Author name code: bryans ADS astronomy entries on 2022-09-14 author:"Bryans, Paul" ------------------------------------------------------------------------ Title: Exploration of the Physical and Spectroscopic Characteristics of Coronal Rain Authors: Tyson, Kalista; Lacatus, Daniela; Paraschiv, Alin; Bryans, Paul Bibcode: 2021AGUFMSH45B2381T Altcode: The correlation between the phenomenon known as coronal rain and the origin of the Suns heating and cooling mechanisms has become a popular area for exploration in recent years. In this study, we explored the specifics of how plasma flows are triggered and how material moves along closed magnetic field entities. Using spectroscopic data from the Interface Region Imaging Spectrograph (IRIS), we analyzed the Mg II, Si IV and C II emission lines in relation to the different magnetic structures, allowing us to study plasma under different emitting regimes. We have extracted spectroscopic characteristics of these emission lines for an off-limb prolonged coronal rain event taking place above a quiescent active region system. Additionally, we augmented our dataset with SDO/AIA coronal observations, highlighting corresponding higher temperature structures. We report a case where recurring coronal rain episodes occur over timescales of several hours. Our work reveals a multitude of complex, differently oriented, and turbulent, structures under what appeared to be a standard coronal rain event. Title: Measuring the Magnetic Origins of Solar Flares, Coronal Mass Ejections, and Space Weather Authors: Judge, Philip; Rempel, Matthias; Ezzeddine, Rana; Kleint, Lucia; Egeland, Ricky; Berdyugina, Svetlana V.; Berger, Thomas; Bryans, Paul; Burkepile, Joan; Centeno, Rebecca; de Toma, Giuliana; Dikpati, Mausumi; Fan, Yuhong; Gilbert, Holly; Lacatus, Daniela A. Bibcode: 2021ApJ...917...27J Altcode: 2021arXiv210607786J We take a broad look at the problem of identifying the magnetic solar causes of space weather. With the lackluster performance of extrapolations based upon magnetic field measurements in the photosphere, we identify a region in the near-UV (NUV) part of the spectrum as optimal for studying the development of magnetic free energy over active regions. Using data from SORCE, the Hubble Space Telescope, and SKYLAB, along with 1D computations of the NUV spectrum and numerical experiments based on the MURaM radiation-magnetohydrodynamic and HanleRT radiative transfer codes, we address multiple challenges. These challenges are best met through a combination of NUV lines of bright Mg II, and lines of Fe II and Fe I (mostly within the 4s-4p transition array) which form in the chromosphere up to 2 × 104 K. Both Hanle and Zeeman effects can in principle be used to derive vector magnetic fields. However, for any given spectral line the τ = 1 surfaces are generally geometrically corrugated owing to fine structure such as fibrils and spicules. By using multiple spectral lines spanning different optical depths, magnetic fields across nearly horizontal surfaces can be inferred in regions of low plasma β, from which free energies, magnetic topology, and other quantities can be derived. Based upon the recently reported successful sub-orbital space measurements of magnetic fields with the CLASP2 instrument, we argue that a modest space-borne telescope will be able to make significant advances in the attempts to predict solar eruptions. Difficulties associated with blended lines are shown to be minor in an Appendix. Title: Hinode and IRIS Synoptic Observations of Solar Cycle Transition at Mid-Latitudes Authors: Egeland, R.; Centeno, R.; Lacatus, D.; de Toma, G.; Bryans, P.; McIntosh, S. Bibcode: 2021AAS...23811324E Altcode: Recent observations by McIntosh et al. using SDO/AIA coronal bright point density and the magnetogram-derived large scale open magnetic flux "g-nodes" have traced out extended solar cycle activity bands that originate at ~55 degrees latitude and propagate toward the equator. When the opposite hemisphere bands "terminate" at the equator, this event corresponds with the rapid rise of new cycle flux and active regions at mid-latitudes, ~35 degrees. We present weekly synoptic high-resolution observations of mid-latitude (35-40 degrees) magnetic flux and chromospheric emission from Hinode SOT/SP and IRIS starting from March 2017 until today, covering the end of cycle 24 and the beginnings of cycle 25. After carefully correcting for instrumental shifts, noise, and solar B-angle effects, we analyze time series of mean magnetic flux, chromospheric line intensity, and statistical properties of magnetic regions for signals of a developing cycle 25 and the passage of the activity bands in these typically quiet mid-latitude regions. Initial results show that the statistical properties of our activity metrics are roughly constant over the four year period, with a step function increase in activity that corresponds to a change to a lower observation latitude. Finally, we investigate the correspondence of SDO/AIA coronal bright points in our observational field of view to chromospheric emission and photospheric magnetic features. Title: Investigating the Chromospheric Footpoints of the Solar Wind Authors: Bryans, Paul; McIntosh, Scott W.; Brooks, David H.; De Pontieu, Bart Bibcode: 2020ApJ...905L..33B Altcode: Coronal holes present the source of the fast solar wind. However, the fast solar wind is not unimodal—there are discrete, but subtle, compositional, velocity, and density structures that differentiate different coronal holes as well as wind streams that originate within one coronal hole. In this Letter we exploit full-disk observational "mosaics" performed by the Interface Region Imaging Spectrograph (IRIS) spacecraft to demonstrate that significant spectral variation exists within the chromospheric plasma of coronal holes. The spectral differences outline the boundaries of some—but not all—coronal holes. In particular, we show that the "peak separation" of the Mg II h line at 2803 Å illustrates changes in what appear to be open magnetic features within a coronal hole. These observations point to a chromospheric source for the inhomogeneities found in the fast solar wind. These chromospheric signatures can provide additional constraints on magnetic field extrapolations close to the source, potentially on spatial scales smaller than from traditional coronal hole detection methods based on intensity thresholding in the corona. This is of increased importance with the advent of Parker Solar Probe and Solar Orbiter and the ability to accurately establish the connectivity between their in situ measurements and remote sensing observations of the solar atmosphere. Title: A New Facility for Airborne Solar Astronomy: NASA's WB-57 at the 2017 Total Solar Eclipse Authors: Caspi, Amir; Seaton, Daniel B.; Tsang, Constantine C. C.; DeForest, Craig E.; Bryans, Paul; DeLuca, Edward E.; Tomczyk, Steven; Burkepile, Joan T.; Casey, Thomas "Tony"; Collier, John; Darrow, Donald "DD"; Del Rosso, Dominic; Durda, Daniel D.; Gallagher, Peter T.; Golub, Leon; Jacyna, Matthew; Johnson, David "DJ"; Judge, Philip G.; Klemm, Cary "Diddle"; Laurent, Glenn T.; Lewis, Johanna; Mallini, Charles J.; Parent, Thomas "Duster"; Propp, Timothy; Steffl, Andrew J.; Warner, Jeff; West, Matthew J.; Wiseman, John; Yates, Mallory; Zhukov, Andrei N.; NASA WB-57 2017 Eclipse Observing Team Bibcode: 2020ApJ...895..131C Altcode: 2020arXiv200409658C NASA's WB-57 High Altitude Research Program provides a deployable, mobile, and stratospheric platform for scientific research. Airborne platforms are of particular value for making coronal observations during total solar eclipses because of their ability both to follow the Moon's shadow and to get above most of the atmospheric air mass that can interfere with astronomical observations. We used the 2017 August 21 eclipse as a pathfinding mission for high-altitude airborne solar astronomy, using the existing high-speed visible-light and near/midwave infrared imaging suite mounted in the WB-57 nose cone. In this paper, we describe the aircraft, the instrument, and the 2017 mission; operations and data acquisition; and preliminary analysis of data quality from the existing instrument suite. We describe benefits and technical limitations of this platform for solar and other astronomical observations. We present a preliminary analysis of the visible-light data quality and discuss the limiting factors that must be overcome with future instrumentation. We conclude with a discussion of lessons learned from this pathfinding mission and prospects for future research at upcoming eclipses, as well as an evaluation of the capabilities of the WB-57 platform for future solar astronomy and general astronomical observation. Title: Novel Measurements of Solar Corona during the July 2 2019 Total Eclipse over Chile Authors: Monaghan, A.; Bryans, P.; Berkey, B.; Rivera, Y. Bibcode: 2019AGUFMSA33B3153M Altcode: Physical features of the solar corona such as temperature, density, and magnetic field, have been demonstrated to affect the polarization of coronal light making polarimetry one of the most crucial diagnostic tools for solar research. Although the history of polarimetry in solar physics is long, the ever-advancing world of technology continually provides opportunities for implementation with new instruments and new methods. The pursuit of new measurements could shed light on long-standing unsolved problems of the solar corona, and increase our understanding of the corona, solar weather, and our sun. The PolarCam snapshot micropolarizer camera from 4D Technologies could hold the potential for novel exploration of the solar corona. Developed for use in interferometric measurements, the PolarCam is sensitive to linearly polarized light on a pixel scale and has the unique potential for size- and weight-constrained measurements such as CubeSat deployment. Similarly, the relatively unexplored Si X emission line (1.43 microns) could provide novel measurements of the solar corona, and shows great promise for magnetometry.

The 2019 Total Solar Eclipse in Chile provided an opportunity for the exploration of the Si X line as well as an investigation into the potential of PolarCam and similar technology. A team from the High Altitude Observatory (HAO) in Boulder observed the eclipse from Cerro Tololo Inter-American Observatory, taking measurements of Si X (1.43 micron) and white-light (734 nm) polarization. PolarCam observations, taken during total solar eclipse, were quantitatively compared with ground-based white-light coronagraph measurements, demonstrating the capabilities and limitations of such a detector for coronal measurements. The instrument's potential for future deployment in expeditions or cubesat missions is also evaluated. Finally, preliminary data from the Si X experiment is presented and possible avenues for further exploration are proposed. Title: Probing the solar corona with Sun-grazing comets: comparing MHDsimulations with EUV observations Authors: Jia, Y. D.; Pesnell, W. D.; Liu, W.; Downs, C.; Bryans, P. Bibcode: 2019AGUFMSH13A..03J Altcode: Sun -grazing comets can dive within one solar radii of the Sun 's surface. The cometary materials expand along the comet's orbit, and undergo various stages of fierce thermal-chemical reactions on the scales of seconds to minutes. These reactions ionize cometary ions through successive charge states , which is revealed by certain emission lines in the AIA images. Such plasma reaction processes are significantly affected by the transient structures in the corona, and thus these structures are revealed by the structures and shapes of the comet tail. We combine three numerical models: a global corona model, particle transportation model, and cometary plasma interaction model into one framework to simulate the interaction of Sun -grazing comets in the low corona. In our framework, cometary ejecta are vaporized and then ionized via multiple channels, and then confined by the coronal magnetic field. Constrained by imaging observations of the and cometary interaction images, we apply our framework to trace back to the local condition of the ambient corona, and its spatiotemporal variation. Previously, our model confirmed the importance of the ambient magnetic field vector in shaping the tail. In this study, we use the C/2011 W3 (Lovejoy) perihelion to determine the local plasma and field conditions in the corona. Our framework is capable of resolving structures from thousands of meters to tens of million meters, so we can identify the fine spatial variations in plasma density and magnetic field intensity, which may be visible in future/on-going close-up coronal observations. Title: Coronal Hole Variation from Chromosphere to Solar Wind Authors: Bryans, P. Bibcode: 2019AGUFMSH53B3369B Altcode: Coronal holes (CHs) are most commonly defined as long-lived regions of reduced intensity in EUV images, and known to be the source of the fast solar wind. Recent analysis of the spectral characteristics of CHs, using data from the Interface Region Imaging Spectrograph (IRIS) and the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode, belies their apparent uniformity in imaging data. Despite the typical assertion that CHs are the source of the fast solar wind, EIS measurements show regions within a CH with indications of slow-wind composition in the corona. The spectral signatures of these regions extend to the chromosphere, as evidenced in the Mg II lines measured by IRIS, with the possibility that differences in the coronal composition could also have signatures in the lower solar atmosphere. In this presentation we will explore what these spectroscopic measurements reveal about the underlying magnetic field and discuss the implications of variations in the chromosphere and corona on the solar wind. Title: Novel observations of the middle corona during the 2017 total solar eclipse Authors: Caspi, A.; Seaton, D. B.; Tsang, C.; DeForest, C.; Bryans, P.; Samra, J.; DeLuca, E.; Tomczyk, S.; Burkepile, J.; Gallagher, P.; Golub, L.; Judge, P. G.; Laurent, G. T.; West, M.; Zhukov, A. Bibcode: 2019AGUFMSH13A..10C Altcode: Total solar eclipses offer rare opportunities to study the middle corona. This intriguing region contains complex interfaces and transitions between physical regimes, but has historically been under-observed due to the challenges of observing its dim emission so close to the bright inner corona and blinding solar disk. The unique circumstances of a total solar eclipse coupled with a high-altitude observing platform provide nearly space-quality observing conditions, including for wavelengths inaccessible by ground-based observatories, but with availability of ground-quality resources, including high-speed, high-resolution, wide-field coronography typically inaccessible from space. We used the 2017 August 21 "Great American" total solar eclipse to observe the solar corona from ~1.02 to ~3 RSun in both visible (533.9 ± 4.75 nm) and medium-wave infrared (3-5 μm) light using stabilized telescopes on two of NASA's WB-57F high-altitude research aircraft. This pathfinding mission utilized existing instrumentation to evaluate the platform performance, guide instrumentation development, and explore new discovery space for future studies of the middle corona.

We present the high-speed (30 Hz), high-resolution (3 arcsec/pixel) visible and IR observations obtained during the eclipse, and analysis of these observations in the context of coronal structure and dynamics. We discuss the limitations of the prototype data and pathways forward for future instrumentation and missions optimized for the range of observable parameters in the middle corona. We also discuss the benefits of such eclipse studies to an understanding of the corona as a single, unified system, from its origins at the solar surface to its extension into the heliosphere, particularly within the context of a developing multi- and inter-disciplinary research collaboration, COHERENT (the "Corona as a Holistic Environment" Research Network). Title: Solar Eclipse Observations from the Ground and Air from 0.31 to 5.5 Microns Authors: Judge, Philip; Berkey, Ben; Boll, Alyssa; Bryans, Paul; Burkepile, Joan; Cheimets, Peter; DeLuca, Edward; de Toma, Giuliana; Gibson, Keon; Golub, Leon; Hannigan, James; Madsen, Chad; Marquez, Vanessa; Richards, Austin; Samra, Jenna; Sewell, Scott; Tomczyk, Steven; Vera, Alysha Bibcode: 2019SoPh..294..166J Altcode: We present spectra and broad-band polarized light data from a novel suite of instruments deployed during the 21st August 2017 total solar eclipse. Our goals were to survey solar spectra at thermal infrared wavelengths during eclipse, and to test new technology for measuring polarized coronal light. An infrared coronal imaging spectrometer, flown at 14.3 km altitude above Kentucky, was supported on the ground by observations from Madras, Oregon (elevation 683 m) and Camp Wyoba on Casper Mountain, Wyoming (2402 m). In Wyoming we deployed a new infrared Fourier Transform Spectrometer (FTS), three low-dispersion spectrometers loaned to us by Avantes, a novel visible-light camera PolarCam, sensitive to linear polarization, and one of two infrared cameras from FLIR Systems, the other operated at Madras. Circumstances of eclipse demanded that the observations spanned 17:19 to 18:26 UT. We analyze spectra of the limb photosphere, the chromosphere, prominences, and coronal lines from 310 nm to 5.5 μm. We calibrated data photometrically using the solar disk as a source. Between different spectrometers, the calibrations were consistent to better than 13%. But the sensitivities achieved were insufficient to detect coronal lines from the ground. The PolarCam data are in remarkable agreement with polarization data from the K-Cor synoptic instrument on Mauna Loa, and with FLIR intensity data acquired in Madras. We discuss new results, including a detection of the He I 1083 nm multiplet in emission during the whole of totality. The combination of the FTS and AIR-Spec spectra reveals for the first time the effects of the telluric extinction on the infrared coronal emission lines, to be observed with upcoming Daniel K. Inouye Solar Telescope. Title: Instrument Calibration of the Interface Region Imaging Spectrograph (IRIS) Mission Authors: Wülser, J. -P.; Jaeggli, S.; De Pontieu, B.; Tarbell, T.; Boerner, P.; Freeland, S.; Liu, W.; Timmons, R.; Brannon, S.; Kankelborg, C.; Madsen, C.; McKillop, S.; Prchlik, J.; Saar, S.; Schanche, N.; Testa, P.; Bryans, P.; Wiesmann, M. Bibcode: 2018SoPh..293..149W Altcode: The Interface Region Imaging Spectrograph (IRIS) is a NASA small explorer mission that provides high-resolution spectra and images of the Sun in the 133 - 141 nm and 278 - 283 nm wavelength bands. The IRIS data are archived in calibrated form and made available to the public within seven days of observing. The calibrations applied to the data include dark correction, scattered light and background correction, flat fielding, geometric distortion correction, and wavelength calibration. In addition, the IRIS team has calibrated the IRIS absolute throughput as a function of wavelength and has been tracking throughput changes over the course of the mission. As a resource for the IRIS data user, this article describes the details of these calibrations as they have evolved over the first few years of the mission. References to online documentation provide access to additional information and future updates. Title: Interaction between cool material from Sun-grazing comets and the low corona Authors: Jia, Yingdong; Pesnell, William; Liu, Wei; Downs, Cooper; Bryans, Paul Bibcode: 2018cosp...42E1613J Altcode: Sun-grazing comets dive into altitudes lower than 1 solar radius from the chromosphere. Cool materials of temperature lower than 10 ^{3}K explode from the comet into the 10 ^{6} K corona. These materials undergone various stages of rapid chemical reactions in scales of seconds to minutes. Such reactions Structures in such images of various wavelengths indicate strong variation in ambient conditions of the corona. We combine three numerical models: low corona model, particle transportation model, and cometary plasma interaction model into one framework to model the interaction of Sun-grazing comets in the low corona. In our framework, cometary vapor are ionized via multiple channels, and then detained by the coronal magnetic field. In seconds, these ions are further ionized into their highest charge state, which is revealed by certain emission lines. Constrained by coronal graphs and cometary interaction images, we apply our framework to trace back to the local condition of the ambient corona, and its spatial/time variation. Our frame work is able to resolve structures of sub-million meters to tens of million meters. Once trained by multiple stages of the comet's journey in the low corona, this framework can identify the fine spatial variations in plasma density and magnetic field intensity, which may be visible to future close-up observations. Title: New Coronal Science from NASA WB-57F High-Altitude Aircraft Observations of the 2017 Total Solar Eclipse Authors: Caspi, Amir; DeLuca, . Edward; Tomczyk, Steven; DeForest, Craig; Bryans, Paul; Seaton, Daniel; Tsang, Constantine Bibcode: 2018cosp...42E.526C Altcode: Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface, using ground-based and airborne observatories that would otherwise be dominated by the intense solar disk and high sky brightness. Studying the corona is critical to gaining a better understanding of physical processes that occur on other stars and astrophysical objects, as well as understanding the dominant driver of space weather that affects human assets at Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler; numerous theories abound, but are difficult to constrain due to the limited sensitivities and cadences of prior measurements. The stability of large-scale coronal structures and the extent of their reach to the middle and outer corona are also not well known, limited in large part by sensitivities and fields of view of existing observations.Airborne observations during a total eclipse provide unique advantages. By flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near-IR also become available due to significantly reduced water absorption. An airborne observatory can also follow the Moon's shadow, increasing the total observing time by 50% or more.We present current results of solar coronal measurements from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 high-altitude research aircraft, each equipped with two 8.7" telescopes feeding high-sensitivity visible (green line and nearby continuum) and medium-wave IR (3-5 {μ}m) cameras operating at high cadence (30 Hz) with ∼3 arcsec/pixel platescale and ±3 R_{sun} fields of view. The aircraft flew along the eclipse path, separated by ∼110 km, to observe a summed ∼7.5 minutes of totality in both visible and MWIR. These observations enable groundbreaking studies of high-speed coherent motion - including possible Alfvén waves and nanojets - in the lower and middle corona that could shed light on coronal heating processes and the formation and stability of coronal structures. Our MWIR observations of a cool prominence and hot coronal active region plasma will be combined with spectra from the AIR-Spec instrument, flown concurrently on NCAR's HIAPER GV. We review the WB-57 eclipse mission and the current results of analysis on the visible and IR coronal measurements, along with an outlook for future analysis and missions. Title: Eclipse Science from 50,000 Feet: New Coronal Results from NASA WB-57F High-Altitude Aircraft Observations of the 2017 Total Solar Eclipse Authors: Caspi, Amir; Tsang, Constantine; Seaton, Daniel B.; DeForest, Craig; Bryans, Paul; DeLuca, Edward; Tomczyk, Steven; Burkepile, Joan; Casey, Thomas Anthony; Collier, John; Darrow, Donald DD; Del Rosso, Dominic; Durda, Daniel D.; Gallagher, Peter; Gascar, Jasmine; Golub, Leon; Jacyna, Matthew; Johnson, David DJ; Judge, Philip G.; Klemm, Cary; Laurent, Glenn Thomas; Lewis, Johanna; Mallini, Charles; Parent, Thomas Duster; Propp, Timothy; Steffl, Andrew; Warner, Jeff; West, Matthew John; Wiseman, John; Yates, Mallory; Zhukov, Andrei Bibcode: 2018tess.conf31302C Altcode: Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface. Studying the corona is critical to gaining a better understanding of the dominant driver of space weather that affects human assets on Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler. The stability of large-scale coronal structures and the extent of their reach to the middle and outer corona are also not well known, limited in large part by sensitivities and fields of view of existing observations.

Airborne observations during a total eclipse provide unique advantages. By flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near-IR also become available due to significantly reduced water absorption. An airborne observatory can also follow the Moon's shadow, increasing the total observing time by 50% or more.

We present current results of solar coronal measurements from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 high-altitude research aircraft, each equipped with two 8.7-inch telescopes feeding high-sensitivity visible (green line and nearby continuum) and medium-wave IR (3-5 μm) cameras operating at high cadence (30 Hz) with ∼3 arcsec/pixel platescale and ±3 Rsun fields of view. The two aircraft flew along the eclipse path, separated by ∼110 km, to observe a total of ∼7.5 minutes of totality in both visible and MWIR. These observations enable groundbreaking studies of high-speed coherent motion - including possible Alfvén waves and nanojets - in the lower and middle corona that could shed light on coronal heating processes and the formation and stability of coronal structures. Our MWIR observations of a cool prominence and hot coronal active region plasma will be combined with spectra from the AIR-Spec instrument, flown concurrently on NCAR's HIAPER GV. We review the WB-57 eclipse mission and the current results of analysis on the visible and IR coronal measurements, along with an outlook for future analysis and missions. Title: Chasing the Great American 2017 Total Solar Eclipse: Coronal Results from NASA's WB-57F High-Altitude Research Aircraft Authors: Caspi, A.; Tsang, C.; DeForest, C. E.; Seaton, D. B.; Bryans, P.; Burkepile, J.; Casey, T. A.; Collier, J.; Darrow, D.; DeLuca, E.; Durda, D. D.; Gallagher, P.; Golub, L.; Judge, P. G.; Laurent, G. T.; Lewis, J.; Mallini, C.; Parent, T.; Propp, T.; Steffl, A.; Tomczyk, S.; Warner, J.; West, M. J.; Wiseman, J.; Zhukov, A. Bibcode: 2017AGUFMSH24A..05C Altcode: Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface, using ground-based and airborne observatories that would otherwise be dominated by the intense solar disk and high sky brightness. Studying the corona is critical to gaining a better understanding of physical processes that occur on other stars and astrophysical objects, as well as understanding the dominant driver of space weather that affects human assets at Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler; numerous theories abound, but are difficult to constrain due to the limited sensitivities and cadences of prior measurements. The origins and stability of coronal fans, and the extent of their reach to the middle and outer corona, are also not well known, limited in large part by sensitivities and fields of view of existing observations. Airborne observations during the eclipse provide unique advantages; by flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near- IR also become available due to significantly reduced water absorption. For an eclipse, an airborne observatory can also follow the shadow, increasing the total observing time by 50% or more. We present results of solar coronal measurements from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 high-altitude research aircraft, each equipped with two 8.7" telescopes feeding high-sensitivity visible (green-line) and medium-wave IR (3-5 μm) cameras operating at high cadence (30 Hz) with 3 arcsec/pixel platescale and ±3 R_sun fields of view. The aircraft flew along the eclipse path, separated by 110 km, to observe a summed 7.5 minutes of totality in both visible and NIR, enabling groundbreaking studies of high-speed wave motions and nanojets in the lower corona, the structure and extent of coronal fans, and constraints on a potential primordial dust ring around the Sun. We review the mission, and the results of analysis on the visible and IR coronal measurements. Title: Multi-wavelength observations of the solar atmosphere from the August 21, 2017 total solar eclipse Authors: Tomczyk, S.; Boll, A.; Bryans, P.; Burkepile, J.; Casini, R.; DeLuca, E.; Gibson, K. L.; Judge, P. G.; McIntosh, S. W.; Samra, J.; Sewell, S. D. Bibcode: 2017AGUFMSH24A..04T Altcode: We will conduct three experiments at the August 21, 2017 total solar eclipse that we call the Rosetta Stone experiments. First, we will obtain narrow-bandpass images at infrared wavelengths of the magnetically sensitive coronal emission lines of Fe IX 2855 nm, Mg VIII 3028 nm and Si IX 3935 nm with a FLIR thermal imager. Information on the brightness of these lines is important for identifying the optimal lines for coronal magnetometry. These images will also serve as context images for the airborne AirSpec IR coronal spectroscopy experiment (Samra et al). Second, we will obtain linear polarization images of the visible emission lines of Fe X 637 nm and Fe XI 789 nm as well as the continuum polarization near 735 nm. These will be obtained with a novel detector with an integral array of linear micro-polarizers oriented at four different angles that enable polarization images without the need for liquid crystals or rotating elements. These measurements will provide information on the orientation of magnetic fields in the corona and serve to demonstrate the new detector technology. Lastly, we will obtain high cadence spectra as the moon covers and uncovers the chromosphere immediately after 2nd contact and before third contact. This so-called flash spectrum will be used to obtain information about chromospheric structure at a spatial resolution higher than is possible by other means. In this talk, we will describe the instrumentation used in these experiments and present initial results obtained with them. This work is supported by a grant from NASA, through NSF base funding of HAO/NCAR and by generous loans of equipment from our corporate partners, FLIR, 4D Technologies and Avantes. Title: Digging into the corona: A modeling framework trained with Sun-grazing comet observations Authors: Jia, Y. D.; Pesnell, W. D.; Bryans, P.; Downs, C.; Liu, W.; Schwartz, S. J. Bibcode: 2017AGUFMSH11B2437J Altcode: Images of comets diving into the low corona have been captured a few times in the past decade. Structures visible at various wavelengths during these encounters indicate a strong variation of the ambient conditions of the corona. We combine three numerical models: a global coronal model, a particle transportation model, and a cometary plasma interaction model into one framework to model the interaction of such Sun-grazing comets with plasma in the low corona. In our framework, cometary vapors are ionized via multiple channels and then captured by the coronal magnetic field. In seconds, these ions are further ionized into their highest charge state, which is revealed by certain coronal emission lines. Constrained by observations, we apply our framework to trace back to the local conditions of the ambient corona, and their spatial/time variation over a broad range of scales. Once trained by multiple stages of the comet's journey in the low corona, we illustrate how this framework can leverage these unique observations to probe the structure of the solar corona and solar wind. Title: Surveying the IR corona during the 2017 solar eclipse Authors: Bryans, P.; Hannigan, J. W.; Sewell, S. D.; Judge, P. G. Bibcode: 2017AGUFMSH13B2479B Altcode: The spectral emission of the infrared solar corona is the most promising direct diagnostic of the coronal magnetic field, and yet remains poorly measured. During the 2017 total solar eclipse, we will perform the first spectral survey of the IR corona using the NCAR Airborne Interferometer. This Fourier Transform Infrared Spectrometer is configured to observe the coronal spectrum from 1.5 to 5.5 microns at R 10,000 from a ground-based site. The location is atop Casper Mountain, Wyoming (42.73ºN, 106.32ºW, 2400 masl), 8 km from the center-line of totality. In this presentation, we will outline the need for such measurements, describe the instrument design and adaptation for the eclipse measurement, observation scheme, and present preliminary results. We will also discuss implications for observing infrared coronal lines from the ground, for example with the upcoming DKIST facility. Title: ASPIRE - Airborne Spectro-Polarization InfraRed Experiment Authors: DeLuca, E.; Cheimets, P.; Golub, L.; Madsen, C. A.; Marquez, V.; Bryans, P.; Judge, P. G.; Lussier, L.; McIntosh, S. W.; Tomczyk, S. Bibcode: 2017AGUFMSH13B2480D Altcode: Direct measurements of coronal magnetic fields are critical for taking the next step in active region and solar wind modeling and for building the next generation of physics-based space-weather models. We are proposing a new airborne instrument to make these key observations. Building on the successful Airborne InfraRed Spectrograph (AIR-Spec) experiment for the 2017 eclipse, we will design and build a spectro-polarimeter to measure coronal magnetic field during the 2019 South Pacific eclipse. The new instrument will use the AIR-Spec optical bench and the proven pointing, tracking, and stabilization optics. A new cryogenic spectro-polarimeter will be built focusing on the strongest emission lines observed during the eclipse. The AIR-Spec IR camera, slit jaw camera and data acquisition system will all be reused. The poster will outline the optical design and the science goals for ASPIRE. Title: First results from the NASA WB-57 airborne observations of the Great American 2017 Total Solar Eclipse Authors: Caspi, Amir; Tsang, Constantine; DeForest, Craig; Seaton, Daniel B.; Bryans, Paul; Tomczyk, Steven; Burkepile, Joan; Judge, Phil; DeLuca, Edward E.; Golub, Leon; Gallagher, Peter T.; Zhukov, Andrei; West, Matthew; Durda, Daniel D.; Steffl, Andrew J. Bibcode: 2017SPD....4810701C Altcode: Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface, using ground-based and airborne observatories that would otherwise be dominated by the intense solar disk and high sky brightness. Studying the corona is critical to gaining a better understanding of physical processes that occur on other stars and astrophysical objects, as well as understanding the dominant driver of space weather that affects human assets at Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler; numerous theories abound, but are difficult to constrain due to the limited sensitivities and cadences of prior measurements. The origins and stability of coronal fans, and the extent of their reach to the middle and outer corona, are also not well known, limited in large part by sensitivities and fields of view of existing observations.Airborne observations during the eclipse provide unique advantages; by flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near-IR also become available due to significantly reduced water absorption. For an eclipse, an airborne observatory can also follow the shadow, increasing the total observing time by 50% or more.We present the first results from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 research aircraft, each equipped with two 8.7" telescopes feeding high-sensitivity visible (green-line) and near-IR (3-5 µm) cameras operating at high cadence (30 Hz) with ~3 arcsec/pixel platescale and ±3 R_sun fields of view. The aircraft will fly along the eclipse path, separated by ~90 km, to observe a summed ~8 minutes of totality in both visible and NIR, enabling groundbreaking studies of high-speed wave motions and nanojets in the lower corona, the structure and extent of coronal fans, and constraints on a potential primordial dust ring around the Sun. Title: On the Connection between Propagating Solar Coronal Disturbances and Chromospheric Footpoints Authors: Bryans, P.; McIntosh, S. W.; De Moortel, I.; De Pontieu, B. Bibcode: 2016ApJ...829L..18B Altcode: The Interface Region Imaging Spectrograph (IRIS) provides an unparalleled opportunity to explore the (thermal) interface between the chromosphere, transition region, and the coronal plasma observed by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO). The SDO/AIA observations of coronal loop footpoints show strong recurring upward propagating signals—“propagating coronal disturbances” (PCDs) with apparent speeds of the order of 100-120 km s-1. That signal has a clear signature in the slit-jaw images of IRIS in addition to identifiable spectral signatures and diagnostics in the Mg iih (2803 Å) line. In analyzing the Mg iih line, we are able to observe the presence of magnetoacoustic shock waves that are also present in the vicinity of the coronal loop footpoints. We see there is enough of a correspondence between the shock propagation in Mg iih, the evolution of the Si IV line profiles, and the PCD evolution to indicate that these waves are an important ingredient for PCDs. In addition, the strong flows in the jet-like features in the IRIS Si IV slit-jaw images are also associated with PCDs, such that waves and flows both appear to be contributing to the signals observed at the footpoints of PCDs. Title: Post Flare Giant Arches and Run-Away Reconnection Authors: West, Matthew; Seaton, Daniel B.; Savage, Sabrina; Bryans, Paul Bibcode: 2016SPD....4740206W Altcode: The nature of post-flare giant arches and their relation to regular post flare loops has long been debated, especially in the context of how post-flare giant arches can sustain their growth for such long periods. In this presentation we discuss how magnetic reconnection can be sustained to such great heights, and the role the background corona plays in maintaining this growth. We use observations from 14 October 2014, when the SWAP EUV solar telescope on-board the PROBA2 spacecraft observed an eruption that led to the formation of perhaps the largest post-eruptive loop system seen in the solar corona in solar cycle 24. These loops grew to a height of approximately 400000 km (>0.5 solar-radii). We provide evidence of on-going reconnection, through observations spanning from the chromosphere to the middle corona, and discuss how only certain conditions can maintain prolonged growth. Title: Measuring the IR solar corona during the 2017 eclipse Authors: Bryans, Paul; Hannigan, James; Philip, Judge; Larson, Brandon; Sewell, Scott; McIntire, Lauren Bibcode: 2016SPD....4730105B Altcode: On 21 August 2017 a total solar eclipse will pass across the continental United States, offering a unique opportunity to conduct scientific research of the solar atmosphere. With the light from the Sun eclipsed, the solar corona becomes visible in a way not possible when swamped by the light from the photosphere. The infrared (IR) spectrum of the corona, in particular, is predicted to contain some of the most magnetically sensitive spectral lines. However, no comprehensive survey of this spectral range has been carried out to date. Here, we describe a Fourier Transform Spectrometer, currently under construction at NCAR, to measure the IR spectrum from 2 to 12 microns. We will discuss the operation of the experiment, which will be deployed along the path of totality in Wyoming, and the scientific results we hope to obtain. Title: On the Absence of EUV Emission from Comet C/2012 S1 (ISON) Authors: Bryans, Paul; Pesnell, W. Dean Bibcode: 2016ApJ...822...77B Altcode: When the sungrazing comet C/2012 S1 (ISON) made its perihelion passage within two solar radii of the Sun’s surface, it was expected to be a bright emitter at extreme ultraviolet (EUV) wavelengths. However, despite solar EUV telescopes repointing to track the orbit of the comet, no emission was detected. This “null result” is interesting in its own right, offering the possibility of placing limits on the size and composition of the nucleus. We explain the lack of detection by considering the properties of the comet and the solar atmosphere that determine the intensity of EUV emission from sungrazing comets. By comparing these properties with those of sungrazing comet C/2011 W3 (Lovejoy), which did emit in the EUV, we conclude that the primary factor resulting in non-detectable EUV emission from C/2012 S1 (ISON) was an insufficiently large nucleus. We conclude that the radius of C/2012 S1 (ISON) was at least a factor of four less than that of C/2011 W3 (Lovejoy). This is consistent with white-light observations in the days before perihelion that suggested the comet was dramatically reducing in size on approach. Title: Observed Variability of the Solar Mg II h Spectral Line Authors: Schmit, D.; Bryans, P.; De Pontieu, B.; McIntosh, S.; Leenaarts, J.; Carlsson, M. Bibcode: 2015ApJ...811..127S Altcode: 2015arXiv150804714S The Mg ii h&k doublet are two of the primary spectral lines observed by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These lines are tracers of the magnetic and thermal environment that spans from the photosphere to the upper chromosphere. We use a double-Gaussian model to fit the Mg ii h profile for a full-Sun mosaic data set taken on 2014 August 24. We use the ensemble of high-quality profile fits to conduct a statistical study on the variability of the line profile as it relates the magnetic structure, dynamics, and center-to-limb viewing angle. The average internetwork profile contains a deeply reversed core and is weakly asymmetric at h2. In the internetwork, we find a strong correlation between h3 wavelength and profile asymmetry as well as h1 width and h2 width. The average reversal depth of the h3 core is inversely related to the magnetic field. Plage and sunspots exhibit many profiles that do not contain a reversal. These profiles also occur infrequently in the internetwork. We see indications of magnetically aligned structures in plage and network in statistics associated with the line core, but these structures are not clear or extended in the internetwork. The center-to-limb variations are compared to predictions of semi-empirical model atmospheres. We measure a pronounced limb darkening in the line core that is not predicted by the model. The aim of this work is to provide a comprehensive measurement baseline and preliminary analysis on the observed structure and formation of the Mg ii profiles observed by IRIS. Title: Full-Sun IRIS observations and what they reveal about chromosphere and transition region variation across the disk Authors: Bryans, Paul; McIntosh, Scott W. Bibcode: 2015TESS....120313B Altcode: The recent launch of the Interface Region Imaging Spectrometer (IRIS) has resulted in the first high-resolution spectroscopy of the chromosphere and transition region. The wavelength range sampled by IRIS allows us to measure emission and absorption lines across a range of heights in the lower solar atmosphere. However, the IRIS field-of-view is limited to 175 arcsec2, so simultaneous observations of these spectral lines is not possible across the entire disk. To overcome this problem we have performed full-disk mosaics, where we build up observations of the entire Sun using 184 different IRIS pointings. An analysis of these mosaics has highlighted interesting variations in the spectral line profiles across the disk. In this presentation we will summarize these findings and speculate on what physical insights they reveal. Title: Coronal Diagnostics from Cometary Emission Authors: Bryans, Paul; Pesnell, William D; Seaton, Daniel B; West, Matthew J Bibcode: 2014AAS...22442203B Altcode: The extreme ultraviolet (EUV) emission observed from sungrazing comets as they pass through the solar atmosphere can be used to infer the properties of the corona. In this paper we will discuss several of these properties that can be estimated from the EUV observations of Comet Lovejoy from AIA/SDO and SWAP/PROBA2. The longevity of the emission allows us to constrain the coronal electron density through which the comet passes. We will also discuss how dispersion of the emitting cometary material we can be used to estimate the local Alfven speed in the corona. Finally, measuring the deformation of the magnetic field as it is impacted by the comet can be used to estimate the magnetic field strength in this location. In the absence of the comet, none of these parameters are directly measurable in the corona. Sungrazing comets are thus unique probes of the solar atmosphere. Title: The Time-dependent Chemistry of Cometary Debris in the Solar Corona Authors: Pesnell, W. D.; Bryans, P. Bibcode: 2014ApJ...785...50P Altcode: Recent improvements in solar observations have greatly progressed the study of sungrazing comets. They can now be imaged along the entirety of their perihelion passage through the solar atmosphere, revealing details of their composition and structure not measurable through previous observations in the less volatile region of the orbit further from the solar surface. Such comets are also unique probes of the solar atmosphere. The debris deposited by sungrazers is rapidly ionized and subsequently influenced by the ambient magnetic field. Measuring the spectral signature of the deposited material highlights the topology of the magnetic field and can reveal plasma parameters such as the electron temperature and density. Recovering these variables from the observable data requires a model of the interaction of the cometary species with the atmosphere through which they pass. The present paper offers such a model by considering the time-dependent chemistry of sublimated cometary species as they interact with the solar radiation field and coronal plasma. We expand on a previous simplified model by considering the fully time-dependent solutions of the emitting species' densities. To compare with observations, we consider a spherically symmetric expansion of the sublimated material into the corona and convert the time-dependent ion densities to radial profiles. Using emissivities from the CHIANTI database and plasma parameters derived from a magnetohydrodynamic simulation leads to a spatially dependent emission spectrum that can be directly compared with observations. We find our simulated spectra to be consistent with observation. Title: What EUV Observations of Comet ISON Reveal About the Solar Corona Authors: Bryans, P.; Pesnell, W. D. Bibcode: 2013AGUFM.P31A1787B Altcode: Recent advances in space-based solar observations have greatly progressed the study of sungrazing comets. They can now be imaged along the entirety of their perihelion passage, revealing details of their composition, structure, and size. Such comets are also unique probes of the solar corona. The debris deposited by sungrazers is rapidly ionized and subsequently forced to follow the ambient magnetic field. In this paper we present preliminary results from EUV observations of Comet ISON. We estimate the size of the comet nucleus based on the EUV radiance and compare with independent estimates. The variation of the EUV emission with wavelength provides limits on the density of the ambient corona, and the motion of ionized debris will be used to infer the coronal magnetic field structure. Title: Time-dependent chemisty of outgassed cometary detritus in the solar corona Authors: Bryans, Paul; Pesnell, W. D. Bibcode: 2013SPD....44...32B Altcode: Recent observations of sungrazing comets have opened an exciting novel methof of probing the solar atmosphere. As well as providing valuable insight on the magnetic field of the lower corona, sungrazing comets also promise the potential of measuring the solar wind as their detritus follows the open field lines of the corona. In this work, we model the chemisty of the material sublimated from comets as they skim across the Sun. This material, largely water ice, is rapidly dissociated and ionized by the solar radiation field and coronal electrons. We track the evolution of the ionizing material as it expands into the corona using a generalized Haser-like model. Based on these results, we have predicted the emission resulting from these ions in different regions of the corona and compared the results with SDO/AIA observations. Title: What Will Comet ISON Debris Teach Us About the Sun? Authors: Pesnell, W. D.; Bryans, P. Bibcode: 2013SPD....44...34P Altcode: Comet ISON is a large sun-grazing comet due to pass perihelion on November 28, 2013. It will go through the corona 2.7 Rsun above the surface, much higher than earlier EUV comets. We will use our time-dependent models of cometary debris to discuss how the trail of Comet ISON can be used to probe the solar corona. The debris trail left behind as a sun-grazing comet passes by the Sun undergoes different chemical processes at different distances from the Sun. Near the Sun the material is rapidly converted to atomic ions and becomes part of the solar corona. Far from the Sun the evaporated material can remain in molecular form for a long time, while the grains of asteroidal material can exist long enough to become meteors in planetary atmospheres. The larger fragments may survive as independent comets, until the next perihelion passage. In between those limits the material moves in the solar wind acceleration region. The debris could become entrained in the solar wind and be measured by satellites far from the Sun. This material would be observed as abundance anomalies in the solar wind. We will describe the fate of the cometary debris trail left by Comet ISON and what the trail can tell us about the solar corona and solar wind. Title: EUV Emission from Sungrazing Comets Authors: Bryans, Paul; Pesnell, W. Dean Bibcode: 2013enss.confE..33B Altcode: The EUV emission resulting from comets' passage through the solar atmosphere has opened many exciting avenues of study. The observations show the sublimated cometary material to interact with ambient magnetic field and highlight magnetic features that are not normally visible with EUV telescopes. The first step, however, is to explain why the comet produces the EUV emission. In this talk, I will outline a model that describes the interaction of the cometary atmosphere with the quiescent solar background and results in such emission. In particular, the model accurately predicts the temporal and wavelength response of the emission detected by SDO/AIA. After describing the emission process, I will go on to discuss what we can learn about the corona from these observations. Title: Can we use comets as solar probes? Authors: Bryans, P. Bibcode: 2012AGUFMSH13B2251B Altcode: The EUV emission resulting from comets' passage through the solar atmosphere has opened many exciting avenues of study. The observations show the sublimated cometary material to interact with ambient magnetic field and highlight magnetic features that are not normally visible with EUV telescopes. The first step, however, is to explain why the comet produces the EUV emission. In this talk, I will outline a model that describes the interaction of the cometary atmosphere with the quiescent solar background and results in such emission. In particular, the model accurately predicts the temporal and wavelength response of the emission detected by SDO/AIA. After describing the emission process, I will go on to discuss what we can learn about the corona from these observations. Title: Investigating Coronal Activity by Release Using Sublimation Authors: Moore, T. E.; Bryans, P.; Pesnell, W. D.; Thompson, B. J. Bibcode: 2012AGUFMSH21D..05M Altcode: Plasma tails left by sun-grazing comets are visible in EUV, expanding their traditional role as "windsocks" into the low corona and serving as natural "chemical release" experiments. SDO obtained spectrally resolved video imagery of passages as close as 0.15 Rs to the solar photosphere at 12 sec frame cadence. Vaporized cometary materials form sublimation trails or "subtrails" that persist as long as 20 min. in 13.1 and 17.1 nm channels. Striation along local magnetic flux tubes implies filamentation of the visible plasma, and the subtrails exhibit substantial deviations from the comet orbital track. These reveal coronal winds and shears with velocities that are comparable to the comet velocity of up to 600 km/s. We analyze the likely origins and directionality of these winds and their implications for coronal heating in the altitude range where ion-neutral collision mean free paths are longer than the gyro radius but shorter than the atmospheric scale height, that is, the solar transition region. With active impact or photo-ionization, and charge exchange, the inferred super-thermal, sub-Alfvenic ion-neutral relative velocities will lead to ion pick-up distributions that decay or relax into "kappa" distributions with super-thermal power law tails that are relevant to the formation of the corona. Title: Time-dependent Chemistry of Detritus from Sun-grazing Comets Authors: Pesnell, W. D.; Bryans, P. Bibcode: 2012AGUFMSH13B2253P Altcode: As a sun-grazing comet passes the Sun at perihelion it leaves behind a trail of water vapor and detritus. The latter are grains of stony material that rapidly heat and vaporize in the intense radiation field of the solar photosphere. A large amount of O is produced from both the water and the stony material. The atomic material does not continue along the comet's orbital path but appears to move along the ambient magnetic field. This requires an ionization mechanism that rapidly converts the neutral atoms into ions. We propose two models of the time-dependent chemistry that can be used to calculate the ionization balance of O and Fe. One is an extension of the Haser model to include many stages of ionization but without recombination. The advantage is that an analytic solution can be derived for an arbitrary numbers of ionization stages. Once the time dependence is known it can be converted to the radial profile in either spherical or cylindrical symmetry. The other model integrates in time the equations describing ionization/recombination balance. Both types of solutions can be numerically inverted to estimate the radiance profiles. The models give the same sequence to the ionization stages, but the time dependence and radial profiles are shown to differ. Although we concentrate on the O and Fe chemistry because it is observed from SDO/AIA, any atom can be considered. Title: The Extreme-ultraviolet Emission from Sun-grazing Comets Authors: Bryans, P.; Pesnell, W. D. Bibcode: 2012ApJ...760...18B Altcode: 2012arXiv1209.5708B The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory has observed two Sun-grazing comets as they passed through the solar atmosphere. Both passages resulted in a measurable enhancement of extreme-ultraviolet (EUV) radiance in several of the AIA bandpasses. We explain this EUV emission by considering the evolution of the cometary atmosphere as it interacts with the ambient solar atmosphere. Molecules in the comet rapidly sublimate as it approaches the Sun. They are then photodissociated by the solar radiation field to create atomic species. Subsequent ionization of these atoms produces a higher abundance of ions than normally present in the corona and results in EUV emission in the wavelength ranges of the AIA telescope passbands. Title: The Journey of Sungrazing Comet Lovejoy Authors: Bryans, Paul; A'Hearn, M.; Battams, K.; Biesecker, D.; Bodewits, D.; Boice, D.; Brown, J.; Caspi, A.; Chodas, P.; Hudson, H.; Jia, Y.; Jones, G.; Keller, H. U.; Knight, M.; Linker, J.; Lisse, C.; Liu, W.; McIntosh, S.; Pesnell, W. D.; Raymond, J.; Saar, S.; Saint-Hilaire, P.; Schrijver, C.; Snow, M.; Tarbell, T.; Thompson, W.; Weissman, P.; Comet Lovejoy Collaboration Team Bibcode: 2012AAS...22052507B Altcode: Comet Lovejoy (C/2011 W3) was the first sungrazing comet, observed by space-based instruments, to survive perihelion passage. First observed by ground-based telescopes several weeks prior to perihelion, its journey towards the Sun was subsequently recorded by several solar observatories, before being observed in the weeks after perihelion by a further array of space- and ground-based instruments. Such a surfeit of wide-ranging observations provides an unprecedented insight into both sungrazing comets themselves, and the solar atmosphere through which they pass. This paper will summarize what we have learnt from the observations thus far and offer some thoughts on what future sungrazing comets may reveal about comets, the Sun, and their interaction. Title: The EUV Emission from Sun-Grazing Comets Authors: Bryans, Paul; Pesnell, W. D. Bibcode: 2012AAS...22042305B Altcode: The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) has, to date, viewed two Sun-grazing comets as they passed through the solar corona. Both passages resulted in the significant enhancement of Extreme Ultraviolet (EUV) emission in several of the AIA bandpasses. We explain this EUV emission by considering the evolution of the cometary atmosphere as it interacts with the ambient solar atmosphere. Water ice in the comet rapidly sublimates as it approaches the Sun. This water vapor is then photodissociated by the solar radiation field to create atomic H and O. Other molecules present in the comet also evaporate and dissociate to give atomic Fe and other metals. Subsequent ionization of these atoms produces a high abundance of ions not normally present at the temperature of the corona and results in EUV emission in the wavelength ranges of the AIA telescopes. Understanding the EUV emission places constraints on the cometary composition and provides valuable insight to the nature of the upper solar atmosphere. Title: The EUV Emission in Comet-Solar Corona Interactions Authors: Bryans, P.; Pesnell, W. D.; Schrijver, C. J.; Brown, J. C.; Battams, K.; Saint-Hilaire, P.; Liu, W.; Hudson, H. S. Bibcode: 2011AGUFMSH34B..05B Altcode: The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) viewed a comet as it passed through the solar corona on 2011 July 5. This was the first sighting of a comet by a EUV telescope. For 20 minutes, enhanced emission in several of the AIA wavelength bands marked the path of the comet. We explain this EUV emission by considering the evolution of the cometary atmosphere as it interacts with the ambient solar atmosphere. Water ice in the comet rapidly sublimates as it approaches the Sun. This water vapor is then photodissociated, primarily by Ly-α, by the solar radiation field to create atomic H and O. Other molecules present in the comet also evaporate and dissociate to give atomic Fe and other metals. Subsequent ionization of these atoms can be achieved by a number of means, including photoionization, electron impact, and charge exchange with coronal protons and other highly-charged species. Finally, particles from the cometary atmosphere are thermalized to the background temperature of the corona. Each step could cause emission in the AIA bandpasses. We will report here on their relative contribution to the emission seen in the AIA telescopes. Title: New Collisional Ionization Equilibrium Calculations for Optically Thin Plasmas Authors: Savin, D. W.; Bryans, P.; Mitthumsiri, W.; Badnell, N. R.; Gorczyca, T. W.; Laming, J. M. Bibcode: 2011nlaw.confC...5S Altcode: Reliably interpreting spectra from electron-ionized laboratory and cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and their reliability are often highly suspect. We have carried out state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Mg-like ions of all elements from He to Zn as well as for Al- like to Ar-like ions of Fe. We have also carried out state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H to Zn. Using our data and the most recently recommended electron impact ionization data, we present improved collisional ionization equilibrium (CIE) calculations. Here, as an example, we present our calculated fractional ionic abundances for iron using these data and compare them with those from the previously recommended CIE calculations. Title: Comparison of Vector Magnetograms from the Solenoidal and Irrotational Components of the Magnetic Field Authors: Bryans, Paul; Pesnell, W. D. Bibcode: 2011SPD....42.2108B Altcode: 2011BAAS..43S.2108B According to the Helmholtz Theorem, the solar magnetic field can be defined in terms of an irrotational and a solenoidal component. We will discuss the partitioning of the field into these components as a means of attributing elements of the magnetic field to its vorticity and divergence. We will then discuss the advantages of this decomposition as a metric for comparing vector magnetograms of varying spatial and temporal resolution. Title: Properties of a Polar Coronal Hole During the Solar Minimum in 2007 Authors: Hahn, M.; Bryans, P.; Landi, E.; Miralles, M. P.; Savin, D. W. Bibcode: 2010ApJ...725..774H Altcode: 2010arXiv1010.4277H We report measurements of a polar coronal hole during the recent solar minimum using the Extreme Ultraviolet Imaging Spectrometer on Hinode. Five observations are analyzed that span the polar coronal hole from the central meridian to the boundary with the quiet-Sun corona. We study the observations above the solar limb in the height range of 1.03-1.20 R sun. The electron temperature T e and emission measure (EM) are found using a geometric mean emission measure method. The EM derived from the elements Fe, Si, S, and Al are compared in order to measure relative coronal-to-photospheric abundance enhancement factors. We also studied the ion temperature T i and the non-thermal velocity v nt using the line profiles. All these measurements are compared to polar coronal hole observations from the previous (1996-1997) solar minimum and to model predictions for relative abundances. There are many similarities in the physical properties of the polar coronal holes between the two minima at these low heights. We find that the electron density, T e, and T i are comparable in both minima. T e shows a comparable gradient with height. Both minima show a decreasing T i with increasing charge-to-mass ratio q/M. A previously observed upturn of T i for ions above q/M>0.25 was not found here. We also compared relative coronal-to-photospheric elemental abundance enhancement factors for a number of elements. These ratios were ~1 for both the low first ionization potential (FIP) elements Si and Al and the marginally high FIP element S relative to the low FIP element Fe, as is expected based on earlier observations and models for a polar coronal hole. These results are consistent with no FIP effect in a polar coronal hole. Title: Properties of the Solar Corona above a Polar Coronal Hole during the Solar Minimum in 2007 Authors: Hahn, Michael; Landi, E.; Bryans, P.; Miralles, M. P.; Savin, D. W. Bibcode: 2010shin.confE.150H Altcode: Observations have shown that the latest solar minimum differs from the previous one in 1996-1997. Here we present the analysis of EUV spectra of the north polar coronal hole observed during the recent minimum 16 November 2007. The data were taken using the Extreme ultraviolet Imaging Spectrometer (EIS) on Hinode. Five observations span the coronal hole in the longitudinal direction from the center to the boundary with the quiet sun corona and extend radially from the solar disk to about 1.2 Rsun. We use the geometric mean emission measure (GEM) approach to determine the plasma emission measure (EM) and electron temperature. The GEM analysis shows that the observations are nearly isothermal, but there are indications of a small contribution from higher temperature plasma along the line of sight. To investigate the temperature structure in more detail we are performing a differential emission measure (DEM) analysis. The upper and lower bounds on the ion temperature are also measured using line widths. Our results are compared to spectroscopic measurements of polar coronal holes obtained from observations carried out during the previous solar minimum in 1996-1997. Title: Multiple Component Outflows in an Active Region Observed with the EUV Imaging Spectrometer on Hinode Authors: Bryans, P.; Young, P. R.; Doschek, G. A. Bibcode: 2010ApJ...715.1012B Altcode: 2010arXiv1004.5085B We have used the Extreme Ultraviolet Imaging Spectrometer on the Hinode spacecraft to observe large areas of outflow near an active region. These outflows are seen to persist for at least 6 days. The emission line profiles suggest that the outflow region is composed of multiple outflowing components, Doppler-shifted with respect to each other. We have modeled this scenario by imposing a double-Gaussian fit to the line profiles. These fits represent the profile markedly better than a single-Gaussian fit for Fe XII and XIII emission lines. For the fastest outflowing components, we find velocities as high as 200 km s-1. However, there remains a correlation between the fitted line velocities and widths, suggesting that the outflows are not fully resolved by the double-Gaussian fit and that the outflow may be comprised of further components. Title: Properties of the Solar Corona above a Polar Coronal Hole during the Recent Solar Minimum Authors: Hahn, Michael; Landi, E.; Bryans, P.; Miralles, M.; Savin, D. Bibcode: 2010AAS...21640105H Altcode: 2010BAAS...41..857H Recent observations have shown that the latest solar minimum differs from the previous one in 1996-1997. Here we present the analysis of EUV spectra of the north polar coronal hole observed in November 2007, during the current minimum. The data were taken using the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. Five observations span the coronal hole in the longitudinal direction from the center to the boundary with the quiet sun corona and extend radially from the solar disk to about 1.2 solar radii to. We use the geometric mean emission measure (GEM) approach to determine the plasma emission measure (EM) and electron temperature. From the EM we estimate the relative elemental abundances. We also determine upper and lower bounds on the ion temperature using measured line widths. We then compare our results to spectroscopic measurements of polar coronal holes obtained from observations carried out during the previous solar minimum in 1996-1997. Title: Coronal Active Region Loop Variability Observed with Hinode/EIS Authors: Bryans, Paul Bibcode: 2010AAS...21640720B Altcode: Using the Extreme Ultraviolet Spectrometer (EIS) on the Hinode spacecraft, we have studied the properties of active region loops along their length. Here, we present results of the variation of the temperature, density and filling factor with respect to height in the loop. In particular, we find differences in the electron density between loop footpoints that provide important constraints on models used to explain coronal loop heating. Title: Updated Collisional Ionization Equilibrium Calculated for Optically Thin Plasmas Authors: Savin, Daniel Wolf; Bryans, P.; Badnell, N. R.; Gorczyca, T. W.; Laming, J. M.; Mitthumsiri, W. Bibcode: 2010HEAD...11.1504S Altcode: 2010BAAS...42..678S Reliably interpreting spectra from electron-ionized cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and their reliability are often highly suspect. We have carried out state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He to Zn as well as for Al-like to Ar-like ions of Fe. We have also carried out state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H to Zn. Using our data and the recommended electron impact ionization data of Dere (2007), we present improved collisional ionization equilibrium calculations (Bryans et al. 2006, 2009). We compare our calculated fractional ionic abundances using these data with those presented by Mazzotta et al. (1998) for all elements from H to Ni. This work is supported in part by the NASA APRA and SHP SR&T programs. Title: Deriving the coronal hole electron temperature: electron density dependent ionization / recombination considerations Authors: Doyle, John Gerard; Chapman, Steven; Bryans, Paul; Pérez-Suárez, David; Singh, Avninda; Summers, Hugh; Savin, Daniel Wolf Bibcode: 2010RAA....10...91D Altcode: 2009arXiv0909.3195D Comparison of appropriate theoretically derived line ratios with observational data can yield estimates of a plasma's physical parameters, such as electron density or temperature. The usual practice in the calculation of the line ratio is the assumption of excitation by electrons/protons followed by radiative decay. Furthermore, it is normal to use the so-called coronal approximation, i.e. one only considers ionization and recombination to and from the ground-state. A more accurate treatment is to include ionization/recombination to and from metastable levels. Here, we apply this to two lines from adjacent ionization stages, Mg IX 368 Å and Mg X 625 Å, which has been shown to be a very useful temperature diagnostic. At densities typical of coronal hole conditions, the difference between the electron temperature derived assuming the zero density limit compared with the electron density dependent ionization/recombination is small. This, however, is not the case for flares where the electron density is orders of magnitude larger. The derived temperature for the coronal hole at solar maximum is around 1.04 MK compared to just below 0.82 MK at solar minimum. Title: Multiple Component Outflows in Active Regions observed by EIS Authors: Bryans, Paul; Doschek, G. A.; Young, P. R. Bibcode: 2009SPD....40.1221B Altcode: We have used the Extreme Ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft to observe large areas of outflow near an active region. These outflows are seen to persist for a number of days. The emission line profiles suggest that the outflow region is composed of multiple outflowing components, Doppler-shifted with respect to each other. We have modelled this scenario by imposing a double-Gaussian fit to the line profiles; these fits represent the profile markedly better than a single Gaussian fit. For the fastest outflowing components, we find velocities as high as 200 km/s. However, there remains a correlation between the fitted line velocities and widths, suggesting that the outflows are not fully resolved by the double-Gaussian fit and that the outflow may be comprised of further components. Title: Molecular Cloud Chemistry and the Importance of Dielectronic Recombination Authors: Bryans, P.; Kreckel, H.; Roueff, E.; Wakelam, V.; Savin, D. W. Bibcode: 2009ApJ...694..286B Altcode: 2008arXiv0809.4504B Dielectronic recombination (DR) of singly charged ions is a reaction pathway that is commonly neglected in chemical models of molecular clouds. In this study we include state-of-the-art DR data for He+, C+, N+, O+, Na+, and Mg+ in chemical models used to simulate dense molecular clouds, protostars, and diffuse molecular clouds. We also update the radiative recombination (RR) rate coefficients for H+, He+, C+, N+, O+, Na+, and Mg+ to the current state-of-the-art values. The new RR data have little effect on the models. However, the inclusion of DR results in significant differences in gas-grain models of dense, cold molecular clouds for the evolution of a number of surface and gas-phase species. We find differences of a factor of 2 in the abundance for 74 of the 655 species at times of 104-106 yr in this model when we include DR. Of these 74 species, 16 have at least a factor of 10 difference in abundance. We find the largest differences for species formed on the surface of dust grains. These differences are due primarily to the addition of C+ DR, which increases the neutral C abundance, thereby enhancing the accretion of C onto dust. These results may be important for the warm-up phase of molecular clouds when surface species are desorbed into the gas phase. We also note that no reliable state-of-the-art RR or DR data exist for Si+, P+, S+, Cl+, and Fe+. Modern calculations for these ions are needed to better constrain molecular cloud models. Title: A New Approach to Analyzing Solar Coronal Spectra and Updated Collisional Ionization Equilibrium Calculations. II. Updated Ionization Rate Coefficients Authors: Bryans, P.; Landi, E.; Savin, D. W. Bibcode: 2009ApJ...691.1540B Altcode: 2008arXiv0805.3302B We have re-analyzed Solar Ultraviolet Measurement of Emitted Radiation (SUMER) observations of a parcel of coronal gas using new collisional ionization equilibrium (CIE) calculations. These improved CIE fractional abundances were calculated using state-of-the-art electron-ion recombination data for K-shell, L-shell, Na-like, and Mg-like ions of all elements from H through Zn and, additionally, Al- through Ar-like ions of Fe. They also incorporate the latest recommended electron impact ionization data for all ions of H through Zn. Improved CIE calculations based on these recombination and ionization data are presented here. We have also developed a new systematic method for determining the average emission measure (EM) and electron temperature (Te ) of an isothermal plasma. With our new CIE data and a new approach for determining average EM and Te , we have re-analyzed SUMER observations of the solar corona. We have compared our results with those of previous studies and found some significant differences for the derived EM and Te . We have also calculated the enhancement of coronal elemental abundances compared to their photospheric abundances, using the SUMER observations themselves to determine the abundance enhancement factor for each of the emitting elements. Our observationally derived first ionization potential factors are in reasonable agreement with the theoretical model of Laming. Title: VizieR Online Data Catalog: Plasma Recombination rate coefficients (Bryans+, 2006) Authors: Bryans, P.; Badnell, N. R.; Gorczyca, T. W.; Laming, J. M.; Mitthumsiri, W.; Savin, D. W. Bibcode: 2008yCat..21670343B Altcode: Reliably interpreting spectra from electron-ionized cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and are often highly suspect. This translates directly into the reliability of the collisional ionization equilibrium (CIE) calculations. We make use of state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He up to and including Zn. Where measurements exist, these published theoretical DR data agree with recent laboratory work to within typically 35% or better at the temperatures relevant for CIE. We also make use of state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H through to Zn. Here we present improved CIE calculations for temperatures from 104 to 109 K using our data and the recommended electron impact ionization data of Mazzotta et al. (1998, Cat. ) for elements up to and including Ni and Mazzotta (2000, private communication) for Cu and Zn. DR and RR data for ionization stages that have not been updated are also taken from these two additional sources.

(2 data files). Title: The Status of Collisional Ionization Equilibrium Calculations and a New Approach to Emission Eeasure Determinations Authors: Bryans, Paul; Laming, J. M.; Landi, E.; Savin, D. W. Bibcode: 2008AAS...212.0302B Altcode: 2008BAAS...40Q.184B We have calculated improved collisional ionization equilibrium (CIE) fractional abundances using state-of-the-art dielectronic recombination (DR) and radiative recombination (RR) rate coefficients for K-shell, L-shell, Na-like, and Mg-like ions of all elements from H through Zn and M-shell ions of Fe. These data have been compared with other published state-of-the-art DR and RR data and found to agree within 35% and 10%, respectively, in the temperature range where the ion forms in CIE. Where DR measurements exist, theory and experiment agree to within 35% in this temperature range. We have also investigated recent improvements to the recommended electron impact ionization rate coefficient database, concluding that differences of up to a factor of 4 between recent compilations implies that significant additional

experimental and theoretical work is required. Using our new CIE calculations we have re-analyzed solar coronal observations of an isothermal parcel of coronal gas. We have also developed a mathematically rigorous method for determining the average emission measure and temperature of the emitting plasma. Using our new CIE data and our new approach to determining the average emission measure, we use the observations to quantify the first ionization potential effect on the coronal abundances of the emitting elements. We present the results of this analysis and compare our conclusions with those of previous works. Title: Electron-Impact Ionization of Be-like C III, N IV, and O V Authors: Fogle, M.; Bahati, E. M.; Bannister, M. E.; Vane, C. R.; Loch, S. D.; Pindzola, M. S.; Ballance, C. P.; Thomas, R. D.; Zhaunerchyk, V.; Bryans, P.; Mitthumsiri, W.; Savin, D. W. Bibcode: 2008ApJS..175..543F Altcode: We present recent measurements of absolute electron-impact ionization cross sections for Be-like C III, N IV, and O V forming Li-like C IV, N V, and O VI. The measurements were taken using the crossed-beams apparatus at Oak Ridge National Laboratory. A gas cell beam attenuation method was used to independently measure the metastable fractions present in the ion beams. The measured ionization cross sections were compared with calculations using the R-matrix with pseudostates and distorted-wave theoretical methods. Best agreement is found with the R-matrix with pseudostates cross sections results that account for the metastable fractions inferred from the gas attenuation measurements. We present a set of recommended rate coefficients for electron-impact single ionization from the ground state and metastable term of each ion. Title: The Status of Collisional Ionization Equilibrium Calculations and a New Approach to Emission Measure Determinations Authors: Bryans, Paul; Laming, J. M.; Landi, E.; Savin, D. W. Bibcode: 2008HEAD...10.1313B Altcode: We have calculated improved collisional ionization equilibrium (CIE) fractional abundances using state-of-the-art dielectronic recombination (DR) and radiative recombination (RR) rate coefficients for K-shell, L-shell, Na-like, and Mg-like ions of all elements from H through Zn and M-shell ions of Fe. These data have been compared with other published state-of-the-art DR and RR data and found to agree within 35% and 10%, respectively, in the temperature range where the ion forms in CIE. Where DR measurements exist, theory and experiment agree to within 35% in this temperature range. We have also investigated recent improvements to the recommended electron impact ionization rate coefficient database, concluding that differences of up to a factor of 5 between recent compilations implies that significant additional experimental and theoretical work is required. Using our new CIE calculations we have re-analyzed solar coronal observations of an isothermal parcel of coronal gas. We have also developed a mathematically rigorous method for determining the average emission measure and temperature of the emitting plasma. Using our new CIE data and our new approach to determining the average emission measure, we use the observations to quantify the first ionization potential effect on the coronal abundances of the emitting elements. We present the results of this analysis and compare our conclusions with those of previous works. Title: Implications for Atomic Physics from New Ionization Balance Calculations and Solar Physics Observations Authors: Bryans, Paul; Landi, Enrico; Savin, Daniel Bibcode: 2007APS..DMP.R1107B Altcode: We have used state-of-the-art electron-ion recombination data for K-shell, L-shell, and Na-like ions of H through Zn to calculate improved collisional ionization equilibrium (CIE) fractional abundances for ions of all these elements. We present the implications of these new CIE results for observations of the solar atmosphere and discuss a number of atomic systems showing puzzling discrepancies between observations and solar models. These discrepancies suggest errors in the underlying atomic data. Based on this, we highlight those atomic processes that require improved theoretical or experimentally-derived rate coefficients. Title: Collisional Ionization Equilibrium for Optically Thin Plasmas. I. Updated Recombination Rate Coefficients for Bare through Sodium-like Ions Authors: Bryans, P.; Badnell, N. R.; Gorczyca, T. W.; Laming, J. M.; Mitthumsiri, W.; Savin, D. W. Bibcode: 2006ApJS..167..343B Altcode: 2006astro.ph..4363B Reliably interpreting spectra from electron-ionized cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and are often highly suspect. This translates directly into the reliability of the collisional ionization equilibrium (CIE) calculations. We make use of state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He up to and including Zn. Where measurements exist, these published theoretical DR data agree with recent laboratory work to within typically 35% or better at the temperatures relevant for CIE. We also make use of state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H through to Zn. Here we present improved CIE calculations for temperatures from 104 to 109 K using our data and the recommended electron impact ionization data of Mazzotta et al. for elements up to and including Ni and Mazzotta for Cu and Zn. DR and RR data for ionization stages that have not been updated are also taken from these two additional sources. We compare our calculated fractional ionic abundances using these data with those presented by Mazzotta et al. for all elements from H to Ni. The differences in peak fractional abundance are up to 60%. We also compare with the fractional ionic abundances for Mg, Si, S, Ar, Ca, Fe, and Ni derived from the modern DR calculations of Gu for the H-like through Na-like ions, and the RR calculations of Gu for the bare through F-like ions. These results are in better agreement with our work, with differences in peak fractional abundance of less than 10%. Title: Updated Ionization Balance Calculations for Collisionally Ionized Plasmas Authors: Bryans, Paul; Badnell, N. R.; Gorczcya, T. W.; Laming, J. M.; Mitthumsiri, W.; Savin, D. W. Bibcode: 2006HEAD....9.1835B Altcode: 2006BAAS...38R.387B Reliably interpreting spectra from electron-ionized cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and their reliability are often highly suspect. We have carried out state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He to Zn. We have also carried out state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H to Zn. Using our data and the recommended electron impact ionization data of [1], we present improved collisional ionization equilibrium calculations. We compare our

calculated fractional ionic abundances using these data with those presented

by [1] for all elements from H to Ni, and with the fractional abundances derived from the modern DR and RR calculations of [2] for Mg, Si, S, Ar, Ca, Fe, and Ni.

[1] Mazzotta, P. et al., 1998, A&AS, 133, 403

[2] Gu, M. F., 2003a, ApJ, 590, 1131; 2003b, 589, 1085; 2004, 153, 389

This work is supported in part by NASA. Title: Updated Coronal Equilibrium Calculations Authors: Bryans, Paul; Badnell, N. R.; Gorczyca, T. W.; Laming, J. M.; Mitthumsiri, W.; Savin, D. W. Bibcode: 2006SPD....37.0101B Altcode: 2006BAAS...38..215B Reliably interpreting solar spectra requires accurate ionization balance calculations. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and are often highly suspect. This translates directly into the reliability of the collisional ionization equilibrium (CIE) calculations. We make use of state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He through to Zn. We also make use of state-of-the-art radiative recombination (RR) rate coefficient calculations for the bar e through Na-like ions of all elements from H to Zn. Here we present improved CIE calculations for temperatures from 1e4 to 1e9 K using our data and the recommended electron impact ionization data of Mazzotta et al. (1998, A&AS, 133, 403) for elements up through Ni and Mazzotta (private communication) for Cu and Zn. DR and RR data for ionization stages that have not been updated are also taken from these two additional sources. We compare our calculated fractional ionic abundances using these data with those presented by Mazzotta et al. for all elements from H to Ni. The differences in peak fractional abundance are up to 60%. We also compare with the fractional ionic abundances for Mg, Si, S, Ar, Ca, Fe, and Ni derived from the modern DR calculations of Gu (2003a, ApJ, 590, 1131; 2004, ApJ, 153, 389) for the H-like through Na-like ions, and the RR calculations of Gu (2003b, ApJ, 589, 1085) for the bare through F-like ions. These results are in better agreement with our work, with differences in peak fractional abundance of less than 10%.

This work was supported in part by the NASA Solar SR&T and LWS programs, theOffice of Naval Research, and PPARC. Title: A Plasma Mechanism explaining the Asymmetric X-ray Emission from the Supernova Authors: Kellett, B. J.; Bingham, R.; Bryans, P.; Torney, M.; Summers, H.; Shapiro, V.; Spicer, Ds Bibcode: 2006sgrb.confE..31K Altcode: The interaction of the expanding shock from a supernova explosion with thesurrounding environment is a powerful source of radiation in variousspectral bands at different stages in the development of the supernovaremnant. Studying the X-rays generated by such objects is therefore likelyto reveal details of these on going interactions. For example, the X-rayemission from the relatively old supernova remnant PKS1209-52 is highlyasymmetric - 75% of the total emission arises from the eastern side of theshock. We describe a possible model that can explain this extra emissionfrom the eastern lobe of the remnant as resulting from a recent encounterbetween the shock front and a small, dense, interstellar cloud. Theparticular mechanism is a plasma streaming instability known as themodified two-stream instability. The presence of the cloud makes itpossible to extract some of the kinetic energy of the shock wave andconvert this into X-ray emission via high-energy electrons generated fromlower hybrid waves in the plasma interaction region. We have carried out2-D fluid simulation of the interaction which agrees very well with theobserved geometry of the source. Finally, the neutron star remnant of theoriginal supernova explosion is seen to generate cyclotron absorptionfeatures in its X-ray emission spectrum that reveal the detailed dynamicsof the magnetic field of the neutron star itself. Planned laboratoryexperiments to study the results will be outlined. Title: Collisional Ionization Equilibrium for Optically Thin Plasmas Authors: Bryans, P.; Mitthumsiri, W.; Savin, D. W.; Badnell, N. R.; Gorczyca, T. W.; Laming, J. M. Bibcode: 2006nla..conf..166B Altcode: Reliably interpreting spectra from electron-ionized cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and their reliability are often highly suspect. We have utilized state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He to Zn. We have also utilized state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H to Zn. Using our data and the recommended electron impact ionization data of tet{Mazz98a}, we have calculated improved collisional ionization equilibrium calculations. We compare our calculated fractional ionic abundances using these data with those presented by tet{Mazz98a} for all elements from H to Ni, and with the fractional abundances derived from the modern DR and RR calculations of tet{Gu03a,Gu03b,Gu04a} for Mg, Si, S, Ar, Ca, Fe, and Ni. Title: Evidence for explosive event activity originating in the chromosphere Authors: Doyle, J. G.; Ishak, B.; Ugarte-Urra, I.; Bryans, P.; Summers, H. P. Bibcode: 2005A&A...439.1183D Altcode: We report on a joint SUMER, CDS, TRACE study, concentrating on a region which shows prolonged EUV explosive event (EE) activity in the transition region line N v 1238 Å, yet little evidence of such activity in another transition region line O v 629 Å (formed at a similar temperature) which was observed simultaneously. A possible explanation for the lack of major activity in the O v line in several explosive events could be that they originate in the lower chromosphere. This is consistent with the enhancements in the C i 1249 Å line and with the findings of another study which reported time delays between the chromospheric and transition region lines in some EE's using high cadence observations (10 s exposure time) obtained with the SUMER spectrometer in H i Ly 6 (20 000 K) and S vi (200 000 K). Using the generalized collisional-radiative picture, including the population of metastable levels, we derive the density dependent contribution function for both N v 1238 and O v 629 for four values of the electron density; 106 cm-3 representing the low density limit, 109 cm-3 for a typical quiet Sun electron density plus 1011 cm-3 and 1012 cm-3 for an active region. These calculations show that with increasing electron density, both lines shift to slightly lower temperatures. However, the major difference is in the relative increase in the line flux with increasing density. For N v, increasing the density to 1011 cm-3 results in a 60% increase in the line flux, while O v shows a 30% decrease. Increasing the electron density to 1012 cm-3 results in a factor of two decrease in the O v flux, thus making it difficult to detect explosive event activity in this line if the event is formed in the chromosphere. Other explosive events which show simultaneous activity in both lines are probably formed in the transition region. In one such event, activity is observed in both N v and O v, yet nothing in C i. In this event we also observe an increase in the TRACE 173 emission, delayed by ≈40 s compared to the transition region lines. Title: X-Ray Emission from Comets and Nonmagnetic Planets. Theory and Comparison with CHANDRA Observations Authors: Shapiro, V. D.; Bingham, R.; Kellett, B. J.; Quest, K.; Mendis, D. A.; Bryans, P.; Torney, M.; Summers, H. P. Bibcode: 2005PhST..116...83S Altcode: Mass loading of the solar wind by newly created cometary photoions as well as counterstreaming fluxes of protons in the mantle regions at the ionospheric boundaries of nonmagnetic planets Mars, Venus result in the modified two stream instability MTSI and excitation of the intense lower hybrid wave turbulence. Electrons are efficiently energized by these waves in the magnetic field aligned direction up to KeV energies confirmed by in situ observations and interacting with cometary or planetary atmospheres producing X-Ray emission by combination of Bremsstrahlung and line K-shell radiation. Analytical study of the nonlinear evolution of MTSI as well as numerical simulations of instability development in the mantle regions of nonmagnetic planets has been performed and it basically confirms the scenario of electron acceleration. Using the above described mechanism of X-ray emission produced in impacts of energetic electrons with ions and neutrals we employed ADAS atomic data code to analyze X-ray spectrum emitted by comet Linear and obtained a good fit with recent CHANDRA observations. The theoretical model also predicts strong x-ray emission from nonmagnetic planets such as Mars and Venus. Title: The effect of metastable level populations on the ionization fraction of Li-like ions Authors: Doyle, J. G.; Summers, H. P.; Bryans, P. Bibcode: 2005A&A...430L..29D Altcode: Lines from Li-like ions have been known to produce theoretical intensities under-estimated compared to lines of a similar formation temperature. Here we investigate this anomalous behaviour whereby the ionization fractions are calculated using the ADAS code considering the electron density dependence of dielectronic recombination coupled with collisional ionization from metastable levels. For the lines investigated, the line contribution functions show a clear dependence with increasing electron density. For example, C IV 1548 Å shows over a factor of three enhancement for Ne = 1012 cm-3. The increase in the higher temperature lines is lower, but are still in the range of 30 to 60%. Furthermore, all the lines have their peak contribution shifted to lower temperature. Calculating the total radiative power output at an electron density of 1011 cm-3, we find that the difference in the transition region is 10-15% while above 106 K the difference is around 30% compared to the low density value. Title: A New Mechanism Explaining the Asymmetric X-Ray Emission from Supernova Remnant PKS 1209-52 Authors: Bingham, R.; Kellett, B. J.; Bryans, P.; Summers, H. P.; Torney, M.; Shapiro, V. D.; Spicer, D. S.; O'Brien, M. Bibcode: 2004ApJ...601..896B Altcode: The interaction of a supernova remnant with its surrounding environment is a powerful source of radiation in various spectral regions and at different stages in its development. The study of these emissions can therefore help to investigate the interstellar medium surrounding a supernova. For example, the highly asymmetric X-ray emission from PKS 1209-52 has previously been described as resulting from the supernova shock front on the eastern side of the remnant interacting with a small, dense interstellar cloud (or cloud core). In this paper we describe a possible mechanism through which the kinetic energy of the expanding shock is converted to energetic electrons. The particular interaction is a plasma streaming instability known as the modified two-stream instability that creates plasma waves in the lower hybrid frequency range that can then go on to accelerate electrons to high energy. A Fokker-Planck equation describing the diffusion of the electrons to high energies by lower hybrid waves is solved for both Gaussian and Lorentzian wave spectral distributions. We also simulate the interaction between the supernova remnant with the dense interstellar cloud using a two-dimensional fluid code. The nonthermal electrons can then generate X-ray emission via bremsstrahlung and also line radiation through interactions with the ambient medium. The maximum energy of these electrons is limited to the few keV energy range and therefore does not lead to any synchrotron radio emission that would otherwise lead to a radio asymmetry in the remnant that is not seen. Title: X-ray Emission From Planets Venus and Mars: Theoretical Model and Numerical Simulations Authors: Bryans, P.; Quest, K. B.; Shapiro, V. D.; Bingham, R.; Tourner, M. Bibcode: 2003AGUFMSM31C1122B Altcode: Recently X-ray emission from non-magnetic planets Venus and Mars have been discovered by Chandra X-ray telescopes [1,2]. Analysis of observational data shows that either charge exchange model or fluorescent scattering of solar x-rays cannot explain the whole set of observational data. The premise of this paper is that x-ray emission of both planets is a combination of line k-shell radiation and Bremmstrahlung produced by energetic electrons interacting with planetary atmospheres. Due to the absence of their planetary magnetospheres, planetary bow shocks are located quite close to the ionospheres and on both planets their ionospheres are directly exposed to the shocked solar wind flow. In situ observations revealed the existence at the ionospheric boundaries of strongly turbulent layer -- the so-called plasma mantle. Previous hybrid simulations (kinetic ions and hydro dynamical electrons) have shown that mantle turbulence is produced by interaction of counterstreaming ion populations of the solar wind and planetary ionospheres. Recently developed particle in cell (fully kinetic) code demonstrated that mantle turbulence is responsible for electron acceleration in an agreement with in-situ observations that revealed the presence in mantle electrons with energies up to several hundred eV.[3] In the present paper we incorporated energetic electron distribution obtained by numerical simulations into ADAS code [4] and compared results with observations.

1. K. Dennerl et.al. A&A 286, 319 (2002). 2. K. Dennerl, A&A 394, 1119-1128 (2002). 3. K. Szego et.al. J6R 112, 2175 (1997) 4. http: adas.phystretch ac.uk Title: X-ray Emission from Planets Venus and Mars. Theoretical Model and Numerical Simulations. Authors: Bryans, Paul; Quest, Kevin; Shapiro, Vitali; Bingham, Robert; Torney, Martin Bibcode: 2003APS..DPPGP1136B Altcode: Recently X-ray emission from non-magnetic planets Venus and Mars have been discovered by Chandra X-ray telescopes [1,2]. Analysis of observational data shows that either charge exchange model or fluorescent scattering of solar x-rays cannot explain the whole set of observational data. The premise of this paper is that x-ray emission of both planets is a combination of line k-shell radiation and Bremmstrahlung produced by energetic electrons interacting with planetary atmospheres. Due to the absence of their planetary magnetospheres, planetary bow shocks are located quite close to the ionospheres and on both planets their ionospheres are directly exposed to the shocked solar wind flow. In situ observations revealed the existence at the ionospheric boundaries of strongly turbulent layer -- the so-called plasma mantle. Previous hybrid simulations (kinetic ions and hydro dynamical electrons) have shown that mantle turbulence is produced by interaction of counterstreaming ion populations of the solar wind and planetary ionospheres. Recently developed particle in cell (fully kinetic) code deomonstrated that mantle turbulence is responsible for electron acceleration in an agreement with in-situ observations that revealed the presence in mantle electrons with energies up to several hundred eV.[3] In the present paper we incorporated energetic electron distribution obtained by numerical simulations into ADAS code and compared results with observations. 1. K. Dennerl et. al. A, 286, 319 (2002) 2. K. Dennerl et. al. A, 394, 1119-1128 (2002 3. K. Szego et. al., JGR, 112, 2175 (1997) 4. http: adas.phystretch ac.uk Title: A Plasma Mechanism Explaining the Asymmetric X-ray Emission from the Supernova Remnant PKS1209-52. Authors: Kellett, Barry; Bingham, Robert; Bryans, Paul; Torney, Martin; Summers, Hugh; Shapiro, Vitali; Spicer, Daniel Bibcode: 2003APS..DPPGP1149K Altcode: The interaction of the expanding shock from a supernova explosion with the surrounding environment is a powerful source of radiation in various spectral bands at different stages in the development of the supernova remnant. Studying the X-rays generated by such objects is therefore likely to reveal details of these on going interactions. For example, the X-ray emission from the relatively old supernova remnant PKS1209-52 is highly asymmetric - 75arises from the eastern side of the shock. We describe a possible model that can explain this extra emission from the eastern lobe of the remnant as resulting from a recent encounter between the shock front and a small, dense, interstellar cloud. The particular mechanism is a plasma streaming instability known as the modified two-stream instability. The presence of the cloud makes it possible to extract some of the kinetic energy of the shock wave and convert this into X-ray emission via high-energy electrons generated from lower hybrid waves in the plasma interaction region. We have carried out 2-D fluid simulation of the interaction which agree very well with the observed geometry of the source. Finally, the neutron star remnant of the original supernova explosion is seen to generate cyclotron absorption features in its X-ray emission spectrum that reveal the detailed dynamics of the magnetic field of the neutron star itself. Title: Coronal dimming and the coronal mass ejection onset Authors: Harrison, R. A.; Bryans, P.; Simnett, G. M.; Lyons, M. Bibcode: 2003A&A...400.1071H Altcode: A set of five observations of extreme-ultraviolet (EUV) coronal dimming associated with coronal mass ejection (CME) activity is examined. Using spectroscopic data, plasma characteristics across a broad range of temperatures from 20 000 K to 2 million K are determined. The dimming events are found to coincide in time, and to coincide spatially, with the projected onset times and locations of the associated CMEs. The spectral data confirm that the dimming is due to mass-loss, and not temperature variations. The actual mass-loss calculated from the degree of dimming, using two different methods, shows that the extracted mass in each case, is of the same order as the mass of the associated CME. In some cases, the EUV observations are limited to relatively small regions under the CME events and it is expected that we do not witness the mass-loss associated with the entire event, for these. However, we believe that this analysis has provided a method for locating the source region of the trigger for a CME eruption, and that the dimming characteristics can be used to distinguish between onset processes of the CME. In particular, the gradual nature of the dimming process, which takes place over several hours, suggests that either the CME has a continuous driver rather than a sudden impulsive onset, or the low coronal response to a CME extends over a long period. Title: EUV Sprays: Jet-like eruptive activity on the solar limb Authors: Harrison, R. A.; Bryans, P.; Bingham, R. Bibcode: 2001A&A...379..324H Altcode: Jet-like eruptive events have been detected in the extreme ultraviolet (EUV) observations from the Solar and Heliospheric Observatory (SOHO) spacecraft. Some jet-like events are shown and for one event, that of January 22 2000, we provide a detailed analysis of the EUV observations. The January 22 observation was part of an on-going campaign to observe the onset of coronal mass ejections (CMEs) using extreme ultraviolet spectroscopy. A high-temperature fan-like jet was first detected in emission lines from plasmas at one million K and over, and it appears to be the onset of a narrow mass ejection identified later in coronagraph data. This was followed by a dramatic jet or finger of cool (<=250 000 K), rotating plasma which extended vertically, high into the corona. It extended well beyond the field of view of the instrument and appears to relate to a small ejected cloud which is detected in subsequent coronagraph data. The spectroscopic characteristics are used to provide plasma diagnostic information for these two events, and this combined with images for a wide range of temperatures allows a thorough investigation of the processes leading to such eruptions. A simple accreting magnetic field model is used to descibe the basic features of the jet activity.