altcode: Due to the optically thin nature of the white light emission, all measurements of the energetics and dynamics of a CME are based on sky-plane projected quantities. The extent and distribution of the CME material along the line of sight is unknown. Thus, CME measurements have an inherent degree of uncertainty. In this paper, I identify the various (possible) sources of errors associated with measurements of CME mass and energy (e.g., instrumental, random, projections effects, etc) and give an error budget for the final measurements. I apply these errors to the statistics of mass and energy for several thousand CMEs observed with LASCO in 1996-2003. Title: Calibration Results for the STEREO/SECCHI COR2 Coronagraphs Authors: Vourlidas, A.; Plunkett, S.; Korendyke, C.; Gong, Q.; Socker, D.; Howard, R. Bibcode: 2004AGUFMSH21B0409V Altcode: The two SECCHI instrument suites aboard the upcoming STEREO mission include the COR2 coronagraphs which observe the middle/outer corona; namely, from 2.5 to 15 solar radii. As of the end of August 2004, both COR2 instruments have been assembled and delivered to the SECCHI project and their perfomance has been measured and analyzed. The coronagraphs have met (and in some cases, exceeded) their performance requirements. Here, we present in detail the results of the calibration (photometry, polarization, stray light levels, etc) of the COR2 coronagraphs. We compare these new coronagraphs to the LASCO ones and discuss how they will contribute to the scientific success of the STEREO mission. Title: Planetary Auroral Storms Trace a CME-driven Interplanetary Shock Throughout the Solar System, from the Sun to Saturn at 9 AU Authors: Prange, R.; Pallier, L.; Hansen, K. C.; Howard, R.; Vourlidas, A.; Courtin, R.; Parkinson, C. Bibcode: 2004AGUFM.P51A1419P Altcode: Hubble Space Telescope FUV images taken in December 2000 revealed for the first time au auroral storm on Saturn. The Sun, the Earth, Jupiter and Saturn were practically aligned at that time, allowing the solar wind plasma to flow by all three planets successively within ~1 month. Observations of Jupiter coordinated with Cassini measurements in the nearby solar wind were also executed during this period. Using a recently developped MHD code and solar wind measurements in the Earth vicinity, we establish that (1) the strong auroral event on Saturn was related to the interaction of an interplanetary shock with its magnetosphere, (2) this shock was initiated by a series of CMEs on the Sun observed by SOHO. We follow the propagation of the shock throughout the solar system, from the Earth where auroral storms are recorded, to Jupiter where the auroral activity is strongly enhanced, and to Saturn where it ultimately activates the observed unusual polar source. This is the first report of consecutive auroral responses to a propagating interplanetary shock. It indicates that shocks retain their properties and their ability to trigger planetary auroral activity thoughout the solar system, thereby unifying our understanding of solar-planetary interactions. We discuss also the similarities and differences observed between the planetary auroral responses. Title: Modeling of CME Visibility for the STEREO Mission Authors: Howard, R. A.; Patel, N. S.; Thernisien, A.; Marque, C.; Vourlidas, A. Bibcode: 2004AGUFMSH21D..06H Altcode: One of the objectives of the STEREO mission is to determine the three-dimensional configuration of CMEs. The STEREO mission consists of two identical spacecraft, one leading Earth and the other trailing Earth, which will separate from each other at the rate of about 45 degrees per year. To understand the visibility of CMEs and the ability to discern the 3D structure, we have been developing a "forward modeling" capability (RAYTRACE) described in another paper at this meeting. This capability complements the inversion technique we have also been developing. Using RAYTRACE we may compute synthetic total and polarized brightness images using the Thomson scattering formulae from an assumed electron density model. Several (geometric) models of a CME have been defined - loop, spherical shell, cylindrical shell and a graduated cylindrical shell (GCS). Since the GCS model is a reasonable simulation of a flux-rope CME, we have used it to investigate the appearance of a CME as a function of STEREO separation angle. In this model the angular size in the two directions, the height of the leading edge, the orientation of the structure in the corona and the radial electron density distribution can be specified. We present the results of this study and compare the simulations with observed CMEs from LASCO. Title: Modelling of the Quiet Sun Emission in the Metric Radio Range Authors: Marque, C.; Wang, Y.; Thernisien, A. F.; Howard, R. A.; Vourlidas, A.; Patel, N. S. Bibcode: 2004AGUFMSH21B0424M Altcode: The thermal emission from the Quiet Sun can be mapped in the metric radio range when the solar activity is low, and plasma emissions due to non-maxwellian distributions of electrons are weak or non-existent. This occurs mainly in the vicinity of the solar cycle minimum. Metric radio observations have been used in the past to infer the mean coronal temperature, and to map and study large scale coronal structures. Earlier simulations using symmetrical electron density distributions and uniform temperatures were succesful to depict some of the properties of the Quiet Sun emission but are not suitable in detailed comparisons with observations, and furthermore, they predict limb brightening in the high frequency range of the metric domain (150-450 MHz), which has not been observed so far. In this paper, we present simulations of the Quiet Sun emission based on Potential Field Source Surface extrapolations, which are used to build a global density and temperature model of the corona at a given date. Scaling laws involving the loop footpoint field strength and loop length govern the density and temperature distribution in this model. Synthetic radio images are then computed using raytracing techniques, taking into account the refraction of radio waves in the corona, and are compared with actual observations provided by the Nancay Radioheliograph. Title: Raytracing Software for the Simulation of the Solar K-Corona Authors: Thernisien, A. F.; Patel, N. S.; Howard, R. A.; Marqué, C.; Vourlidas, A. Bibcode: 2004AGUFMSH21B0404T Altcode: In this talk we will present RAYTRACE, a raytracing software developed at the U.S. Naval Research Laboratory. The program is an implementation of the Thomson scattering equations applied to the solar corona (Billings 1966). Synthetic coronal images in total or polarized brightness can be calculated using models of various coronal structures. We have implemented many models for quiescent and dynamic coronal stuctures such as streamers, the heliospheric current sheet (HCS), jets and CMEs. The models are generally analytic representations of the volume electron density, but a generic data cube of electron density can also be used. The core of the program has been written in C++ pimarily for computation speed. An earlier version was written in IDL, but was quite slow. Due to the processing speed of common computers, a high resolution image (512 x 512) of the HCS streamer belt for instance can be generated in less than 1 minute (Pentium 4, 2.5 GHz, 512 Mb RAM, Linux OS). A graphical user interface has been developed in IDL and allows the user to easily enter the parameters required for each model, specifying the position and orientation of the observer and structure, the size and resolution of the images, and then to visualize the output and compare the results to actual coronal images obtained by SOHO/LASCO and in the future by the STEREO/SECCHI coronagraphs (COR1 and COR2). Some of the main features of the front-end interface include mesh plot positioning of structures in space, parameter tuning for the structures and movie making. Different studies have already been done using this software, such as the inversion of the electron density of the streamer belt or the modeling of CMEs for the STEREO mission (presented in another paper at this meeting). Title: An interplanetary shock traced by planetary auroral storms from the Sun to Saturn Authors: Prangé, Renée; Pallier, Laurent; Hansen, Kenneth C.; Howard, Russ; Vourlidas, Angelos; Courtin, Régis; Parkinson, Chris Bibcode: 2004Natur.432...78P Altcode: A relationship between solar activity and aurorae on Earth was postulated long before space probes directly detected plasma propagating outwards from the Sun. Violent solar eruption events trigger interplanetary shocks that compress Earth's magnetosphere, leading to increased energetic particle precipitation into the ionosphere and subsequent auroral storms. Monitoring shocks is now part of the `Space Weather' forecast programme aimed at predicting solar-activity-related environmental hazards. The outer planets also experience aurorae, and here we report the discovery of a strong transient polar emission on Saturn, tentatively attributed to the passage of an interplanetary shock-and ultimately to a series of solar coronal mass ejection (CME) events. We could trace the shock-triggered events from Earth, where auroral storms were recorded, to Jupiter, where the auroral activity was strongly enhanced, and to Saturn, where it activated the unusual polar source. This establishes that shocks retain their properties and their ability to trigger planetary auroral activity thoughout the Solar System. Our results also reveal differences in the planetary auroral responses on the passing shock, especially in their latitudinal and local time dependences. Title: Energy partition in two solar flare/CME events Authors: Emslie, A. G.; Kucharek, H.; Dennis, B. R.; Gopalswamy, N.; Holman, G. D.; Share, G. H.; Vourlidas, A.; Forbes, T. G.; Gallagher, P. T.; Mason, G. M.; Metcalf, T. R.; Mewaldt, R. A.; Murphy, R. J.; Schwartz, R. A.; Zurbuchen, T. H. Bibcode: 2004JGRA..10910104E Altcode: Using coordinated observations from instruments on the Advanced Composition Explorer (ACE), the Solar and Heliospheric Observatory (SOHO), and the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we have evaluated the energetics of two well-observed flare/CME events on 21 April 2002 and 23 July 2002. For each event, we have estimated the energy contents (and the likely uncertainties) of (1) the coronal mass ejection, (2) the thermal plasma at the Sun, (3) the hard X-ray producing accelerated electrons, (4) the gamma-ray producing ions, and (5) the solar energetic particles. The results are assimilated and discussed relative to the probable amount of nonpotential magnetic energy available in a large active region. Title: Radio Observations of Coronal Mass Ejection4 Authors: Vourlidas, Angelos Bibcode: 2004ASSL..314..223V Altcode: In this chapter we review the status of CME observations in radio wavelengths with an emphasis on imaging. It is an area of renewed interest since 1996 due to the upgrade of the Nançay Radioheliograph in conjunction with the continuous coverage of the solar corona from the EIT and LASCO instruments aboard SOHO. Also covered are analyses of Nobeyama Radioheliograph data and spectral data from a plethora of spectrographs around the world. We will point out the shortcomings of the current instrumentation and the ways that FASR could contribute. A summary of the current understanding of the physical processes that are involved in the radio emission from CMEs is be given. Title: Electron Density Inversion and Modeling of a streamer using EIT-LASCO Data of January 2004 Authors: Thernisien, A. F.; Howard, R. A.; Marqué, Ch.; Vourlidas, A. Bibcode: 2004AAS...204.7101T Altcode: 2004BAAS...36Q.797T We present in this poster the electron density characterisation of a streamer observed by LASCO under 2 different angles of view. At the end of January 2004, due to a favorable configuration of the Solar corona, we are able to observe a streamer, first, from the side, and then, 7 days later, from the face. Using electron density inversion technics we have determined the density profiles characterising the lenght and the thickness of the streamer. Those density profiles were then used to refine a 3D model of a streamer that is compared to LASCO observations using ray tracing technics. Title: Mass and Kinetic Energy Distributions of Coronal Mass Ejections in 1996-2002 Authors: Vourlidas, A.; Patsourakos, S. Bibcode: 2004AAS...204.7303V Altcode: 2004BAAS...36..800V We present the mass and kinetic energy distributions of coronal mass ejections observed by LASCO between 1996 and 2002. The sample includes more than 4000 events. Events with projected widths larger than 120 deg were excluded because of uncertainties in the calculation of the mass and speed for such large events.

We compare the LASCO mass and energy distribution to similar distributions from Solwind and soft x-ray flares. In particular, we find that the CME kinetic energy distribution follows a power law similar to the one found for solar flares. The implications of our findings are discussed in the paper. Title: Simulations of the Quiet Sun Emission at Metric and Decimetric Radio Wavelengths Authors: Marqué, C.; Wang, Y. M.; Thernisien, A. F.; Vourlidas, A.; Howard, R. A. Bibcode: 2004AAS...204.7104M Altcode: 2004BAAS...36Q.797M In the metric and decimetric radio range, solar emission is dominated by non-thermal radiation from electron populations accelerated during flares or continuous processes. When the solar activity is low, mainly during the solar cycle minimum, the thermal emission from the corona can be mapped, and structures such as coronal holes, active regions or filament cavities can be observed. The radio thermal emission is sensitive to the electron density and temperature, and radio rays suffer refraction effects when their frequency is close to the local plasma frequency. A model of the electron density and temperature distribution is thus needed to compute the thermal radiation at a given frequency. Axisymetric and homogeneous electron density models have been successfully used for the last fourty years to described the basic properties of this thermal emission. Nevertheless, these density models are not suitable for describing the corona at a given date.

We present in this poster more realistic simulations using a Potential Field Source Surface extrapolation and realistic electron density distributions. Assuming hydrostatic equilibrium, the density is determined by the strength of the magnetic field and the length of the magnetic loops: n=n0(B,L)*f(r). Different n0 and f functions are used and the corresponding results are compared to real data. Title: Coronal Mass Ejections When the Sun Went Wild Authors: Gopalswamy, N.; Yashiro, S.; Vourlidas, A.; Lara, A.; Stenborg, G.; Kaiser, M. L.; Howard, R. A. Bibcode: 2004AAS...204.4709G Altcode: 2004BAAS...36..738G The Large Angle and Spectrometric Coronagraph (LASCO) on board SOHO detected more than five dozen CMEs from three active regions (NOAA ARs 0484, 0486, and 0488) during the October-November 2003 super storms. The CMEs were accompanied by X-class flares, solar energetic particles, and interplanetary shocks. We compare the statistical properties of these super-storm CMEs with those of the general population of CMEs observed during cycle 23. We find that (i) the super-storm CMEs are faster and wider than average, and hence possess enormous energy, (ii) nearly 20 percent of the ultra-fast CMEs (speed > 2000 km/s) occurred during the October-November interval, including the fastest CME of cycle 23 (2700 km/s), and (iii) the rate of full-halo CMEs was nearly four times the average rate during cycle 23. As expected, many of these CMEs were driving shocks near the Sun as inferred from the Wind/WAVES radio data and at least eight of them impacted Earth. These strong shocks accelerated solar energetic particles, which remained at hazardous levels for many days. We discuss the implications of these extreme properties of CMEs for the solar energy source. Title: Coronal Mass Ejection Masses From CMEs Identified in Interplanetary Scintillation (IPS) Tomography and LASCO Coronagraph Images Authors: Rappoport, S. A.; Jackson, B. V.; Hick, P. P.; Buffington, A.; Vourlidas, A. Bibcode: 2004AAS...204.3802R Altcode: 2004BAAS...36..712R To optimize the information from individual radio source observations of the sky covering large elongations, we have developed a Computer-Assisted Tomography (CAT) program. We fit STELab (Nagoya University, Japan) interplanetary scintillation (IPS) observations to a time-dependent, three-dimensional heliospheric model. These observations allow us to create "sky maps" covering 10 to 80 degrees in elongation, in which we can track CMEs observed earlier in LASCO coronagraph images. These events have approximately the same shapes and extents as observed closer to the Sun. Here we map several CMEs in 3-dimensions as they move outward to 1 AU. Masses for each of the events are determined from the reconstruction analysis and are compared with plane of the sky masses obtained from calibrated LASCO coronagraph images. Title: A Study of the Kinematic Evolution of Coronal Mass Ejections Authors: Zhang, J.; Dere, K. P.; Howard, R. A.; Vourlidas, A. Bibcode: 2004ApJ...604..420Z Altcode: We report the kinematic properties of a set of three coronal mass ejections (CMEs) observed with the LASCO (Large Angle and Spectrometric Coronagraph) on the Solar and Heliospheric Observatory (SOHO) spacecraft, which showed characteristics of impulsive, intermediate, and gradual acceleration, respectively. The first CME had a 30 minute long fast acceleration phase during which the average acceleration was about 308 m s-2 this acceleration took place over a distance of about 3.3 Rsolar (from 1.3 to 4.6 Rsolar, height measured from disk center). The CME characterized by intermediate acceleration had a long acceleration phase of about 160 minutes during which the average acceleration was about 131 m s-2 the CME traveled a distance of at least 4.3 Rsolar, reaching a height of 7.0 Rsolar at the end of the acceleration phase. The CME characterized by gradual acceleration had no fast acceleration phase. Instead, it displayed a persistent weak acceleration lasting more than 24 hr with an average acceleration of only 4.0 m s-2 throughout the LASCO field of view (from 1.1 to 30 Rsolar). This study demonstrates that the final velocity of a CME is determined by a combination of acceleration magnitude and acceleration duration, both of which can vary significantly from event to event. The first two CME events were associated with soft X-ray flares. We found that in the acceleration phase there was close temporal correlation both between the CME velocity and the soft X-ray flux of the flare and between the CME acceleration and derivative of the X-ray flux. These correlations indicate that the CME large-scale acceleration and the flare particle acceleration are strongly coupled physical phenomena occurring in the corona. Title: Solar Physics from Space for the Next Solar Cycle Authors: Vourlidas, Angelos; Patsourakos, Spiros Bibcode: 2004hell.conf...78V Altcode: No abstract at ADS Title: Masses and Energetics of CMEs Observed by SOHO/LASCO Authors: Howard, R. A.; Morrill, J.; Vourlidas, A.; Buzasi, D.; Esfandiari, E.; Rich, N.; Thernisien, A. Bibcode: 2003AGUFMSH41B0460H Altcode: The LASCO data base contains over 5000 CMEs, observed from 1996-2001. We have developed an automated procedure to calibrate the associated LASCO images and to calculate the CME properties. Of the total number of CMEs, we have been able to calculate the mass and energetics of about 80% of the total number of events. Here we report on the analysis of the mass and energy properties of over 3000 CMEs and compare them to previous observations of CMEs. Title: Direct Detection of a Coronal Mass Ejection-Associated Shock in Large Angle and Spectrometric Coronagraph Experiment White-Light Images Authors: Vourlidas, A.; Wu, S. T.; Wang, A. H.; Subramanian, P.; Howard, R. A. Bibcode: 2003ApJ...598.1392V Altcode: 2003astro.ph..8367V The Large Angle and Spectrometric Coronagraph Experiment (LASCO) C2 and C3 coronagraphs recorded a unique coronal mass ejection (CME) on 1999 April 2. The event did not have the typical three-part CME structure and involved a small-filament eruption without any visible overlying streamer ejecta. The event exhibited an unusually clear signature of a wave propagating at the CME flanks. The speed and density of the CME front and flanks were consistent with the existence of a shock. To better establish the nature of the white-light wave signature, we employed a simple MHD simulation using the LASCO measurements as constraints. Both the measurements and the simulation strongly suggest that the white-light feature is the density enhancement from a fast-mode MHD shock. In addition, the LASCO images clearly show streamers being deflected when the shock impinges on them. It is the first direct imaging of this interaction. Title: Comparisons Between Noise Storm Emissions and CME Events Authors: Marque, C.; Vourlidas, A. Bibcode: 2003AGUFMSH21B0119M Altcode: In this poster, we present preliminary comparisons between noise storm emissions and CME occurrences as observed with the Nançay Radioheliograph and the LASCO coronagraph on board SOHO. We looked for modifications of the noise storm parameters (flux) and possible appearances or disappearances temporarily associated with CME initiation and propagation in the low corona. On-disk EUV images have also been used to locate the area where the CMEs were originating from. Title: LASCO C2 and C3 Level-1 Images: Calibration and Pipeline Processing Authors: Thernisien, A. F.; Morrill, J.; Llebaria, A.; Rich, N.; Vourlidas, A.; Esfandiari, E.; Wang, D.; Korendyke, C.; Moses, D.; Biesecker, D.; Bout, M.; Lamy, P.; Howard, R. A. Bibcode: 2003AGUFMSH41B0461T Altcode: The LASCO C2 and C3 coronagraphs have provided coronal observations since May, 1996. Initial calibrations have been available during most of this time period. We have subsequently completed a re-evaluation and refinement of these calibration procedures. We are now able to present the final version of the level-1 data using the latest improvements from in-flight calibration results. Further details on the LASCO calibration and level-1 data access are presented at http://lasco-www.nrl.navy.mil/level_1/lascocal_index.html. In this presentation we will sum up the different aspects of the LASCO C2-C3 image corrections such as vignetting, absolute photometry, time corrections, geometric distortion, sun center position, and spacecraft orientation. Title: Physical Parameters of the 2000 February 11 Coronal Mass Ejection: Ultraviolet Spectra versus White-Light Images Authors: Ciaravella, A.; Raymond, J. C.; van Ballegooijen, A.; Strachan, L.; Vourlidas, A.; Li, J.; Chen, J.; Panasyuk, A. Bibcode: 2003ApJ...597.1118C Altcode: We present spectra of a three-part coronal mass ejection (CME) observed by the Ultraviolet Coronagraph Spectrometer aboard SOHO on 2000 February 11. Images of the CME in different spectral lines show how the morphology depends on the temperature, density, and outflow speed of the ejected plasma. The H I Lyα is the line that best resembles the white-light data, although it can be rather different where the outflow speed severely dims its radiative component. We estimate the ranges of temperature and density in the front, prominence core, and void. We also estimate the outflow speed that is the true speed of the ejecta as obtained from the Doppler dimming technique, its component projected on the plane of the sky, and the line-of-sight speed for the three components of the CME. The plasma in the front was denser, cooler, and more depleted in O and Si than the ambient coronal streamer. These characteristics indicate that it originated in the closed field core of the pre-CME streamer. The leading edge was not the projection of a simple spherical shell onto the plane of the sky. The line profiles suggest a wide looplike structure, although a more complete shell that was brighter in some areas could also match the data. The prominence has a structure in temperature and density with the hotter top end emitting in the Mg X and Si XII lines while the bottom end was much cooler and visible only in the H I Lyman lines. Emission in the void was rather faint. The outflow speed obtained from Doppler dimming of the radiative lines, the line-of-sight speed measured from the Doppler shift of the lines, and the plane-of-the-sky speed estimated from the comparison of the images taken at 2.3 and 2.6 Rsolar give speeds much lower than those estimated at greater heights (>4 Rsolar) from LASCO and indicate a stronger acceleration at lower heights. Title: Constraints on Coronal Mass Ejection Dynamics from Simultaneous Radio and White-Light Observations Authors: Reiner, M. J.; Vourlidas, A.; Cyr, O. C. St.; Burkepile, J. T.; Howard, R. A.; Kaiser, M. L.; Prestage, N. P.; Bougeret, J. -L. Bibcode: 2003ApJ...590..533R Altcode: Simultaneous radio and white-light observations are used to deduce information on the dynamics of two coronal mass ejection (CME) events that occurred about 2 hr apart on 2001 January 20 and that were associated with eruptions from the same active region on the Sun. The analysis combines both space-based and ground-based data. The radio data were obtained from the WAVES experiment on the Wind spacecraft and from the Culgoora radiospectrograph in Australia. The white-light data were from the LASCO experiment on SOHO and from the Mk4 coronameter at the Mauna Loa Solar Observatory. For these CME events we demonstrate that the frequency drift rate of the type II radio emissions, generated by the shocks driven by the white-light CMEs, are consistent with the plane-of-sky height-time measurements, provided that the propagation direction of the CMEs and their associated radio sources was along a radial line from the Sun at a solar longitude of ~E50°. These results imply that the ``true'' CME speeds were estimated to be ~1.4 times higher than the measured plane-of-sky speeds and that the CMEs originated from solar eruptions centered near E50°. This CME origin is consistent with the known active region and flare site associated with these two CME events. Furthermore, we argue that the type II radio emissions generated by these CMEs must have originated in enhanced density regions of the corona. We investigate whether the type II radiation could have originated in one or more dense coronal streamers, whose densities were estimated from the polarization brightness measurements made by LASCO at that time. Finally, we use these radio and white-light observations to speculate about the dynamics and scales involved in the interaction between these two CMEs. Title: Filament Eruptions in the Metric Radio Range Authors: Marqué, Ch.; Vourlidas, A. Bibcode: 2003SPD....34.2302M Altcode: 2003BAAS...35R.851M The aim of this paper is to show that metric radio diagnostics can be used to study the motion and behavior of eruptive filaments from the site of the eruption up to the coronagraphic field of view, allowing a complete coverage of these events at medium and high altitudes.

I will illustrate this with an example of a filament eruption that occurred on May 27th 2002 ansd I will discuss the radio observations in terms of interaction with coronal structures and filament cavity detection.

Ch. Marqué is funded by a NASA contract to NRL. Title: High-Resolution Views of the Solar Atmosphere Authors: Vourlidas, A.; Korendyke, C. Bibcode: 2003SPD....34.2009V Altcode: 2003BAAS...35..845V The study of many of the outstanding phenomena of the solar atmosphere (coronal heating, flares and coronal mass ejection) has persistently shown that observations of physical processes at ever smaller scales are needed for their understanding. Here I report on the results from the latest NRL sounding rocket payload, the Very Advanced ULtraviolet Telescope (VAULT). In two successful flights, the instrument achieved 0.33 arcsecond resolution, the highest ever from a space platform. VAULT obtained spectrally pure images of the upper chromosphere/lower transition region in the Lya line (1216A). A number of space-borne and ground-based obsrvatories supported the VAULT flights. The first results from the analysis of these datasets will be presented. Title: Why was there no Solar Energetic Particle Event Associated with the Gamma-ray-line Flare of 2002 July 23? Authors: Gopalswamy, N.; Dennis, B. R.; Kaiser, M. L.; Krucker, S.; Lin, R. P.; Vourlidas, A. Bibcode: 2003SPD....34.2202G Altcode: 2003BAAS...35..850G We investigated the coronal and interplanetary (IP) events associated with two X-class flares on 2002 July 20 and 23. Both flares were associated with ultra-fast (>2000 km s-1) coronal mass ejections (CMEs) and IP shocks. We use white-light, EUV, hard X-ray and radio observations to trace the origin of the CMEs to active region 0039 located close to the east limb. The July 20 flare was partly occulted by the east limb, yet it resulted in a major solar energetic particle event with intensity ∼ 20 pfu in the >10 MeV channel (1 pfu = 1 particle per (cm2 s sr MeV)). The July 23 event was the first gamma-ray-line flare detected by RHESSI, but it did not show any enhancement in SEPs above the elevated background from the July 20 event. We identified two distinguishing factors between the July 2 and July 23 CMEs: (1) The July 20 CME had a higher kinetic energy, and (2) The July 20 CME was interacting with another fast CME (1350 km s-1) that preceded by less than an hour from the same region; there were also two other CMEs on July 19 from the same region. Thus the coronal and IP environment of the July 20 event was highly disturbed due to preceding CMEs (as compared to the July 23 event). We suggest that the different coronal/IP environments may be responsible for the lack of SEP event associated with the July 23 event. Title: Mass and energy properties of LASCO CMEs Authors: Vourlidas, A.; Buzasi, D.; Howard, R. A.; Esfandiari, E. Bibcode: 2002ESASP.506...91V Altcode: 2002svco.conf...91V; 2002ESPM...10...91V We present measurements of the dynamical (mass, potential energy) and kinetic (speed, kinetic energy) properties of coronal mass ejections (CMEs). The sample includes the majority of white light CMEs observed between 1996-2000. In particular, we investigate the mass and energy distributions of CMEs and compare it to similar analyses from past coronagraphs. Title: Observations of CMEs in the Rising and Declining Phases of Solar Cycle 23 Authors: Howard, R. A.; Plunkett, S. P.; St. Cyr, O. C.; Vourlidas, A. Bibcode: 2002AGUSMSH41A..02H Altcode: The most complete observations of CMEs throughout a solar cycle, previously, were conducted from 1979 through 1989 using a combination of the P78-1/Solwind and SMM coronagraphs. Aside from the variation in the occurrence rate of CMEs throughout the cycle, perhaps the most interesting effect of the solar cycle was the occurrence of CMEs in the outer corona along the magnetic neutral line. The LASCO experiment on the SOHO satellite has been observing the solar corona since the start of cycle 23, except for a brief 4-month hiatus in 1998. The new observations have several important improvements over the previous ones - increased sensitivity, increased spatial coverage and continuous solar viewing. In this paper, we examine the nature of CME observations during the rising and declining phases to determine if there is a difference between the CMEs that occur during these two phases. Title: Calibration of the LASCO C3 Coronal Images Authors: Morrill, J.; Biesecker, D.; Esfandiari, A.; Korendyke, C.; Moses, D.; Rich, N.; Vourlidas, A.; Wang, D.; Howard, R. A.; Lamy, P.; Llebaria, A.; Thernisien, A. Bibcode: 2002AAS...200.5503M Altcode: 2002BAAS...34R.732M The LASCO C3 coronagraph has provided coronal observations since May, 1996. Preliminary calibrations have been available during most of this time period. However, some aspects of the calibration have required re-evaluation and we are just completing a complete review of the calibration procedure for these images. In this presentation we will discuss the steps required to correct LASCO C3 images. This includes corrections required by both optical and electrical characteristics of the instrument as well as timimg and spacecraft pointing driven correctons. Title: Radio Signatures of Coronal Mass Ejections Authors: Vourlidas, A. Bibcode: 2002AAS...200.4906V Altcode: 2002BAAS...34..722V The SOHO mission and in particular the LASCO/EIT imaging of the near-Sun enviroment brought the study of coronal mass ejections (CMEs) to the forefront of solar physics research. Solar radiophysics, especially in low frequencies have benefited from the renewed interest on outer corona events and the availability of new or renovated radio instruments both in space and on the ground. Now spectrometric and imaging observations of CMEs and related phenomena are routinely available and their analysis has begun to contribute important insights to the physics of CMEs. In this paper, I review the significant amount of radio CME work that has accumulated since the beggining of the current solar cycle and outline the ways in which radio coronal observations could become even more important in the future. Title: Solar energetic electron events and coronal shocks Authors: Klassen, A.; Bothmer, V.; Mann, G.; Reiner, M. J.; Krucker, S.; Vourlidas, A.; Kunow, H. Bibcode: 2002A&A...385.1078K Altcode: Mildly relativistic electrons appear during the solar energetic particle events. A detailed investigation on the origin of such electrons is presented for four particlular solar events. The mildly relativistic electrons have been detected at energies of 0.25-0.7 MeV by COSTEP/SOHO and below 0.392 MeV by Wind 3-DP experiments. Coronal shocks associated with these electron events are identified from the metric-to-decametric solar type II radio bursts. All selected events were associated with solar activity at western longitudes, so that the magnetic footpoints connecting the spacecraft with the Sun were close to the flare/shock/CME site. The associated type II bursts were accompanied by so-called shock accelerated (SA) type III bursts appearing to be emerging from the type II emission site. We found: (1) that all of the 0.25-0.7 MeV electron events were released during or after, but never simultaneously with the onset of type II bursts and CMEs. The time delay between the type II burst onset and the release of the mildly relativistic electrons is in the range of 11.5-45 min; (2) that the mildly relativistic electrons were released rather at the end of SA type III bursts or somewhat later; (3) that the mildly relativistic electrons were released when the associated type II burst and the CME reached a certain height (h ~ 1-4 R_s) above the photosphere. For the four events studied, it is concluded that mildly relativistic electrons at 0.25-0.7 MeV energies measured in the interplanetary medium from solar energetic particle events are accelerated by coronal shock waves, commonly in association with white-light CMEs. Title: Solar Phenomena Associated with ``EIT Waves'' Authors: Biesecker, D. A.; Myers, D. C.; Thompson, B. J.; Hammer, D. M.; Vourlidas, A. Bibcode: 2002ApJ...569.1009B Altcode: In an effort to understand what an ``EIT wave'' is and what its causes are, we have looked for correlations between the initiation of EIT waves and the occurrence of other solar phenomena. An EIT wave is a coronal disturbance, typically appearing as a diffuse brightening propagating across the Sun. A catalog of EIT waves, covering the period from 1997 March through 1998 June, was used in this study. For each EIT wave, the catalog gives the heliographic location and a rating for each wave, where the rating is determined by the reliability of the observations. Since EIT waves are transient, coronal phenomena, we have looked for correlations with other transient, coronal phenomena: X-ray flares, coronal mass ejections (CMEs), and metric type II radio bursts. An unambiguous correlation between EIT waves and CMEs has been found. The correlation of EIT waves with flares is significantly weaker, and EIT waves frequently are not accompanied by radio bursts. To search for trends in the data, proxies for each of these transient phenomena are examined. We also use the accumulated data to show the robustness of the catalog and to reveal biases that must be accounted for in this study. Title: Analysis of Lasco Observations of Streamer Blowout Events Authors: Vourlidas, A.; Howard, R. A.; Morrill, J. S.; Munz, S. Bibcode: 2002stma.conf..201V Altcode: No abstract at ADS Title: On the Correlation between Coronal and Lower Transition Region Structures at Arcsecond Scales Authors: Vourlidas, A.; Klimchuk, J. A.; Korendyke, C. M.; Tarbell, T. D.; Handy, B. N. Bibcode: 2001ApJ...563..374V Altcode: We compare the morphology of active region structures observed in the 171 Å (T~9×105 K) and Lyα (T~2×104 K) lines. The coronal data were obtained by the Transition Region and Coronal Explorer (TRACE) in support of the Very High Angular Resolution Ultraviolet Telescope (VAULT) sounding rocket launch, which acquired subarcsecond resolution images of an active region in the Lyα line, on 1999 May 7. Using a pair of calibrated, nearly simultaneous images, we find that: (i) a very good correlation exists between the Lyα and 171 Å intensities in the TRACE moss regions, (ii) we can identify several identical structures in some (but not all) moss areas, and (iii) the correlations are greatly reduced at the footpoints of the 171 Å large-scale loops. We derive a lower limit for the Lyα emission measure, under the assumption of effectively optically thin emission, and compare it to the 171 Å emission measure. As in previous studies, we find an excess of Lyα material compared to the amount expected for a thermal conduction-dominated corona-chromosphere transition region, even for structures that appear to be identical in the two wavelengths. This result implies that some other mechanism besides classical heat conduction from the corona must contribute to the observed Lyα intensities. The observations do not support the idea of a physically distinct cool loop component within active regions. Title: Statistical analysis of coronal shock dynamics implied by radio and white-light observations Authors: Reiner, M. J.; Kaiser, M. L.; Gopalswamy, N.; Aurass, H.; Mann, G.; Vourlidas, A.; Maksimovic, M. Bibcode: 2001JGR...10625279R Altcode: For 19 solar eruptive events we present a statistical comparison of the shock dynamics derived from the measured frequency drift rates of metric and decametric-hectometric (D-H) type II radio bursts with the dynamics of the associated coronal mass ejection (CME). We find that the shock speed parameters derived from the D-H type II radio emissions generated in the high corona (~2-4RsolarRsolar=696,000km) are well correlated with the corresponding CME plane-of-the-sky speeds (correlation coefficient=0.71). On the other hand, we find no obvious correlation between the shock speed parameters derived from the metric type II radio bursts, generated in the middle corona (1.4-2Rsolar), and the corresponding CME speeds (correlation coefficient=-0.07). In general, we also find no clear correlation between the shock speed parameters derived from the metric type II bursts and the D-H radio emissions (correlation coefficient=0.3). However, the metric type II radio bursts sometimes include a second component that is possibly related to the D-H radio emissions. These statistical comparisons of the shock dynamics, implied by the observed metric and D-H type II frequency drift rates, provide further evidence for two distinct coronal shocks. Our statistical analyses are proceeded by two specific examples that illustrate the methodology used in this study. Title: Tracing shock waves from the corona to 1 AU: Type II radio emission and relationship with CMEs Authors: Leblanc, Yolande; Dulk, George A.; Vourlidas, Angelos; Bougeret, Jean-Louis Bibcode: 2001JGR...10625301L Altcode: We report on 10 type II bursts observed with ground-based spectrographs in the meter-decameter range, and with the Radio and Plasma Wave Investigation on the Wind spacecraft from 13.8 to 0.01 MHz. We have selected events with contemporaneous observations of flares and of coronal mass ejections (CMEs) by Large-Angle and Spectrometric Coronagraph (LASCO) telescopes. We trace the history of each event from the time of the impulsive phase of the flare, the CME liftoff time, and the start time of the radio bursts. We derive the speed of the type II shock by using a coronal/solar wind density model, and the height-time progression is compared with that of the CME as observed in the plane of the sky and then converted into the radial direction. For most events a shock at 1 AU was observed in situ. The results show the following: (1) All type II bursts occurred within 2 or 3 min of the impulsive phase of a flare. (2) The speeds of the disturbances from the time of the flares to the time of the shocks at 1 AU were very similar to the speeds of the type II-emitting shocks; they were in the range of 600 to 1300 kms-1. (3) When the type II burst was observed far out in the solar wind, the progression of the type II source had about the same speed in the solar wind as in the corona. (4) The CME liftoffs were before the flares and the type II bursts by 1-24 min for most of the selected events. As a consequence, in the corona, the type II bursts, being behind the fronts of the CMEs, are usually blast waves. (5) When a shock and CME material are observed at 1 AU, the time of arrival implies a deceleration of the CME in the solar wind, as is observed in the LASCO data. (6) Somewhere in the solar wind the shocks very likely become piston-driven, related to the CME. Title: Coronal Mass Ejection of 2000 July 14 Flare Event: Imaging from Near-Sun to Earth Environment Authors: Manoharan, P. K.; Tokumaru, M.; Pick, M.; Subramanian, P.; Ipavich, F. M.; Schenk, K.; Kaiser, M. L.; Lepping, R. P.; Vourlidas, A. Bibcode: 2001ApJ...559.1180M Altcode: We report the results of our investigation of interplanetary effects caused by the large solar flare (X5.7/3B) that occurred on 2000 July 14. In association with this event a bright, fast, halo coronal mass ejection (CME) was observed. The analysis of multiwavelength, high-cadence images obtained from the Nançay Radioheliograph shows the on-disk signatures of the initiation of the CME at low-coronal heights, <=2 Rsolar. The formation of the CME inferred from the radio data indicates a nearly developed halo at the low corona. The white-light images and CME follow-up measurements in the interplanetary medium also show, in agreement with the radio data, the propagation of the fully developed halo CME. The inference on the consequences of the CME in the inner heliosphere is from the interplanetary scintillation (IPS) observations obtained with the Ooty Radio Telescope and multiantenna system at the Solar-Terrestrial Environment Laboratory. Scintillation measurements at Ooty on a grid of a large number of radio sources provided an opportunity to image the disturbance associated with the CME at different distances from the Sun before its arrival at the near-Earth space. The scintillation data in particular also played a crucial role in understanding the radial evolution of the speed of the CME in the inner heliosphere. The ``speed-distance'' plot indicates a two-level deceleration: (1) a low decline in speed at distances within or about 100 solar radii and (2) a rapid decrease at larger distances from the Sun. The linear increase in the size of the CME with radial distance is also briefly discussed. The expansion of the CME, formation of the halo in the low corona, and its speed history in the interplanetary medium suggest a driving energy, which is likely supplied by the twisted magnetic flux rope system associated with the CME. Title: The Coronal Mass Ejection of 1998 April 20: Direct Imaging at Radio Wavelengths Authors: Bastian, T. S.; Pick, M.; Kerdraon, A.; Maia, D.; Vourlidas, A. Bibcode: 2001ApJ...558L..65B Altcode: We observed the fast coronal mass ejection (CME) of 1998 April 20 with the radioheliograph at Nançay, France, between 164 and 432 MHz. Spectroscopic data were obtained between 40 and 800 MHz by the spectrometer at Tremsdorf, Germany, and between 20 kHz and 14 MHz with the WAVES instrument on board the Wind spacecraft. Energetic particle data were obtained from the Wind 3D Plasma and Energetic Particle experiment. The CME was observed in white light by the Large-Angle Spectrometric COronagraph experiment on board the Solar and Heliospheric Observatory spacecraft. For the first time, the expanding CME loops are imaged directly at radio wavelengths. We show that the radio-emitting CME loops are the result of nonthermal synchrotron emission from electrons with energies of ~0.5-5 MeV interacting with magnetic fields of ~0.1 to a few gauss. They appear nearly simultaneously with the onset of an associated type II radio burst, shock-accelerated type III radio bursts, and the initiation of a solar energetic particle event. We suggest possible sources of the energetic electrons responsible for this ``radio CME'' and point out diagnostic uses for synchrotron emission from CME loops. Title: Determination of three-dimensional structure of coronal streamers and relationship to the solar magnetic field Authors: Liewer, P. C.; Hall, J. R.; De Jong, M.; Socker, D. G.; Howard, R. A.; Crane, P. C.; Reiser, P.; Rich, N.; Vourlidas, A. Bibcode: 2001JGR...10615903L Altcode: We have determined the location, in three dimensions, of eight quasi-stable coronal ``streamers'' from an analysis of Solar and Heliospheric Observatory (SOHO) Large-Angle and Spectrometric Coronagraph images acquired over approximately one solar rotation. We use the locations to attempt to determine the solar origin of the streamers. Comparison of the streamers' locations (longitude and latitude at the R~2.5RS source surface) with that of the current sheet computed from a potential source surface model show that all of the streamers lie in or near the heliospheric current sheet. We assume that the streamers coincide with magnetic field lines and use a potential source surface magnetic model to map the location of the streamers from the source surface (R~2.5RS) to the photosphere. We find that many of the streamers are associated with strong magnetic field active regions. When a streamer and its associated active region are visible simultaneously, the active region is seen to be bright in the SOHO extreme ultraviolet imaging telescope (EIT) EUV full disk images. This, and other evidence, leads us to conclude that many of the bright streamers are the result of scattering from regions of enhanced density associated with active region outflow, and not a result of line-of-sight viewing through folds in a warped current sheet with uniform density. Title: SOHO Observations of a Coronal Mass Ejection Authors: Akmal, Arya; Raymond, John C.; Vourlidas, Angelos; Thompson, Barbara; Ciaravella, A.; Ko, Y. -K.; Uzzo, M.; Wu, R. Bibcode: 2001ApJ...553..922A Altcode: We describe a coronal mass ejection (CME) observed on 1999 April 23 by the Ultraviolet Coronagraph Spectrometer (UVCS), the Extreme-Ultraviolet Imaging Telescope (EIT), and the Large-Angle and Spectrometric Coronagraphs (LASCO) aboard the Solar and Heliospheric Observatory (SOHO). In addition to the O VI and C III lines typical of UVCS spectra of CMEs, this 480 km s-1 CME exhibits the forbidden and intercombination lines of O V at λλ1213.8 and 1218.4. The relative intensities of the O V lines represent an accurate electron density diagnostic not generally available at 3.5 Rsolar. By combining the density with the column density derived from LASCO, we obtain the emission measure of the ejected gas. With the help of models of the temperature and time-dependent ionization state of the expanding gas, we determine a range of heating rates required to account for the UV emission lines. The total thermal energy deposited as the gas travels to 3.5 Rsolar is comparable to the kinetic and gravitational potential energies. We note a core of colder material radiating in C III, surrounded by hotter material radiating in the O V and O VI lines. This concentration of the coolest material into small regions may be a common feature of CMEs. This event thus represents a unique opportunity to describe the morphology of a CME, and to characterize its plasma parameters. Title: High-resolution Imaging of the Upper Solar Chromosphere: First Light Performance of the Very-high-Resolution Advanced ULtraviolet Telescope Authors: Korendyke, C. M.; Vourlidas, A.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Morrill, J. S.; Moses, J. D.; Moulton, N. E.; Socker, D. G. Bibcode: 2001SoPh..200...63K Altcode: The Very-high-resolution Advanced ULtraviolet Telescope (VAULT) experiment was successfully launched on 7 May 1999 on a Black Brant sounding rocket vehicle from White Sands Missile Range. The instrument consists of a 30 cm UV diffraction limited telescope followed by a two-grating, zero-dispersion spectroheliograph tuned to isolate the solar Lα emission line. During the flight, the instrument successfully obtained a series of images of the upper chromosphere with a limiting resolution of ∼ 0.33 arc sec. The resulting observations are the highest-resolution images of the solar atmosphere obtained from space to date. The flight demonstrated that sub-arc second ultraviolet images of the solar atmosphere are achievable with a high-quality, moderate-aperture space telescope and associated optics. Herein, we describe the payload and its in-flight performance. Title: Solar Phenomena Associated With EIT Waves Authors: Myers, D. C.; Biesecker, D. A.; Thompson, B. J.; Vourlidas, A. Bibcode: 2001AGUSM..SH51B03M Altcode: Observations with the Extreme Ultraviolet Imaging Telescope (EIT) on SOHO revealed the existence of transient waves which appear to propagate across the disk from a localized starting point. These EIT waves may be the coronal counterpart of previously discovered Moreton waves. Moreton waves have long been thought to be associated with solar flares, though this may have been because flares are more easily observed than other phenomena, such as Coronal Mass Ejections. EIT waves are observed much more often than Moreton waves, though this may also be due to detection efficiency. In this study, we hope to gain a better understanding of EIT waves, and in particular their initiation, through their relationship to other solar events. This study uses a complete catalog of EIT waves observed from March, 1997 to June, 1998; a period in which 175 waves were found. For each wave, the following ancillary data sets were examined for co-temporal and co-spatial events: GOES X-ray Monitor, LASCO Coronagraph, and Type II radio burst data. EIT waves are classified according to a system which measures the reliability of the existence of the event. We investigate the rate at which each class of EIT wave is associated with flares, CMEs and Type II events. Data are further divided into limb and disk events in order to correct for detection efficiency and biases. An investigation of EUV dimmings is also included as they offer clues to the relationship between EIT waves, flares and CME's. Title: Issues on the Morphological Studies of LASCO CMEs Authors: Vourlidas, A. Bibcode: 2001AGUSM..SH42A03V Altcode: Over the last 5 years, the phenomenon of coronal mass ejections (CMEs) has been under intense investigation from a variety of instruments. The correlation between remote sensing observations (CMEs) and in situ measurements (ICMEs) remains uncertain due to the lack of coverage between 30 Rs and the Earth. Nevertheless, there have been several efforts to directly relate structures in CMEs and ICMEs. This approach can be problematic, however, at least from the coronagraphic point of view. In this talk, I will present some of the issues arising in LASCO CME observations (morphology, evolution, sources, instrumental restrictions) that could invalidate the assumptions for direct correspondance between CMEs and ICMEs. Title: Ultra-High Resolution Observations of the Upper Chromosphere: First Results From the NRL VAULT Sounding Rocket Payload Authors: Vourlidas, A.; Korendyke, C. M.; Dere, K. P.; Klimchuk, J. A. Bibcode: 2001AGUSM..SP61A03V Altcode: The Very high resolution Advanced ULtraviolet Telescope (VAULT) is a new spectroscopic imaging instrument. The instrument was launched on May 7, 1999 as a sounding rocket payload. The goal of the first VAULT flight was to obtain sub-arcsecond images of the Sun in the light of Lya (1216 Å). VAULT directly imaged an active region plage, fliaments and the fine structures in the supergranule boundaries and network with the unprecented spatial resolution of 0.33 arcseconds. We present the VAULT images and the first results from the comparison of the Lya data to observations from other instruments and in particular with a sequence of TRACE 171 Å images taken during the VAULT flight. Title: Comparison of Type II Radio Emissions with CME Dynamics Measured by the LASCO White-light Coronagraph Authors: Reiner, M. J.; St. Cyr, O. C.; Vourlidas, A.; Kaiser, M. L.; Prestage, N. P. Bibcode: 2001AGUSM..SH61A03R Altcode: We compare the observed frequency drift rate of metric and decametric type II radio emissions with the CME dynamics measured by the LASCO coronagraph. The radio data relate to the "true" CME/shock height and "true" CME projected liftoff time, but require knowledge of the coronal density profile since the observed radio frequency is related to the plasma density in the source region. The coronagraph data, on the other hand, measure the CME projected height and liftoff time. We attempt to determine the "true" dynamics of a CME by requiring consistency between the radio and white-light data. The technique will be illustrated for a CME observed on January 20, 2001 for which there were both well-defined frequency-drifting metric and decametric type II radio emissions. On this day there were two CMEs ejected from the sun about 2 hours apart, with the second CME overtaking and interacting with the first. We will also demonstrate how, in this case, the required consistency between the radio and white-light data can indicate changes in the coronal density profile encountered by the CME-driven shocks for these two CME events. Title: Deriving the Electron Density of the Solar Corona from the Inversion of Total Brightness Measurements Authors: Hayes, A. P.; Vourlidas, A.; Howard, R. A. Bibcode: 2001ApJ...548.1081H Altcode: Usually, the electron density structure of the white-light solar corona is estimated from the inversion of polarized brightness measurements. The inversion technique was developed in the 1950s and has remained largely unchanged since. Here, for the first time, we expand this technique to total brightness observations to take advantage of the extensive Large Angle and Spectrometric Coronagraphs (LASCO) archive. We compare our technique to both theoretical coronal models and actual observations and show that it is as robust and accurate as the widely used polarized brightness inversion. The quantitative analysis of white-light coronal data critically depends on the removal of the F corona. We briefly describe an improved F corona model we derived using the LASCO time series data. Title: In-flight performance of the Very high Angular resolution ULtraviolet Telescope sounding rocket payload Authors: Korendyke, Clarence M.; Vourlidas, A.; Cook, John W.; Dere, Kenneth P.; Feldman, R.; Howard, Russell A.; Lilley, D. N.; Morrill, Jeff S.; Moses, J. Daniel; Moulton, Norman E.; Moye, Robert W.; Roberts, D. E.; Shepler, E. L.; Smith, J. K.; Socker, Dennis G.; Spears, T. R.; Waymire, R. S.; Brown, Wayne E.; Tarbell, Theodore D.; Berger, Tom; Handy, Brian N. Bibcode: 2000SPIE.4139..340K Altcode: The Very high Angular Resolution ULtraviolet Telescope experiment was successfully launched on May 7, 1999 on a Black Brant sounding rocket vehicle from White Sands Missile Range. The instrument consists of a 30 cm UV diffraction limited telescope followed by a double grating spectroheliograph tuned to isolate the solar Lyman (alpha) emission line. During the flight, the instrument successfully obtained a series of images of the upper chromosphere with a limiting resolution of approximately 0.33 arc-seconds. The resulting observations are the highest resolution images of the solar atmosphere obtained from space to date. The flight demonstrated that subarc-second ultraviolet images of the solar atmosphere are achievable with a high quality, moderate aperture space telescope and associated optics. Herein, we describe the payload and its in- flight performance. Title: Flare- and coronal mass ejection (CME)-associated type II bursts and related radio emissions Authors: Leblanc, Yolande; Dulk, George A.; Vourlidas, Angelos; Bougeret, Jean-Louis Bibcode: 2000JGR...10518225L Altcode: We report on two events that occurred within 6 hours of each other on November 3, 1997. They were observed with ground-based spectrographs in the meter to decameter range and with the WAVES experiment on the Wind spacecraft at longer wavelengths. Complementary observations were made with Extreme Ultraviolet Imaging Telescope (EIT) and Large Angle and Spectrometric Coronagraph (LASCO) experiments on the Solar and Heliospheric Observatory (SOHO). The two events are very similar in many ways: both consist of type III bursts, type II shocks, shock-accelerated type III bursts proceeding from the type II to low frequencies, and type IV continuum. Flares and coronal mass ejections (CMEs) are associated with the two events. We trace the history of the two events from the time of the impulsive phase of the flare, which is coincident with the start time of the radio bursts and 10 to 30 min after the CME liftoff from the Sun. We derive the height-time progression of the type II shocks by using a coronal-solar wind density model and compare it with the progression of the CME in the plane of the sky. The results show that the speeds of the type II shocks in the low corona were high, 900-950 km s-1. Then, at a height of ~2RS, the fast shocks decelerate and become slower shocks, <~380 km s-1. We discuss (1) the relationship between these type II shocks, flares and CMEs, including the apparent deceleration of the type II shocks, (2) the hypotheses of blast wave versus piston-driven shocks, (3) the acceleration of electrons at the shock front producing the shock-accelerated type III bursts, and (4) the acceleration of electrons that become trapped in the expanding loops of the CME and emit type IV continuum. Title: Simultaneous SOHO and Ground-Based Observations of a Large Eruptive Prominence and Coronal Mass Ejection Authors: Plunkett, S. P.; Vourlidas, A.; Šimberová, S.; Karlický, M.; Kotrč, P.; Heinzel, P.; Kupryakov, Yu. A.; Guo, W. P.; Wu, S. T. Bibcode: 2000SoPh..194..371P Altcode: Coronal mass ejections (CMEs) are frequently associated with erupting prominences near the solar surface. A spectacular eruption of the southern polar crown prominence was observed on 2 June 1998, accompanied by a CME that was well-observed by the LASCO coronagraphs on SOHO. The prominence was observed in its quiescent state and was followed throughout its eruption by the SOHO EIT and later by LASCO as the bright, twisted core of the CME. Ground-based Hα observations of the prominence were obtained at the Ondřejov Observatory in the Czech Republic. A great deal of fine structure was observed within the prominence as it erupted. The prominence motion was found to rotate about its axis as it moved outward. The CME contained a helical structure that is consistent with the ejection of a magnetic flux rope from the Sun. Similar structures have been observed by LASCO in many other CMEs. The relationship of the flux rope to other structures in the CME is often not clear. In this event, the prominence clearly lies near the trailing edge of the structure identified as a flux rope. This structure can be observed from the onset of the CME in the low corona all the way out to the edge of the LASCO field of view. The initiation and evolution of the CME are modeled using a fully self-consistent, 3D axisymmetric, MHD code. Title: Radio-rich solar eruptive events Authors: Gopalswamy, N.; Kaiser, M. L.; Thompson, B. J.; Burlaga, L. F.; Szabo, A.; Lara, A.; Vourlidas, A.; Yashiro, S.; Bougeret, J. -L. Bibcode: 2000GeoRL..27.1427G Altcode: We report on the analysis of a large number of solar eruptive events that produced radio emission in the dekameter-hectometric (DH) radio window (1-14 MHz), newly opened by the Wind/WAVES experiment. The distinguishing characteristics of coronal mass ejections (CMEs) associated with the DH type II radio bursts are larger-than-average width and speed. Flares of all sizes (X-ray importance B to X) occurring at all longitudes were associated with the DH type II bursts and CMEs. We found a global enhancement in EUV over an area much larger than the flaring active region in the beginning many events. A comparison between the ‘Shock Associated’ events and microwave bursts shows that at least half of the events do not have temporal relation. A majority of the DH type II bursts were associated with IP shocks and kilometric type II bursts. In particular, we found a very close relationship between the kilometric type II bursts and the IP shocks. Title: Large-Angle Spectrometric Coronagraph Measurements of the Energetics of Coronal Mass Ejections Authors: Vourlidas, A.; Subramanian, P.; Dere, K. P.; Howard, R. A. Bibcode: 2000ApJ...534..456V Altcode: We examine the energetics of coronal mass ejections (CMEs) with data from the large-angle spectrometric coronagraphs (LASCO) on SOHO. The LASCO observations provide fairly direct measurements of the mass, velocity, and dimensions of CMEs. Using these basic measurements, we determine the potential and kinetic energies and their evolution for several CMEs that exhibit flux-rope morphologies. Assuming flux conservation, we use observations of the magnetic flux in a variety of magnetic clouds near the Earth to determine the magnetic flux and magnetic energy in CMEs near the Sun. We find that the potential and kinetic energies increase at the expense of the magnetic energy as the CME moves out, keeping the total energy roughly constant. This demonstrates that flux-rope CMEs are magnetically driven. Furthermore, since their total energy is constant, the flux-rope parts of the CMEs can be considered a closed system above ~2 Rsolar. Title: Determination of Three-Dimensional Geometry of Coronal Streamers using LASCO Data Authors: Liewer, P. C.; Hall, J. R.; De Jong, E. M.; Socker, D. G.; Howard, R. A.; Crane, P.; Reiser, P.; Rich, N. B.; Vourlidas, A. Bibcode: 2000SPD....31.1501L Altcode: 2000BAAS...32..848L The structure of the outer corona as revealed by the SOHO/LASCO coronagraphs is dominated by bright ray-like streamers which may persist for days or weeks. From analysis of approximately 1 month of SOHO/LASCO C3 coronagraph images, we have determined in three-dimensions the locations of 8 bright ray-like radial ``streamers" seen in the outer corona (R > 3 RSUN). Comparison of the steamers' locations (longitude and latitude at the source surface) with that of the current sheet as computed from a potential-source-surface model shows that all of the streamers lie in or near the heliospheric current sheet. The potential-source-surface magnetic model is used to map the locations of the streamers from the source surface (R = 2.5 RSUN) to the photosphere. We find that many of the streamers are associated with strong magnetic field active regions. When the streamers and active region are both visible, the active regions are seen to be bright in the SOHO/EIT data. From a previous analysis of SOHO/LASCO C2&C3 images near solar minimum, Wang et al. (1997) found that the bright streamers seen in the coronagraph images were the results of line-of-sight viewing of a convoluted or "folded" uniform density heliospheric plasma sheet and not a result of coronal density enhancements. In our analysis of a more active SUN, not all of the steamers lie at folds in the current sheet. This, along with their associations with active regions, leads us to conclude that some of the bright streamers are apparently the result of scattering from regions of enhanced density, associated with active region outflow, and not a result of line-of-sight viewing, consistent with the suggestion by Wang et al. (2000). Wang, Y.-M. et al., Ap. J. 485, 875 (1997). Wang, Y.-M., Sheeley, N. R., Jr., and Rich, N. B., Geophys. Res. Lett. 27, 149 (2000). Title: Model for Radio Thermal Emission at 328 and 1446 MHz from EUV Observations Authors: Cook, J. W.; Newmark, J. S.; Vourlidas, A. Bibcode: 2000SPD....31.0221C Altcode: 2000BAAS...32..814C We have modeled the contribution to solar radio emission at 328 and 1446 MHz from free-free thermal bremsstrahlung emission, using a full disk differential emission measure (DEM) map of the Sun. The DEM map is produced from four EUV images (171 A, 195 A, 284 A, and 304 A) for a selected day from the EIT instrument on the SOHO satellite, using a method developed previously by Cook, Newmark, and Moses. The EIT instrument images the Sun out to 1.4 R, with a pixel size of 2.6 arc sec and spatial resolution of 2 pixels. We perform the radiative transfer calculation, determining the optical depth scale for free-free emission and the emergent absolute intensity for each pixel in the field-of-view using the individual DEM of that pixel, and transforming integrals over the line-of-sight into integrals over temperature via the DEM. We can compare our model calculation with the VLA radio observations of Vourlidas from 1998 January 31. Our model is in good agreement outside of active regions, where free-free emission should truly be the dominant emission mechanism. In areas such as sunspots, where the strong magnetic field leads to additional gyro resonance radiation, the difference between the observed total intensity and our calculated thermal component should be a good estimate of the nonthermal gyro radiation. This work is supported by NASA under W-19,348 and by the Office of Naval Research. Title: Solar Phenomena Associated With EIT Waves Authors: Myers, D. C.; Biesecker, D. A.; Vourlidas, A.; Thompson, B. J. Bibcode: 2000SPD....31.0273M Altcode: 2000BAAS...32..824M In an effort to understand what causes an "EIT wave" or what effects an EIT wave might have, we are investigating whether EIT waves can be associated directly with any other solar phenomena. An EIT wave is a coronal disturbance, typically appearing as a bright rim, observed to propagate across the Sun. Waves at the solar limb are identified by the deflections of magnetic fields that they cause. We have taken a working catalogue of "EIT waves" and determined what, if any, solar phenomena are associated with each wave. We have thus far looked for an association with GOES X-ray flares and with LASCO coronal mass ejections. This poster shows the work accomplished thus far, in particular, that there is a strong association with GOES flux increases and that waves with a higher quality rating tend to have a higher GOES flux level. We also plan to determine if there is an association with radio transients, particularly type II events. The EIT wave catalogue was compiled by examining EIT difference images of the Sun from the start of higher cadence images (24-March-1997). Each wave is classified by a quality rating from 0 to 6. The quality rating describes a confidence level that the given times contain an EIT wave, with 0 being the lowest certainty and 6 the highest. The catalogue of EIT waves, and this study, are still being expanded and will eventually encompass all EIT waves observed with a high image cadence from 1996 through 1998. Title: Comets C/1999 J6, C/1999 U5, C/1999 W1, C/1999 Y3 Authors: Biesecker, D. A.; Hammer, D.; Marsden, B. G.; Oates, M.; Vourlidas, A. Bibcode: 2000IAUC.7386....1B Altcode: 2000IAUC.7386Q...1B Further to IAUC 7376 and 7383, D. A. Biesecker reports observations (measures by D. Hammer and himself, reductions by B. G. Marsden) of four more comets seen in 1999 SOHO data, all but C/1999 J6 being presumed Kreutz sungrazers. Comets C/1999 J6 (visible in both C2 and C3 data) and C/1999 U5 (visible in only the C3 telescope) show no tail. However, C/1999 W1 and C/1999 Y3, which were both visible with only the C2 telescope, did show tails. Selected V magnitudes from Biesecker for C/1999 J6: May 10.750 UT, 8.1; 10.833, 7.3; 10.935, 6.5; 11.088, 5.9; 11.269, 5.5, 11.338, 4.9; 11.462, 5.1. Comet C/1999 J6 was first noted by M. Oates via the SOHO Web page; C/1999 U5 and C/1999 W1 were discovered by Biesecker, and C/1999 Y3 was discovered by A. Vourlidas of the SOHO team. Full astrometry and orbital elements appear on the MPECs indicated below. 1999 UT R.A. (2000) Decl. MPEC Comet May 10.726 3 05.0 +15 48 2000-F30 C/1999 J6 Oct. 31.495 14 06.8 -17 27 2000-F31 C/1999 U5 Nov. 23.188 15 55.1 -22 06 2000-F32 C/1999 W1 Dec. 21.496 18 04.0 -25 03 2000-F33 C/1999 Y3 Title: Sungrazing Comets Authors: Hammer, D.; Marsden, B. G.; Lewis, D.; Vourlidas, A.; Schenk, K.; Lovejoy, T.; Biesecker, D. A. Bibcode: 2000IAUC.7376....2H Altcode: 2000IAUC.7376R...1H; 2000IAUC.7376B...1H Biesecker also reports observations (measures by D. Hammer and himself, reductions by B. G. Marsden) of some older Kreutz sungrazing comets seen in SOHO C3 data; full astrometry and parabolic orbital elements appear on the MPECs indicated below. Comet C/1999 O2 developed a short tail, C/1999 O3 had a short tail evident, C/1999 Q3 showed a tail, and C/1999 R3 showed evidence for a tail; the other four comets showed no evident tail. Comets C/1999 O2 and C/1999 P4 were discovered by D. Lewis, C/1999 P5 by A. Vourlidas, C/1999 Q2 and C/1999 R3 by K. Schenk, and C/1999 Q3 by Biesecker, while comets C/1999 O3 and C/1999 Q1 were first noted by T. Lovejoy via the SOHO Web page. 1999 UT R.A. (2000) Decl. MPEC Comet July 21.888 7 49.5 +18 13 2000-E28 C/1999 O2 31.446 8 22.4 +16 25 2000-E29 C/1999 O3 Aug. 9.429 8 58.2 +14 39 2000-E30 C/1999 P4 12.138 9 06.3 +13 30 2000-E31 C/1999 P5 23.821 9 51.1 +10 39 2000-E32 C/1999 Q1 24.471 9 54.2 +10 11 2000-E33 C/1999 Q2 30.738 10 10.4 + 7 49 2000-E34 C/1999 Q3 Sept. 4.863 10 25.5 + 5 40 2000-E35 C/1999 R3 Title: COMET C/19 Authors: Vourlidas, A.; Hammer, D.; Biesecker, D.; Marsden, B. G. Bibcode: 2000MPEC....E...31V Altcode: No abstract at ADS Title: COMET C/19 Authors: Vourlidas, A.; Hammer, D.; Biesecker, D.; Marsden, B. G. Bibcode: 2000MPEC....F...33V Altcode: No abstract at ADS Title: LASCO and EIT Observations of Coronal Mass Ejections Authors: Dere, K. P.; Vourlidas, A.; Subramanian, Prasad Bibcode: 2000astro.ph..2061D Altcode: We present a brief overview of LASCO and EIT observations of CMEs. We discuss CME energetics, the relation of CMEs to streamers and conclude with some insights into the source regions of CMEs. Title: Development of Coronal Mass Ejections: Radio Shock Signatures Authors: Maia, Dalmiro; Pick, Monique; Vourlidas, Angelos; Howard, Russel Bibcode: 2000ApJ...528L..49M Altcode: We present observational imaging evidence for the existence of metric radio bursts closely associated with the front edge of coronal mass ejections (CMEs). These radio bursts drift in frequency similarly to type II bursts. They are weak and usually go undetected on spectrograph data. We find the same measured projected velocity for the displacement of, respectively, the radio source (when observed at two or more frequencies) and the CME leading edge. The position of the emitting source coincides with the CME leading edge. Among the events analyzed, the fastest of them, with a velocity over 1400 km s-1, was associated with interplanetary type II bursts. Title: Coronal Mass Ejections and Large Scale Structure of the Corona Authors: Maia, D.; Vourlidas, A.; Pick, M.; Howard, R.; Schwenn, R.; Lamy, P. Bibcode: 2000AdSpR..25.1843M Altcode: A comparative study of two events accompanied by both a flare and a CME has been performed. The data analysis has been made by comparing the observations of the LASCO/SOHO coronagraphs with those of the Nancay radioheliograph. The observations show a clear connection between coronal green and red line transient activity, burst radio emission and the CME development which is due to successive loop interactions. Signatures of these interactions are given by the radio emission. One can identify successive sequences in the evolution of the coronal restructuring leading to the full development of the CME. Identification and timing of these sequences result from the radio emission analysis. For flare-CME events , the evolution takes place in the low corona and is extremely fast of the order, on a few minutes Title: LASCO/Nancay Observations of the CME on 20 April 1998: White Light Sources of Type-II Radio Emission Authors: Vourlidas, A.; Maia, D.; Pick, M.; Howard, R. A. Bibcode: 1999ESASP.448.1003V Altcode: 1999ESPM....9.1003V; 1999mfsp.conf.1003V No abstract at ADS Title: LASCO Measurements of the Energetics of Coronal Mass Ejections Authors: Vourlidas, Angelos; Subramanian, Prasad; Dere, K. P.; Howard, R. A. Bibcode: 1999astro.ph.12069V Altcode: We examine the energetics of Coronal Mass Ejections (CMEs) with data from the LASCO coronagraphs on SOHO. The LASCO observations provide fairly direct measurements of the mass, velocity and dimensions of CMEs. Using these basic measurements, we determine the potential and kinetic energies and their evolution for several CMEs that exhibit a flux-rope morphology. Assuming flux conservation, we use observations of the magnetic flux in a variety of magnetic clouds near the Earth to determine the magnetic flux and magnetic energy in CMEs near the Sun. We find that the potential and kinetic energies increase at the expense of the magnetic energy as the CME moves out, keeping the total energy roughly constant. This demonstrates that flux rope CMEs are magnetically driven. Furthermore, since their total energy is constant, the flux rope parts of the CMEs can be considered to be a closed system above $\sim$ 2 $R_{\sun}$. Title: Calibrated H I Lyman α Observations with TRACE Authors: Handy, B. N.; Tarbell, T. D.; Wolfson, C. J.; Korendyke, C. M.; Vourlidas, A. Bibcode: 1999SoPh..190..351H Altcode: Since shortly after launch in April 1998, the Transition Region and Coronal Explorer (TRACE) observatory has amassed a collection of H i Lα (1216 Å) observations of the Sun that have been not only of high spatial and temporal resolution, but also span a duration in time never before achieved. The Lα images produced by TRACE are, however, composed of not only the desired line emission, but also local ultraviolet continuum and longer wavelength contamination. This contamination has frustrated attempts to interpret TRACE observations in H i Lα. The Very Advanced Ultraviolet Telescope (VAULT) sounding rocket payload was launched from White Sands Missile range 7 May 1999 at 20:00 UT. The VAULT telescope for this flight was a dedicated H i Lα imaging spectroheliograph. We use TRACE observations in the 1216 Å and 1600 Å channels along with observations from the VAULT flight to develop a method for removing UV continuum and longer wavelength contamination from TRACE Lα images. Title: Development Of Coronal Mass Ejections : Radio Shock Signatures Authors: Maia, D.; Pick, M.; Vourlidas, A. Bibcode: 1999ESASP.446..473M Altcode: 1999soho....8..473M This study presents joint observations of Coronal Mass Ejections from the EIT telescope and LASCO coronagraphs on SOHO and from the Nan ay Radioheliograph. The contribution of radio observations to the present knowledge of origin and development of CMEs will be reviewed. In particular, this study will focuss on the following points : - The radio detection in the corona of the leading edge of CMEs and the association with shocks ; - The identification of successive sequences leading to the full development of CMEs and the timing of these sequences. The radio detection of coronal waves- The radio counterpart seen in projection over the solar disk of halo CME events. Title: Sungrazing Comets Authors: Biesecker, D. A.; Marsden, B. G.; Vourlidas, A. Bibcode: 1999IAUC.7204....1B Altcode: 1999IAUC.7204A...1B; 1999IAUC.7204Q...1B D. A. Biesecker, SM&A Corporation and Goddard Space Flight Center, reports observations of three more apparent Kreutz sungrazing comets found in images taken with both the C2 and C3 coronagraphs aboard SOHO. Astrometric measurements made by Biesecker (and reduced by B. G. Marsden), together with orbital elements by Marsden, are given on MPECs 1999-M08 (C/1999 K9), 1999-M09 (C/1999 K10), and 1999-M10 (C/1999 L4). 1999 UT R.A. (2000) Decl. Comet May 23.698 4 03.8 +18 13 C/1999 K9 31.698 4 33.4 +19 47 C/1999 K10 June 1.448 4 33.9 +19 37 C/1999 L4 Comets C/1999 K9 and C/1999 L4 were discovered by A. Vourlidas; C/1999 K10 was discovered by Biesecker. No tail is evident for C/1999 K9 on images obtained during May 23-24. No tail is visible in the May 31-June 1 images of C/1999 K10; this object was extremely faint in the C3 images. A faint tail is visible is visible in the June 1 images of C/1999 L4, which was again very difficult to measure in the C3 frames. Title: Large-scale structure and coronal dynamics from joint radio, SOHO/EIT and coronagraph observations Authors: Pick, M.; Maia, D.; Vourlidas, A.; Benz, A. O.; Howard, R.; Thompson, B. J. Bibcode: 1999AIPC..471..649P Altcode: 1999sowi.conf..649P This study presents joint observations of an `halo' coronal mass ejection from the EIT telescope and LASCO coronagraphs on SOHO, from the Nançay Radioheliograph (NRH) and the Zurich ETH radiospectrograph (Phoenix-2). This event includes different manifestations: a coronal wave and a dimming region detected by EIT, a CME showing bright discrete portions above east and west limbs. Radio signatures of all these manifestations are found and the interpretation is briefly discussed. Title: Radio signatures of a fast coronal mass ejection development on November 6, 1997 Authors: Maia, D.; Vourlidas, A.; Pick, M.; Howard, R.; Schwenn, R.; Magalhães, A. Bibcode: 1999JGR...10412507M Altcode: The Oporto radiospectrograph and the Nançay radioheliograph recorded a radio event on November 6, 1997, closely related in time with a flare on National Oceanic and Atmospheric Administration (NOAA) active region 8100. At the beginning of the event the radio sources are located on a rather small volume in the vicinity of the flare site. In a timescale of only a few minutes the radio emission sites spread over a large volume in the corona, covering a range of 100° in heliolatitude. During the period of the radio event the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO) observed an extremely fast coronal mass ejection (CME), with a velocity around 2000 kms-1. This CME presents the particularity of having a fast lateral expansion, giving it a shape reminiscent of a ``coat hanger.'' There is a very good association between the latitudinal extent and time development of the CME seen by LASCO and the radio sources recorded by the radio instruments. Title: LASCO Measurements of Erupting Flux Ropes Authors: Vourlidas, A.; Subramanian, P.; Dere, K. P.; Howard, R. A. Bibcode: 1999AAS...19410103V Altcode: 1999BAAS...31..998V It is commonly assumed that Coronal Mass Ejections from the Sun are magnetically driven. We address this question with data from the LASCO coronagraphs aboard the SOHO spacecraft. These observations provide fairly direct measurements of the energetics of CMEs. We determine the kinetic and gravitational energies and their evolution for several helical CMEs. We estimate the evolution of the magnetic energy based on the conservation of magnetic flux and observations of magnetic clouds near the Earth. From the magnitude and variation of these three forms of energy, we examine the energetics of CMEs from the perspective that they are driven through their internal magnetic energy. Title: The Increase in Mass of CMEs due to Propagation Authors: Howard, R. A.; Dere, K. P.; Sheeley, N. R., Jr.; Subramanian, P.; Vourlidas, A.; Wang, D. Bibcode: 1999AAS...19410102H Altcode: 1999BAAS...31..998H The question we would like to address is whether coronal mass ejections snowplow ambient material. Some of the CMEs observed by the LASCO coronagraph on SOHO have a clearly defined loop-like front, meaning that the trailing edge of the front can be clearly defined. We measure the mass in the front of the CME in this subclass. We find that for some of the events, the mass in the leading edge increases, implying that the CME is indeed "snowplowing" ambient material. If there is a significant increase in mass, then the CME frontal speed might decrease to conserve momentum. We estimate the amount of ambient material, using a model of coronal densities, and find that it is consistent with the mass increase. We can also estimate the height in the corona, below the occulting disk, from where the original material in the CME is released. These concepts as well as conditions for when the mass increases will be discussed. Title: IDL-based Database of Solar Active Regions Authors: Gary, D. E.; Grechnev, V. V.; Shabarova, L. V.; Vourlidas, A.; Nishio, M. Bibcode: 1999ASPC..172..391G Altcode: 1999adass...8..391G A database on solar active regions has been implemented in IDL (Interactive Data Language). The observational parameters of the regions are stored in a multi-level structure array that is distributed as a standard IDL save file. Convenient access to the data is provided by an application equipped with a graphical user interface (GUI). A variety of search modes are implemented. Full-disk 17 GHz radio maps produced by the Nobeyama Radioheliograph provide the basis for the database. Title: Nonthermal Radio Signatures of Coronal Disturbances with and without Coronal Mass Ejections Authors: Aurass, H.; Vourlidas, A.; Andrews, M. D.; Thompson, B. J.; Howard, R. H.; Mann, G. Bibcode: 1999ApJ...511..451A Altcode: This study presents data on two events from the Extreme-UV Imaging Telescope (EIT) and the Large Angle and Spectroscopic Coronagraph instruments (C1, C2, and C3), Geostationary Operational Environmental Satellite (GOES) soft X-ray data, and 40-800 MHz radio spectra of the Astrophysical Institute Potsdam. At first glance, the two events appear similar. However, one event decays after a flare-related ejection of cold and hot matter into the lower corona causing only brightness changes in EIT and C1, while the other event marks the onset of a coronal mass ejection (CME) that propagates with a leading-edge speed of ~530 km s-1 between 2 and 30 Rsolar. The radio data reveal two differences between the CME and non-CME events: (1) a characteristic faint type III burst group in the time interval with the first clearly CME-related structural change in the coronagraph images and (2) a continuum emission with a frequency drift during the passage of the CME matter through the C1 field of view. Furthermore, we show that the radio spectral data can provide essential information on the timing of the early stages of CME formation and the initial mass motions associated with the ejection. Title: Comet C/1998 K7 (SOHO) Authors: Vourlidas, A.; Gregory, S.; Biesecker, D. A.; Williams, G. V.; Marsden, B. G. Bibcode: 1999MPEC....A...24V Altcode: No abstract at ADS Title: Near-Sun Comets Authors: Biesecker, D.; Williams, G. V.; Schenk, K.; Stezelberger, S.; Vourlidas, A. Bibcode: 1998IAUC.6952....1B Altcode: 1998IAUC.6952Q...1B; 1998IAUC.6952A...1B D. Biesecker, Space Applications Corporation, NASA Goddard Space Flight Center, reports provisional data (reduced by G. V. Williams) on nine more comets found in C3 coronagraphic data. Except for the first comet (2 deg from the sun at its closest with maximum tail length 0.5 deg), they appear to be Kreutz sungrazers and were also observed by C2. Orbit computations are deferred until more definitive astrometry can be done. Comets X/1998 G3, G4, K10 and K11 (these last two having 0.5-deg tails and being among the brightest Kreutz comets, with K11 following K10 along the Kreutz track 4 hr later) were discovered by K. Schenk; H2 and K9 (the latter not showing a tail) by S. Stezelberger; J2 and K8 by Biesecker; and K7 by A. Vourlidas. 1998 UT R.A. (2000) Decl. Apr. 10.526 1 42.2 +12 06 X/1998 G3 10.526 1 29.9 + 5 43 X/1998 G4 29.113 2 45.5 +11 31 X/1998 H2 May 10.323 3 21.5 +14 38 X/1998 J2 16.406 3 42.0 +16 05 X/1998 K7 19.240 3 49.7 +17 07 X/1998 K8 27.742 4 23.0 +17 53 X/1998 K9 31.073 4 37.0 +17 27 X/1998 K10 30.706 4 39.1 +16 50 X/1998 K11 Title: The November 6, 1997 event: Radio signatures of the CME development Authors: Maia, D.; Vourlidas, A.; Pick, M.; Howard, R.; Schwenn, R.; Magalhaes, A.; Carneiro, J.; Agostinho, R. Bibcode: 1998cee..workE..57M Altcode: The analysis of the November 6, 1997 event has taken advantage of the new capabilities of the OPorto Radiospectrograph and of the Nanccay Radioheliograph. The evolution of this event shows successive phases in time scales of a fraction of a second. It is shown that the CME observed by the LASCO/SOHO coronograph is the result of successive interactions of multiple loop systems which occur over a latitude range of about 100circ. These magnetic loop interactions lead to the creation of several electron acceleration sites which are widely separated in the corona. There is a close correspondance between the evolution of the CME seen by LASCO and the extend of radio sources seen by the radioheliograph. The association with particles detected by in situ measurements in the interplanetary medium is also presented. Title: Solar origin of accelerated particles detected in the corona and in the interplanetary medium Authors: Pick, M.; Maia, D.; Howard, R.; Vourlidas, A. Bibcode: 1998cee..workE..58P Altcode: We discuss the solar origin of accelerated particles detected in the corona and in the interplanetary medium. This synthesis lies on the study of several events which have been observed by the Nanccay Radioheliograph and the LASCO/SOHO instrument. The in-situ measurements of particles in the interplanetary medium have been made by ULYSSES, WIND, ACE and SOHO. Title: Nonthermal Radio Signatures of Coronal Disturbances with and without Mass Ejections Authors: Aurass, H.; Vourlidas, A.; Andrews, M. D.; Thompson, B. J.; Howard, R. H.; Mann, G. Bibcode: 1998cee..workE..20A Altcode: We show that the radio signature of nonthermal electrons can be a sensitive indicator of small scale energy release related to topological changes in coronal magneto-plasma structures. We compare two events using images from the Extreme-UV Imaging Telescope (EIT) and the Large Angle and Spectroscopic Coronagraph (LASCO) instruments, GOES soft X-ray data, and 40--800 MHz radio spectra of the AI Potsdam. At first glance, both events appear similar. One event decays after a prominence eruption causing only brightness changes in the EIT and C1 images. But the other event marks the onset of a large coronal mass ejection (CME) that propagates with a speed of ~530kms^{-1} between 2--30 R_odot. The CME formation is accompanied by an unspectacular faint group of metric drift bursts starting in the spectral range 170--200 MHz (at a height 1.20-1.25 R_odot) and lasts for ~3 min. During the CME lift-off, the frequency drift of an associated type IV continuum translates to a speed of ~90kms^{-1}. The same speed is obtained from the height change of leading CME features in LASCO-C1. The non-CME event is accompanied by a non-drifting continuum and lacks any type III burst activity. We offer a number of explanations for the CME absence. Also, in the non-CME case we show that the post-prominence eruption current sheet can be detected in the EIT and C1 images. Its lower part appears as a bright blob in EIT on the top of a loop arcade. The brightness of this blob corresponds to a soft X-ray long duration event (LDE) decay. Our study suggests that prominence eruptions and soft X-ray LDEs are insufficient to reveal a CME. Title: The Structure of "halo" Coronal Mass Ejections Authors: Vourlidas, A.; Howard, R. A.; Dere, K. P.; Passwaters, S. E. Bibcode: 1997AAS...191.7305V Altcode: 1997BAAS...29.1321V We investigate the relation between the structure of "halo" coronal mass ejections (CMEs) and the global coronal structure. In particular, we compare two "halo" events which occured on October 21, 1997 and were observed with the SoHO/LASCO coronographs at a high cadence. Although the two CME occured at different locations on the solar disk, they both exhibit similar morphology which appear to be influenced by the global coronal structure. By comparing the data from the coronaraphs, EIT and magnetograms, we will attempt to decipher the interplay between the ejected material and the surrounding corona. Title: The Structure of the Solar Corona above Sunspots as Inferred from Radio, X-Ray, and Magnetic Field Observations Authors: Vourlidas, A.; Bastian, T. S.; Aschwanden, M. J. Bibcode: 1997ApJ...489..403V Altcode: We present observations of a solar active region, NOAA/USAF no. 7123, during 1992 April 3-10. The database includes high-angular-resolution radio, soft X-ray, magnetograph, and Hα observations. The radio observations include VLA maps in the Stokes I and V parameters at 4.7 and 8.4 GHz. The soft X-ray observations were obtained by the Soft X-Ray Telescope on board the Yohkoh satellite, the magnetograms were obtained at Kitt Peak, Mt. Wilson, and Big Bear, and the Hα data were obtained at Big Bear.

The lead sunspot in the active region is studied here. In particular, the polarization properties and brightness temperature spectrum are used to constrain the thermal structure of the corona over the sunspot. It is found that the 4.7 GHz emission of the sunspot is polarized in the sense of the ordinary mode, in contradiction with simple gyroresonance models that predict that the spot should be polarized in the sense of the extraordinary mode. We model the spectral and temporal evolution of the polarization structure in two frequencies, 4.7 and 8.4 GHz, using gyroresonance models to fit one-dimensional brightness temperature profiles across the spot in each polarization and frequency. The constraints provided by the X-ray and magnetic field observations help us to derive a qualitatively self-consistent picture for the daily evolution of the spot. We attribute the excess of the o-mode emission to the magnetic field configuration and to the temperature inhomogeneities across the spot. Namely, we find that (1) the umbral and penumbral environments are distinct, with the X-rays and the o-mode radio emission coming from the hotter penumbral loops, while the observed x-mode emission originates from the cooler umbral loops; (2) there exist temperature inhomogeneities in both the radial and vertical direction over the spot; and (3) the umbral magnetic field remains more confined in the corona than that predicted by a dipole model. Instead, a field configuration based on the magnetohydrostatic equilibrium model of Low gives a better agreement with the observations. Title: Sunspot Gyroresonance Emission at 17 GHz: A Statistical Study Authors: Vourlidas, A.; Gary, D. E.; Shibasaki, K. Bibcode: 1997SPD....28.0134V Altcode: 1997BAAS...29..885V Our statistical study is based on a compilation of the daily Nobeyama Radioheliograph full-disk maps obtained at 17 GHz between July 1992 -- December 1994. It includes 533 active regions, 20% of which appear to have gyroresonance cores during some part of their disk crossing. At least one of the regions reaches coronal temperatures (T>10(6) K) while several others show a polarization reversal at the extreme limb. Our study indicates that the gyroresonance cores are polarized in the sense of the x-mode and are due to s=3 (B=2024 G) and/or s=4 (B=1518 G) gyroresonance absorption in the transition region and/or corona. We also investigate the dependence between various physical quantities such as brightness temperature, degree of polarization, spot area, photospheric magnetic field and heliographic longitude and comment on the polarization reversals at the limb. A more detailed study of individual active regions, that have been also observed with the Owens Valley Solar Array, will follow. Title: Multiband VLA Observations of Solar Active Regions: Implications for the Distribution of Coronal Plasma Authors: Vourlidas, A.; Bastian, T. S. Bibcode: 1996ApJ...466.1039V Altcode: We present high-quality radio observations of a solar active region (NOAA/USAF region 5131) made by the Very Large Array in the 0.33, 1.5, 4.7, and 8.4 0Hz frequency bands. The observations were made during the IAU-sanctioned International Solar Month on 1988 September 1 and 4. In addition to the radio maps, the database includes images from the Solar Maximum Mission Soft X-ray Polychromator in the Fe XVII line, photo spheric magnetograms, and Hα filtergrams. Because coverage in only a single wavelength is available, the soft X-ray data are used for qualitative comparisons.

We identify those areas of the active region from which the radio emission is predominantly due to thermal bremsstrahlung emission. To account for the observed four-point radio spectra in these areas, we examine three different models, which characterize the corona in terms of a single plasma component, two components, and multiple components. The latter differs somewhat from past models. In particular, we take explicit account of the highly inhomogeneous structure of active regions through a multilayer slab model in which the thermal distribution is constrained by the generic form of the differential emission measure. While multicomponent models provide the best agreement with the observations, we find that a complete model must include both free-free and gyroresonance opacity. We compare our radio data and model results with those resulting from previous studies. Title: On the Peculiar Radio Polarization of a Sunspot and the Distibution of the Coronal Plasma Authors: Vourlidas, A.; Bastian, T. S.; Aschwanden, M. J. Bibcode: 1996AAS...188.3602V Altcode: 1996BAAS...28..873V A comprehensive set of microwave, soft x-ray and magnetic observations of solar active region NOAA/USAF 7123 was obtained during 4--9 April, 1992. The observations show an unusual 4.7 GHz source which is polarized in the sense of the ordinary mode over the umbra of the leading spot. A detailed analysis of the daily radio and soft X-ray maps of the spot indicates that (i) the umbral magnetic field is strongly confined, (ii) the umbral and penumbral loops have distinct atmospheres and (iii) temperature gradients may exist both radially and vertically over the spot. A possible scenario for the temporal evolution of the spot is also presented. Title: On the radio polarization from sunspots Authors: Vourlidas, Angelos Bibcode: 1996PhDT........23V Altcode: No abstract at ADS Title: Joint Radio and Soft X-Ray Imaging of an `Anemone' Active Region Authors: Vourlidas, A.; Bastian, T. S.; Nitta, N.; Aschwanden, M. J. Bibcode: 1996SoPh..163...99V Altcode: The Very Large Array and the Soft X-ray Telescope (SXT) aboard the Yohkoh satellite jointly observed the rapid growth and decay of a so-called `anemone' active region on 3-6 April, 1992 (AR 7124). The VLA obtained maps of the AR 7124 at 1.5, 4.7, and 8.4 GHz. In general, discrete coronal loop systems are rarely resolved at 1.5 GHz wavelengths because of limited brightness contrast due to optical depth effects and wave scattering. Due to its unusual anemone-like morphology, however, several discrete loops or loop systems are resolved by both the VLA at 1.5 GHz and the SXT in AR 7124. Title: Active Region 7123: Its Peculiar Radio Polarization and the Distribution of the Umbral Coronal Plasma Authors: Vourlidas, A.; Bastian, T. S.; Aschwanden, M. J. Bibcode: 1995AAS...18710105V Altcode: 1995BAAS...27.1426V A comprehensive set of microwave and soft x-ray observations of solar active region 7123 was obtained during 3--10 April, 1992. Here, we present a detailed analysis of the polarized radio emission from the sunspot-associated component of AR 7123. We use the VLA observations at 1.5, 4.7 and 8.4 GHz, supported by the available x-ray and magnetic data. We concentrate on understanding the 4.7 GHz o-mode polarization over the umbra of the leading spot of AR 7123 and its variation with aspect angle within the physical context provided by the x-ray observations (SXT/Yohkoh) and past work on umbral atmospheres. Title: Aspect Angle Dependence of the Polarized Radio Emission from AR 7123 Authors: Vourlidas, A.; Bastian, T. S.; Aschwanden, M. J.; Nitta, N. Bibcode: 1995SPD....26..701V Altcode: 1995BAAS...27..965V No abstract at ADS Title: Joint Radio and Soft X-ray Imaging of an ``Anemone'' Active Region Authors: Vourlidas, A.; Bastian, T. S.; Aschwanden, M.; Nitta, N. Bibcode: 1994AAS...185.8609V Altcode: 1994BAAS...26Q1465V The Very Large Array and the Soft X-ray Telescope aboard the Yohkoh satellite observed the rapid growth and decay of a so-called ``anemone'' active region on 3-6 April (AR 7124). In general, discrete coronal loop systems are rarely resolved at radio wavelengths due to optical depth effects and scattering. In the case of AR 7124, however, several discrete loops or loop systems are resolved by both the VLA and the SXT, probably due to its unusual ``anemone''-like morphology. Furthermore, the region exhibited a significant amount of variability, especially on April 3, marked by many subflares and intensity changes as has been reported in flare patrol observations. In the present study, physical parameters derived from multiband radio and soft x-ray techniques for discrete loops are compared. The temporal evolution of these parameters is also examined. Title: A Multiband Study of Radio Emission from Solar Active Regions Authors: Vourlidas, Angelos; Bastian, T. S. Bibcode: 1994ASPC...68..369V Altcode: 1994sare.conf..369V No abstract at ADS Title: The Structure of Solar Active Regions Authors: Vourlidas, A.; Bastian, T. S. Bibcode: 1992AAS...180.4204V Altcode: 1992BAAS...24..796V In past years, x-ray observations of solar active regions have lead to the expectation of greater brightness temperatures at radio wavelengths than those typically observed. It has been suggested that cool plasma in the corona along the line of sight attenuates radio emission via free-free absorption. If such plasma is present, it has consequences for both the microwave spectrum and its polarization properties. In order to test these ideas, high quality radio and x-ray maps are required. We present a comprehensive set of observations of a large solar active region (NOAO/USAF number 5131) made during the IAU sanctioned International Solar Month in September, 1988. The VLA was used to image the Sun in the 90, 20, 6 and 3.6 cm bands between 1--4 September. To improve the image quality we used the technique of frequency synthesis at 3.6, 6 and 20 cm. The final maps are among the best in dynamic range yet obtained. In addition to the radio maps, the data base includes images from the SMM XRP in Fe XVII, magnetograms, and Hα observations. We reconcile the x-ray and radio observations with a simple model which differs somewhat from past models. Rather than relying on a screen of cool plasma between the source and the observer, we take explicit account of the highly inhomogeneous structure of solar active regions. We briefly compare and contrast the consequences of this model with existing models.