Author name code: temmer ADS astronomy entries on 2022-09-14 author:"Temmer, Manuela" ------------------------------------------------------------------------ Title: COSPAR Roadmap update from the ISWAT clusters H1 and 2 Authors: Temmer, Manuela; Richardson, Ian G.; Vourlidas, Angelos; Bisi, Mario M.; Scolini, Camilla; Heinemann, Stephan; Paouris, Evangelos Bibcode: 2022cosp...44.3523T Altcode: We present the COSPAR Roadmap update paper from the ISWAT clusters H1 and 2. These two clusters are focused on interplanetary space and its dynamic features such as stream interaction regions and coronal mass ejections, the major drivers of space weather. The interplay between these phenomena changes the structure of interplanetary space on various temporal and spatial scales and effects the propagation behavior of individual events. The limitations of observational data and current models lead to large uncertainties in our understanding of solar wind structures, making reliablespace weather forecasts difficult. The solar wind also becomes more complex as solar activity increases. We discuss the current understanding of dynamic changes in interplanetary space, indicate the caveats related to data and models, and provide recommendations for future studies. Title: SODA - Satellite Orbit DecAy near-real time forecast Authors: Drescher, Lukas; Temmer, Manuela; Mayer-Gürr, Torsten; Krauss, Sandro; Kroisz, B. Sofia; Behzadpour, Saniya; Süsser-Rechberger, Barbara Bibcode: 2022cosp...44..826D Altcode: Based on the results by Krauss et al. (2018, 2020), we investigate the correlation between the interplanetary magnetic field of ICMEs and the variation of the neutral density in the thermosphere. Within the FFG funded project SWEETS (space weather effects on low Earth orbiting satellites) we analyze a large sample of about 300 ICMEs (interplanetary coronal mass ejections) from 2002 to 2017 and how they relate to the orbit decay of satellites. The density estimates are based on accelerometer measurements (CHAMP, GRAACE, GRACE-FO) as well as on kinematic orbits of the satellite missions Swarm, TerraSAR-X, Tandem-X and Sentinel 1, 3. Thus, our investigations covering altitudes between 300 to 800 km. We find that strong magnetic field variations in the Bz component trigger geomagnetic storms which lead to an increase in the neutral density and subsequently the aerodynamic drag. As a result, the satellites at very low altitudes may drop by several tens to a hundred of meters during an extreme ICME event. From the statistical study we derive an empirical relation between Bz value and orbit drop for satellites in a normalized height of 490km. Using that relation, we established a tool that enables to detect potential orbit drops in near real-time. This forecast/nowcast service, called SODA (Satellite Orbit DecAy) is implemented in the ESA Ionospheric Weather SSP program/Ionospheric Weather Expert Service Centre (I-ESC). Title: Determination of CME orientation and consequences for their propagation Authors: Martinic, Karmen; Vrsnak, Bojan; Veronig, Astrid; Dumbovic, Mateja; Temmer, Manuela Bibcode: 2022cosp...44.2441M Altcode: The configuration of the interplanetary magnetic field and features of the related ambient solar wind in the ecliptic and meridional plane are different. Therefore, one can expect that the orientation of the flux rope axis of a coronal mass ejection (CME) influences the propagation of the CME itself. However, the determination of the CME's orientation remains a challenging task to perform. This study aims to provide a reference to different CME orientation determination methods in the near-Sun environment. Also, it aims to investigate the non-radial flow in the sheath region of the interplanetary CME (ICME) in order to provide the first proxy to relate the ICME orientation with its propagation. We investigated 22 isolated CME-ICME events in the period 2008-2015. We first determined the CME orientation in the near-Sun environment using a 3D reconstruction of the CME with the graduated cylindrical shell (GCS) model applied to coronagraphic images provided by the STEREO and SOHO missions. The CME orientation in the near-Sun environment was determined using an ellipse fitting technique to the CME outer front as determined from the SOHO/LASCO coronagraph. In the near-Earth environment, we obtained the orientation of the corresponding ICME using in-situ plasma and field data and also investigated the non-radial flow in its sheath region. The ability of GCS and ellipse fitting to determine the CME orientation is found to be limited to reliably distinguish only between the high or low inclination of the events. Most of the CME-ICME pairs under investigation were found to be characterized by a low inclination. The majority of CME-ICME pairs have a consistent estimation of tilt from remote and in situ data. The observed non-radial flows in the sheath region show a greater y-direction to z-direction flow ratio for high-inclination events indicating that CME orientation could have an impact to the CME propagation. Title: Development and evaluation of Drag-Based Ensemble Model (DBEM) Authors: Čalogović, Jaša; Vrsnak, Bojan; Veronig, Astrid; Dumbovic, Mateja; Temmer, Manuela Bibcode: 2022cosp...44.3443C Altcode: The Drag-based Model (DBM) is a well-known 2D analytical model for simulating the heliospheric propagation of Coronal Mass Ejections (CMEs). Main output is the prediction of the CME arrival time and speed at Earth or any other given target in the solar system. Due to a very short computational time of DBM (< 0.01s), the probabilistic Drag-Based Ensemble Model (DBEM) was developed by making an ensemble of n different input parameters to account for possible variability (uncertainties) in the input parameters. Using such an approach to obtain the distribution and significance of the DBM results, the DBEM determines the CME hit chance, most probable arrival times and speeds, quantifies the prediction uncertainties and calculates the confidence intervals. As an important tool for space weather forecasters, the fully operational DBM/DBEM web application is integrated as one of the ESA Space Situational Awareness portal services (https://swe.ssa.esa.int/current-space-weather). In the last few years, DBM/DBEM has been constantly improved with various new features such as Graduated Cylindrical Shell (GCS) option for the CME geometry input, the CME propagation visualizations as well as a new DBEM version employing the variable solar wind speeds. The model development, new features and the corresponding model evaluations will be presented. Title: How properties of large-scale solar wind structures drive magnetosheath jet properties Authors: Koller, Florian; Temmer, Manuela; Preisser, Luis; Roberts, Owen; Weiss, B. Stefan; Plaschke, Ferdinand Bibcode: 2022cosp...44.1611K Altcode: The Earth's magnetosheath consists of turbulent, shocked solar wind (SW) plasma. Magnetosheath jets are dynamic pressure enhancements which are frequently observed within this region. They travel anti-sunward from the bow shock to the Earth's magnetopause and can be geoeffective. While several generation mechanisms have been proposed, jets are generally linked to processes at the quasi-parallel bow shock and the foreshock. Our goal is to analyze, how these jets are related to large-scale SW structures, in particular coronal mass ejections (CMEs) as well as stream interaction regions (SIRs) and associated high speed streams (HSSs). We use jets detected by the THEMIS spacecraft between 2008 to 2020. The number of detected jets is lower during the passing of CMEs. Significantly more jets are observed during SIRs and HSSs. We find that jets are unlikely to appear during a mix of low Alfvénic Mach numbers and high IMF cone angles, which are SW conditions often found during CMEs and their associated sheaths. These conditions may inhibit the formation of a well-defined foreshock and therefore affecting the jet generation. We analyze whether jets differ during each type of large-scale SW structure and discuss the different possible origin mechanisms. Title: Magnetosheath jets during a CME and SIR passage: A case study. Authors: Preisser, Luis; Temmer, Manuela; Roberts, Owen; Koller, M. Florian; Plaschke, Ferdinand Bibcode: 2022cosp...44.1642P Altcode: Large scale solar wind (SW) structures called Coronal Mass Ejections (CMEs) and Stream Interaction Regions (SIRs) travel through the interplanetary medium, where they might impact the Earth's magnetosphere. Jets are localized structures characterized by an enhancement in dynamic pressure observed propagating through the Earth's magnetosheath (EMS) transporting mass, momentum and energy and being able to reach and perturb the Earth's magnetopause. Although jets have been studied since 20 years, how the different SW conditions triggered by CMEs and SIRs change the production of jets in the EMS, is a topic that is just beginning to be explored. In this case study we characterize jets observed by THEMIS during a CME and a SIR passage. We find clear differences in number and size between the jets associated with the CME regions arriving at the EMS as well as in comparison with the characteristics of jets associated with the SIR passage. Comparing WIND and THEMIS data we discuss how these differences are linked to the SW conditions and with different jet generation mechanisms. Title: Understanding our capabilities in observing and modelling Coronal Mass Ejections Authors: Verbeke, Christine; Mays, M. Leila; Riley, Pete; Mierla, Marilena; Cremades, Hebe; Dumbovic, Mateja; Temmer, Manuela; Scolini, Camilla; Hinterreiter, Jürgen; Paouris, Evangelos; Palmerio, Erika; Kay, Christina; Balmaceda, Laura Bibcode: 2022cosp...44.3441V Altcode: Coronal Mass Ejections (CMEs) are large-scale eruptions of plasma and magnetic fields from the Sun. They are considered to be the main drivers of strong space weather events at Earth and their arrival time and associated shocks are one of the key aspects of space weather. Multiple models have been developed over the past decades to be able to predict the propagation of CMEs in the interplanetary space and their arrival time at Earth. Such models require input from observations, which can be used to fit the CME to an appropriate structure. The forecasting of CME arrival has proven to be exceedingly challenging. One of the major setbacks is the uncertainty of the CME observational input. When determining input parameters for CME propagation models, it is common procedure to derive kinematic parameters from remote-sensing data. The resulting parameters can be used as inputs for the CME propagation models to obtain an arrival prediction time of the CME f.e. at Earth. However, when fitting the CME structure to obtain the needed parameters for simulations, different geometric structures and also different parts of the CME structure can be fitted. These aspects, together with the fact that 3D reconstructions strongly depend on the subjectivity and judgement of the scientist performing them, may lead to uncertainties in the fitted parameters. Up to now, no large study has tried to map these uncertainties and to evaluate how they affect the modelling of CMEs. We will discuss these limits in the scope of the CME input analysis that is performed by the ISSI Bern team on "Understanding Our Capabilities In Observing and Modelling Coronal Mass Ejections". Title: Evolution of ICME sheath and leading-edge structure in the inner heliosphere Authors: Temmer, Manuela; Bothmer, Volker Bibcode: 2022cosp...44.1439T Altcode: We investigate a data sample of 40 interplanetary CME (ICME) events from Helios 1 and 2 data that cover the distance range 0.3-1au. For comparison, we add a sample of 5 ICMEs observed with Parker Solar Probe during 2018-2021. From the solar wind plasma and magnetic field measurements, we extract the ICME sub-structures sheath, leading-edge, and magnetic ejecta. We analyze their characteristic parameters as function of distance and present the main findings of this study: a) the average starting distance for actual sheath formation appears to be located at a distance of about 13 Rs; b) the sheath density becomes dominant over the magnetic ejecta density beyond 38 Rs; c) the sheath size could be related to the ambient solar wind density and magnetic ejecta characteristics; d) a local linear relation between sheath density and ambient solar wind speed was found; e) the leading-edge does not increase in size over distance and might be an isolated structure wedged in between sheath and magnetic ejecta. With Parker Solar Probe approaching the Sun as close as 10Rs, we will certainly detect more CME events to obtain measurements that might re-affirm the presented results. The current findings can be applied to help improve CME propagation models. Title: Stellar CME search using large datasets: Balmer line asymmetries in optical SDSS spectra Authors: Koller, Florian; Odert, Petra; Leitzinger, Martin; Veronig, Astrid; Temmer, Manuela; Beck, Paul G. Bibcode: 2022cosp...44.1386K Altcode: On the Sun, a strong correlation between highly energetic flares and coronal mass ejections (CMEs) has been well established. Highly energetic flares have also been frequently detected on all late-type stars. However, the association with CMEs proved to be difficult in the stellar case. Large datasets are a necessity to increase the probability of detecting these sparse events. In order to find stellar flares and associated CMEs, we used optical spectra provided by the Sloan Digital Sky Survey (SDSS) data release 14. The sample consisted of F, G, K, and M main-sequence type stars, resulting in available spectra for more than 630 000 stars. We made use of the individual spectral exposures provided by the SDSS. Flares were detected by searching for significant amplitude changes in the Hα and Hβ spectral lines. We searched for CMEs by identifying asymmetries in the Balmer lines caused by the Dopplereffect, which indicate plasma motions in the line of sight. We detected 281 flares on late-type stars (spectral types K3 - M9) and calculated their Hα flare energies. Six possible CME candidates were identified that show excess flux in Balmer line wings, five of which show red wing enhancements. Our mass estimates for the CME candidates range from 6×10$ ^{16}$ -‑ 6×10$ ^{18}$g, and the highest projected velocities are 300 -‑ 700km s$ ^{‑1}$. Our low detection rate of CMEs agrees with previous studies. Title: Galactic cosmic rays as signatures of interplanetary transients Authors: Dumbovic, Mateja; Kühl, Patrick; Heber, Bernd; Vrsnak, Bojan; Temmer, Manuela; Kirin, Anamarija; Hörlöck, Malte; Jensen, Stefan; Benko, Ilona; Kramaric, Luka Bibcode: 2022cosp...44.1255D Altcode: Coronal mass ejections (CMEs), interplanetary shocks, and corotating interaction regions (CIRs) drive heliospheric variability, causing various interplanetary as well as planetary disturbances. One of their very common in-situ signatures are short-term reductions in the galactic cosmic ray (GCR) flux (i.e. Forbush decreases), which are measured by ground-based instruments at Earth and Mars, as well as various spacecraft throughout the heliosphere (most recently by Solar Orbiter). In general, interplanetary magnetic structures interact with GCRs producing depressions in the GCR flux. Therefore, different types of interplanetary magnetic structures cause different types of Forbush decreases, allowing us to distinguish between them. We recently developed and employed two different analytical models to explain CME-related and CIR-related Forbush decreases, using an expansion-diffusion and the convection-diffusion approaches, respectively. We used observation-based generic CME and CIR profiles as the theoretical background for the models and tested the models on various case studies. Moreover, the CME-related Forbush decrease model (ForbMod, Dumbovic et al., 2018; 2020) is brought one step further, as it also considers the energy dependance of the detector with which the measurements are made. ForbMod is tested through model-to-observations comparison to analyse to how many CMEs it is applicable and could ultimately provide a helpful tool to analyse Forbush decreases. With new modelling efforts, as well as observational analysis we are one step closer in utilizing GCR measurements to provide information on interplanetary transients, especially where other measurements (e.g. plasma, magnetic field) are lacking. Title: Acceleration and Expansion of a Coronal Mass Ejection in the High Corona: Role of Magnetic Reconnection Authors: Zhuang, Bin; Lugaz, Noé; Temmer, Manuela; Gou, Tingyu; Al-Haddad, Nada Bibcode: 2022ApJ...933..169Z Altcode: 2022arXiv220602090Z The important role played by magnetic reconnection in the early acceleration of coronal mass ejections (CMEs) has been widely discussed. However, as CMEs may have expansion speeds comparable to their propagation speeds in the corona, it is not clear whether and how reconnection contributes to the true acceleration and expansion separately. To address this question, we analyze the dynamics of a moderately fast CME on 2013 February 27, associated with a continuous acceleration of its front into the high corona, even though its speed had reached ~700 km s-1, which is faster than the solar wind. The apparent acceleration of the CME is found to be due to its expansion in the radial direction. The true acceleration of the CME, i.e., the acceleration of its center, is then estimated by taking into account the expected deceleration caused by the drag force of the solar wind acting on a fast CME. It is found that the true acceleration and the radial expansion have similar magnitudes. We find that magnetic reconnection occurs after the eruption of the CME and continues during its propagation in the high corona, which contributes to its dynamic evolution. Comparison between the apparent acceleration related to the expansion and the true acceleration that compensates the drag shows that, for this case, magnetic reconnection contributes almost equally to the expansion and to the acceleration of the CME. The consequences of these measurements for the evolution of CMEs as they transit from the corona to the heliosphere are discussed. Title: Observations of CME source regions/lower-atmospheric manifestations Authors: Temmer, Manuela Bibcode: 2022cosp...44.1357T Altcode: The Sun is an active star that influences the Earth as well as the entire solar system. Most dynamic phenomena are observed as coronal mass ejections (CMEs). While CMEs frequently occur at the Sun, they are obviously less numerous when it comes to stars. Do we miss specific observing techniques? This talk will give an overview on the diverse manifestations of CME related signatures on the Sun that are observed during the CME early evolution phase. Strong and fast events can be most clearly related to their source regions that often show bright flare emissions as the reconnection process starts which drives the CME. In the wake of the eruption, CMEs expand and leave low atmospheric footprints, such as disappearing filaments or dark dimming regions, and may generate coronal waves. Weak and slow CMEs might not be detected by such footprints as they start from higher up in the corona (stealth CMEs). In the radio wavelength, typical signatures of type II and III bursts can give hint to propagating shocks and the opening of magnetic field. The ambient conditions in which the CME erupts, such as strong overlying closed magnetic fields, nearby coronal holes (open magnetic field) or multiple eruptions (transient open field), may alter the ability to generate specific signatures. Title: From CME - CH proximity on the Sun to ICME - CIR interaction at Earth: a case study Authors: Geyer, Paul; Dumbovic, Mateja; Temmer, Manuela Bibcode: 2022cosp...44.1121G Altcode: The interaction between interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs) leads to a variety of changes both in the trajectory and the morphology of the former. This means that the solar wind (SW) conditions at Earth's orbit due to interacting heliospheric structures may deviate significantly from the case of sole ICME or CIR passage. Studying the interaction of these large-scale structures in the heliosphere thus provides a basis for a more accurate space weather prediction of the associated near-Earth effects and enhances the accuracy of CME propagation models. The eruption of a flare related CME southwest to the center of the solar disk was observed by SDO/AIA on February 4, 2014. A coronal hole (CH) east of the disk center is also present at that time. The CME is listed by the DONKI database and associated to the in-situ magnetic field and plasma signatures detected at L1 3 days later. After the arrival of a fast forward shock on February 7, 2014 typical sheath properties are observed, followed by a region of low fluctuations, plasma beta and temperature - typical ICME signatures. A SW flow angle reversal is observed at the beginning of this interval, indicating east-west flow deflection normally observed around stream interfaces. The region of typical ICME signatures is interrupted by a phase of decreased field magnitude simultaneously occurring with the disturbance of the flow speed. Finally, at the trailing part of the in-situ event we observe the passage of a high-speed stream. The proximity of the coronal source regions of ICME and CIR clearly results in their interaction and thus morphological changes visible in plasma and magnetic field data. This view is also supported by WSA-ENLIL simulations showing the coincident arrival and apparent merging of the CIR and ICME at Earth. The separation of two intervals of weak magnetic field fluctuations by a region of strong fluctuations indicates a fundamental rearrangement of the magnetic field associated with the ICME. This is supported by the non-bidirectional electron pitch angle data. The complexity of this event demonstrates the need to study the interaction of the coronal source regions and their respective SW structures in a holistic way. Title: Determination of coronal mass ejection orientation and consequences for their propagation Authors: Martinić, K.; Dumbović, M.; Temmer, M.; Veronig, A.; Vršnak, B. Bibcode: 2022A&A...661A.155M Altcode: 2022arXiv220410112M Context. The configuration of the interplanetary magnetic field and features of the related ambient solar wind in the ecliptic and meridional plane are different. Therefore, one can expect that the orientation of the flux-rope axis of a coronal mass ejection (CME) influences the propagation of the CME itself. However, the determination of the CME orientation, especially from image data, remains a challenging task to perform. Aim. This study aims to provide a reference to different CME orientation determination methods in the near-Sun environment. Also, it aims to investigate the non-radial flow in the sheath region of the interplanetary CME (ICME) in order to provide the first proxy to relate the ICME orientation with its propagation.
Methods: We investigated 22 isolated CME-ICME events in the period 2008-2015. We determined the CME orientation in the near-Sun environment using the following: (1) a 3D reconstruction of the CME with the graduated cylindrical shell (GCS) model applied to coronagraphic images provided by the STEREO and SOHO missions; and (2) an ellipse fitting applied to single spacecraft data from SOHO/LASCO C2 and C3 coronagraphs. In the near-Earth environment, we obtained the orientation of the corresponding ICME using in situ plasma and field data and also investigated the non-radial flow in its sheath region.
Results: The ability of GCS and ellipse fitting to determine the CME orientation is found to be limited to reliably distinguish only between the high or low inclination of the events. Most of the CME-ICME pairs under investigation were found to be characterized by a low inclination. For the majority of CME-ICME pairs, we obtain consistent estimations of the tilt from remote and in situ data. The observed non-radial flows in the sheath region show a greater y direction to z direction flow ratio for high-inclination events, indicating that the CME orientation could have an impact on the CME propagation. Title: Magnetosheath Jet Occurrence Rate in Relation to CMEs and SIRs Authors: Koller, Florian; Temmer, Manuela; Preisser, Luis; Plaschke, Ferdinand; Geyer, Paul; Jian, Lan K.; Roberts, Owen W.; Hietala, Heli; LaMoury, Adrian T. Bibcode: 2022JGRA..12730124K Altcode: Magnetosheath jets constitute a significant coupling effect between the solar wind (SW) and the magnetosphere of the Earth. In order to investigate the effects and forecasting of these jets, we present the first-ever statistical study of the jet production during large-scale SW structures like coronal mass ejections (CMEs), stream interaction regions (SIRs) and high speed streams (HSSs). Magnetosheath data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft between January 2008 and December 2020 serve as measurement source for jet detection. Two different jet definitions were used to rule out statistical biases induced by our jet detection method. For the CME and SIR + HSS lists, we used lists provided by literature and expanded on incomplete lists using OMNI data to cover the time range of May 1996 to December 2020. We find that the number and total time of observed jets decrease when CME-sheaths hit the Earth. The number of jets is lower throughout the passing of the CME-magnetic ejecta (ME) and recovers quickly afterward. On the other hand, the number of jets increases during SIR and HSS phases. We discuss a few possibilities to explain these statistical results. Title: How the area of solar coronal holes affects the properties of high-speed solar wind streams near Earth: An analytical model Authors: Hofmeister, Stefan J.; Asvestari, Eleanna; Guo, Jingnan; Heidrich-Meisner, Verena; Heinemann, Stephan G.; Magdalenic, Jasmina; Poedts, Stefaan; Samara, Evangelia; Temmer, Manuela; Vennerstrom, Susanne; Veronig, Astrid; Vršnak, Bojan; Wimmer-Schweingruber, Robert Bibcode: 2022A&A...659A.190H Altcode: 2022arXiv220315689H Since the 1970s it has been empirically known that the area of solar coronal holes affects the properties of high-speed solar wind streams (HSSs) at Earth. We derive a simple analytical model for the propagation of HSSs from the Sun to Earth and thereby show how the area of coronal holes and the size of their boundary regions affect the HSS velocity, temperature, and density near Earth. We assume that velocity, temperature, and density profiles form across the HSS cross section close to the Sun and that these spatial profiles translate into corresponding temporal profiles in a given radial direction due to the solar rotation. These temporal distributions drive the stream interface to the preceding slow solar wind plasma and disperse with distance from the Sun. The HSS properties at 1 AU are then given by all HSS plasma parcels launched from the Sun that did not run into the stream interface at Earth distance. We show that the velocity plateau region of HSSs as seen at 1 AU, if apparent, originates from the center region of the HSS close to the Sun, whereas the velocity tail at 1 AU originates from the trailing boundary region. Small HSSs can be described to entirely consist of boundary region plasma, which intrinsically results in smaller peak velocities. The peak velocity of HSSs at Earth further depends on the longitudinal width of the HSS close to the Sun. The shorter the longitudinal width of an HSS close to the Sun, the more of its "fastest" HSS plasma parcels from the HSS core and trailing boundary region have impinged upon the stream interface with the preceding slow solar wind, and the smaller is the peak velocity of the HSS at Earth. As the longitudinal width is statistically correlated to the area of coronal holes, this also explains the well-known empirical relationship between coronal hole areas and HSS peak velocities. Further, the temperature and density of HSS plasma parcels at Earth depend on their radial expansion from the Sun to Earth. The radial expansion is determined by the velocity gradient across the HSS boundary region close to the Sun and gives the velocity-temperature and density-temperature relationships at Earth their specific shape. When considering a large number of HSSs, the assumed correlation between the HSS velocities and temperatures close to the Sun degrades only slightly up to 1 AU, but the correlation between the velocities and densities is strongly disrupted up to 1 AU due to the radial expansion. Finally, we show how the number of particles of the piled-up slow solar wind in the stream interaction region depends on the velocities and densities of the HSS and preceding slow solar wind plasma. Title: Dynamic Time Warping as a Means of Assessing Solar Wind Time Series Authors: Samara, E.; Laperre, B.; Kieokaew, R.; Temmer, M.; Verbeke, C.; Rodriguez, L.; Magdalenić, J.; Poedts, S. Bibcode: 2022ApJ...927..187S Altcode: 2021arXiv210907873S Over the last decades, international attempts have been made to develop realistic space weather prediction tools aiming to forecast the conditions on the Sun and in the interplanetary environment. These efforts have led to the development of appropriate metrics to assess the performance of those tools. Metrics are necessary to validate models, to compare different models, and to monitor the improvements to a certain model over time. In this work, we introduce dynamic time warping (DTW) as an alternative way of evaluating the performance of models and, in particular, of quantifying the differences between observed and modeled solar wind time series. We present the advantages and drawbacks of this method, as well as its application to Wind observations and EUHFORIA predictions at Earth. We show that DTW can warp sequences in time, aiming to align them with the minimum cost by using dynamic programming. It can be applied for the evaluation of modeled solar wind time series in two ways. The first calculates the sequence similarity factor, a number that provides a quantification of how good the forecast is compared to an ideal and a nonideal prediction scenario. The second way quantifies the time and amplitude differences between the points that are best matched between the two sequences. As a result, DTW can serve as a hybrid metric between continuous measurements (e.g., the correlation coefficient) and point-by-point comparisons. It is a promising technique for the assessment of solar wind profiles, providing at once the most complete evaluation portrait of a model. Title: Generic profile of a long-lived corotating interaction region and associated recurrent Forbush decrease Authors: Dumbović, M.; Vršnak, B.; Temmer, M.; Heber, B.; Kühl, P. Bibcode: 2022A&A...658A.187D Altcode: 2022arXiv220109623D Context. Corotating interaction regions (CIRs), formed by the interaction of slow solar wind and fast streams that originate from coronal holes (CHs), produce recurrent Forbush decreases, which are short-term depressions in the galactic cosmic ray (GCR) flux.
Aims: Our aim is to prepare a reliable set of CIR measurements to be used as a textbook for modeling efforts. For that purpose, we observe and analyse a long-lived CIR, originating from a single CH, recurring in 27 consecutive Carrington rotations 2057-2083 in the time period from June 2007-May 2009.
Methods: We studied the in situ measurements of this long-lived CIR as well as the corresponding depression in the cosmic ray (CR) count observed by SOHO/EPHIN throughout different rotations. We performed a statistical analysis, as well as the superposed epoch analysis, using relative values of the key parameters: the total magnetic field strength, B, the magnetic field fluctuations, dBrms, plasma flow speed, v, plasma density, n, plasma temperature, T, and the SOHO/EPHIN F-detector particle count, and CR count.
Results: We find that the mirrored CR count-time profile is correlated with that of the flow speed, ranging from moderate to strong correlation, depending on the rotation. In addition, we find that the CR count dip amplitude is correlated to the peak in the magnetic field and flow speed of the CIR. These results are in agreement with previous statistical studies. Finally, using the superposed epoch analysis, we obtain a generic CIR example, which reflects the in situ properties of a typical CIR well.
Conclusions: Our results are better explained based on the combined convection-diffusion approach of the CIR-related GCR modulation. Furthermore, qualitatively, our results do not differ from those based on different CHs samples. This indicates that the change of the physical properties of the recurring CIR from one rotation to another is not qualitatively different from the change of the physical properties of CIRs originating from different CHs. Finally, the obtained generic CIR example, analyzed on the basis of superposed epoch analysis, can be used as a reference for testing future models. Title: Characteristics and evolution of sheath and leading edge structures of interplanetary coronal mass ejections in the inner heliosphere based on Helios and Parker Solar Probe observations Authors: Temmer, Manuela; Bothmer, Volker Bibcode: 2022arXiv220204391T Altcode: Aims: We statistically investigate the plasma and magnetic field characteristics of the upstream regions of interplanetary coronal mass ejections (ICMEs) and their evolution as function of distance to the Sun in the inner heliosphere. We use a sample of 40 well-observed ICMEs from Helios 1/2 (0.3-1au) and 5 from Parker Solar Probe (0.32-0.75au). For each event we identify four main density structures, namely shock, sheath, leading edge (LE), and magnetic ejecta (ME) itself. Methods: We derive separately for each structure averaged plasma and magnetic field parameter values as well as duration and place the results into comparison with the upstream solar wind (SW) to investigate the interrelation between the different density structures. Results: The sheath structure presumably consists of compressed plasma due to the turbulent SW material following the shock. The sheath lies ahead of a region of compressed ambient SW, the LE, which is typically found directly in front of the magnetic driver and seems to match the bright leading edge commonly observed in remote sensing observations of CMEs. The sheath becomes denser than the ambient SW at about 0.06au, which we interpret as the average starting distance for actual sheath formation. Between 0.09-0.28au the sheath structure density starts to dominate over the density within the ME. The ME density seems to fall below the ambient SW density over 0.45-1.07au. Besides the well-known expansion of the ME, the sheath size shows a weak positive correlation with distance, while the LE seems not to expand with distance from the Sun. We further find a moderate anti-correlation between sheath density and local SW plasma speed upstream of the ICME shock. An empirical relation is derived connecting the ambient SW speed with sheath and LE density that can be used for modeling of ICME evolution. Constraints to those results are given. Title: Validation scheme for solar coronal models: Constraints from multi-perspective observations in EUV and white light Authors: Wagner, A.; Asvestari, E.; Temmer, M.; Heinemann, S. G.; Pomoell, J. Bibcode: 2022A&A...657A.117W Altcode: 2021arXiv211001893W; 2021arXiv211001893A Context. In this paper, we present a validation scheme to investigate the quality of coronal magnetic field models, which is based on comparisons with observational data from multiple sources.
Aims: Many of these coronal models may use a range of initial parameters that produce a large number of physically reasonable field configurations. However, that does not mean that these results are reliable and comply with the observations. With an appropriate validation scheme, which is the aim of this work, the quality of a coronal model can be assessed.
Methods: The validation scheme was developed with the example of the EUropean Heliospheric FORecasting Information Asset (EUHFORIA) coronal model. For observational comparison, we used extreme ultraviolet and white-light data to detect coronal features on the surface (open magnetic field areas) and off-limb (streamer and loop) structures from multiple perspectives (Earth view and the Solar Terrestrial Relations Observatory - STEREO). The validation scheme can be applied to any coronal model that produces magnetic field line topology.
Results: We show its applicability by using the validation scheme on a large set of model configurations, which can be efficiently reduced to an ideal set of parameters that matches best with observational data.
Conclusions: We conclude that by using a combined empirical visual classification with a mathematical scheme of topology metrics, a very efficient and objective quality assessment for coronal models can be performed. Title: On the influence of CMEs and SIRs on the generation of magnetosheath jets Authors: Koller, Florian; Temmer, Manuela; Preisser, Luis; Plaschke, Ferdinand; Roberts, Owen Bibcode: 2021AGUFMSH25G..34K Altcode: Magnetosheath jets are dynamic pressure enhancements observed in the Earths magnetosheath. They are significant coupling elements between the solar wind and the magnetosphere of the Earth. Jets are frequently generated at the Earths bow shock and travel downstream to the magnetopause, where they can trigger reconnection and initiate geomagnetic substorms. It is so far unexplored how these jets relate to large scale solar wind structures that are associated to the solar cycle and solar activity. To gain insights into these relations, we analyze jet generation during the passing of coronal mass ejections (CMEs) and stream interaction regions (SIRs). In our statistical analysis, we use magnetosheath jets detected by the THEMIS spacecraft between 2008 to 2020, and identify all overlaps with CME and SIR intervals. We report that magnetosheath jets can be generated at all times, but they appear much more frequently during SIRs, while the numbers of observed jets decrease significantly during CMEs. To explain this statistical difference, we inspect how the solar wind conditions related to the observed jets differ during CMEs and SIRs. Title: Characteristics of magnetosheath jets during an CME passage. Authors: Preisser, Luis; Plaschke, Ferdinand; Koller, Florian; Temmer, Manuela; Roberts, Owen Bibcode: 2021AGUFMSH25G..32P Altcode: Jets are localized enhancements in the dynamic pressure observed downstream of the Earths bow shock which propagate through the Earths magnetosheath (EMS) transporting mass, momentum and energy. Coronal Mass Ejections (CMEs) are large scale solar wind events traveling through the interplanetary medium. As the CME crosses the EMS, its structure (upstream side shock/sheath magnetic ejecta) changes the magnetosheath environment. How these changes in the EMS region produced by the passage of a CME affect the production of jets is a topic not yet explored. In this work we characterize jets observed by THEMIS spacecraft during such a passage. We find differences in number and size between jets located in the CME upstream region and those located in the corresponding CME downstream region. Comparing WIND and THEMIS A, D, E data we discuss how these differences can be associated to different jet generation mechanisms and if they are or not related with the transmission of the CME structure into the EMS. Title: The 2019 International Women's Day Event: A Two-step Solar Flare with Multiple Eruptive Signatures and Low Earth Impact Authors: Dumbovic, Mateja; Veronig, Astrid; Podladchikova, Tatiana; Thalmann, Julia; Chikunova, Galina; Dissauer, Karin; Magdalenic, Jasmina; Temmer, Manuela; Guo, Jingnan; Samara, Evangelia Bibcode: 2021AGUFMSH32A..08D Altcode: We present a detailed analysis of an eruptive event that occurred on early 2019 March 8 in active region AR 12734, to which we refer as the International Women's day event. The event under study is intriguing in several aspects: 1) low-coronal eruptive signatures come in ''pairs'' (a double-peak flare, two coronal dimmings, and two EUV waves); 2) although the event is characterized by a complete chain of eruptive signatures, the corresponding coronagraphic signatures are weak; 3) although the source region of the eruption is located close to the center of the solar disc and the eruption is thus presumably Earth-directed, heliospheric signatures are very weak with little Earth-impact. We analyze a number of multi-spacecraft and multi-instrument (both remote-sensing and in situ) observations, including Soft X-ray, (extreme-) ultraviolet (E)UV), radio and white-light emission, as well as plasma, magnetic field and particle measurements. We employ 3D NLFF modeling to investigate the coronal magnetic field configuration in and around the active region, the GCS model to make a 3D reconstruction of the CME geometry and the 3D MHD numerical model EUHFORIA to model the background state of the heliosphere. Our results indicate two subsequent eruptions of two systems of sheared and twisted magnetic fields, which merge already in the upper corona and start to evolve further out as a single entity. The large-scale magnetic field significantly influences both, the early and the interplanetary evolution of the structure. During the first eruption the stability of the overlying field was disrupted which enabled the second eruption. We find that during the propagation in the interplanetary space the large-scale magnetic field, i.e. , the location of heliospheric current sheet between the AR and the Earth likely influences propagation and the evolution of the erupted structure(s). Title: The Dynamic Time Warping Technique as an Alternative Way to Evaluate Space Weather Predictions Authors: Samara, Evangelia; Chane, Emmanuel; Laperre, Brecht; Kieokaew, Rungployphan; Temmer, Manuela; Verbeke, Christine; Rodriguez, Luciano; Magdalenic, Jasmina; Poedts, Stefaan Bibcode: 2021AGUFMSH55C1860S Altcode: In this work, the Dynamic Time Warping (DTW) technique is presented as an alternative method to quantify differences between observed and modeled time series in solar wind forecasting. The method was initially developed for speech recognition purposes and over the years it met great interest by other scientific fields. In the frame of this study, we show for the first time how we can apply DTW to assess the performance of modeled time series produced by space weather forecasting tools. Dynamic Time Warping can quantify how similar two time series are by providing a temporal alignment between them, in an optimal way, under certain restrictions. We further discuss the benefits and limitations of this method compared to other widely used metrics and we show examples on how the technique is applied to predicted solar wind time series modeled by EUHFORIA. Title: Quantifying Capabilities in Observing Coronal Mass Ejections Authors: Verbeke, Christine; Mays, M.; Kay, Christina; Mierla, Marilena; Riley, Pete; Palmerio, Erika; Dumbovic, Mateja; Scolini, Camilla; Temmer, Manuela; Paouris, Evangelos; Hinterreiter, Jurgen; Balmaceda, Laura; Cremades, Hebe Bibcode: 2021AGUFMSH55C1854V Altcode: Coronal Mass Ejections (CMEs) are large-scale eruptions of plasma and magnetic fields from the Sun. They are considered to be the main drivers of strong space weather events at Earth. Multiple models have been developed over the past decades to predict the propagation of CMEs and their possible arrival time at Earth. Such models require input from observations, which can be used to fit the CME to an appropriate structure.When determining parameters associated to the CME structure, it is common procedure to derive such kinematic parameters from remote-sensing data. The resulting parameters can be used as input for CME propagation models to obtain an arrival time prediction of the CME e.g. at Earth. However, different geometric structures and different parts of the CME structure can be fitted, and these aspects, together with the fact that most 3D reconstructions are performed by a scientist, creating a subjectivity of the fit, may lead to uncertainties in the fitted parameters. To our knowledge, so far, no large scale study has tried to map these uncertainties and how these affect the modelling of arrival time models.As a start for this work, we focused on the effect cause by the influence and subjectivty of the performing scientist. We have designed a synthetic situation where the true geometric parameters are known in order to quantify such uncertainties for the first time and discuss the results. We explore further work of the associated ISSI team. Title: Earth-affecting solar transients: a review of progresses in solar cycle 24 Authors: Zhang, Jie; Temmer, Manuela; Gopalswamy, Nat; Malandraki, Olga; Nitta, Nariaki V.; Patsourakos, Spiros; Shen, Fang; Vršnak, Bojan; Wang, Yuming; Webb, David; Desai, Mihir I.; Dissauer, Karin; Dresing, Nina; Dumbović, Mateja; Feng, Xueshang; Heinemann, Stephan G.; Laurenza, Monica; Lugaz, Noé; Zhuang, Bin Bibcode: 2021PEPS....8...56Z Altcode: 2020arXiv201206116Z This review article summarizes the advancement in the studies of Earth-affecting solar transients in the last decade that encompasses most of solar cycle 24. It is a part of the effort of the International Study of Earth-affecting Solar Transients (ISEST) project, sponsored by the SCOSTEP/VarSITI program (2014-2018). The Sun-Earth is an integrated physical system in which the space environment of the Earth sustains continuous influence from mass, magnetic field, and radiation energy output of the Sun in varying timescales from minutes to millennium. This article addresses short timescale events, from minutes to days that directly cause transient disturbances in the Earth's space environment and generate intense adverse effects on advanced technological systems of human society. Such transient events largely fall into the following four types: (1) solar flares, (2) coronal mass ejections (CMEs) including their interplanetary counterparts ICMEs, (3) solar energetic particle (SEP) events, and (4) stream interaction regions (SIRs) including corotating interaction regions (CIRs). In the last decade, the unprecedented multi-viewpoint observations of the Sun from space, enabled by STEREO Ahead/Behind spacecraft in combination with a suite of observatories along the Sun-Earth lines, have provided much more accurate and global measurements of the size, speed, propagation direction, and morphology of CMEs in both 3D and over a large volume in the heliosphere. Many CMEs, fast ones, in particular, can be clearly characterized as a two-front (shock front plus ejecta front) and three-part (bright ejecta front, dark cavity, and bright core) structure. Drag-based kinematic models of CMEs are developed to interpret CME propagation in the heliosphere and are applied to predict their arrival times at 1 AU in an efficient manner. Several advanced MHD models have been developed to simulate realistic CME events from the initiation on the Sun until their arrival at 1 AU. Much progress has been made on detailed kinematic and dynamic behaviors of CMEs, including non-radial motion, rotation and deformation of CMEs, CME-CME interaction, and stealth CMEs and problematic ICMEs. The knowledge about SEPs has also been significantly improved. An outlook of how to address critical issues related to Earth-affecting solar transients concludes this article. Title: Space weather: the solar perspective Authors: Temmer, Manuela Bibcode: 2021LRSP...18....4T Altcode: 2021arXiv210404261T The Sun, as an active star, is the driver of energetic phenomena that structure interplanetary space and affect planetary atmospheres. The effects of Space Weather on Earth and the solar system is of increasing importance as human spaceflight is preparing for lunar and Mars missions. This review is focusing on the solar perspective of the Space Weather relevant phenomena, coronal mass ejections (CMEs), flares, solar energetic particles (SEPs), and solar wind stream interaction regions (SIR). With the advent of the STEREO mission (launched in 2006), literally, new perspectives were provided that enabled for the first time to study coronal structures and the evolution of activity phenomena in three dimensions. New imaging capabilities, covering the entire Sun-Earth distance range, allowed to seamlessly connect CMEs and their interplanetary counterparts measured in-situ (so called ICMEs). This vastly increased our knowledge and understanding of the dynamics of interplanetary space due to solar activity and fostered the development of Space Weather forecasting models. Moreover, we are facing challenging times gathering new data from two extraordinary missions, NASA's Parker Solar Probe (launched in 2018) and ESA's Solar Orbiter (launched in 2020), that will in the near future provide more detailed insight into the solar wind evolution and image CMEs from view points never approached before. The current review builds upon the Living Reviews article by Schwenn from 2006, updating on the Space Weather relevant CME-flare-SEP phenomena from the solar perspective, as observed from multiple viewpoints and their concomitant solar surface signatures. Title: HI-based CME Modeling and the Influence of the Drag-force on the CME Frontal Shape Authors: Amerstorfer, Tanja; Hinterreiter, Jurgen; Temmer, Manuela; Weiss, Andreas; Bauer, Maike; Moestl, Christian; Barnard, Luke; Reiss, Martin; Pomoell, Jens; Amerstorfer, Ute Bibcode: 2021AGUFMSH33A..03A Altcode: Modeling the evolution of coronal mass ejections through the inner heliosphere is still just as challenging as imprecise.A small fleet of spacecraft is currently operating in an orbit around the Sun and offers the possibility to verify model results by comparing them to in situ arrivals at different heliocentric distances, longitudes and latitudes.However, deformations of a CME front can be very local making them hard to model and difficult to verify. These distortions are mainly caused by the interaction of CME and ambient solar wind and lead to large differences between different propagation models. With the help of heliospheric imagers it is possible to constrain the elongation of the CME front to a certain degree. Additionally, these observations can be utilized to derive information on the CME kinematics, the CME mass and the drag-force exerted by the solar wind. We present the first HI-based CME model allowing a CME front to react to the ambient solar wind in a local manner leading to frontal deformations. Three different ambient solar wind models serve as input to the model and underline the need of more precise solar wind modeling in order to improve CME arrival prediction models. Title: Searching for flares and associated CMEs on cool stars using Balmer lines in SDSS spectra Authors: Koller, Florian; Leitzinger, Martin; Temmer, Manuela; Odert, Petra; Beck, Paul; Veronig, Astrid Bibcode: 2021AGUFM.U43B..04K Altcode: Flares and coronal mass ejections (CMEs) shape the environment of stars and can severely affect the atmospheres and therefore the habitability of exoplanets. In the case of our Sun, we find that highly energetic flares and CMEs are strongly correlated. While we find frequent and highly energetic flares on all late-type stars, determining the association with stellar CMEs proves to be more difficult. To further constrain the activity of late-type main-sequence stars, we aimed to detect and classify stellar flares and potential stellar CME signatures. For that, we used optical spectra provided by the Sloan Digital Sky Survey (SDSS) data release 14. The sample was constrained to all F, G, K, and M main-sequence type stars, which resulted in available spectra for more than 630 000 stars. We made use of the individual spectral exposures provided by the SDSS. To automatically detect flares, we searched for significant amplitude changes in the $H\alpha$ and $H\beta$ spectral lines after a Gaussian profile was fit to each line core. We searched for CMEs by identifying asymmetries in the Balmer lines caused by the Dopplereffect, which indicate plasma motions in the line of sight. We report 281 flares on late-type stars (spectral types K3 M9). Six possible CME candidates were identified that show excess flux in Balmer line wings. We calculated $H\alpha$ Flare energies and estimated the masses of the CME candidates. The $H\alpha$ flare energies we derived range from $3 \times 10^{28} - 2 \times 10^{33}$ erg. We find that the $H\alpha$ flare energy increases with earlier types, while the fraction of flaring times increases with later types. Our mass estimates for the CME candidates range from $6 \times 10^{16} - 6 \times 10^{18}$ g, and the highest projected velocities are $\sim 300 - 700$ km s$^{-1}$. We conclude that our low detection rate of CMEs agrees with previous studies, suggesting that the CME occurrence rate that can be detected with optical spectroscopy is low for late-type main-sequence stars. Title: Drag-Based CME Modeling With Heliospheric Images Incorporating Frontal Deformation: ELEvoHI 2.0 Authors: Hinterreiter, Jürgen; Amerstorfer, Tanja; Temmer, Manuela; Reiss, Martin A.; Weiss, Andreas J.; Möstl, Christian; Barnard, Luke A.; Pomoell, Jens; Bauer, Maike; Amerstorfer, Ute V. Bibcode: 2021SpWea..1902836H Altcode: 2021arXiv210808075H The evolution and propagation of coronal mass ejections (CMEs) in interplanetary space is still not well understood. As a consequence, accurate arrival time and arrival speed forecasts are an unsolved problem in space weather research. In this study, we present the ELlipse Evolution model based on HI observations (ELEvoHI) and introduce a deformable front to this model. ELEvoHI relies on heliospheric imagers (HI) observations to obtain the kinematics of a CME. With the newly developed deformable front, the model is able to react to the ambient solar wind conditions during the entire propagation and along the whole front of the CME. To get an estimate of the ambient solar wind conditions, we make use of three different models: Heliospheric Upwind eXtrapolation model (HUX), Heliospheric Upwind eXtrapolation with time dependence model (HUXt), and EUropean Heliospheric FORecasting Information Asset (EUHFORIA). We test the deformable front on a CME first observed in STEREO-A/HI on February 3, 2010 14:49 UT. For this case study, the deformable front provides better estimates of the arrival time and arrival speed than the original version of ELEvoHI using an elliptical front. The new implementation enables us to study the parameters influencing the propagation of the CME not only for the apex, but for the entire front. The evolution of the CME front, especially at the flanks, is highly dependent on the ambient solar wind model used. An additional advantage of the new implementation is given by the possibility to provide estimates of the CME mass. Title: How to Estimate the Far-Side Open Flux Using STEREO Coronal Holes Authors: Heinemann, Stephan G.; Temmer, Manuela; Hofmeister, Stefan J.; Stojakovic, Aleksandar; Gizon, Laurent; Yang, Dan Bibcode: 2021SoPh..296..141H Altcode: 2021arXiv210902375H Global magnetic field models use as input synoptic data, which usually show "aging effects" as the longitudinal 360∘ information is not obtained simultaneously. Especially during times of increased solar activity, the evolution of the magnetic field may yield large uncertainties. A significant source of uncertainty is the Sun's magnetic field on the side of the Sun invisible to the observer. Various methods have been used to complete the picture: synoptic charts, flux-transport models, and far side helioseismology. In this study, we present a new method to estimate the far-side open flux within coronal holes using STEREO EUV observations. First, we correlate the structure of the photospheric magnetic field as observed with the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory (HMI/SDO) with features in the transition region. From the 304 Å intensity distribution, which we found to be specific to coronal holes, we derive an empirical estimate for the open flux. Then we use a large sample of 313 SDO coronal hole observations to verify this relation. Finally, we perform a cross-instrument calibration from SDO to STEREO data to enable the estimation of the open flux at solar longitudes not visible from Earth. We find that the properties of strong unipolar magnetic elements in the photosphere, which determine the coronal hole's open flux, can be approximated by open fields in the transition region. We find that structures below a threshold of 78 % (STEREO) or 94 % (SDO) of the solar disk median intensity as seen in 304 Å filtergrams are reasonably well correlated with the mean magnetic flux density of coronal holes (cc=sp 0.59 ). Using the area covered by these structures (AOF) and the area of the coronal hole (ACH), we model the open magnetic flux of a coronal hole as |ΦCH|=0.25 ACHexp (0.032 AOF) with an estimated uncertainty of 40 to 60 %. Title: Coronal Hole Detection and Open Magnetic Flux Authors: Linker, Jon A.; Heinemann, Stephan G.; Temmer, Manuela; Owens, Mathew J.; Caplan, Ronald M.; Arge, Charles N.; Asvestari, Eleanna; Delouille, Veronique; Downs, Cooper; Hofmeister, Stefan J.; Jebaraj, Immanuel C.; Madjarska, Maria S.; Pinto, Rui F.; Pomoell, Jens; Samara, Evangelia; Scolini, Camilla; Vršnak, Bojan Bibcode: 2021ApJ...918...21L Altcode: 2021arXiv210305837L Many scientists use coronal hole (CH) detections to infer open magnetic flux. Detection techniques differ in the areas that they assign as open, and may obtain different values for the open magnetic flux. We characterize the uncertainties of these methods, by applying six different detection methods to deduce the area and open flux of a near-disk center CH observed on 2010 September 19, and applying a single method to five different EUV filtergrams for this CH. Open flux was calculated using five different magnetic maps. The standard deviation (interpreted as the uncertainty) in the open flux estimate for this CH ≍ 26%. However, including the variability of different magnetic data sources, this uncertainty almost doubles to 45%. We use two of the methods to characterize the area and open flux for all CHs in this time period. We find that the open flux is greatly underestimated compared to values inferred from in situ measurements (by 2.2-4 times). We also test our detection techniques on simulated emission images from a thermodynamic MHD model of the solar corona. We find that the methods overestimate the area and open flux in the simulated CH, but the average error in the flux is only about 7%. The full-Sun detections on the simulated corona underestimate the model open flux, but by factors well below what is needed to account for the missing flux in the observations. Under-detection of open flux in coronal holes likely contributes to the recognized deficit in solar open flux, but is unlikely to resolve it. Title: Modelling a multi-spacecraft coronal mass ejection encounter with EUHFORIA Authors: Asvestari, E.; Pomoell, J.; Kilpua, E.; Good, S.; Chatzistergos, T.; Temmer, M.; Palmerio, E.; Poedts, S.; Magdalenic, J. Bibcode: 2021A&A...652A..27A Altcode: 2021arXiv210511831A Context. Coronal mass ejections (CMEs) are a manifestation of the Sun's eruptive nature. They can have a great impact on Earth, but also on human activity in space and on the ground. Therefore, modelling their evolution as they propagate through interplanetary space is essential.
Aims: EUropean Heliospheric FORecasting Information Asset (EUHFORIA) is a data-driven, physics-based model, tracing the evolution of CMEs through background solar wind conditions. It employs a spheromak flux rope, which provides it with the advantage of reconstructing the internal magnetic field configuration of CMEs. This is something that is not included in the simpler cone CME model used so far for space weather forecasting. This work aims at assessing the spheromak CME model included in EUHFORIA.
Methods: We employed the spheromak CME model to reconstruct a well observed CME and compare model output to in situ observations. We focus on an eruption from 6 January 2013 that was encountered by two radially aligned spacecraft, Venus Express and STEREO-A. We first analysed the observed properties of the source of this CME eruption and we extracted the CME properties as it lifted off from the Sun. Using this information, we set up EUHFORIA runs to model the event.
Results: The model predicts arrival times from half to a full day ahead of the in situ observed ones, but within errors established from similar studies. In the modelling domain, the CME appears to be propagating primarily southward, which is in accordance with white-light images of the CME eruption close to the Sun.
Conclusions: In order to get the observed magnetic field topology, we aimed at selecting a spheromak rotation angle for which the axis of symmetry of the spheromak is perpendicular to the direction of the polarity inversion line (PIL). The modelled magnetic field profiles, their amplitude, arrival times, and sheath region length are all affected by the choice of radius of the modelled spheromak. Title: Multi-channel coronal hole detection with convolutional neural networks Authors: Jarolim, R.; Veronig, A. M.; Hofmeister, S.; Heinemann, S. G.; Temmer, M.; Podladchikova, T.; Dissauer, K. Bibcode: 2021A&A...652A..13J Altcode: 2021arXiv210414313J Context. A precise detection of the coronal hole boundary is of primary interest for a better understanding of the physics of coronal holes, their role in the solar cycle evolution, and space weather forecasting.
Aims: We develop a reliable, fully automatic method for the detection of coronal holes that provides consistent full-disk segmentation maps over the full solar cycle and can perform in real-time.
Methods: We use a convolutional neural network to identify the boundaries of coronal holes from the seven extreme ultraviolet (EUV) channels of the Atmospheric Imaging Assembly (AIA) and from the line-of-sight magnetograms provided by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). For our primary model (Coronal Hole RecOgnition Neural Network Over multi-Spectral-data; CHRONNOS) we use a progressively growing network approach that allows for efficient training, provides detailed segmentation maps, and takes into account relations across the full solar disk.
Results: We provide a thorough evaluation for performance, reliability, and consistency by comparing the model results to an independent manually curated test set. Our model shows good agreement to the manual labels with an intersection-over-union (IoU) of 0.63. From the total of 261 coronal holes with an area > 1.5 × 1010 km2 identified during the time-period from November 2010 to December 2016, 98.1% were correctly detected by our model. The evaluation over almost the full solar cycle no. 24 shows that our model provides reliable coronal hole detections independent of the level of solar activity. From a direct comparison over short timescales of days to weeks, we find that our model exceeds human performance in terms of consistency and reliability. In addition, we train our model to identify coronal holes from each channel separately and show that the neural network provides the best performance with the combined channel information, but that coronal hole segmentation maps can also be obtained from line-of-sight magnetograms alone.
Conclusions: The proposed neural network provides a reliable data set for the study of solar-cycle dependencies and coronal-hole parameters. Given the fast and robust coronal hole segmentation, the algorithm is also highly suitable for real-time space weather applications.

Movies are available at https://www.aanda.org Title: 2019 International Women's Day event. Two-step solar flare with multiple eruptive signatures and low Earth impact Authors: Dumbović, M.; Veronig, A. M.; Podladchikova, T.; Thalmann, J. K.; Chikunova, G.; Dissauer, K.; Magdalenić, J.; Temmer, M.; Guo, J.; Samara, E. Bibcode: 2021A&A...652A.159D Altcode: 2021arXiv210615417D Context. We present a detailed analysis of an eruptive event that occurred on 2019 March 8 in the active region AR 12734, which we refer as the International Women's Day event. The event under study is intriguing based on several aspects: (1) low-coronal eruptive signatures come in `pairs', namely, there is a double-peaked flare, two coronal dimmings, and two extreme ultraviolet (EUV) waves; (2) although the event is characterized by a complete chain of eruptive signatures, the corresponding coronagraphic signatures are weak; and (3) although the source region of the eruption is located close to the center of the solar disc and the eruption is thus presumably Earth-directed, heliospheric signatures are very weak with very weak Earth impact.
Aims: In order to understand the initiation and evolution of this particular event, we performed a comprehensive analysis using a combined observational-modeling approach.
Methods: We analyzed a number of multi-spacecraft and multi-instrument (both remote-sensing and in situ) observations, including soft X-ray, EUV, radio and white-light emission, as well as plasma, magnetic field, and particle measurements. We employed 3D nonlinear force-free modeling to investigate the coronal magnetic field configuration in and around the active region, the graduated cylindrical shell model to make a 3D reconstruction of the CME geometry, and the 3D magnetohydrodynamical numerical model EUropean Heliospheric FORecasting Information Asset to model the background state of the heliosphere.
Results: Our results reveal a two-stage C1.3 flare, associated with two EUV waves that occur in close succession and two-stage coronal dimmings that evolve co-temporally with the flare and type II and III radio bursts. Despite its small GOES class, a clear drop in magnetic free energy and helicity is observed during the flare. White light observations do not unambiguously indicate two separate CMEs, but rather a single entity most likely composed of two sheared and twisted structures corresponding to the two eruptions observed in the low corona. The corresponding interplanetary signatures are that of a small flux rope swith indications of strong interactions with the ambient plasma, which result in a negligible geomagnetic impact.
Conclusions: Our results indicate two subsequent eruptions of two systems of sheared and twisted magnetic fields, which already begin to merge in the upper corona and start to evolve further out as a single entity. The large-scale magnetic field significantly influences both the early and the interplanetary evolution of the structure. During the first eruption, the stability of the overlying field was disrupted, enabling the second eruption. We find that during the propagation in the interplanetary space the large-scale magnetic field, that is, the location of heliospheric current sheet between the AR and the Earth, is likely to influence propagation, along with the evolution of the erupted structure(s).

Movies are available at https://www.aanda.org Title: Probabilistic Drag-Based Ensemble Model (DBEM) Evaluation for Heliospheric Propagation of CMEs Authors: Čalogović, Jaša; Dumbović, Mateja; Sudar, Davor; Vršnak, Bojan; Martinić, Karmen; Temmer, Manuela; Veronig, Astrid M. Bibcode: 2021SoPh..296..114C Altcode: 2021arXiv210706684C The Drag-based Model (DBM) is a 2D analytical model for heliospheric propagation of Coronal Mass Ejections (CMEs) in ecliptic plane predicting the CME arrival time and speed at Earth or any other given target in the solar system. It is based on the equation of motion and depends on initial CME parameters, background solar wind speed, w and the drag parameter γ . A very short computational time of DBM (< 0.01 s) allowed us to develop the Drag-Based Ensemble Model (DBEM) that takes into account the variability of model input parameters by making an ensemble of n different input parameters to calculate the distribution and significance of the DBM results. Thus the DBEM is able to calculate the most likely CME arrival times and speeds, quantify the prediction uncertainties and determine the confidence intervals. A new DBEMv3 version is described in detail and evaluated for the first time determining the DBEMv3 performance and errors by using various CME-ICME lists and it is compared with previous DBEM versions, ICME being a short-hand for interplanetary CME. The analysis to find the optimal drag parameter γ and ambient solar wind speed w showed that somewhat higher values (γ ≈0.3 ×10−7 km−1, w ≈ 425 km s−1) for both of these DBEM input parameters should be used for the evaluation than the previously employed ones. Based on the evaluation performed for 146 CME-ICME pairs, the DBEMv3 performance with mean error (ME) of −11.3 h, mean absolute error (MAE) of 17.3 h was obtained. There is a clear bias towards the negative prediction errors where the fast CMEs are predicted to arrive too early, probably due to the model physical limitations and input errors (e.g. CME launch speed). This can be partially reduced by using larger values for γ resulting in smaller prediction errors (ME =−3.9 h, MAE = 14.5 h) but at the cost of larger prediction errors for single fast CMEs as well as larger CME arrival speed prediction errors. DBEMv3 showed also slight improvement in the performance for all calculated output parameters compared to the previous DBEM versions. Title: Drag-based model (DBM) tools for forecast of coronal mass ejection arrival time and speed Authors: Dumbović, Mateja; Čalogović, Jaša; Martinić, Karmen; Vršnak, Bojan; Sudar, Davor; Temmer, Manuela; Veronig, Astrid Bibcode: 2021FrASS...8...58D Altcode: 2021arXiv210314292D Forecasting the arrival time of coronal mass ejections (CMEs) and their associated shocks is one of the key aspects of space weather research and predictions. One of the commonly used models is, due to its simplicity and calculation speed, the analytical drag-based model (DBM) for heliospheric propagation of CMEs. DBM relies on the observational fact that slow CMEs accelerate whereas fast CMEs decelerate, and is based on the concept of MHD drag, which acts to adjust the CME speed to the ambient solar wind. Although physically DBM is applicable only to the CME magnetic structure, it is often used as a proxy for the shock arrival. In recent years, the DBM equation has been used in many studies to describe the propagation of CMEs and shocks with different geometries and assumptions. Here we give an overview of the five DBM versions currently available and their respective tools, developed at Hvar Observatory and frequently used by researchers and forecasters. These include: 1) basic 1D DBM, a 1D model describing the propagation of a single point (i.e. the apex of the CME) or concentric arc (where all points propagate identically); 2) advanced 2D self-similar cone DBM, a 2D model which combines basic DBM and cone geometry describing the propagation of the CME leading edge which evolves self-similarly; 3) 2D flattening cone DBM, a 2D model which combines basic DBM and cone geometry describing the propagation of the CME leading edge which does not evolve self-similarly; 4) DBEMv1, an ensemble version of the 2D flattening cone DBM which uses CME ensembles as an input and 5) DBEMv3, an ensemble version of the 2D flattening cone DBM which creates CME ensembles based on the input uncertainties. All five versions have been tested and published in recent years and are available online or upon request. We provide an overview of these five tools, of their similarities and differences, as well as discuss and demonstrate their application. Title: Properties of stream interaction regions at Earth and Mars during the declining phase of SC 24 Authors: Geyer, Paul; Temmer, Manuela; Guo, Jingnan; Heinemann, Stephan G. Bibcode: 2021A&A...649A..80G Altcode: 2021arXiv210205948G
Aims: We inspect the evolution of stream interaction regions (SIRs) from Earth to Mars, covering the distance range 1-1.5 AU, over the declining phase of solar cycle 24 (2014-2018). So far, studies only analyzed SIRs measured at Earth and Mars at different times. We compare existing catalogs for both heliospheric distances and arrive at a clean dataset for the identical time range. This allows a well-sampled statistical analysis and for the opposition phases of the planets an in-depth analysis of SIRs as they evolve with distance.
Methods: We use in situ solar wind data from OMNI and the Mars Atmosphere and Volatile EvolutioN spacecraft as well as remote sensing data from Solar Dynamics Observatory. A superposed epoch analysis is performed for bulk speed, proton density, temperature, magnetic field magnitude and total perpendicular pressure. Additionally, a study of events during the two opposition phases of Earth and Mars in the years 2016 and 2018 is conducted. SIR related coronal holes with their area as well as their latitudinal and longitudinal extent are extracted and correlated to the maximum bulk speed and duration of the corresponding high speed solar wind streams following the stream interaction regions.
Results: We find that while the entire solar wind high speed stream shows no expansion as it evolves from Earth to Mars, the crest of the high speed stream profile broadens by about 17%, and the magnetic field and total pressure by about 45% around the stream interface. The difference between the maximum and minimum values in the normalized superposed profiles increases slightly or stagnates from 1-1.5 AU for all parameters, except for the temperature. A sharp drop at zero epoch time is observed in the superposed profiles for the magnetic field strength at both heliospheric distances. The two opposition phases reveal similar correlations of in situ data with coronal hole parameters for both planets. Maximum solar wind speed has a stronger dependence on the latitudinal extent of the respective coronal hole than on its longitudinal extent. We arrive at an occurrence rate of fast forward shocks three times higher at Mars than at Earth. Title: Current status of project SWEETS: Estimating thermospheric neutral mass densities from satellite data at various altitudes Authors: Krauss, Sandro; Suesser-Rechberger, Barbara; Behzadpour, Saniya; Mayer-Guerr, Torsten; Temmer, Manuela; Kroisz, Sofia; Drescher, Lukas Bibcode: 2021EGUGA..23.4174K Altcode: Within the project SWEETS (funded by the FFG Austria) it is intended to develop a forecasting model, to predict the expected impact of solar events, like coronal mass ejections (CMEs), on satellites at different altitudes between 300-800 km. For the realization, scientific data, such as kinematic orbit information and accelerometer measurements, from a wide variety of satellites are incorporated. Based on the evaluation of the impact of several hundred solar events on the thermosphere the forecasting will be realized through a joint analysis and evaluation of solar wind plasma and magnetic field data observed at the Lagrange point L1.In this contribution we show first preliminary results of thermospheric densities estimates based on kinematic orbit information for different satellite missions (e.g., TerraSAR-X, TanDEM-X, Swarm A-C, GRACE, GRACE-FO, CHAMP). To validate the outcome, we compare the results with state-of-the-art thermospheric models as well as with densities estimated from accelerometer measurements if available. Finally, for some specific CME events we will perform a comparison between the post-processed density estimates and results from our preliminary forecasting tool. Title: Statistical study of CMEs, lateral overexpansion and SEP events Authors: Adamis, Alexandros; Veronig, Astrid; Podladchikova, Tatiana; Dissauer, Karin; Miteva, Rositsa; Guo, Jingnan; Haberle, Veronika; Dumbovic, Mateja; Temmer, Manuela; Kozarev, Kamen; Magdalenic, Jasmina; Kay, Christina Bibcode: 2021EGUGA..23.3216A Altcode: We present a statistical study on the early evolution of coronal mass ejections (CMEs), to better understand the effect of CME (over)- expansion and how it relates to the production of Solar Energetic Particle (SEP) events. We study the kinematic CME characteristics in terms of their radial and lateral expansion, from their early evolution in the Sun"s atmosphere as observed in EUV imagers and coronagraphs. The data covers 72 CMEs that occurred in the time range of July 2010 to September 2012, where the twin STEREO spacecraft where in quasiquadrature to the Sun-Earth line. From the STEREO point-of-view, the CMEs under study were observed close to the limb. We calculated the radial and lateral height (width) versus time profiles and derived the corresponding peak and mean velocities, accelerations, and angular expansion rates, with particular emphasis on the role of potential lateral overexpansion in the early CME evolution. We find high correlations between the radial and lateral CME velocities and accelerations. CMEs that are associated tend to be located at the high-value end of the distributions of velocities, widths, and expansion rates compared to nonSEP associated events. Title: Statistical relations between in-situ measured Bz component and thermospheric density variations Authors: Kroisz, Sofia; Drescher, Lukas; Temmer, Manuela; Krauss, Sandro; Süsser-Rechberger, Barbara; Mayer-Gürr, Torsten Bibcode: 2021EGUGA..23.4773K Altcode: Through advanced statistical investigation and evaluation of solar wind plasma and magnetic field data, we investigate the statistical relation between the magnetic field Bz component, measured at L1, and Earth"s thermospheric neutral density. We will present preliminary results of the time series analyzes using in-situ plasma and magnetic field measurements from different spacecraft in near Earth space (e.g., ACE, Wind, DSCOVR) and relate those to derived thermospheric densities from various satellites (e.g., GRACE, CHAMP). The long and short term variations and dependencies in the solar wind data are related to variations in the neutral density of the thermosphere and geomagnetic indices. Special focus is put on the specific signatures that stem from coronal mass ejections and stream or corotating interaction regions. The results are used to develop a novel short-term forecasting model called SODA (Satellite Orbit DecAy). This is a joint study between TU Graz and University of Graz funded by the FFG Austria (project "SWEETS"). Title: Multi-Channel Coronal Hole Detection with Convolutional Neural Networks Authors: Jarolim, Robert; Veronig, Astrid; Hofmeister, Stefan; Heinemann, Stephan; Temmer, Manuela; Podladchikova, Tatiana; Dissauer, Karin Bibcode: 2021EGUGA..23.1490J Altcode: Being the source region of fast solar wind streams, coronal holes are one of the key components which impact space weather. The precise detection of the coronal hole boundary is an important criterion for forecasting and solar wind modeling, but also challenges our current understanding of the magnetic structure of the Sun. We use deep-learning to provide new methods for the detection of coronal holes, based on the multi-band EUV filtergrams and LOS magnetogram from the AIA and HMI instruments onboard the Solar Dynamics Observatory. The proposed neural network is capable to simultaneously identify full-disk correlations as well as small-scale structures and efficiently combines the multi-channel information into a single detection. From the comparison with an independent manually curated test set, the model provides a more stable extraction of coronal holes than the samples considered for training. Our method operates in real-time and provides reliable coronal hole extractions throughout the solar cycle, without any additional adjustments. We further investigate the importance of the individual channels and show that our neural network can identify coronal holes solely from magnetic field data. Title: Comparative study of halo CME arrival predictions Authors: Yordanova, Emiliya; Dumbovic, Mateja; Temmer, Manuela; Scolini, Camilla; Magdalenic, Jasmina; Thompson, William J.; Sorriso-Valvo, Luca; Dimmock, Andrew P.; Rosenqvist, Lisa Bibcode: 2021EGUGA..2314187Y Altcode: Halo coronal mass ejections (CMEs) are one of the most effective drivers of intense geomagnetic storms. Despite the recent advances in space weather forecasting, the accurate arrival prediction of halo CMEs remains a challenge. This is because in general CMEs interact with the background solar wind during their propagation in the interplanetary space. In addition, in the case of halo CMEs, the accurate estimation of their kinematics is difficult due to projection effects in the plane-of-sky.In this study, we are revisiting the arrival of twelve geoeffective Earth-directed fast halo CMEs using an empirical and a numerical approaches. For this purpose we refine the input to the Drag-based Model (DBM) and to the EUropean Heliospheric Forecasting Information Asset (EUHFORIA), which are recently available for users from the ESA Space Situational Awareness Portal (http://swe.ssa.esa.int).The DBM model has been tested using different values for the input drag parameter. On average, the predicted arrival times are confined in the range of ± 10 h. The closest arrival to the observed one has been achieved with a drag value higher than the recommended for fast CMEs. Setting a higher drag also helped to obtain a closer to the observed CME arrival speed prediction. These results suggest that the exerted solar wind drag was higher than expected. Further, we are searching for clues about the CME propagation by performing EUHFORIA runs using the same CME kinematics. Preliminary results show that both models perform poorly for CMEs that have possibly undergone CME-CME interaction, underlying again the importance of taking into account the state of the interplanetary space in the CME forecast. Title: Deriving CME volume and density from remote sensing data Authors: Temmer, Manuela; Holzknecht, Lukas; Dumbovic, Mateja; Vrsnak, Bojan; Sachdeva, Nishtha; Heinemann, Stephan G.; Dissauer, Karin; Scolini, Camilla; Asvestari, Eleanna; Veronig, Astrid M.; Hofmeister, Stefan Bibcode: 2021EGUGA..23.2535T Altcode: Using combined STEREO-SOHO white-light data, we present a method to determine the volume and density of a coronal mass ejection (CME) by applying the graduated cylindrical shell model (GCS) and deprojected mass derivation. Under the assumption that the CME mass is roughly equally distributed within a specific volume, we expand the CME self-similarly and calculate the CME density for distances close to the Sun (15-30 Rs) and at 1 AU. The procedure is applied on a sample of 29 well-observed CMEs and compared to their interplanetary counterparts (ICMEs). Specific trends are derived comparing calculated and in-situ measured proton densities at 1 AU, though large uncertainties are revealed due to the unknown mass and geometry evolution: i) a moderate correlation for the magnetic structure having a mass that stays rather constant and ii) a weak correlation for the sheath density by assuming the sheath region is an extra mass - as expected for a mass pile-up process - that is in its amount comparable to the initial CME deprojected mass. High correlations are derived between in-situ measured sheath density and the solar wind density and solar wind speed as measured 24 hours ahead of the arrival of the disturbance. This gives additional confirmation that the sheath-plasma indeed stems from piled-up solar wind material. While the CME interplanetary propagation speed is not related to the sheath density, the size of the CME may play some role in how much material is piled up. Title: Constraining the CME parameters of the spheromak flux rope implemented in EUHFORIA Authors: Asvestari, Eleanna; Pomoell, Jens; Kilpua, Emilia; Good, Simon; Chatzistergos, Theodosios; Temmer, Manuela; Palmerio, Erika; Poedts, Stefaan; Magdalenic, Jasmina Bibcode: 2021EGUGA..23.3291A Altcode: Coronal mass ejections (CMEs) are primary drivers of space weather phenomena. Modelling the evolution of the internal magnetic field configuration of CMEs as they propagate through the interplanetary space is an essential part of space weather forecasting. EUHFORIA (EUropean Heliospheric FORecasting Information Asset) is a data-driven, physics-based model, able to trace the evolution of CMEs and CME-driven shocks through realistic background solar wind conditions. It employs a spheromak-type magnetic flux rope that is initially force-free, providing it with the advantage of modelling CME as magnetised structures. For this work we assessed the spheromak CME model employed in EUHFORIA with a test CME case study. The selected CME eruption occurred on the 6th of January 2013 and was encountered by two spacecraft, Venus Express and STEREO--A, which were radially aligned at the time of the CME passage. Our focus was to constrain the input parameters, with particular interest in: (1) translating the angular widths of the graduated cylindrical shell (GCS) fitting to the spheromak radius, and (2) matching the observed magnetic field topology at the source region. We ran EUHFORIA with three different spheromak radii. The model predicts arrival times from half to a full day ahead of the one observed in situ. We conclude that the choice of spheromak radius affected the modelled magnetic field profiles, their amplitude, arrival times, and sheath region length. Title: CME arrival time predictions with a deformable front Authors: Hinterreiter, Jürgen; Amerstorfer, Tanja; Reiss, Martin A.; Weiss, Andreas J.; Möstl, Christian; Temmer, Manuela; Bauer, Maike; Bailey, Rachel L.; Amerstorfer, Ute V. Bibcode: 2021EGUGA..23.5830H Altcode: We present the first results of our newly developed CME arrival prediction model, which allows the CME front to deform and adapt to the changing solar wind conditions. Our model is based on ELEvoHI and makes use of the WSA/HUX (Wang-Sheeley-Arge/Heliospheric Upwind eXtrapolation) model combination, which computes large-scale ambient solar wind conditions in the interplanetary space. With an estimate of the solar wind speed and density, we are able to account for the drag exerted on different parts of the CME front. Initially, our model relies on heliospheric imager observations to confine an elliptical CME front and to obtain an initial speed and drag parameter for the CME. After a certain distance, each point of the CME front is propagating based on the conditions in the heliosphere. In this case study, we compare our results to previous arrival time predictions using ELEvoHI with a rigid CME front. We find that the actual arrival time at Earth and the arrival time predicted by the new model are in very good agreement. Title: Evolution of stream interaction regions from 1 to 1.5 AU Authors: Geyer, Paul; Temmer, Manuela; Guo, Jingnan; Heinemann, Stephan Bibcode: 2021EGUGA..2312513G Altcode: We inspect the evolution of stream interaction regions from Earth to Mars for the declining solar cycle 24. In particular, the opposition phases of the two planets are analyzed in more detail. So far, there is no study comparing the long-term properties of stream interaction regions and accompanying high-speed streams at both planets for the same time period. We build a catalogue covering a dataset of all measured stream interaction regions at Earth and Mars for the time period December 2014 - November 2018. The number of events (>120) allows for a strong statistical basis. To build the catalogue we use near-earth OMNI data as well as measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. For the opposition phase, we additionally use image data from the Solar Dynamics Observatory to complement the in-situ observations. Bulk speed, proton density, temperature, magnetic field magnitude and total perpendicular pressure are statistically evaluated using a superposed epoch analysis. For the opposition phase, coronal holes that are linked to individual streams are identified. The extracted coronal hole areas (using CATCH) and their longitudinal/latitudinal extension are correlated to the duration and maximum bulk speed of the high-speed stream following the passage of a stream interaction region. We find that an expansion of the stream interface from 1 to 1.5 AU is most visible in magnetic field and total perpendicular pressure. The duration of the high-speed stream does not increase significantly from Earth to Mars, however, the stream crest seems to increase. The amplitudes of the SW parameters are found to only slightly increase or stagnate from 1 - 1.5 AU. We arrive at similar correlation coefficients for both planets with the properties of the related coronal holes. There is a stronger linking of maximum bulk speed to latitudinal extent of the coronal hole than to the longitudinal. On average, the occurrence rate of fast forward shocks increases from Earth to Mars. Title: Why are ELEvoHI CME Arrival Predictions Different if Based on STEREO A or STEREO B Heliospheric Imager Observations? Authors: Hinterreiter, Jürgen; Amerstorfer, Tanja; Reiss, Martin A.; Möstl, Christian; Temmer, Manuela; Bauer, Maike; Amerstorfer, Ute V.; Bailey, Rachel L.; Weiss, Andreas J.; Davies, Jackie A.; Barnard, Luke A.; Owens, Mathew J. Bibcode: 2021SpWea..1902674H Altcode: 2021arXiv210207478H Accurate forecasting of the arrival time and arrival speed of coronal mass ejections (CMEs) is an unsolved problem in space weather research. In this study, a comparison of the predicted arrival times and speeds for each CME based, independently, on the inputs from the two STEREO vantage points is carried out. We perform hindcasts using ELlipse Evolution model based on Heliospheric Imager observations (ELEvoHI) ensemble modeling. An estimate of the ambient solar wind conditions is obtained by the Wang Sheeley Arge/Heliospheric Upwind eXtrapolation (WSA/HUX) model combination that serves as input to ELEvoHI. We carefully select 12 CMEs between February 2010 and July 2012 that show clear signatures in both STEREO A and STEREO B HI time elongation maps, that propagate close to the ecliptic plane, and that have corresponding in situ signatures at Earth. We find a mean arrival time difference of 6.5 h between predictions from the two different viewpoints, which can reach up to 9.5 h for individual CMEs, while the mean arrival speed difference is 63 km s−1. An ambient solar wind with a large speed variance leads to larger differences in the STEREO A and STEREO B CME arrival time predictions (cc = 0.92). Additionally, we compare the predicted arrivals, from both spacecraft, to the actual in situ arrivals at Earth and find a mean absolute error of 7.5 ± 9.5 h for the arrival time and 87 ± 111 km s−1 for the arrival speed. There is no tendency for one spacecraft to provide more accurate arrival predictions than the other. Title: Search for flares and associated CMEs on late-type main-sequence stars in optical SDSS spectra Authors: Koller, Florian; Leitzinger, Martin; Temmer, Manuela; Odert, Petra; Beck, Paul G.; Veronig, Astrid Bibcode: 2021A&A...646A..34K Altcode: 2020arXiv201200786K
Aims: This work aims to detect and classify stellar flares and potential stellar coronal mass ejection (CME) signatures in optical spectra provided by the Sloan Digital Sky Survey (SDSS) data release 14. The sample is constrained to all F, G, K, and M main-sequence type stars, resulting in more than 630 000 stars. This work makes use of the individual spectral exposures provided by the SDSS.
Methods: An automatic flare search was performed by detecting significant amplitude changes in the Hα and Hβ spectral lines after a Gaussian profile was fit to the line core. CMEs were searched for by identifying asymmetries in the Balmer lines caused by the Doppler effect of plasma motions in the line of sight.
Results: We identified 281 flares on late-type stars (spectral types K3 - M9). We identified six possible CME candidates showing excess flux in Balmer line wings. Flare energies in Hα were calculated and masses of the CME candidates were estimated. The derived Hα flare energies range from 3 × 1028 - 2 × 1033 erg. The Hα flare energy increases with earlier types, while the fraction of flaring times increases with later types. Mass estimates for the CME candidates are in the range of 6 × 1016 - 6 × 1018 g, and the highest projected velocities are ~300-700 km s-1.
Conclusions: The low detection rate of CMEs we obtained agrees with previous studies, suggesting that for late-type main-sequence stars the CME occurrence rate that can be detected with optical spectroscopy is low.

Table C.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/646/A34 Title: Quo vadis, European Space Weather community? Authors: Lilensten, Jean; Dumbović, Mateja; Spogli, Luca; Belehaki, Anna; Van der Linden, Ronald; Poedts, Stefaan; Barata, Teresa; Bisi, Mario M.; Cessateur, Gaël; De Donder, Erwin; Guerrero, Antonio; Kilpua, Emilia; Korsos, Marianna B.; Pinto, Rui F.; Temmer, Manuela; Tsagouri, Ioanna; Urbář, Jaroslav; Zuccarello, Francesca Bibcode: 2021JSWSC..11...26L Altcode: This paper was written by a group of European researchers believing that now is the right time to frame the Space Weather and Space Climate discipline in Europe for future years. It is devoted to openly discussing the organisation and sustainability of the European Space Weather community and its assets in the (near) future. More specifically, we suggest that the European Space Weather community lacks a uniting organisation to help the community to sustain and develop the successful efforts made thus far. Our aim is not to draw a complete and exhaustive panorama of Space Weather throughout the world, nor even throughout Europe. It is not a new white paper on the science and applications: there exist many (e.g. Tsurutani et al., 2020 Nonlinear Processes Geophys 27(1): 75-119); nor another roadmap: several important have been published recently (e.g. Schrijver et al., 2015. Adv Space Res 55(12): 2745-2807; Opgenoorth et al., 2019. J Space Weather Space Clim 9: A37). Our aim is to question our practices and organisation in front of several changes that have occurred in the recent years and to set the ground to provide coordinated answers to these questions being posed in Europe, and to make these answers discussed throughout the world. This group was assembled first through a series of sessions devoted to the sustainability of Space Weather research during the European Space Weather Week (ESWW) series of meetings, specifically: ESWW 14 (2017), ESWW 15 (2018), and ESWW 16 (2019). It then grew from discussions and personal contacts. The authors do not pretend to identify the full range of opinions in Europe, although they do come from 13 different European countries with a large span of ages (around half are below the age of 40 years old at the time of writing) with a good gender balance ending with a diverse mix of young and motivated scientists and senior people who have played a role in shaping the Space Weather community in Europe. The questions and the propositions to organise Space Weather in Europe in the future result from their discussions through these meetings and through remote meetings during the pandemic. We wish to share them with all those who consider themselves as members of the European Space Weather community and/or are interested in its future and to propose actions. We do this, bearing in mind that Europe plays a key international role in Space Weather which extends beyond the ESA and EU/EC geographic area. Title: Statistical Approach on Differential Emission Measure of Coronal Holes using the CATCH Catalog Authors: Heinemann, Stephan G.; Saqri, Jonas; Veronig, Astrid M.; Hofmeister, Stefan J.; Temmer, Manuela Bibcode: 2021SoPh..296...18H Altcode: 2021arXiv210213396H Coronal holes are large-scale structures in the solar atmosphere that feature a reduced temperature and density in comparison to the surrounding quiet Sun and are usually associated with open magnetic fields. We perform a differential emission measure analysis on the 707 non-polar coronal holes in the Collection of Analysis Tools for Coronal Holes (CATCH) catalog to derive and statistically analyze their plasma properties (i.e. temperature, electron density, and emission measure). We use intensity filtergrams of the six coronal EUV filters from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory, which cover a temperature range from ≈105.5 to 107.5K. Correcting the data for stray and scattered light, we find that all coronal holes have very similar plasma properties with an average temperature of 0.94 ±0.18 MK, a mean electron density of (2.4 ±0.7 )×108cm−3, and a mean emission measure of (2.8 ±1.6 )×1026cm−5. The temperature distribution within the coronal holes was found to be largely uniform, whereas the electron density shows a 30 to 40% linear decrease from the boundary towards the inside of the coronal hole. At distances greater than 20″ (≈15 Mm) from the nearest coronal hole boundary, the density also becomes statistically uniform. The coronal hole temperature may show a weak solar-cycle dependency, but no statistically significant correlation of plasma properties with solar-cycle variations could be determined throughout the observed period between 2010 and 2019. Title: Towards solving the source to impact chain of Space Weather processes Authors: Temmer, Manuela Bibcode: 2021cosp...43E.643T Altcode: Space Weather is of global and major interest that sustains an exciting and wealthy interdisciplinary research community. In that respect, science and development of forecasting tools needs to understand the chain of action that causes Space Weather, starting from processes at the Sun, in interplanetary space, and impact at Earth. The initiative called iSWAT (international Space Weather Action Teams) aims towards tackling the broad spectrum of issues and addresses individual communities to form interdisciplinary partnerships maximizing return on investments to national and international space weather programs. With that iSWAT fosters information and knowledge exchange between international research groups on solar-, heliospheric- and geo-space in order to improve existing and to develop new models. In that broad spectrum of topics, I will specifically focus on the modeling of the background solar wind and embedded coronal mass ejections. Title: Deriving CME Density From Remote Sensing Data and Comparison to In Situ Measurements Authors: Temmer, M.; Holzknecht, L.; Dumbović, M.; Vršnak, B.; Sachdeva, N.; Heinemann, S. G.; Dissauer, K.; Scolini, C.; Asvestari, E.; Veronig, A. M.; Hofmeister, S. J. Bibcode: 2021JGRA..12628380T Altcode: 2020arXiv201106880T We determine the three dimensional geometry and deprojected mass of 29 well observed coronal mass ejections (CMEs) and their interplanetary counterparts (ICMEs) using combined Solar Terrestrial Relations Observatory Solar and Heliospheric Observatory white light data. From the geometry parameters, we calculate the volume of the CME for the magnetic ejecta (flux rope type geometry) and sheath structure (shell like geometry resembling the (I)CME frontal rim). Working under the assumption that the CME mass is roughly equally distributed within a specific volume, we expand the CME self similarly and calculate the CME density for distances close to the Sun (15-30 Rs) and at 1 AU. Specific trends are derived comparing calculated and in situ measured proton densities at 1 AU, though large uncertainties are revealed due to the unknown mass and geometry evolution: (1) a moderate correlation for the magnetic structure having a mass that stays rather constant (cc ≈ 0.56 - 0.59), and (2) a weak correlation for the sheath density (cc ≈ 0.26) by assuming the sheath region is an extra mass—as expected for a mass pile up process—that is in its amount comparable to the initial CME deprojected mass. High correlations are derived between in situ measured sheath density and the solar wind density (cc ≈ -0.73) and solar wind speed (cc ≈ 0.56) as measured 24 h ahead of the arrival of the disturbance. This gives additional confirmation that the sheath plasma indeed stems from piled up solar wind material. While the CME interplanetary propagation speed is not related to the sheath density, the size of the CME may play some role in how much material could be piled up. Title: Improving Understanding and Assessment of the Ambient Solar Wind Authors: Reiss, Martin; Moestl, Christian; Linker, Jon; Mullinix, Richard; Rastaetter, Lutz; Temmer, Manuela; Arge, Charles; MacNeice, Peter; Wiegand, Chiu; Muglach, Karin; Ko, Kuen Bibcode: 2021cosp...43E2398R Altcode: The Sun's magnetic field drives the evolving ambient solar wind flow and the magnetic field embedded within it. Thus, studying the magnetic field configuration in the solar atmosphere is of crucial importance for improving our understanding of and ultimately predicting space weather from Sun to Earth. Coronal holes are regions of low intensity emission in EUV and X-ray images. Coronal holes are closely associated with open magnetic field lines, along which the solar wind accelerates to supersonic speeds. Therefore, they play a central role in shaping the structure of the heliosphere and defining key properties in interplanetary space, such as the solar wind bulk speed, magnetic field strength, and field orientation. Answering vital research questions related to the ambient solar wind requires an interdisciplinary strategy and the coordinated collaboration of international partners. Here we present the COSPAR ISWAT activities for improving the understanding and assessment of the evolving ambient solar wind flow embedded in the 'Coronal Hole Boundary Working Team' and the 'Ambient Solar Wind Validation Team'. Specifically, we present our progress in evaluating the uncertainty of coronal hole boundary locations in solar observations, and our progress in establishing an online hub for validation of ambient solar wind models. In context, we demonstrate the first application of a new online platform enabling developers and end-users to directly assess the quality of state-of-the-art solar wind model solutions. To conclude, we present the objectives, current status and roadmaps of both action teams, and discuss the main challenges we face in the realization of our objectives. Title: Life-time evolution and magnetic structure of coronal holes Authors: Heinemann, Stephan; Pomoell, Jens; Temmer, Manuela; Bourdin, Philippe Bibcode: 2021cosp...43E1024H Altcode: The study of the evolution of coronal holes (CHs) is especially important in the context of high--speed solar wind streams emanating from them. Slow and high speed stream interaction regions may deliver large amount of energy into the Earth's magnetosphere-termosphere-ionosphere system system, cause geomagnetic storms, and shape interplanetary space. The open magnetic structure, its evolution and interplay with the local and global fields strongly defines the coronal and solar wind properties. Only by understanding these we can attempt to create a full picture of our heliosphere. By statistically investigating the long--term evolution of 16 well observed CHs, which are distributed in time over a full solar cycle, we aim to reveal processes that drive the observed changes in the CH parameters. We use remote sensing image data from SDO and focus on coronal, morphological and underlying photospheric magnetic field characteristics as well as investigate the evolution of the associated high--speed streams from in-situ measurements. The analysis of the observational data is supported by modeling, based on synthetic data in order to simulate the small-scale magnetic field topology in 3 dimensions. We find that the CH area evolution mostly shows a rough trend of growing to a maximum followed by a decay. No correlation of the area evolution to the evolution of the signed magnetic flux and signed magnetic flux density enclosed in the projected coronal hole area was found. From this we conclude that the magnetic flux within the extracted coronal hole boundaries is not the main cause for its area evolution. This is supported by the model results. Change rates of the signed mean magnetic flux density and the signed magnetic flux are derived to be dependent on the solar cycle rather than on the evolution of the individual CH. This clearly hints towards that the global magnetic field gives significant contribution to the evolution of open magnetic field structures on the Sun. The velocities of the high speed streams emanating from the CHs are found to be linearly related to the area of the individual CH, however the slopes vary. Title: Forecasting the arrival time of coronal mass ejections Authors: Dumbovic, Mateja; Mays, M. Leila; Riley, Pete; Mierla, Marilena; Kay, Christina; Vrsnak, Bojan; Veronig, Astrid; Cremades, Hebe; Čalogović, Jaša; Verbeke, Christine; Temmer, Manuela; Sudar, Davor; Scolini, Camilla; Hinterreiter, Jürgen; Paouris, Evangelos; Palmerio, Erika; Balmaceda, Laura Bibcode: 2021cosp...43E1038D Altcode: Forecasting the arrival time of coronal mass ejections (CMEs) and their associated shocks is one of the key aspects of space weather. In recent years many models have been developed by various research groups aiming to forecast CME arrival time. The models differ based on the input, approach, assumptions and complexity ranging from simple empirical and analytical to complex numerical and machine learning models. One of the commonly used models is, due to its simplicity and calculation speed, the analytical drag-based (ensemble) model [DB(E)M] for heliospheric propagation of CMEs. DB(E)M relies on the observational fact that slow CMEs accelerate whereas fast CMEs decelerate, and is based on the concept of MHD drag, which acts to adjust the CME speed to the ambient solar wind. However, regardless of the model, forecasting CME arrival time has proven to be exceedingly challenging. One of the major setbacks is the uncertainty of the CME observational input, which is still substantial despite state-of-the-art remote observational capacities such as high-resolution EUV imagers and stereoscopic observations. Another major setback is the uncertainty in the CME propagation itself, due to e.g. unrealistic background solar wind and/or complex interactions. These limits will be discussed in the scope of DB(E)M and the CME input analysis performed by the ISSI Bern team on the "Understanding Our Capabilities In Observing And Modeling Coronal Mass Ejections". Title: Stereoscopic view on CMEs; differences in predicted CME arrivals based on STEREO-A/STEREO-B HI data Authors: Hinterreiter, Jürgen; Moestl, Christian; Amerstorfer, Ute; Amerstorfer, Tanja; Temmer, Manuela; Reiss, Martin; Bailey, Rachel; Weiss, Andreas J.; Bauer, Maike Bibcode: 2021cosp...43E1039H Altcode: Over the last decades numerous models to predict the arrival times and speeds of CMEs (coronal mass ejections) have been developed. They range from computationally very fast drag-based models to expensive MHD models. However, uncertainties in the forecasts are large for all the models available so far. In this study, we use ELEvoHI (ELlipse Evolution model based on Heliospheric Imager observations) ensemble modeling for CME post-event arrival prediction. The model assumes an elliptical shape of the CME front within the ecliptic plane and makes use of time-elongation profiles provided by HI (Heliospheric Imager) onboard the STEREO (Solar TErrestrial RElations Observatory) twin spacecraft. In addition, ELEvoHI utilizes an ambient solar wind provided by the Wang-Sheeley-Arge model to account for the drag force that is exerted on the CME during the propagation in the heliosphere. For this study, we carefully select 12 CMEs between February 2010 and July 2012. The CMEs have to fulfill the following three criteria: 1) clear signatures in STEREO-A and STEREO-B HI images, 2) corresponding in-situ signature, and 3) propagation close to the ecliptic plane. Based on typical input data we analyze the arrival times and speeds of each CME using STEREO-A and STEREO-B time-elongation profiles and compare them with each other. The results show differences up to 10 hours and 200 km/s. We give possible reasons for the discrepancies in relation to the input data and dependencies on the two vantage points. Title: ISWAT H2 Cluster: CME structure, evolution and propagation through heliosphere Authors: Verbeke, Christine; Mays, M. Leila; Temmer, Manuela; Kay, Christina Bibcode: 2021cosp...43E2417V Altcode: Coronal mass ejections (CMEs) are energetically the most powerful phenomena in the solar system. Most of the times related to solar flare emissions, CMEs consist of magnetic field and plasma that is impulsively ejected into interplanetary space. To make progress in improving current state-of-the-art CME propagation models, validation and scientific peer-review qualification is needed. iSWAT is an international, community driven effort and provides the required platform to challenge currentmodels and to exchange our experience with peers in order to improve our work. We give an overview on the available teams in the H2 cluster and their aims for the H2 cluster. Title: Observational study of CME propagation and geo-effectiveness Authors: Temmer, Manuela Bibcode: 2021cosp...43E1784T Altcode: Coronal mass ejections (CMEs) are the most powerful dynamic phenomena in our solar system. The propagation behavior of these transient events in interplanetary space is strongly dependent on their initial parameters, like size and mass, kinematics, and the ambient solar wind structure. As CMEs evolve, different structures are observed, typically covering a shock-sheath region and a driver, pre-sumably consisting of a magnetic flux rope. The structures can be observed and distinguished partly in remote sensing image data and more clearly from in-situ measurements by their different character-istics. Both structures undergo changes on their way from Sun to Earth that modifies the degree of impact and geoeffectiveness. While during propagation presumably mass is built up in the sheath's front region, the orientation of the interplanetary magnetic field affects the magnetic structure by re-ducing or increasing the amount of magnetic flux due to reconnection with the interplanetary magnetic field. When hitting Earth, differences in the magnetospheric responses are found between the magnetic and the shock-sheath region. This talk will review different perspectives of CME evolution in inter-planetary space and their interaction with the solar wind, with special aspects from new solar missions Parker Solar Probe and Solar Orbiter. Title: Statistical Analysis of SDO-era Coronal Holes using CATCH Authors: Heinemann, Stephan; Temmer, Manuela Bibcode: 2021cosp...43E1014H Altcode: Coronal holes are regions of open magnetic field configuration in the solar corona and can be observed as large-scale dark structures in the extreme ultraviolet and X-ray spectrum. Deriving reliably the coronal hole boundary is crucial, as its area, underlying magnetic field, and other properties such as shape and intensity, give important hints towards high speed solar wind acceleration processes. In this study we present a new threshold-based extraction method that is modulated using the intensity gradient along the coronal hole boundary. It is implemented as a user-friendly SSWIDL-GUI and is part of the official distribution. The Collection of Analysis Tools for Coronal Holes (CATCH) enables the user to download data, perform guided coronal hole extraction and analyze the underlying photospheric magnetic field. We used CATCH to evaluate all non-polar coronal holes of the SDO-era. We used 193 Å filtergrams taken by the Atmospheric Imaging Assembly (AIA) and line-of-sight magnetograms taken by the Heliospheric and Magnetic Imager (HMI), both on board the Solar Dynamics Observatory (SDO) to investigate 707 coronal holes near the central meridian during the time period of 2010 and 2019. We find coronal holes distributed across latitudes of $\pm 60^\circ$ and sizes between $1.6\times10^9$ km$^{2}$. to $1.8\times10^{11}$ km$^{2}$. The absolute value of the mean signed magnetic field strength is on average of 2.9$\pm$1.9 G. We find no distinct trend towards a preferred hemisphere in abundance or size. Variations in the local and global conditions significantly change the threshold needed for reliable coronal hole extraction and thus, we can highlight the importance of individually assessing and extracting coronal holes. Title: The COSPAR ISWAT initiative for open validation analysis for models of the evolving ambient solar wind Authors: Reiss, Martin; Kuznetsova, Maria; Mullinix, Richard; Rastaetter, Lutz; Temmer, Manuela; MacNeice, Peter; Wiegand, Chiu; Muglach, Karin Bibcode: 2021cosp...43E2363R Altcode: Validation analysis plays a critical role in applied space weather research and prediction. First and foremost to inform developers and users of space weather models about the strengths and weaknesses of the models, and also to provide an unbiased assessment of progress over time. Here we present the activities of the Ambient Solar Wind Validation Team embedded in the COSPAR ISWAT initiative. The objective of this action team is to establish an online hub for validation analysis of ambient solar wind models in correspondence with the space weather community, allowing developers and end-users to directly assess the quality of state-of-the-art model solutions. To this end, we choose and agree on a set of comprehensive validation metrics reflecting the community needs and integrate them into the existing Comprehensive Assessment of Models and Events using Library Tools (CAMEL) web application hosted by NASA's Community Coordinated Modelling Center. CAMEL is an interactive visualization tool allowing developers and users to compare space weather and space science model output to observations. Specifically, we make use of CAMEL to quantitatively assess the relationship between state-of-the-art solar wind model solutions and observational data in terms of point-to-point statistics and more advanced event-based validation measures. In this presentation, we will demonstrate the first application of the new online platform with examples of state-of-the-art model solutions. We will also discuss the main challenges we face in the realization of our objectives, and present the current status and the roadmap of the action team. Title: Estimating the magnetic flux within an eruptive flux rope Authors: Temmer, Manuela; Rodriguez, Luciano; Dissauer, Karin; Veronig, Astrid; Tschernitz, Johannes; Thalmann, Julia K.; Hinterreiter, Jürgen Bibcode: 2021cosp...43E1741T Altcode: Erupting magnetic flux ropes develop into coronal mass ejections (CMEs) as they evolve and finally propagate into interplanetary space. Those large scale eruptions are observed to be frequently related to dynamic surface phenomena such as coronal waves and dimming regions. The better we are able to estimate initial CME parameters such as kinematics, geometry, and magnetic properties, the more precisely we can feed state-of-the-art CME propagation models and with that improve CME forecasting. In that respect, we report on a well-observed flare-CME event from 1 October 2011 focusing on the dynamic evolution of the CME and its embedded magnetic field. Using combined STEREO and SDO observations together with nonlinear force-free (NLFF) modeling we derive separately the flare reconnection and dimming flux. We find that already before the start of the impulsive flare phase magnetic reconnection was ongoing, that added magnetic flux to the flux rope before its final eruption. As the dimming evolves over a longer time span than the flaring phase, we find that the dimming flux increases by more than 25% after the end of the flare. This indicates that magnetic flux is still added to the flux rope after eruption and that the derived flare reconnection flux is most probably a lower limit for estimating the magnetic flux within the flux rope. Title: Modeling Coronal Mass Ejections with EUHFORIA Authors: Verbeke, Christine; Schmieder, Brigitte; Rodriguez, Luciano; Poedts, Stefaan; Magdalenic, Jasmina; Pomoell, Jens; Temmer, Manuela; Asvestari, Eleanna; Scolini, Camilla; Heinemann, Stephan; Hinterreiter, Jürgen; Samara, Evangelia Bibcode: 2021cosp...43E2358V Altcode: Fully understanding the origin and evolution of Coronal Mass Ejections (CMEs) from the Sun to the Earth remains a major topic in current solar-terrestrial physics and is of key importance to improve our space weather prediction capabilities. CMEs can drive strong space weather disturbances at Earth, and their dynamical pressure, magnetic field configuration and interaction with the solar wind can significantly alter their arrival time and impact at Earth. One of the key parameters that determine the geo-effectiveness of the CME is its internal magnetic configuration. With the EUHFORIA inner-heliosphere magnetohydrodynamics model, we can model a magnetised CME using a Linear Force Free Spheromak (LFFS) model, in order to model the internal magnetic structure of the CME throughout the inner heliosphere. In this talk, we present an overview of the model assessment efforts that have been made with EUHFORIA over the past years. We discuss the validation of the solar wind, as well as the development of the LFFS model. We focus on determining the sensitivity of the LFFS model input parameters, as well as some case studies to show our improved modeling of the CME magnetic field structures at Earth. Finally, we discuss current limitations and future improvements of the EUHFORIA model. Title: CME evolution and the corresponding Forbush decrease: modelling vs multi-spacecraft observation Authors: Dumbovic, Mateja; Moestl, Christian; Podladchikova, Tatiana; Guo, Jingnan; Heber, Bernd; Vrsnak, Bojan; Dissauer, Karin; Veronig, Astrid; Amerstorfer, Tanja; Temmer, Manuela; Carcaboso, Fernando; Kirin, Anamarija Bibcode: 2021cosp...43E1747D Altcode: One of the very common in-situ signatures of interplanetary coronal mass ejections (ICMEs), as well as other interplanetary transients are Forbush decreases (FDs), i.e. short-term reductions in the galactic cosmic ray (GCR) flux. FD phenomena are caused by the interaction of GCRs with a magnetic structure, therefore it is expected that different types of interplanetary substructures cause different types of GCR time profiles, allowing us to distinguish between shock/sheath, flux rope and SIR-type of FDs. Moreover, since the interaction of GCRs and CME magnetic structure (i.e. flux rope) occurs all the way from Sun to Earth, FDs reflect the evolutionary properties of CMEs. We apply modelling to different ICME regions in order to obtain a generic FD profile. We model the shock/sheath-related FD using the propagating diffusive barrier (PDB) model, the flux-rope-related FD using the diffusion model for the expanding flux rope (ForbMod), and the exponential time profile approximates the recovery after the event. The modeled generic FD profile qualitatively agrees with our current observation-based understanding of FDs. In addition, we test ForbMod against a set of multi-spacecraft observations of the same ICME. We find a reasonable agreement of the ForbMod model with multi-spacecraft measurements, indicating that modelled FDs reflect well the flux rope evolution. Title: Evolution of coronal mass ejections and the corresponding Forbush decreases: modelling vs. multi-spacecraft observations Authors: Dumbovic, M.; Vrsnak, B.; Guo, J.; Heber, B.; Dissauer, K.; Carcaboso-Morales, F.; Temmer, M.; Veronig, A.; Podladchikova, T.; Moestl, C.; Amerstorfer, T.; Kirin, A. Bibcode: 2020AGUFMSH046..08D Altcode: One of the very common in situ signatures of interplanetary coronal mass ejections (ICMEs), as well as other interplanetary transients, are Forbush decreases (FDs), i.e. short-term reductions in the galactic cosmic ray (GCR) flux. A two-step FD is often regarded as a textbook example, which presumably owes its specific morphology to the fact that the measuring instrument passed through the ICME head-on, encountering first the shock front (if developed), then the sheath and finally the CME magnetic structure. The interaction of GCRs and the shock/sheath region, as well as the CME magnetic structure, occurs all the way from Sun to Earth, therefore, FDs are expected to reflect the evolutionary properties of CMEs and their sheaths. We apply modelling to different ICME regions in order to obtain a generic two-step FD profile, which qualitatively agrees with our current observation-based understanding of FDs. We next adapt the models for energy dependence to enable comparison with different GCR measurement instruments (as they measure in different particle energy ranges). We test these modelling efforts against a set of multi-spacecraft observations of the same event, using the Forbush decrease model for the expanding flux rope (ForbMod). We find a reasonable agreement of the ForbMod model for the GCR depression in the CME magnetic structure with multi-spacecraft measurements, indicating that modelled FDs reflect well the CME evolution. Title: Drag-based Forecast for CME Arrival Authors: Yordanova, E.; Jaklovsky, S.; Dumbovic, M.; Temmer, M.; Dimmock, A. P.; Rosenqvist, L. Bibcode: 2020AGUFMSH0030013Y Altcode: The accurate estimation of the CME arrival times at 1 AU is of key importance for space weather forecast. It is a challenging issue, since when a CME expands, it inevitably interacts with the solar corona and the ambient solar wind occupying the interplanetary space. This often results in modification of the CME's plasma properties and propagation path. There are various approaches in use for arrival time prediction - either based on MHD modeling or empirical relations between parameters measured from coronagraphs and in-situ at L1. Here, we investigate the performance of the recent Drag Based Ensemble Model (DBEM, Dumbović et al., 2018; Žic et al., 2015) available for users from the ESA Space Situational Awareness Portal (http://swe.ssa.esa.int). DBEM provides an ensemble of probabilistic predictions for CME arrivals based on the Drag-Based Model (DBM, Vršnak et al., 2013) which assumes that the propagation of a CME is dependent solely on the magnetohydrodynamic drag (in analogy to the aerodynamic drag) exerted to the CME from the ambient solar wind.

We have selected to test a set of twelve geoeffective Earth-directed fast halo CMEs. For the model runs, we use as input CMEs' shock speed and the velocity of the respective preceding solar wind measured by WIND spacecraft. We perform test runs with values of the drag parameter: (0.1, 0.2 and 0.3)x10-7 km-1. Overall, the model produced a wide distribution of arrival times. The predictions were rather good, being confined in the range of ± 10 h. In addition, the model provides prediction for the CME arrival speeds, which in our case seem to be overestimated for all drag values. The closest predicted arrival time to about -2.5 h on average, was achieved by setting the drag value to 0.2x10-7 km-1. When matching also the predicted to the observed arrival speeds, the best average result was achieved with drag parameter 0.3x10-7 km-1, corresponding to +4.5 h CME arrival time. These drag values are higher than the recommended 0.1x10-7 km-1 for fast CMEs, suggesting that the exerted solar wind drag was higher than anticipated. This implies that further improvement in the CME arrival forecast requires more detailed and precise knowledge of the preconditioning of the interplanetary space through which the CMEs are propagating.

References:

Dumbović, M., et al., The Drag-based Ensemble Model (DBEM) for Coronal Mass Ejection Propagation. Astrophys. J., 854:180, 2018

Žic, M. et al., Heliospheric Propagation of Coronal Mass Ejections: Drag-based Model Fitting. Astrophys. J. Suppl., 218:32, 2015

Vršnak, B., et al., Propagation of Interplanetary Coronal Mass Ejections: The Drag-Based Model, Solar Phys. 285:295-315, 2013 Title: CME-CME Interactions as Sources of CME Helio-Effectiveness: the Early September 2017 Events Authors: Scolini, C.; Chané, E.; Temmer, M.; Pomoell, J.; Kilpua, K. E. J.; Dissauer, K.; Veronig, A.; Palmerio, E.; Dumbovic, M.; Guo, J.; Rodriguez, L.; Poedts, S. Bibcode: 2020AGUFMSH0440017S Altcode: Coronal Mass Ejections (CMEs) are the main source of intense space weather disturbances in the heliosphere. It is known that the capability of individual CMEs to drive strong space weather events at Earth (called "geo-effectiveness") and other locations (here referred to as "helio-effectiveness") primarily depends on their speed, density, and magnetic field strength and orientation at the impact location. Moreover, previous studies established that CME--CME interactions can significantly alter the properties of individual CMEs, in such a way that their geo-effectiveness is often dramatically amplified. However, the actual quantification of this amplification has been rarely investigated, and previous studies have mostly focused on the near-Earth region only, i.e. without considering its full space-time evolution as the CMEs propagate to 1 AU and beyond.

Here, we present a study on the role of CME--CME interactions as sources of CME helio-effectiveness by performing simulations of complex CME events with the EUHFORIA heliospheric model. As a case study, we consider a sequence of CMEs observed in early September 2017. As their source region rotated on the solar disk, CMEs were launched over a wide range of longitudes, interacting with each other and paving the way for the propagation of the following ones. At Earth, their interaction resulted in an intense geomagnetic storm. Using initial parameters derived from remote-sensing observations, we perform global simulations of magnetised CMEs with EUHFORIA, investigating how their interactions affected the propagation and internal properties of individual CME structures. Taking advantage of 3D simulation outputs, we quantify the amplification of the helio-effectiveness of the individual CMEs involved, as a function of the interaction phase and of the location within the CME structure. Additionally, we explore the possibility of the existence of a "helio-effectiveness amplification zone", i.e. a characteristic heliocentric distance at which CME--CME interactions have the highest probability to develop into helio-effective events. Results from this study benchmark our current prediction capabilities in the case of complex CME events, and provide new insights on their large-scale evolution and potential impact throughout the heliosphere. Title: Characteristics of a long-lived CIR and the corresponding depression in the GCR flux Authors: Dumbovic, M.; Vrsnak, B.; Temmer, M.; Heber, B. Bibcode: 2020AGUFMSH0440026D Altcode: We observe a long-lived CIR recurring in 27 consecutive Carrington rotations 2057-2083 in the time period from June 2007 - May 2009. We characterize the in situ measurements of this long-lived CIR as well as the corresponding depression in the GCR count observed by SOHO/EPHIN, and analyze them throughout different rotations. We find that the behavior of the flow speed peak roughly shows a rising phase and a declining phase. This is similar to the evolutionary profile of some observed coronal hole areas, but without a clear peak. The GCR count evolutionary profile roughly follows that of the flow speed peak, but moreover we find that the inverted GCR count time-profile matches very well with that of the flow speed throughout different rotations. We perform a statistical analysis and find the GCR count amplitude correlated to the peak in the magnetic field and flow speed, as expected based on previous statistical studies. In order to characterize a generic CIR profile for modelling purposes, we perform the superposed epoch analysis using relative values of the key parameters. Based on the observed properties we propose a simple analytical model starting from the basic Fokker-Planck equation. Title: COSPAR International Space Weather Action Teams: Addressing Challenges Across the Field of Space Weather. Authors: Kuznetsova, M. M.; Belehaki, A.; Bisi, M. M.; Bruinsma, S.; Fung, S. F.; Glover, A.; Grande, M.; Guo, J.; Jun, I.; Linker, J.; Mann, I. R.; Masson, A.; Mendoza, A. M. M.; Murray, S. A.; Nandy, D.; Opgenoorth, H. J.; Pevtsov, A. A.; Plainaki, C.; Reiss, M.; Sutton, E. K.; Temmer, M.; Usoskin, I. G.; Yao, Z.; Yardley, S.; Zheng, Y. Bibcode: 2020AGUFMSH0030022K Altcode: Advanced predictions of space weather impacts require improved understanding and modeling capabilities of coupled chains of space environment processes. It is necessary to assemble parts of the source-to-impact puzzle by identifying, addressing and solving problems focused on specific physical domains, and then to connect all validated solutions from space weather origins on the sun to impacts on coupled geospace system, humans and technologies. To address the need for multi-disciplinary international space weather research community connecting experts in space weather phenomena across all domains and experts in space environment impact, the COSPAR Panel on Space Weather facilitated establishment of a network of International Space Weather Action Teams (ISWAT, https://www.iswat-cospar.org, @IswatCosparOrg). ISWAT serves as a global hub for community coordinated topical collaborations focused on different aspects of space weather including advancing understanding, assessment and improvement of modeling capabilities, transitioning advances in research to operations, optimized utilization of available observations, and generating inputs to future instrumentation deployment. Action teams are building blocks of ISWAT initiative. ISWAT action teams are organized into domain-based ISWAT clusters. Action teams are working in coordinated effort across physical domain and across borders. The primary ISWAT goal is to advance space weather predictive capabilities based on best science available. The ISWAT currently includes more than 250 active participants and more than 50 action teams. The presentation will overview the outcome from the COSPAR ISWAT Inaugural Working Meeting in February 2020, highlight recent progress in advancing physics-based predictive capabilities and discuss plans for transforming COSPAR space weather Roadmap into a living document maintained by the community. Title: Exploration and Forecasting of Thermospheric Variations at Different Altitudes Within the Framework of Project SWEETS Authors: Krauss, S.; Suesser-Rechberger, B.; Temmer, M.; Mayer-Guerr, T.; Drescher, L.; Kroisz, S. Bibcode: 2020AGUFMSM050..09K Altcode: Owing to advances in solar research in the recent decades, today we know that coronal mass ejections (CMEs) cause the most comprehensive spectrum of space weather disturbances. These huge clouds of magnetized plasma are propagating from the solar corona into interplanetary space with typical transit times that range between two and five days, depending on the initial speed, the mass, the size as well as the speed and density of the surrounding solar wind plasma. During strong geomagnetic storms, induced by CMEs, the neutral density of the Earth's thermosphere is subject to strong fluctuations and, thus, a critical parameter for low Earth-orbiting satellites. The enhanced energy input from the solar wind to the magnetosphere causes heating and expansion of the Earth's thermosphere, which affects Earth-orbiting satellites in such a way that the drag force acting on the spacecraft is enhanced and leads to an additional storm induced orbit decay.

Within the project SWEETS (FFG funded) it is intended to develop a forecasting model, to predict the expected impact of solar events on satellites at different altitudes between 300-800 km. For the realization, scientific data, such as kinematic orbit information and accelerometer measurements, from a wide variety of satellites will be incorporated. Through a joint analysis and evaluation of solar wind plasma and magnetic field data observed at the Lagrange point L1, first preliminary results of predicted thermospheric density increases and associated satellite orbit decay rates are shown. Title: VizieR Online Data Catalog: Search for flares and CMEs in SDSS data (Koller+, 2021) Authors: Koller, F.; Leitzinger, M.; Temmer, M.; Odert, P.; Beck, P. G.; Veronig, A. Bibcode: 2020yCat..36460034K Altcode: This file contains the complete list of flares found by this work and their most important derived or collected parameters. The in-depth description of the derivation of these parameters is given in the article.

The optical spectra by SDSSS data release 14 (2018ApJS..235...42A) that we used in this work consist of several single spectra, which are combined to a final coadded spectrum for each observed object. We used the single spectra to find temporal changes in Balmer lines, indicating flaring events. With the latest GAIA data release (2018A&A...616A...1G), we were able to derive energy and luminosity values for the flares. We focused on the Halpha Balmer line due to the better S/N. Our methods were based on line fitting algorithms to detect changes from one observation to another.

Similar to the work by Hilton et al. (2010, Cat. J/AJ/140/1402) we give stellar coordinates as RAdeg and DEdeg as the first parameters to distinguish between the objects. In addition to that, the Plate-MJD-Fiber number serves as a unique identifier for the flaring SDSS spectrum. The stellar position is not enough because objects can be observed multiple times at different surveys by SDSS, resulting in different sets of single spectra. The method and the categorization of the S/N bins are defined in the article.

The spectral type classified by SDSS and by other literature is given. The distance and the source for the value is given when possible. The defined quiet flag and the consideration flag give insight on the reliability of the derived values. Whether a flare was also detected in Hilton et al. (2010, Cat. J/AJ/140/1402) is given in a separate column. The flare energy, the luminosity, and the associated errors were derived using the SDSS spectra as is described in the article (see Sect.4.2.2) and given here in units of W and W/s (J).

The peak spectrum and the spectrum used in the calculation as the reference are given. Their number refer to the chronological order of the single spectra. The number of available single spectra (in the optical red domain containing Halpha) and the number of single spectra in a flaring state are given. The overall time of these flaring spectra is summed and given in units of minutes.

Additional comments made during the visual inspection of all flaring spectra are added.

(1 data file). Title: A new method for estimating global coronal wave properties based on their interaction with solar coronal holes Authors: Piantschitsch, I.; Terradas, J.; Temmer, M. Bibcode: 2020A&A...641A..21P Altcode: 2020arXiv200607293P Among the effects of interactions between global coronal waves (CWs) and coronal holes (CHs) is the formation of reflected and transmitted waves. Observations of such events provide us with measurements of different CW parameters, such as phase speed and intensity amplitudes. However, several of these parameters are provided with only intermediate observational quality, whereas other parameters, such as the phase speed of transmitted waves, can hardly be observed in general. We present a new method to estimate crucial CW parameters, such as density and phase speed of reflected as well as transmitted waves, Mach numbers and density values of the CH's interior, by using analytical expressions in combination with the most basic and most accessible observational measurements available. The transmission and reflection coefficients were derived from linear theory and used to calculate estimations for phase speeds of incoming, reflected, and transmitted waves. The obtained analytical expressions were validated by performing numerical simulations of CWs interacting with CHs. This new method enables us to determine in a fast and straightforward way reliable CW and CH parameters from basic observational measurements which provides a powerful tool to better understand the observed interaction effects between CWs and CHs. Title: Solar Flare-CME Coupling throughout Two Acceleration Phases of a Fast CME Authors: Gou, Tingyu; Veronig, Astrid M.; Liu, Rui; Zhuang, Bin; Dumbović, Mateja; Podladchikova, Tatiana; Reid, Hamish A. S.; Temmer, Manuela; Dissauer, Karin; Vršnak, Bojan; Wang, Yuming Bibcode: 2020ApJ...897L..36G Altcode: 2020arXiv200611707G Solar flares and coronal mass ejections (CMEs) are closely coupled through magnetic reconnection. CMEs are usually accelerated impulsively within the low solar corona, synchronized with the impulsive flare energy release. We investigate the dynamic evolution of a fast CME and its associated X2.8 flare occurring on 2013 May 13. The CME experiences two distinct phases of enhanced acceleration, an impulsive one with a peak value of ∼5 km s-2, followed by an extended phase with accelerations up to 0.7 km s-2. The two-phase CME dynamics is associated with a two-episode flare energy release. While the first episode is consistent with the "standard" eruption of a magnetic flux rope, the second episode of flare energy release is initiated by the reconnection of a large-scale loop in the aftermath of the eruption and produces stronger nonthermal emission up to γ-rays. In addition, this long-duration flare reveals clear signs of ongoing magnetic reconnection during the decay phase, evidenced by extended hard X-ray bursts with energies up to 100-300 keV and intermittent downflows of reconnected loops for >4 hr. The observations reveal that the two-step flare reconnection substantially contributes to the two-phase CME acceleration, and the impulsive CME acceleration precedes the most intense flare energy release. The implications of this non-standard flare/CME observation are discussed. Title: Evolution of Coronal Mass Ejections and the Corresponding Forbush Decreases: Modeling vs. Multi-Spacecraft Observations Authors: Dumbović, Mateja; Vršnak, Bojan; Guo, Jingnan; Heber, Bernd; Dissauer, Karin; Carcaboso, Fernando; Temmer, Manuela; Veronig, Astrid; Podladchikova, Tatiana; Möstl, Christian; Amerstorfer, Tanja; Kirin, Anamarija Bibcode: 2020SoPh..295..104D Altcode: 2020arXiv200602253D One of the very common in situ signatures of interplanetary coronal mass ejections (ICMEs), as well as other interplanetary transients, are Forbush decreases (FDs), i.e. short-term reductions in the galactic cosmic ray (GCR) flux. A two-step FD is often regarded as a textbook example, which presumably owes its specific morphology to the fact that the measuring instrument passed through the ICME head on, encountering first the shock front (if developed), then the sheath, and finally the CME magnetic structure. The interaction of GCRs and the shock/sheath region, as well as the CME magnetic structure, occurs all the way from Sun to Earth, therefore, FDs are expected to reflect the evolutionary properties of CMEs and their sheaths. We apply modeling to different ICME regions in order to obtain a generic two-step FD profile, which qualitatively agrees with our current observation-based understanding of FDs. We next adapt the models for energy dependence to enable comparison with different GCR measurement instruments (as they measure in different particle energy ranges). We test these modeling efforts against a set of multi-spacecraft observations of the same event, using the Forbush decrease model for the expanding flux rope (ForbMod). We find a reasonable agreement of the ForbMod model for the GCR depression in the CME magnetic structure with multi-spacecraft measurements, indicating that modeled FDs reflect well the CME evolution. Title: A statistical study of the long-term evolution of coronal hole properties as observed by SDO Authors: Heinemann, S. G.; Jerčić, V.; Temmer, M.; Hofmeister, S. J.; Dumbović, M.; Vennerstrom, S.; Verbanac, G.; Veronig, A. M. Bibcode: 2020A&A...638A..68H Altcode: 2019arXiv190702795H; 2019arXiv190702795J Context. Understanding the evolution of coronal holes is especially important when studying the high-speed solar wind streams that emanate from them. Slow- and high-speed stream interaction regions may deliver large amounts of energy into the Earth's magnetosphere-ionosphere system, cause geomagnetic storms, and shape interplanetary space.
Aims: By statistically investigating the long-term evolution of well-observed coronal holes we aim to reveal processes that drive the observed changes in the coronal hole parameters. By analyzing 16 long-living coronal holes observed by the Solar Dynamic Observatory, we focus on coronal, morphological, and underlying photospheric magnetic field characteristics, and investigate the evolution of the associated high-speed streams.
Methods: We use the Collection of Analysis Tools for Coronal Holes to extract and analyze coronal holes using 193 Å EUV observations taken by the Atmospheric Imaging Assembly as well as line-of-sight magnetograms observed by the Helioseismic and Magnetic Imager. We derive changes in the coronal hole properties and look for correlations with coronal hole evolution. Further, we analyze the properties of the high-speed stream signatures near 1AU from OMNI data by manually extracting the peak bulk velocity of the solar wind plasma.
Results: We find that the area evolution of coronal holes shows a general trend of growing to a maximum followed by a decay. We did not find any correlation between the area evolution and the evolution of the signed magnetic flux or signed magnetic flux density enclosed in the projected coronal hole area. From this we conclude that the magnetic flux within the extracted coronal hole boundaries is not the main cause for its area evolution. We derive coronal hole area change rates (growth and decay) of (14.2 ± 15.0)×108 km2 per day showing a reasonable anti-correlation (ccPearson = -0.48) to the solar activity, approximated by the sunspot number. The change rates of the signed mean magnetic flux density (27.3 ± 32.2 mG day-1) and the signed magnetic flux (30.3 ± 31.5 1018 Mx day-1) were also found to be dependent on solar activity (ccPearson = 0.50 and ccPearson = 0.69 respectively) rather than on the individual coronal hole evolutions. Further we find that the relation between coronal hole area and high-speed stream peak velocity is valid for each coronal hole over its evolution, but we see significant variations in the slopes of the regression lines. Title: Prediction of CME arrivals; differences based on stereoscopic heliospheric imager data Authors: Hinterreiter, Jürgen; Amerstorfer, Tanja; Reiss, Martin A.; Temmer, Manuela; Möstl, Christian; Bauer, Maike; Amerstorfer, Ute V.; Bailey, Rachel L.; Weiss, Andreas J. Bibcode: 2020EGUGA..22.7829H Altcode: Forecasting the arrival time and speed of CMEs is of high importance. However, uncertainties in the forecasts are high. We present the results of post-event prediction of CME arrivals using ELEvoHI (ELlipse Evolution model based on Heliospheric Imager observations) ensemble modeling. The model uses time-elongation profiles provided by HI (Heliospheric Imager) onboard STEREO (Solar TErrestrial RElations Observatory) and assumes an elliptical shape of the CME front. The drag force exerted by the ambient solar wind is an essential factor influencing the dynamic evolution of CMEs in the heliosphere. To account for this effect, ELEvoHI utilizes the modeled ambient solar wind provided by the Wang-Sheeley-Arge model. We carefully select 12 CMEs between February 2010 and July 2012, which show clear signatures in STEREO-A and STEREO-B HI images, have a corresponding in-situ signature, and propagate close to the ecliptic plane. As input to ELEvoHI, we make use of STEREO-A and STEREO-B time-elongation profiles for each CME and compare the predicted arrival times and speeds based on both vantage points with each other. We present our model results and discuss possible reasons for the differences in the arrival times of up to 15 hours. Title: Magnetic Flux Emergence in a Coronal Hole Authors: Palacios, Judith; Utz, Dominik; Hofmeister, Stefan; Krikova, Kilian; Gömöry, Peter; Kuckein, Christoph; Denker, Carsten; Verma, Meetu; González Manrique, Sergio Javier; Campos Rozo, Jose Iván; Koza, Július; Temmer, Manuela; Veronig, Astrid; Diercke, Andrea; Kontogiannis, Ioannis; Cid, Consuelo Bibcode: 2020SoPh..295...64P Altcode: 2020arXiv200611779P A joint campaign of various space-borne and ground-based observatories, comprising the Japanese Hinode mission (Hinode Observing Plan 338, 20 - 30 September 2017), the GREGOR solar telescope, and the Vacuum Tower Telescope (VTT), investigated numerous targets such as pores, sunspots, and coronal holes. In this study, we focus on the coronal hole region target. On 24 September 2017, a very extended non-polar coronal hole developed patches of flux emergence, which contributed to the decrease of the overall area of the coronal hole. These flux emergence patches erode the coronal hole and transform the area into a more quiet-Sun-like area, whereby bipolar magnetic structures play an important role. Conversely, flux cancellation leads to the reduction of opposite-polarity magnetic fields and to an increase in the area of the coronal hole. Title: Using Forbush decreases at Earth and Mars to measure the radial evolution of ICMEs Authors: von Forstner, Johan; Guo, Jingnan; Wimmer-Schweingruber, Robert F.; Dumbović, Mateja; Janvier, Miho; Démoulin, Pascal; Veronig, Astrid; Temmer, Manuela; Papaioannou, Athanasios; Dasso, Sergio; Hassler, Donald M.; Zeitlin, Cary J. Bibcode: 2020EGUGA..22.7838V Altcode: Interplanetary coronal mass ejections (ICMEs), large clouds of plasma and magnetic field regularly expelled from the Sun, are one of the main drivers of space weather effects in the solar system. While the prediction of their arrival time at Earth and other locations in the heliosphere is still a complex task, it is also necessary to further understand the time evolution of their geometric and magnetic structure, which is even more challenging considering the limited number of available observation points.Forbush decreases (FDs), short-term drops in the flux of galactic cosmic rays (GCR), can be caused by the shielding from strong and/or turbulent magnetic structures in the solar wind, such as ICMEs and their associated shock/sheath regions. In the past, FD observations have often been used to determine the arrival times of ICMEs at different locations in the solar system, especially where sufficient solar wind plasma and magnetic field measurements are not (or not always) available. One of these locations is Mars, where the Radiation Assessment Detector (RAD) onboard the Mars Science Laboratory (MSL) mission's Curiosity rover has been continuously measuring GCRs and FDs on the surface for more than 7 years.In this work, we investigate whether FD data can be used to derive additional information about the ICME properties than just the arrival time by performing a statistical study based on catalogs of FDs observed at Earth or Mars. In particular, we find that the linear correlation between the FD amplitude and the maximum steepness, which was already seen at Earth by previous authors (Belov et al., 2008, Abunin et al., 2012), is likewise present at Mars, but with a different proprtionality factor.By consulting physics-based analytical models of FDs, we find that this quantity is not expected to be influenced by the different energy ranges of GCR particles observed by the instruments at Earth and Mars. Instead, we suggest that the difference in FD characteristics at the two planets is caused by the radial enlargement of the ICMEs, and particularly their sheath regions, as they propagate from Earth (1 AU) to Mars (~ 1.5 AU). This broadening factor derived from our analysis extends observations for the evolution closer to the Sun by Janvier et al. (2019, JGR Space Physics) to larger heliocentric distances and is consistent with these results. Title: Analysis of a severe geomagnetic storm on August 26, 2018 and the related effects on the GRACE-FO mission Authors: Krauss, Sandro; Temmer, Manuela; Behzadpour, Saniya; Lhotka, Christoph Bibcode: 2020EGUGA..22.3499K Altcode: On August 20, 2018 a complex interplanetary coronal mass ejections (ICME) occurred on the Sun, which subsequently triggered an unexpected large geomagnetic storm on August 25. We present a detailed analysis of the ICME eruption and explore the occurred perturbation of the neutral mass density in the upper Earth's atmosphere. The analysis is based on accelerometer observations from the satellite mission GRACE Follow-On as well as interplanetary magnetic field measurements by the DSCOVR and ACE spacecraft. Through the evaluation of solar observations by the SECCHI instrument on-board of the STEREO-A satellite in form of white-light, the early evolution of the ICME can be aptly illustrated. Furthermore, due to the heating and the subsequent expansion of the thermosphere also the drag force acting on the spacecraft is enhanced. This leads to an additional storm induced orbit decay, which we calculate by means of variations in the semi-major axis. The findings are compared with predictions from our preliminary thermospheric forecasting tool, which is based on the study by Krauss et al. 2018. Title: Understanding our capabilities in observing and modelling Coronal Mass Ejections Authors: Verbeke, Christine; Mierla, Marilena; Mays, M. Leila; Kay, Christina; Dumbovic, Mateja; Temmer, Manuela; Palmerio, Erika; Paouris, Evangelos; Cremades, Hebe; Riley, Pete; Scolini, Camilla; Hinterreiter, Juergen Bibcode: 2020EGUGA..2220456V Altcode: Coronal Mass Ejections (CMEs) are large-scale eruptions of plasma and magnetic fields from the Sun. They are considered to be the main drivers of strong space weather events at Earth. Multiple models have been developed over the past decades to be able to predict the propagation of CMEs and their arrival time at Earth. Such models require input from observations, which can be used to fit the CME to an appropriate structure.When determining input parameters for CME propagation models, it is common procedure to derive kinematic parameters from remote-sensing data. The resulting parameters can be used as inputs for the CME propagation models to obtain an arrival prediction time of the CME f.e. at Earth. However, when fitting the CME structure to obtain the needed parameters for simulations, different geometric structures and also different parts of the CME structure can be fitted. These aspects, together with the fact that 3D reconstructions strongly depend on the subjectivity and judgement of the scientist performing them, may lead to uncertainties in the fitted parameters. Up to now, no large study has tried to map these uncertainties and to evaluate how they affect the modelling of CMEs. Fitting a large set of CMEs within a selected period of time, we aim to investigate the uncertainties in the CME fittings in detail. Each event is fitted multiple times by different scientists. We discuss statistics on uncertainties of the fittings. We also present some first results of the impact of these uncertainties on CME propagation modelling.Acknowledgements: This work has been partly supported by the International Space Science Institute (ISSI) in the framework of International Team 480 entitled: Understanding Our Capabilities In Observing And Modelling Coronal Mass Ejections'. Title: Observation-based modelling of magnetised CMEs in the inner heliosphere with EUHFORIA Authors: Scolini, Camilla; Pomoell, Jens; Chané, Emmanuel; Poedts, Stefaan; Rodriguez, Luciano; Kilpua, Emilia; Temmer, Manuela; Verbeke, Christine; Dissauer, Karin; Veronig, Astrid; Palmerio, Erika; Dumbović, Mateja Bibcode: 2020EGUGA..22.1777S Altcode: Coronal Mass Ejections (CMEs) are the primary source of strong space weather disturbances at Earth and other locations in the heliosphere. Understanding the physical processes involved in their formation at the Sun, propagation in the heliosphere, and impact on planetary bodies is therefore critical to improve current space weather predictions throughout the heliosphere. The capability of CMEs to drive strong space weather disturbances at Earth and other planetary and spacecraft locations primarily depends on their dynamic pressure, internal magnetic field strength, and magnetic field orientation at the impact location. In addition, phenomena such as the interaction with the solar wind and other solar transients along the way, or the pre-conditioning of interplanetary space due to the passage of previous CMEs, can significantly modify the properties of individual CMEs and alter their ultimate space weather impact. Investigating and modeling such phenomena via advanced physics-based heliospheric models is therefore crucial to improve the space weather prediction capabilities in relation to both single and complex CME events. In this talk, we present our progress in developing novel methods to model CMEs in the inner heliosphere using the EUHFORIA MHD model in combination with remote-sensing solar observations. We discuss the various observational techniques that can be used to constrain the initial CME parameters for EUHFORIA simulations. We present current efforts in developing more realistic magnetised CME models aimed at describing their internal magnetic structure in a more realistic fashion. We show how the combination of these two approaches allows the investigation of CME propagation and evolution throughout the heliosphere to a higher level of detail, and results in significantly improved predictions of CME impact at Earth and other locations in the heliosphere. Finally, we discuss current limitations and future improvements in the context of studying space weather events throughout the heliosphere. Title: The impact of coronal hole characteristics and solar cycle activity in reconstructing coronal holes with EUHFORIA Authors: Asvestari, E.; Heinemann, S. G.; Temmer, M.; Pomoell, J.; Kilpua, E.; Magdalenic, J.; Poedts, S. Bibcode: 2020JPhCS1548a2004A Altcode: Modelling with high accuracy the open magnetic field and the fast solar wind in the heliosphere is essential for space weather forecasting purposes. Primary sources of open magnetic field flux are Coronal Holes (CH), uni-polar regions that appear as dark patches in the solar corona when observed in X-ray and extreme-ultraviolet (EUV) images due to having significantly lower density and temperature to their surroundings. Therefore, when assessing how well the open magnetic field and the fast solar wind are modelled one can look at how well the model performs on one of its fundamental functions, that of reconstructing coronal hole areas. In this study we investigate how the CH morphology (i.e. latitudinal position of the centre of mass, area, intensity, elongation) and the solar variability, from high to low activity periods, can affect the results. We also investigated the possibility that the model is reconstructing CHs that are systematically shifted with respect to their observed position. The study is applied on 15 CHs exhibiting different latitudinal position and geometry. We compare the modelled CH areas with boundaries obtained by remote sensing EUV observations using the CATCH tool (Collection of Analysis Tools for Coronal Holes). We found no apparent effect of the CH characteristics on the modelling capabilities. In addition, solar cycle activity seems not to have any effect either. However, we emphasize that our sample is small and this outcome highlights the need for an extended research. Title: CME evolution and the corresponding Forbush decrease: modelling vs multi-spacecraft observation Authors: Dumbovic, Mateja; Vrsnak, Bojan; Guo, Jingnan; Heber, Bernd; Dissauer, Karin; Carcaboso-Morales, Fernando; Temmer, Manuela; Veronig, Astrid; Podladchikova, Tatiana; Möstl, Christian; Amerstorfer, Tanja; Kirin, Anamarija Bibcode: 2020EGUGA..2210446D Altcode: One of the very common in-situ signatures of ICMEs, as well as other interplanetary transients are Forbush decreases (FDs), i.e. short-term reductions in the galactic cosmic ray (GCR) flux. A two-step FD is often regarded as a textbook example, which presumably owns its specific morphology to the fact that the measuring instrument passed through the ICME head-on, encountering first the shock front (if developed), then the sheath and finally the magnetic structure. The interaction of GCRs and the shock/sheath region as well as CME magnetic structure occurs all the way from Sun to Earth, therefore, FDs are expected to reflect the evolutionary properties of CMEs and their sheaths. We apply modelling to different ICME regions in order to obtain a generic two-step FD profile, which qualitatively agrees with our current observation-based understanding of FDs. We next adapt the models for energy dependence to enable comparison with different GCR measurement instruments (as they measure in different particle energy ranges). We test these modelling efforts against a set of multi-spacecraft observations of the same event. Title: Exploring Thermospheric Variations Triggered by Severe Geomagnetic Storm on 26 August 2018 Using GRACE Follow-On Data Authors: Krauss, S.; Behzadpour, S.; Temmer, M.; Lhotka, C. Bibcode: 2020JGRA..12527731K Altcode: With the successful launch of the satellite mission Gravity Recovery and Climate Experiment (GRACE) Follow-On in May 2018 the opportunity arises to resume the analysis of accelerometer data regarding space weather induced perturbations of the Earth's thermosphere. On 21 August 2018 a complex interplanetary coronal mass ejections occurred on the Sun, which subsequently triggered an unexpected large geomagnetic storm on 26 August. We present a detailed analysis of the interplanetary coronal mass ejection eruption and explore the occurred perturbation of the neutral mass density in the upper Earth's atmosphere. Due to the heating and the subsequent expansion of the thermosphere also the drag force acting on the spacecraft is enhanced. This leads to an additional storm-induced orbit decay, which we calculate by means of variations in the semimajor axis. The evaluation is based on the utilization of accelerometer measurements from GRACE Follow-On. For the reduction of disturbing nongravitational forces we implemented a physical shadow function, which incorporates the Earth's oblateness and the atmospheric refraction and extinction. Additionally, the estimation of Earth's reradiation is now based on hourly measurements by the Clouds and the Earth's Radiant Energy System. The resulting atmospheric densities and orbit decays are compared with predictions from our preliminary thermospheric forecasting tool, which is based on the study by Krauss et al. (2018, https://doi.org/10.1029/2018JA025778). The evaluation shows that the maximum estimated orbit decay triggered by the geomagnetic storm on 26 August is in the order of approximately 8.2 m and thus in good accordance with the forecasted value (9.5 m)—predicted with a lead time of about 60 min. Title: Relating CME density derived from remote sensing data to CME sheath solar wind plasma pile up as measured in-situ Authors: Temmer, Manuela; Holzknecht, Lukas; Dumbovic, Mateja; Vrsnak, Bojan; Sachdeva, Nishtha; Heinemann, Stephan; Dissauer, Karin; Scolini, Camilla; Asvestari, Eleanna; Veronig, Astrid; Hofmeister, Stefan Bibcode: 2020EGUGA..22.3341T Altcode: For better estimating the drag force acting on coronal mass ejections (CMEs) in interplanetary space and ram-pressure at planets, improved knowledge of the evolution of CME density/mass is highly valuable. We investigate a sample of 29 well observed CME-ICME events, for which we determine the de-projected 3D mass (STEREO-A and -B data), and the CME volume using GCS modeling (STEREO, SoHO). Expanding the volume to 1AU distance, we derive the density and compare the results to in-situ proton density measurements separately for the ICME sheath and magnetic structure. A fair agreement between calculated and measured density is derived for the magnetic structure as well for the sheath if taking into account mass pile up of solar wind plasma. We give evidence and observational assessment that during the interplanetary propagation of a CME 1) the magnetic structure has rather constant mass and 2) the sheath region at the front of the driver is formed from piled-up mass that is rather depending on the solar wind density ahead of the CME, than on the CME speed. Title: Comparing the Properties of ICME-Induced Forbush Decreases at Earth and Mars Authors: Freiherr von Forstner, Johan L.; Guo, Jingnan; Wimmer-Schweingruber, Robert F.; Dumbović, Mateja; Janvier, Miho; Démoulin, Pascal; Veronig, Astrid; Temmer, Manuela; Papaioannou, Athanasios; Dasso, Sergio; Hassler, Donald M.; Zeitlin, Cary J. Bibcode: 2020JGRA..12527662F Altcode: 2020arXiv200303157V Forbush decreases (FDs), which are short-term drops in the flux of galactic cosmic rays, are caused by the shielding from strong and/or turbulent magnetic structures in the solar wind, especially interplanetary coronal mass ejections (ICMEs) and their associated shocks, as well as corotating interaction regions. Such events can be observed at Earth, for example, using neutron monitors, and also at many other locations in the solar system, such as on the surface of Mars with the Radiation Assessment Detector instrument onboard Mars Science Laboratory. They are often used as a proxy for detecting the arrival of ICMEs or corotating interaction regions, especially when sufficient in situ solar wind measurements are not available. We compare the properties of FDs observed at Earth and Mars, focusing on events produced by ICMEs. We find that FDs at both locations show a correlation between their total amplitude and the maximum hourly decrease, but with different proportionality factors. We explain this difference using theoretical modeling approaches and suggest that it is related to the size increase of ICMEs, and in particular their sheath regions, en route from Earth to Mars. From the FD data, we can derive the sheath broadening factor to be between about 1.5 and 1.9, agreeing with our theoretical considerations. This factor is also in line with previous measurements of the sheath evolution closer to the Sun. Title: CME-CME Interactions as Sources of CME Geoeffectiveness: The Formation of the Complex Ejecta and Intense Geomagnetic Storm in 2017 Early September Authors: Scolini, Camilla; Chané, Emmanuel; Temmer, Manuela; Kilpua, Emilia K. J.; Dissauer, Karin; Veronig, Astrid M.; Palmerio, Erika; Pomoell, Jens; Dumbović, Mateja; Guo, Jingnan; Rodriguez, Luciano; Poedts, Stefaan Bibcode: 2020ApJS..247...21S Altcode: 2019arXiv191110817S Coronal mass ejections (CMEs) are the primary sources of intense disturbances at Earth, where their geoeffectiveness is largely determined by their dynamic pressure and internal magnetic field, which can be significantly altered during interactions with other CMEs in interplanetary space. We analyze three successive CMEs that erupted from the Sun during 2017 September 4-6, investigating the role of CME-CME interactions as a source of the associated intense geomagnetic storm (Dst_{min}=-142 nT on September 7). To quantify the impact of interactions on the (geo)effectiveness of individual CMEs, we perform global heliospheric simulations with the European Heliospheric Forecasting Information Asset (EUHFORIA) model, using observation-based initial parameters with the additional purpose of validating the predictive capabilities of the model for complex CME events. The simulations show that around 0.45 au, the shock driven by the September 6 CME started compressing a preceding magnetic ejecta formed by the merging of two CMEs launched on September 4, significantly amplifying its Bz until a maximum factor of 2.8 around 0.9 au. The following gradual conversion of magnetic energy into kinetic and thermal components reduced the Bz amplification until its almost complete disappearance around 1.8 au. We conclude that a key factor at the origin of the intense storm triggered by the 2017 September 4-6 CMEs was their arrival at Earth during the phase of maximum Bz amplification. Our analysis highlights how the amplification of the magnetic field of individual CMEs in spacetime due to interaction processes can be characterized by a growth, a maximum, and a decay phase, suggesting that the time interval between the CME eruptions and their relative speeds are critical factors in determining the resulting impact of complex CMEs at various heliocentric distances (helioeffectiveness). Title: Differential Emission Measure Plasma Diagnostics of a Long-Lived Coronal Hole Authors: Saqri, Jonas; Veronig, Astrid M.; Heinemann, Stephan G.; Hofmeister, Stefan J.; Temmer, Manuela; Dissauer, Karin; Su, Yang Bibcode: 2020SoPh..295....6S Altcode: 2020arXiv200102259S We use Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) data to reconstruct the plasma properties from differential emission measure (DEM) analysis for a previously studied long-lived, low-latitude coronal hole (CH) over its lifetime of ten solar rotations. We initially obtain a non-isothermal DEM distribution with a dominant component centered around 0.9 MK and a secondary smaller component at 1.5 - 2.0 MK. We find that deconvolving the data with the instrument point spread function (PSF) to account for long-range scattered light reduces the secondary hot component. Using the 2012 Venus transit and a 2013 lunar eclipse to test the efficiency of this deconvolution, significant amounts of residual stray light are found for the occulted areas. Accounting for this stray light in the error budget of the different AIA filters further reduces the secondary hot emission, yielding CH DEM distributions that are close to isothermal with the main contribution centered around 0.9 MK. Based on these DEMs, we analyze the evolution of the emission measure (EM), density, and averaged temperature during the CH's lifetime. We find that once the CH is clearly observed in EUV images, the bulk of the CH plasma reveals a quite constant state, i.e. temperature and density reveal no major changes, whereas the total CH area and the photospheric magnetic fine structure inside the CH show a distinct evolutionary pattern. These findings suggest that CH plasma properties are mostly "set" at the CH formation or/and that all CHs have similar plasma properties. Title: Comparing the Properties of ICME-Induced Forbush Decreases at Earth and Mars Authors: Freiherr von Forstner, J. L.; Guo, J.; Wimmer-Schweingruber, R. F.; Dumbovic, M.; Janvier, M.; Demoulin, P.; Veronig, A.; Temmer, M.; Hassler, D.; Zeitlin, C. Bibcode: 2019AGUFMSH41D3339F Altcode: Forbush decreases (FDs), short-term drops in the flux of galactic cosmic rays (GCR), can be caused by the shielding from strong and/or turbulent magnetic structures in the solar wind, i.e. interplanetary coronal mass ejections (ICMEs) and their associated shocks as well as corotating interaction regions (CIRs). FDs are often used as a proxy for detecting the arrival of ICMEs or CIRs at locations where sufficient in situ solar wind measurements are not or not always available, such as at Mars. The Radiation Assessment Detector (RAD) onboard the Mars Science Laboratory (MSL) mission's Curiosity rover has been continuously measuring the GCR environment on the surface of Mars for more than 7 years since its landing in August 2012 and is thus an excellent source for measurements of FDs at Mars (see e.g. Guo et al. 2018, A&A).

Based on the large catalog of FDs at Mars compiled by Papaioannou et al. (2019, Solar Physics) as well as results from our previous work (Freiherr von Forstner et al., 2019, Space Weather), we study the parameters of FDs at Mars and their relations, focusing on events produced by ICMEs. We then compare these data with catalogs of terrestrial FDs, investigating whether and to what extent the differences of certain FD characteristics between the two planets, at two different heliospheric distances, are related to the evolution of ICMEs between Earth and Mars.

Our results show that there is a linear correlation between the FD amplitude (drop percentage) and the maximum hourly GCR decrease during the FD, which was already found at Earth by previous authors (Belov et al., 2008, Abunin et al., 2012). However, this correlation has a different proprtionality factor at Mars than at Earth, especially for ICME-induced events. As we do not find a clear dependence of this relationship on the observed GCR energy range, we suggest that this difference is probably caused by the expansion of the ICME sheath region as it propagates outward from 1 AU to ∼1.5 AU. The expansion factor derived from our analysis is in line with expansion factors of ICME sheaths within the inner heliosphere observed by <a href="https://doi.org/10.1029/2018JA025949>Janvier et al. (2019, JGR Space Physics). Title: A study of the role of CME-CME interactions on CME geo-effectiveness with EUHFORIA Authors: Scolini, C.; Poedts, S.; Rodriguez, L.; Temmer, M.; Dumbovic, M.; Guo, J.; Veronig, A.; Dissauer, K.; Palmerio, E.; Kilpua, K. E. J.; Pomoell, J. Bibcode: 2019AGUFMSH43D3368S Altcode: Coronal Mass Ejections (CMEs) are the main source of strong space weather disturbances at Earth and other locations in the solar system. While their impact is largely determined by their dynamic pressure and magnetic field, interactions with other CMEs can significantly alter their individual characteristics and enhance their (geo-)effectiveness. As observations in the heliosphere are limited, investigating such phenomena via physics-based models is therefore crucial to advance our understanding of complex CME events, and to assess the prediction capabilities at various locations.

Here we present a comprehensive study of the role of CME-CME interactions on their (geo-)effectiveness, by performing simulations of complex CME events with the EUHFORIA heliospheric solar wind and CME propagation model. As a case study, we consider a sequence of 6 CMEs observed during the unusually active week of 4-10 September 2017. As their source region moved on the solar disk due to the rotation, CMEs were launched over a wide range of longitudes, interacting with each other while paving the way for the propagation of the following ones. CME signatures were observed at Mars and at Earth, where intense disturbances and space weather events were triggered by CME-CME interactions. Using input parameters derived from multi-spacecraft remote-sensing observations of CMEs and their source region, we perform global simulations of the event using the spheromak CME model in EUHFORIA, and we investigate how their interactions affected the evolution of single CME structures and the in-situ properties at Earth and Mars.

Results from this case study are complemented by a parametric study of CME-CME interactions, performed by running a set of simulations varying the initial CME parameters (e.g. speed, waiting time, magnetic field properties, density…), with the aim of quantifying the effect of such changes on their propagation and interaction. Results will benchmark our current prediction capabilities in the case of complex CME events and provide insights on their large-scale evolution in the heliosphere. Title: Improving Modelling Areas of Open-Closed Flux in the Corona Using Remote Sensing Observations Authors: Asvestari, E.; Heinemann, S.; Temmer, M.; Pomoell, J.; Kilpua, K. E. J.; Magdalenic, J.; Poedts, S. Bibcode: 2019AGUFMSH13A..09A Altcode: Modelling the open magnetic field in the heliosphere with high accuracy is essential for space weather forecasting purposes. Primary source of open magnetic field are Coronal Holes (CH). Therefore, when assessing how well we model the open magnetic field one needs to test how well the model performs on one of its fundamental functions, that of reconstructing coronal hole areas. For our study, we used EUHFORIA (European heliospheric forecasting information asset) model which employs an empirical solar wind model that combines the Potential Field Source Surface (PFSS) and the Schatten Current Sheet (SCS) models. Two important free parameters of the PFSS and the SCS models are the source surface height (the outer boundary of the PFSS) and the height of the inner boundary of SCS. Although, a commonly used value for the source surface height is that of 2.5 solar radii, a wider range of allowed heights ranging from 1.5 to 3.25 solar radii exist. Here, we investigate the optimal heights that one should preselect in the model aiming for better reconstruction of open flux areas. We vary the source surface height within the interval [1.4, 3.2]Rs with a step of 0.1Rs, and the SCS inner boundary height within the interval [1.3, 2.8]Rs with the same step, where Rs is one solar radius. The study is applied on 15 CH exhibiting different latitudinal position and geometry. We compare the modelled open flux areas with CH boundaries extracted using remote sensing EUV observations and CATCH (Collection of analysis tools for coronal holes). This study indicates that lower values of the two boundary heights improve the modelling results. EUV image data from instruments having a wide field of view, such as SUVI on board GOES-R, and SWAP on board PROBA2, offer unprecedented possibility to actually observe the heights below which closed loops exist in the corona, and therefore further constrain the height choices in the model by providing a lower limit. Title: Genesis and impulsive evolution of the fast CME associated with the X8.2 flare on 2017 September 10 Authors: Veronig, A.; Podladchikova, T.; Dissauer, K.; Temmer, M.; Seaton, D. B.; Long, D.; Guo, J.; Vrsnak, B.; Harra, L. K.; Kliem, B. Bibcode: 2019AGUFMSH13A..02V Altcode: The X8.2 event of 2017 September 10 provides unique observations to study the genesis, magnetic morphology, impulsive dynamics and shock formation in a very fast coronal mass ejection (CME). As will be discussed in this presentation, fundamental insight in the processes of magnetic reconnection, CME acceleration and shock formation are provided through EUV observations of the middle corona.

Combining the large field-of-view and high-cadence imagery from GOES-16/SUVI and SDO/AIA EUV, respectively, we identify a hot (T ≈ 10-15 MK) bright rim around a quickly expanding cavity, embedded inside a much larger CME shell (T ≈ 1-2 MK). The CME shell develops from a dense set of large AR loops (>0.5Rs) and seamlessly evolves into the CME front observed in LASCO C2. The strong lateral overexpansion of the CME shell acts as a piston initiating the fast and globally propagating EUV shock wave. The hot cavity rim is demonstrated to be a manifestation of the dominantly poloidal flux and frozen-in plasma added to the rising flux rope by magnetic reconnection in the current sheet beneath. The same structure is later observed as the core of the white-light CME, challenging the traditional interpretation of the CME three-part morphology (Veronig et al. 2018).

The large amount of added magnetic flux suggested by these observations can explain the extreme accelerations of the radial and lateral expansion of the CME shell and cavity, all reaching values up to 5-10 km s-2. The acceleration peaks occur simultaneously with the first RHESSI 100-300 keV hard X-ray burst of the associated flare, further underlining the importance of the reconnection process for the impulsive CME evolution in the low and middle corona. Title: International Scientific Coordination on Space Weather: A COSPAR Panel on Space Weather Perspective Authors: Bisi, M. M.; Kuznetsova, M. M.; Temmer, M.; Opgenoorth, H. J.; Belehaki, A.; Bruinsma, S.; Glover, A.; Heynderickx, D.; Linker, J.; Mann, I. R.; Murray, S. A.; Nandy, D. Bibcode: 2019AGUFMSM31C3543B Altcode: The understanding and prediction of space-weather phenomena and their respective impact(s) on society have been widely-acknowledged as an international challenge and something that requires a global coordination and focus. In order to address this need to form more-formal worldwide collaboration and coordination, and to maximise return on such efforts (particularly scientifically), the Committee on Space Research (COSPAR) Panel on Space Weather (PSW) has created a network of International Space Weather Action Teams (ISWATs).

The COSPAR PSW ISWAT initiative is capitalising on established efforts by engaging existing national and international "teams" and "facilitates" to form individual ISWATs that are being grouped into clusters by domains/themes related to different aspects of solar/coronal, heliospheric, ionospheric/atmospheric, and planetary space-weather phenomena. The initiative also includes overarching themes such as dealing with large data sets and model/scientific validations. The ISWAT initiative places a strong encouragement for scientists to go beyond their funding borders to form ISWATs better suited to address challenges that one individual or small group/team may not be able to address alone.

The ISWAT initiative serves as a global hub for community coordinated topical focused collaborations and as a global community voice for the next generation of both scientific and strategic planning - this includes an update of the COSPAR/ILWS space weather scientific roadmap (to transform the roadmap into a living document) and to potentially provide an operational roadmap in parallel.

This presentation will re-introduce the ISWAT initiative, review its current status and plans for community-wide campaigns, highlight the overarching current plans for PSW, and place a focus on two key space-weather areas: the ambient heliosphere/background solar wind (designated as ISWAT theme H1) and CME structure, evolution and propagation through heliosphere (designated as ISWAT theme H2). Title: Showcasing the just released ISWAT website (http://www.iswat-cospar.org) built with a content management platform to serve as an online presence for the ISWAT (International Space Weather Action Teams) - community driven effort hosted by the COSPAR Panel on Space Weather. Authors: Mendoza, A. M. M.; Kuznetsova, M.; Opgenoorth, H. J.; Belehaki, A.; Bisi, M. M.; Bruinsma, S.; Heynderickx, D.; Linker, J.; Mann, I. R.; Murray, S. A.; Nandy, D.; Temmer, M. Bibcode: 2019AGUFMSM31C3181M Altcode: We will showcase the just released ISWAT website (http://www.iswat-cospar.org) built with a content management platform to serve as an online presence for the

ISWAT (International Space Weather Action Teams) - community driven effort hosted by the COSPAR Panel on Space Weather.

The website was created to represent ISWAT overarching goal to serve as a global hub for topical collaborations and focused on different aspects of space weather.

The homepage main's ISWAT image menu shows ISWAT clusters that cover Solar (S), Heliosphere (H) and Geospace (G) domains. Each cluster (S1-S3, H1-H4, G1-G3)

shown in the image is links to dedicated webpages that contain information about cluster goals and links to entry pages of registered action teams.

The "Join ISWAT" link contains 2 interactive forms for joining ISWAT mailing list and for registration of established and emerging international teams focused on different

aspects of space weather. After the registration is confirmed by cluster moderator a link to a new team entry page is added to a submitted cluster site. A team start entry

team page will contain information submitted during registration that may include a link to an external team page as an option. Another interactive form to join a

registered ISWAT team will be added in the near future.

Future planned additions include a Forum to create threaded discussion boards to encourage discussions on global coordination of space weather and invite community inputs to global space weather roadmap updates.

The website will be eventually maintained and facilitated by the COSPAR Panel on Space Weather Chairs/Vice-chairs, ISWAT cluster moderators, and ISWAT team

representatives. Title: International Scientific Coordination on Space Weather: A COSPAR Panel on Space Weather Perspective Authors: Kuznetsova, M.; Bisi, M. M.; Kusano, K.; Fuller-Rowell, T. J.; Mann, I.; Belehaki, A.; Minow, J. I.; Munoz-Jaramillo, A.; Masson, A.; Bruinsma, S.; Bisi, M. M.; Kuznetsova, M. M.; Temmer, M.; Opgenoorth, H. J.; Belehaki, A.; Bruinsma, S.; Glover, A.; Heynderickx, D.; Linker, J.; Mann, I. R.; Murray, S. A.; Nandy, D. Bibcode: 2019AGUFMSM31C3543K Altcode: The understanding and prediction of space-weather phenomena and their respective impact(s) on society have been widely-acknowledged as an international challenge and something that requires a global coordination and focus. In order to address this need to form more-formal worldwide collaboration and coordination, and to maximise return on such efforts (particularly scientifically), the Committee on Space Research (COSPAR) Panel on Space Weather (PSW) has created a network of International Space Weather Action Teams (ISWATs).

The COSPAR PSW ISWAT initiative is capitalising on established efforts by engaging existing national and international "teams" and "facilitates" to form individual ISWATs that are being grouped into clusters by domains/themes related to different aspects of solar/coronal, heliospheric, ionospheric/atmospheric, and planetary space-weather phenomena. The initiative also includes overarching themes such as dealing with large data sets and model/scientific validations. The ISWAT initiative places a strong encouragement for scientists to go beyond their funding borders to form ISWATs better suited to address challenges that one individual or small group/team may not be able to address alone.

The ISWAT initiative serves as a global hub for community coordinated topical focused collaborations and as a global community voice for the next generation of both scientific and strategic planning - this includes an update of the COSPAR/ILWS space weather scientific roadmap (to transform the roadmap into a living document) and to potentially provide an operational roadmap in parallel.

This presentation will re-introduce the ISWAT initiative, review its current status and plans for community-wide campaigns, highlight the overarching current plans for PSW, and place a focus on two key space-weather areas: the ambient heliosphere/background solar wind (designated as ISWAT theme H1) and CME structure, evolution and propagation through heliosphere (designated as ISWAT theme H2). Title: Assessing the Performance of EUHFORIA Modeling the Background Solar Wind Authors: Hinterreiter, Jürgen; Magdalenic, Jasmina; Temmer, Manuela; Verbeke, Christine; Jebaraj, Immanuel Christopher; Samara, Evangelia; Asvestari, Eleanna; Poedts, Stefaan; Pomoell, Jens; Kilpua, Emilia; Rodriguez, Luciano; Scolini, Camilla; Isavnin, Alexey Bibcode: 2019SoPh..294..170H Altcode: 2019arXiv190707461H In order to address the growing need for more accurate space-weather predictions, a new model named EUHFORIA (EUropean Heliospheric FORecasting Information Asset) was recently developed. We present the first results of the performance assessment for the solar-wind modeling with EUHFORIA and identify possible limitations of its present setup. Using the basic EUHFORIA 1.0.4 model setup with the default input parameters, we modeled background solar wind (no coronal mass ejections) and compared the obtained results with Advanced Composition Explorer (ACE) in-situ measurements. For the purposes of statistical study we developed a technique of combining daily EUHFORIA runs into continuous time series. The combined time series were derived for the years 2008 (low solar activity) and 2012 (high solar activity), from which in-situ speed and density profiles were extracted. We find for the low-activity phase a better match between model results and observations compared to the high-activity time interval considered. The quality of the modeled solar-wind parameters is found to be rather variable. Therefore, to better understand the results obtained we also qualitatively inspected characteristics of coronal holes, i.e. the sources of the studied fast streams. We discuss how different characteristics of the coronal holes and input parameters to EUHFORIA influence the modeled fast solar wind, and suggest possibilities for the improvement of the model. Title: Refining halo CME forecast Authors: Yordanova, E.; Werner, E.; Temmer, M.; Dimmock, A. P.; Rosenqvist, L. Bibcode: 2019AGUFMSH32A..07Y Altcode: Halo CMEs are strongly geoeffective due to their direct propagation towards Earth. Therefore, it is of critical importance to accurately predict their arrival time. However, there are certain difficulties that make this task challenging. Usually, the quality of estimation of halo CME kinematics from coronagraph images suffers from projection effects in the plane-of-sky. In addition, the state of the background solar wind through which the CME is propagating should also be accounted for.

In this study, we refine the WSA-ENLIL+Cone model prediction by investigating one of the model input parameters, namely, the density enhancement factor (dcld). This parameter represents the density enhancement of the leading edge of the CME cone relative to the density enhancement of the fast solar wind. The default input is dcld equal to 4, which often results in higher amplitudes and earlier CME arrival times. We take instead the ratio between the density enhancement at the shock produced by the halo CME and the ambient solar wind and revisit the model predictions for already existing WSA-ENLIL+Cone runs. The new forecast results shows significant improvement in the arrival time estimation, suggesting that the custom dcld factor may be useful in space weather operational setting. Title: VizieR Online Data Catalog: Coronal hole parameters (Heinemann+, 2019) Authors: Heinemann, S. G.; Temmer, M.; Heinemann, N.; Dissauer, K.; Samara, E.; Jercic, V.; Hofmeister, S. J.; Veronig, A. M. Bibcode: 2019yCatp058029401H Altcode: Coronal hole parameters such as morphological properties, the intensity, boundary stability as well as properties of the underlying photospheric magnetic field and its fine structure are presented. 718 coronal holes between 2010 and 2019 have been extracted and analyzed from 193A filtergrams taken by AIA/SDO. For each coronal hole the following parameters are given (including uncertainties). Date, Threshold, Category Factor, Area, Intensity (Mean + Median), Position, Extension, Mean Magnetic Field Strength (Signed + Unsigned), Magnetic Flux (Signed + Unsigned), Flux Balance, Skewness (Magnetic Field Distribution), Flux Tube Number (Weak + Strong), Flux Tube Area Ratio (Weak + Strong), Flux Tube Flux Ratio (Weak + Strong).

(1 data file). Title: Reconstructing Coronal Hole Areas With EUHFORIA and Adapted WSA Model: Optimizing the Model Parameters Authors: Asvestari, E.; Heinemann, S. G.; Temmer, M.; Pomoell, J.; Kilpua, E.; Magdalenic, J.; Poedts, S. Bibcode: 2019JGRA..124.8280A Altcode: 2019arXiv190703337A The adopted Wang-Sheeley-Arge (WSA) model embedded in EUHFORIA (EUropean Heliospheric FORecasting Information Asset) is compared to EUV observations. According to the standard paradigm, coronal holes are sources of open flux; thus, we use remote sensing EUV observations and CATCH (Collection of Analysis Tools for Coronal Holes) to extract CH areas and compare them to the open flux areas modeled by EUHFORIA. From the adopted WSA model we employ only the Potential Field Source Surface (PFSS) model for the inner corona and the Schatten Current Sheet (SCS) model for the outer (PFSS+SCS). The height, Rss, of the outer boundary of the PFSS, known as the source surface, and the height, Ri, of the inner boundary of the SCS are important parameters affecting the modeled CH areas. We investigate the impact the two model parameters can have in the modeled results. We vary Rss within the interval [1.4, 3.2]R⊙ with a step of 0.1R⊙, and Ri within the interval [1.3, 2.8]R⊙ with the same step, and the condition that Ri<Rss. This way we have a set of 184 initial parameters to the model, and we assess the model results for all these possible height pairs. We conclude that the default heights used so far fail in modeling accurately CH areas and lower heights need to be considered. Title: Statistical Analysis and Catalog of Non-polar Coronal Holes Covering the SDO-Era Using CATCH Authors: Heinemann, Stephan G.; Temmer, Manuela; Heinemann, Niko; Dissauer, Karin; Samara, Evangelia; Jerčić, Veronika; Hofmeister, Stefan J.; Veronig, Astrid M. Bibcode: 2019SoPh..294..144H Altcode: 2019arXiv190701990H Coronal holes are usually defined as dark structures seen in the extreme ultraviolet and X-ray spectrum which are generally associated with open magnetic fields. Deriving reliably the coronal hole boundary is of high interest, as its area, underlying magnetic field, and other properties give important hints as regards high speed solar wind acceleration processes and compression regions arriving at Earth. In this study we present a new threshold-based extraction method, which incorporates the intensity gradient along the coronal hole boundary, which is implemented as a user-friendly SSW-IDL GUI. The Collection of Analysis Tools for Coronal Holes (CATCH) enables the user to download data, perform guided coronal hole extraction and analyze the underlying photospheric magnetic field. We use CATCH to analyze non-polar coronal holes during the SDO-era, based on 193 Å filtergrams taken by the Atmospheric Imaging Assembly (AIA) and magnetograms taken by the Heliospheric and Magnetic Imager (HMI), both on board the Solar Dynamics Observatory (SDO). Between 2010 and 2019 we investigate 707 coronal holes that are located close to the central meridian. We find coronal holes distributed across latitudes of about ±60∘, for which we derive sizes between 1.6 ×109 and 1.8 ×1011km2. The absolute value of the mean signed magnetic field strength tends towards an average of 2.9 ±1.9 G. As far as the abundance and size of coronal holes is concerned, we find no distinct trend towards the northern or southern hemisphere. We find that variations in local and global conditions may significantly change the threshold needed for reliable coronal hole extraction and thus, we can highlight the importance of individually assessing and extracting coronal holes. Title: Photospheric magnetic structure of coronal holes Authors: Hofmeister, Stefan J.; Utz, Dominik; Heinemann, Stephan G.; Veronig, Astrid; Temmer, Manuela Bibcode: 2019A&A...629A..22H Altcode: 2019arXiv190903806H In this study, we investigate in detail the photospheric magnetic structure of 98 coronal holes using line-of-sight magnetograms of SDO/HMI, and for a subset of 42 coronal holes using HINODE/SOT G-band filtergrams. We divided the magnetic field maps into magnetic elements and quiet coronal hole regions by applying a threshold at ±25 G. We find that the number of magnetic bright points in magnetic elements is well correlated with the area of the magnetic elements (cc = 0.83 ± 0.01). Further, the magnetic flux of the individual magnetic elements inside coronal holes is related to their area by a power law with an exponent of 1.261 ± 0.004 (cc = 0.984 ± 0.001). Relating the magnetic elements to the overall structure of coronal holes, we find that on average (69 ± 8)% of the overall unbalanced magnetic flux of the coronal holes arises from long-lived magnetic elements with lifetimes > 40 h. About (22 ± 4)% of the unbalanced magnetic flux arises from a very weak background magnetic field in the quiet coronal hole regions with a mean magnetic field density of about 0.2-1.2 G. This background magnetic field is correlated to the flux of the magnetic elements with lifetimes of > 40 h (cc = 0.88 ± 0.02). The remaining flux arises from magnetic elements with lifetimes < 40 h. By relating the properties of the magnetic elements to the overall properties of the coronal holes, we find that the unbalanced magnetic flux of the coronal holes is completely determined by the total area that the long-lived magnetic elements cover (cc = 0.994 ± 0.001).

Movie associated to Fig. 2 is available at https://www.aanda.org Title: EVE Flare Diagnostics of in situ Observed Electron Events Authors: Miteva, R.; Samwel, S. W.; Veronig, A.; Koleva, K.; Dechev, M.; Dissauer, K.; Temmer, M.; Kozarev, K.; Zabunov, S. Bibcode: 2019simi.conf..196M Altcode: We present a comparative study between SDO/EVE flare intensity and the peak intensity of solar energetic electrons and protons over solar cycle 24 (2010–2017). For the analysis we selected flare emission in three EUV wavelengths: 94, 133 and 304 Å. Data from 103–175 and 175–315 keV ACE/EPAM energy channels are used to identify and analyze the flux of the in situ observed electrons. SOHO/ERNE data in five energy channels (17–22, 26–32, 40–51, 64–80, 101–131 MeV) is used for the proton signatures of the so-identified electron events. We calculated Pearson correlation coefficients between the electron and proton particle fluxes and the flare EUV intensities, and compare the results with the respective correlations between particle flux and the solar flare GOES class and speed of the coronal mass ejections. Title: STEREOCat Speed de-projection of SEP-Related CMEs Authors: Tsvetkov, Ts.; Miteva, R.; Temmer, M.; Petrov, N. Bibcode: 2019simi.conf..207T Altcode: Particles accelerated to high energies by solar eruptive phenomena can reach the Earth moving along the interplanetary magnetic field lines. We use a list of 156 SOHO ERNE 20 MeV solar energetic particle (SEP) events from solar cycle 24 (2009–2017) with identified solar origin (e.g. flares and CMEs). The aim of this study is to evaluate the 3D parameters of SEP-related CMEs and estimate if they can give us a better insight of SEP production than the previously used 2D velocities. The 3D kinematic properties of the CME set are explored using observations from STEREO SECCHI and SOHO LASCO coronagraphs based on the STEREOCat analysis tool. Title: CME-HSS Interaction and Characteristics Tracked from Sun to Earth Authors: Heinemann, Stephan G.; Temmer, Manuela; Farrugia, Charles J.; Dissauer, Karin; Kay, Christina; Wiegelmann, Thomas; Dumbović, Mateja; Veronig, Astrid M.; Podladchikova, Tatiana; Hofmeister, Stefan J.; Lugaz, Noé; Carcaboso, Fernando Bibcode: 2019SoPh..294..121H Altcode: 2019arXiv190810161H In a thorough study, we investigate the origin of a remarkable plasma and magnetic field configuration observed in situ on June 22, 2011, near L1, which appears to be a magnetic ejecta (ME) and a shock signature engulfed by a solar wind high-speed stream (HSS). We identify the signatures as an Earth-directed coronal mass ejection (CME), associated with a C7.7 flare on June 21, 2011, and its interaction with a HSS, which emanates from a coronal hole (CH) close to the launch site of the CME. The results indicate that the major interaction between the CME and the HSS starts at a height of 1.3 R⊙ up to 3 R⊙. Over that distance range, the CME undergoes a strong north-eastward deflection of at least 30∘ due to the open magnetic field configuration of the CH. We perform a comprehensive analysis for the CME-HSS event using multi-viewpoint data (from the Solar TErrestrial RElations Observatories, the Solar and Heliospheric Observatory and the Solar Dynamics Observatory), and combined modeling efforts (nonlinear force-free field modeling, Graduated Cylindrical Shell CME modeling, and the Forecasting a CME's Altered Trajectory - ForeCAT model). We aim at better understanding its early evolution and interaction process as well as its interplanetary propagation and related in situ signatures, and finally the resulting impact on the Earth's magnetosphere. Title: Assessment and recommendations for a consolidated European approach to space weather - as part of a global space weather effort Authors: Opgenoorth, Hermann J.; Wimmer-Schweingruber, Robert F.; Belehaki, Anna; Berghmans, David; Hapgood, Mike; Hesse, Michael; Kauristie, Kirsti; Lester, Mark; Lilensten, Jean; Messerotti, Mauro; Temmer, Manuela Bibcode: 2019JSWSC...9A..37O Altcode: Over the last 10-20 years there has been an ever-increasing international awareness of risks to modern society from adverse and potentially harmful - and in extreme cases even disastrous - space weather events. Many individual countries and even international organisations like the United Nations (UN) have begun to increase their activities in preparing for and mitigating effects of adverse space weather. As in the rest of the world there is also in Europe an urgent need for coordination of Space Weather efforts in individual countries as well as in and among European organisations such as the European Space Agency (ESA) and the European Union (EU). This coordination should not only improve our ability to meet space weather risks, but also enable Europe to contribute to on-going global space weather efforts. While space weather is a global threat, which needs a global response, it also requires tailored regional and trans-regional responses that require coordination at all levels. Commissioned by the European Space Science Committee (ESSC) of the European Science Foundation, the authors - together with ex-officio advice from ESA and the EU - have over two years assessed European activities in the realm of space weather and formulated a set of recommendations to ESA, the EU and their respective member states, about how to prepare Europe for the increasing impact of adverse space weather effects on man-made infrastructure and our society as a whole. We have also analysed parallel international activities worldwide, and we give advice how Europe could incorporate its future activities into a global scheme. Title: Spectroscopy and Differential Emission Measure Diagnostics of a Coronal Dimming Associated with a Fast Halo CME Authors: Veronig, Astrid M.; Gömöry, Peter; Dissauer, Karin; Temmer, Manuela; Vanninathan, Kamalam Bibcode: 2019ApJ...879...85V Altcode: 2019arXiv190601517V We study the coronal dimming caused by the fast halo CME (deprojected speed v = 1250 km s-1) associated with the C3.7 two-ribbon flare on 2012 September 27, using Hinode/EIS spectroscopy and Solar Dynamics Observatory (SDO)/AIA Differential Emission Measure (DEM) analysis. The event reveals bipolar core dimmings encompassed by hook-shaped flare ribbons located at the ends of the flare-related polarity inversion line, and marking the footpoints of the erupting filament. In coronal emission lines of log T [K] = 5.8-6.3, distinct double-component spectra indicative of the superposition of a stationary and a fast upflowing plasma component with velocities up to 130 km s-1 are observed at these regions, which were mapped by the scanning EIS slit close in time to their impulsive dimming onset. The outflowing plasma component is found to be of the same order as and even dominant over the stationary one, with electron densities in the upflowing component of 2 × 109 cm-3 at log T [K] = 6.2. The density evolution in core-dimming regions derived from SDO/AIA DEM analysis reveals impulsive reductions by 40%-50% within ≲10 minutes and remains at these reduced levels for hours. The mass-loss rate derived from the EIS spectroscopy in the dimming regions is of the same order as the mass increase rate observed in the associated white-light CME (1 × 1012 g s-1), indicating that the CME mass increase in the coronagraphic field of view results from plasma flows from below and not from material piled up ahead of the outward-moving and expanding CME front. Title: Unusual Plasma and Particle Signatures at Mars and STEREO-A Related to CME-CME Interaction Authors: Dumbović, Mateja; Guo, Jingnan; Temmer, Manuela; Mays, M. Leila; Veronig, Astrid; Heinemann, Stephan G.; Dissauer, Karin; Hofmeister, Stefan; Halekas, Jasper; Möstl, Christian; Amerstorfer, Tanja; Hinterreiter, Jürgen; Banjac, Saša; Herbst, Konstantin; Wang, Yuming; Holzknecht, Lukas; Leitner, Martin; Wimmer–Schweingruber, Robert F. Bibcode: 2019ApJ...880...18D Altcode: 2019arXiv190602532D On 2017 July 25 a multistep Forbush decrease (FD) with a remarkable total amplitude of more than 15% was observed by Mars Science Laboratory/Radiation Assessment Detector at Mars. We find that these particle signatures are related to very pronounced plasma and magnetic field signatures detected in situ by STEREO-A on 2017 July 24, with a higher-than-average total magnetic field strength reaching more than 60 nT. In the observed time period STEREO-A was at a relatively small longitudinal separation (46°) to Mars, and both were located at the back side of the Sun as viewed from Earth. We analyze a number of multispacecraft and multi-instrument (both in situ and remote-sensing) observations and employ modeling to understand these signatures. We find that the solar sources are two coronal mass ejections (CMEs) that erupted on 2017 July 23 from the same source region on the back side of the Sun as viewed from Earth. Moreover, we find that the two CMEs interact nonuniformly, inhibiting the expansion of one of the CMEs in the STEREO-A direction, whereas allowing it to expand more freely in the Mars direction. The interaction of the two CMEs with the ambient solar wind adds up to the complexity of the event, resulting in a long, substructured interplanetary disturbance at Mars, where different substructures correspond to different steps of the FD, adding up to a globally large-amplitude FD. Title: Heliospheric Evolution of Magnetic Clouds Authors: Vršnak, B.; Amerstorfer, T.; Dumbović, M.; Leitner, M.; Veronig, A. M.; Temmer, M.; Möstl, C.; Amerstorfer, U. V.; Farrugia, C. J.; Galvin, A. B. Bibcode: 2019ApJ...877...77V Altcode: 2019arXiv190408266V The interplanetary evolution of 11 magnetic clouds (MCs) recorded by at least two radially aligned spacecraft is studied. The in situ magnetic field measurements are fitted to a cylindrically symmetric Gold-Hoyle force-free uniform-twist flux-rope configuration. The analysis reveals that in a statistical sense, the expansion of the studied MCs is compatible with self-similar behavior. However, individual events expose a large scatter of expansion rates, ranging from very weak to very strong expansion. Individually, only four events show an expansion rate compatible with isotropic self-similar expansion. The results indicate that the expansion has to be much stronger when the MCs are still close to the Sun than in the studied 0.47-4.8 au distance range. The evolution of the magnetic field strength shows a large deviation from the behavior expected for the case of isotropic self-similar expansion. In the statistical sense, as well as in most of the individual events, the inferred magnetic field decreases much slower than expected. Only three events show behavior compatible with self-similar expansion. There is also a discrepancy between the magnetic field decrease and the increase of the MC size, indicating that magnetic reconnection and geometrical deformations play a significant role in the MC evolution. About half of the events show a decay of the electric current as expected for self-similar expansion. Statistically, the inferred axial magnetic flux is broadly consistent with remaining constant. However, events characterized by a large magnetic flux show a clear tendency toward decreasing flux. Title: Three-dimensional Reconstructions of Extreme-ultraviolet Wave Front Heights and Their Influence on Wave Kinematics Authors: Podladchikova, Tatiana; Veronig, Astrid M.; Dissauer, Karin; Temmer, Manuela; Podladchikova, Olena Bibcode: 2019ApJ...877...68P Altcode: 2019arXiv190409427P EUV waves are large-scale disturbances in the solar corona initiated by coronal mass ejections. However, solar EUV images show only the wave front projections along the line of sight of the spacecraft. We perform 3D reconstructions of EUV wave front heights using multipoint observations from STEREO-A and STEREO-B, and we study their evolution to properly estimate the EUV wave kinematics. We develop two different methods to solve the matching problem of the EUV wave crest on pairs of STEREO-A/B images by combining epipolar geometry with the investigation of perturbation profiles. The proposed approaches are applicable at the early and maximum stage of the event when STEREO-A/B see different facets of the EUV wave, but also at the later stage when the wave front becomes diffusive and faint. The techniques developed are demonstrated on two events observed at different separations of the STEREO spacecraft (42° and 91°). For the 2007 December 7 event, we find that the emission of the EUV wave front mainly comes from a height range up to 90-104 Mm, decreasing later to 7-35 Mm. Including the varying height of the EUV wave front allows us to correct the wave kinematics for the projection effects, resulting in velocities in the range of 217-266 km s-1. For the 2009 February 13 event, the wave front height almost doubled from 54 to 93 Mm over 10 minutes, and the velocity derived is 205-208 km s-1. In the two events under study, the corrected speeds differ by up to 25% from the uncorrected ones, depending on the wave front height evolution. Title: Investigating the evolution and interactions of the September 2017 CME events with EUHFORIA Authors: Scolini, Camilla; Rodriguez, Luciano; Temmer, Manuela; Guo, Jingnan; Dumbovic, Mateja; Pomoell, Jens; Poedts, Stefaan Bibcode: 2019shin.confE...1S Altcode: Coronal Mass Ejections (CMEs) are the primary source of strong space weather disturbances at Earth and other locations in the heliosphere. While their (geo-)effectiveness is largely determined by their dynamic pressure and magnetic field, phenomena such as the interaction with other transients (CMEs, CIRs…), or the pre-conditioning of interplanetary space due to preceding CMEs, can significantly alter the properties of single CME events and influence their (geo-)effectiveness. Investigating such phenomena via physics-based models is crucial to improve our understanding of interacting CME events, and to assess the prediction capability of extreme space weather events at various locations in the heliosphere.

We present a comprehensive analysis of the CME events that erupted from AR12673 during the unusually active week of September 4-10, 2017, using the EUHFORIA heliospheric model. As AR12673 rotated on the solar disk, CMEs were launched over a wide range of longitudes, interacting with each other and paving the way for the propagation of following CMEs. CME signatures were observed at both Earth and Mars, and associated particle events were reported at Earth, Mars, and STEREO-A. At Earth, an intense geomagnetic storm triggered by a CME sheath interacting with a preceding ejecta was recorded on September 8, 2017.

Using parameters derived from remote-sensing and multi-spacecraft observations of the CMEs and their source region, we simulate the events with both traditional cone CME model, and with a more realistic flux-rope CME model. We investigate how CME-CME interactions affect the spatial and temporal evolution of CME shocks, sheaths and ejecta in the heliosphere, and we compare simulation results with in-situ measurements at Earth and Mars. This study will not only benchmark current prediction capabilities in the case of complex CME events, but will also provide better insights on the large-scale evolution of complex CME events throughout the heliosphere. Title: ELEvoHI ensemble modeling: CME arrival prediction based on heliospheric imager observations Authors: Hinterreiter, Jürgen; Amerstorfer, Tanja; Temmer, Manuela; Möstl, Christian; Reiss, Martin; Amerstorfer, Ute; Bailey, Rachel Bibcode: 2019EGUGA..21.9132H Altcode: We present a statistical study on CME arrival prediction using ELEvoHI (ELlipse Evolution model based on Heliospheric Imager observations) ensemble modeling. ELEvoHI is the current state-of-the-art HI elongation fitting method that utilizes heliospheric imager data obtained by the STEREO (Solar TErrestrial RElations Observatory) twin spacecraft assuming that the drag force exerted by the ambient solar wind is the dominant force influencing the CME propagation in the IP-space. The HI time-elongation profiles needed by ELEvoHI as well as the in-situ data for validating the results are taken from the FP7 HELCATS project. GCS (Graduated Cylindrical Shell) fitting is applied for each CME separately. We perform a cut in the ecliptic plane, based on the GCS fit, to derive the initial values needed for the ELEvoHI ensemble modeling. In this study, we select CMEs in a 12-month interval (June 2009 to June 2010) corresponding to a location of STEREO-B close to Lagrange point 5 (60° trailing Earth), making the model results valuable for future studies (STEREO-A near L5 in mid 2020) and for a planned L5 mission. Our analysis contains two parts: First, a contingency table (hit/false alarms/misses) with the corresponding skill scores and second the times and speeds for the predicted and observed Earth arriving events. The statistical results are compared to other studies and will serve as benchmark for future enhanced ELEvoHI versions. Title: Genesis, magnetic morphology and impulsive evolution of the coronal mass ejection associated with the X8.2 flare on 2017 September 10 Authors: Veronig, Astrid; Podladchikova, Tatiana; Dissauer, Karin; Temmer, Manuela; Seaton, Daniel; Long, David; Guo, Jingnan; Vrsnak, Bojan; Harra, Louise; Kliem, Bernhard Bibcode: 2019EGUGA..21.9243V Altcode: The extreme X8.2 event of 2017 September 10 provides unique observations to study the genesis, magnetic morphology, impulsive dynamics and shock formation in a very fast coronal mass ejection (CME). Combining GOES-16/SUVI and SDO/AIA EUV imagery, we identify a hot (T ≈ 10-15 MK) bright rim around a quickly expanding cavity, embedded inside a much larger CME shell (T ≈ 1-2 MK). The CME shell develops from a dense set of large AR loops (>0.5Rs) and seamlessly evolves into the CME front observed in LASCO C2. The strong lateral overexpansion of the CME shell acts as a piston initiating the fast EUV shock wave. The hot cavity rim is demonstrated to be a manifestation of the dominantly poloidal flux and frozen-in plasma added to the rising flux rope by magnetic reconnection in the current sheet beneath. The same structure is later observed as the core of the white-light CME, challenging the traditional interpretation of the CME three-part morphology. The large amount of added magnetic flux suggested by these observations explains the extreme accelerations of the radial and lateral expansion of the CME shell and cavity, all reaching values up to 5-10 km s-2. The acceleration peaks occur simultaneously with the first RHESSI 100-300 keV hard X-ray burst of the associated flare, further underlining the importance of the reconnection process for the impulsive CME evolution. Finally, the much higher radial propagation speed of the flux rope in relation to the CME shell causes a distinct deformation of the white-light CME front and shock. Title: Statistics of Coronal Dimmings Associated with Coronal Mass Ejections. II. Relationship between Coronal Dimmings and Their Associated CMEs Authors: Dissauer, K.; Veronig, A. M.; Temmer, M.; Podladchikova, T. Bibcode: 2019ApJ...874..123D Altcode: 2018arXiv181001589D We present a statistical study of 62 coronal dimming events associated with Earth-directed coronal mass ejections (CMEs) during the quasi-quadrature period of STEREO and the Solar Dynamics Observatory (SDO). This unique setting allows us to study both phenomena in great detail and compare characteristic quantities statistically. Coronal dimmings are observed on-disk by the SDO/Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager, while the CME kinematics during the impulsive acceleration phase is studied close to the limb with STEREO/EUVI and COR, minimizing projection effects. The dimming area, its total unsigned magnetic flux, and its total brightness, reflecting properties of the total dimming region at its final extent, show the highest correlations with the CME mass (c ∼ 0.6-0.7). Their corresponding time derivatives, describing the dynamics of the dimming evolution, show the strongest correlations with the CME peak velocity (c ∼ 0.6). The highest correlation of c = 0.68 ± 0.08 is found with the mean intensity of dimmings, indicating that the lower the CME starts in the corona, the faster it propagates. No significant correlation between dimming parameters and the CME acceleration was found. However, for events where high-cadence STEREO observations were available, the mean unsigned magnetic field density in the dimming regions tends to be positively correlated with the CME peak acceleration (c = 0.42 ± 0.20). This suggests that stronger magnetic fields result in higher Lorentz forces providing stronger driving force for the CME acceleration. Specific coronal dimming parameters correlate with both CME and flare quantities providing further evidence for the flare-CME feedback relationship. For events in which the CME occurs together with a flare, coronal dimmings statistically reflect the properties of both phenomena. Title: Importance of heliospheric imager track quality for CME arrival prediction accuracy Authors: Amerstorfer, Tanja; Hinterreiter, Jürgen; Möstl, Christian; Davies, Jackie A.; Amerstorfer, Ute V.; Reiss, Martin A.; Temmer, Manuela; Bailey, Rachel L.; Harrison, Richard A. Bibcode: 2019EGUGA..21.7373A Altcode: Operational CME arrival prediction is mainly conducted using magnetohydrodynamic models based on coronagraph observations and magnetograms. Although the Solar TErrestrial RElations Observatory with its heliospheric imagers (HI) provides the possibility to trace a CME's propagation along its path from the Sun to 1 AU, these data can hardly be used to predict CME arrivals in real time (except for a few events in an early phase of the mission). One of the main reasons for that is a large number of data gaps in beacon data, which is available in near real time (in contrast to the complete science data), impeding a proper measurement of the CME front. With regard to a possible future L5 mission carrying HIs we investigate the most suitable way of extracting the time-elongation track of CMEs from HI observations leading to a prediction with the highest possible accuracy. As a first step to reach this goal, we use time-elongation tracks measured from STEREO/HI science data and provided by the FP7 HELCATS team as well as tracks derived using time-elongation maps and tracks measured directly in an HI image time series. These time-elongation tracks are further used as input to our CME ensemble prediction tool ELEvoHI (ELlipse Evolution model based on HI data), which assumes a drag-based interplanetary CME propagation and an elliptical CME frontal shape. ELEvoHI produces post-event predictions of arrival times and speeds at 1 AU for all tracks of each CME under study. By comparing the prediction results from several ways of tracking we attempt to deduce a preferable approach for future studies, e.g. when using data from Parker Solar Probe's Wide-Field Imager for Solar Probe (WISPR), and maybe for future real time predictions when STEREO-A approaches the L5 point. Title: Observational assessment on CME mass pile up in interplanetary space Authors: Temmer, Manuela; Holzknecht, Lukas; Dumbovic, Mateja; Vrsnak, Bojan Bibcode: 2019EGUGA..21.9578T Altcode: Coronal mass ejections (CMEs) propagating in the heliosphere are exposed to a drag force due to the ambient solar wind. Mass pile-up in interplanetary space can have strong effects on the drag force, and with that on the CME propagation time and energy input to the magnetosphere. For a sample of well observed events, we determine the de-projected 3D mass and its evolution up to a distance range of about 15Rs using combined STEREO-SECCHI COR1 and COR2 data, for which no pile-up at the CME front is found (see also Bein et al., 2013). Applying the GCS forward fitting model (Thernisien et al., 2006, 2009) on COR2 data, we obtain the volume of the CMEs. Working under the assumption that the CME mass is constant beyond 15Rs and that the CME undergoes self-similar expansion, we estimate the CME density at the distance of 1AU. The results are compared to in-situ proton density data measured for the associated ICME's sheath and magnetic structure for which we derive a trend towards a mass increase at the CME front. Title: Investigating the evolution and interactions of the September 2017 CME events with EUHFORIA Authors: Scolini, Camilla; Rodriguez, Luciano; Temmer, Manuela; Guo, Jingnan; Dumbovic, Mateja; Pomoell, Jens; Poedts, Stefaan Bibcode: 2019EGUGA..21.1337S Altcode: Coronal Mass Ejections (CMEs) and their Interplanetary counterparts (ICMEs) are the primary source of strong space weather disturbances at Earth and other places in the heliosphere. Key parameters determining the geo-effectiveness of CMEs are their plasma dynamic pressure and internal magnetic field intensity and orientation. In addition, phenomena such as the interaction with other CME structures along the way, or the pre-conditioning of interplanetary (IP) space due to the passage of previous CMEs, can significantly modify the properties of single CME events and influence their geo-effectiveness. Therefore, investigating and modeling such phenomena via physics-based heliospheric models is crucial in order to assess and improve our space weather prediction capability in relation to complex CME events. In this regard, we present a comprehensive analysis of the CME events that erupted from AR 12673 during the unusually active week of September 4-10, 2017, with the aim of validating for the first time the prediction capabilities of the EUHFORIA model in the case of complex CME events. As AR 12673 rotated along with the solar disk, CMEs were launched over a wide range of longitudes, interacting with each other and paving the way for the propagation of the following CMEs. Following the eruptions, ICME-related signatures were observed at both Earth and Mars, while associated particle events were reported at Earth, Mars, and STEREO-A. In terms of impact on Earth, an intense geomagnetic storm, triggered by a strong southward magnetic field associated to an ICME sheath, was recorded on September 8, 2017. In order to study these CME-CME interactions and their influence on the geo-effectiveness of single CMEs, we simulate the events using the EUHFORIA model. With the intent of preserving a predictive approach, we use kinematic, geometric and magnetic input parameters for the CMEs as derived from remote-sensing and multi-spacecraft observations of the CMEs and their source regions. We model CMEs first using an over-simplified cone model, and then a more realistic flux- rope model so to quantify the improvement in the prediction of the interplanetary magnetic field and CME geo-effectiveness at Earth in the latter case. Furthermore, we investigate the modelling of CME-CME interactions considering the spatial and temporal evolution of ICMEs in terms of their shocks, sheaths and ejecta structures in the heliosphere, and we quantify the impact of such phenomena on the propagation and evolution of single CME events. Results from this study will not only benchmark our current prediction capabilities in the case of complex CME events, but will also provide better insights on the large-scale evolution and interaction of complex CME events in the inner heliosphere. Title: Stellar CMEs from an observational point of view Authors: Leitzinger, Martin; Odert, Petra; Vida, Krisztian; Koller, Florian; Veronig, Astrid; Korhonen, Heidi; Guenther, Eike; Hanslmeier, Arnold; Temmer, Manuela; Dissauer, Karin; Greimel, Robert; Kriskovics, Levente; Lammer, Helmut Bibcode: 2019EGUGA..21.6786L Altcode: Stellar activity is mainly characterized by the high energy phenomena such as outbreaks of radiation (flares) and sporadic expulsions of particles into the astrosphere termed coronal mass ejections (CMEs). Both phenomena are known to cause space weather in our solar system. On stars, flares and their parameters are well determined, in contrast to CMEs; their parameters are still not determined statistically. Both phenomena may have severe effects on planetary atmospheres and, in addition, stellar CMEs may play an important role in stellar mass and angular momentum loss and therefore in stellar evolution. Flares are directly detectable from photometric observations, whereas the detection of CMEs requires different observational methods. CMEs have different signatures in different wavelength regimes. Most of the stellar CMEs were detected so far using the method of Doppler-shifted Balmer flux which is accessible via spectroscopic measurements. Several observational programs have been carried out and are planned for the future, including new observations and archival data. Also several attempts to detect stellar CMEs via radio emission have been carried out in the past decades. Finally, the X-ray regime may provide a valuable data pool to look for so-called dimmings, well-known from the Sun, which are closely related to CMEs and which are detectable in X-ray light curves. So far stellar CMEs have been detected rarely and only a handful of distinct events is known, mainly for dMe stars. We report on past, ongoing and future campaigns of stellar CMEs on F-, G-, K-, and M-type pre- and main-sequence stars. Title: Multiple Satellite Analysis of the Earth's Thermosphere and Interplanetary Magnetic Field Variations due to ICME/CIR Events During 2003-2015 Authors: Krauss, Sandro; Temmer, Manuela; Vennerstrom, Susanne Bibcode: 2019EGUGA..21.4180K Altcode: We present a refined statistical analysis based on ICMEs as well as CIRs for the time period 2003-2015 to estimate the impact of different solar wind types on the geomagnetic activity and the neutral density in the Earth's thermosphere. For the time-based delimitation of the events, we rely on the catalog maintained by Richardson and Cane and the corotating interaction region lists provided by S. Vennerstrom and L.K. Jian. These archives are based on in situ measurements from the ACE and/or the Wind spacecraft. On this basis, we will thoroughly investigate about 400 Earth-directed ICME and CIR events. To verify the impact on the Earths thermosphere we determine neutral mass densities by using accelerometer measurements collected by the low-Earth-orbiting satellites GRACE and CHAMP. Subsequently, the atmospheric densities will be to characteristic ICME parameters and since increased solar activity may lead to a decrease of the satellites orbital altitude we additionally assess the orbital decay for each of the events and satellites. Title: The in situ Solar Wind and Galactic Cosmic Ray correlation at Mars and its comparison with Earth observations Authors: Guo, Jingnan; Temmer, Manuela; Veronig, Astrid; Janvier, Miho; Hofmeister, Stefan; Wimmer-Schweingruber, Robert; Halekas, Jasper Bibcode: 2019EGUGA..21.9366G Altcode: The Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have been observing the in situ solar wind properties since its arrival to Mars at the end of 2014. Together with the Galactic Cosmic Ray (GCR) observation continuously monitored by the Radiation Assessment Detector (RAD) on the Martian ground, we are able to analyze the correlation of the solar wind evolution and the modulated GCR variations at Mars. The transient variations (mostly observed as short-term decreases) in these in situ observations are usually related to either the impact of Coronal Mass Ejections (CMEs) erupted from Solar active regions or the pass-by of High Speed Streams (HSS) in the solar wind arising from Coronal Holes (CHs) on the Sun. During the opposition phase in 2016 when Earth and Mars were radially aligned on the same side of the Sun, we observe the stable evolution of a few CHs on the solar surface over several solar rotations and analyze the re-current in situ solar wind and GCR signatures at both Earth and Mars. Title: Unusual plasma and particle signatures at Mars and STEREO-A related to inhibited expansion caused by CME-CME interaction Authors: Dumbovic, Mateja; Guo, Jingnan; Temmer, Manuela; Mays, Leila; Veronig, Astrid; Hofmeister, Stefan; Halekas, Jasper Bibcode: 2019EGUGA..21.6957D Altcode: On July 25 2017 a multi-step Forbush decrease (FD) with the total amplitude of more than 15% was observed by MSL/RAD at Mars and this is one of the biggest FDs ever detected on Mars. We find that these particle signatures are related to very pronounced plasma and magnetic field signatures detected in situ by STEREO-A on July 24 2017, with a higher than average total magnetic field strength reaching more than 60 nT. In the observed time period STEREO-A was longitudinally close to Mars and both were located at the back side of Sun as viewed from Earth. Using multi-spacecraft and multi-instrument (both in situ and remote-sensing) observations, as well as modelling, we find that the solar sources of these in situ signatures are 2 CMEs which erupted on July 23 2017 from the same source region on the back side of the Sun as viewed from Earth and interacted in the interplanetary space, inhibiting the expansion of one of the CMEs. We present a detailed investigation on this complex interaction event on its way from Sun to Mars. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 745782. Title: Multiple EUV wave reflection from a coronal hole Authors: Podladchikova, Tatiana; Veronig, Astrid M.; Podladchikova, Olena; Dissauer, Karin; Vršnak, Bojan; Saqri, Jonas; Piantschitsch, Isabell; Temmer, Manuela Bibcode: 2019EGUGA..21.9793P Altcode: EUV waves are large-scale propagating disturbances in the solar corona initiated by coronal mass ejections. We investigate the multiple EUV wave reflections at a coronal hole boundary, as observed by SDO/AIA on 1 April 2017. The EUV wave originates from Active Region (AR) 12645 close to the disk center and propagates toward the south polar coronal hole with an average velocity of 430 km/s. The interaction of the EUV wave with the coronal hole, which represents a region of high Alfven speed, is observed as a splitting into two wave components: one continues propagation inside the coronal hole with an increased velocity of 850 km/s (transmitted wave), while the other one moves back toward the AR, also with an increased velocity of 600 km/s (reflected wave). The reflected EUV wave is subsequently reflected again from the AR and propagates toward the coronal hole with an average velocity of 350 km/s, where it is reflected for the second time at the coronal hole boundary and propagates again toward the AR with a velocity of 300 km/s. These events are observed over an interval of 40 minutes. The high cadence SDO imagery allows us to study in detail the kinematics of the direct and multiple times reflected EUV wave. In addition, its multi-wavelength EUV imagery allows us to derive the plasma properties of the corona and the EUV wave pulse via Differential Emission Measure analysis. These results are used to compare the observed characteristics of the wave interaction with the coronal hole with simulations. Title: Origin of the two shock waves associated with the September 27/28, 2012 event Authors: Jebaraj, Immanuel Christopher; Magdalenic, Jasmina; Scolini, Camilla; Rodriguez, Luciano; Poedts, Stefaan; Kilpua, Emilia; Krupar, Vratislav; Pomoell, Jens; Temmer, Manuela Bibcode: 2019EGUGA..2116967J Altcode: Coronal mass ejections and flares are solar eruptive phenomena responsible for space weather activities near Earth. They can accelerate particles, and generate shock waves which are a threat to our technologies at Earth and in space. Therefore, predicting shock arrival at Earth has been an important goal for space weather. Space based radio observations provide the unique opportunity to track shock waves in the inner heliosphere. We present the study of CME/flare event on September 27/28, 2012. The GOES C3.1 flare that originated from NOAA AR 1577 was associated with a full-halo CME (first seen in SOHO/LASCO C2 field of view at 23:47) and white light shock wave observed by all three spacecraft STEREO A, STEREO B, and SOHO. The associated radio event shows a group of type III bursts and two somewhat unusual type II bursts with significantly different starting frequencies. To understand the origin of the two shock waves we performed multi-wavelength study, and perform radio triangulation to get their source position in the 3D space. For the radio triangulation study, we used goniopolarimetric measurements from STEREO/WAVES and WIND/WAVES instruments. We also did data-driven modelling of the CME propagation using EUHFORIA cone model (EUropean Heliospheric FORecasting Information Asset) and validate the results by comparison with in-situ data. Results of this study indicate that, although temporal association between the shock and the CME is good, the low frequency type II burst occurs significantly higher in the solar corona than the associated CME and has therefore unclear origin. To understand the origin of the low frequency type II burst we studied preceding event at 10:20 UT (STEREO A/COR2) on September 27, 2012. The radio triangulation study shows that the type II source positions are in the southern solar hemisphere and thus may be associated to the type II emissions in the radio event succeeding it. We therefore discuss different possibilities for the origin of two type II bursts. Title: Radial and Tangential Kinematics and Angular Extent of EUV Coronal Bright Fronts Authors: Kozarev, Kamen; Veronig, Astrid; Temmer, Manuela; Miteva, Rositsa; Dissauer, Karin; Koleva, Kostadinka; Dechev, Momchil; Duchlev, Peter Bibcode: 2019EGUGA..21.9290K Altcode: Large-scale solar coronal compressive waves are often observed in extreme UV (EUV) and white light to precede nascent coronal mass ejections (CMEs), which previous work has shown develop most dynamically (expansion, acceleration) in the low and middle solar corona (below 5-8 solar radii). Multiple studies in the last ten years have suggested that these waves may be manifestations of driven coronal shock waves, and may accelerate ions to solar energetic particle (SEP) energies. A commonly invoked condition for the generation of EUV waves and their capability to produce energetic particles is the presence of rapid lateral expansion of the front and driver behind it. As a step to characterizing this capability, we study the radial and lateral kinematics of a number of EUV off-limb waves in the low corona, and their departure from spherical expansion. We characterize their time-dependent angular extent. We compare the results with the later-stage CME angular sizes and radial kinematics deduced from SOHO/LASCO observations of the events. Title: Analysis of SDO/EVE Flares in Relation to Solar Energetic Protons Authors: Miteva, Rositsa; Koleva, Kostadinka; Dechev, Momchil; Veronig, Astrid; Dissauer, Karin; Kozarev, Kamen; Temmer, Manuela Bibcode: 2019EGUGA..2115190M Altcode: Solar energetic proton (SEP) events from SOHO/ERNE instruments and SDO/EVE solar flares in solar cycle 24 are considered. The SEP-associated flare emission is analyzed in multiple wavelength ranges characterizing flare emission. Background subtraction of the pre-event particle flux and flare emission is performed for each event. Finally, a Pearson correlation analysis is completed between the peak values of the SEP events and the UV and EUV flare intensities. Comparison with the results from flare soft X-ray, hard X-ray and radio emission is presented. This work is supported by the Bilateral project Bulgaria-Austria with the National Science Fund of Bulgaria contract No. NTS/AUSTRIA 01/23 (28.02.2017) and Austria OeAD Project No. BG 11/2017. Title: Reconstructing coronal holes with EUHFORIA Authors: Asvestari, Eleanna; Heinemann, Stephan; Pomoell, Jens; Temmer, Manuela; Kilpua, Emilia; Magdalenic, Jasmina; Poedts, Stefaan Bibcode: 2019EGUGA..21.8085A Altcode: Modelling accurately the ambient solar wind is important for space weather forecasting. EUHFORIA (European Heliospheric Forecasting Information Asset) model employs an empirical solar wind model that is based on the Wang-Sheeley-Arge model. It combines the Potential Field Source Surface (PFSS) and the Schatten Current Sheet (SCS) models. In previous studies it was shown that placing the inner boundary of the SCS model at a radius, Ri, lower than that of the outer boundary of the PFSS model, Rii, improves the simulation output. Here, we investigate the capability of the empirical solar wind model adopted in EUHFORIA to recreate the geometry and size of coronal holes for a large set of pairs of PFSS and SCS radii. We vary Rii within the interval [1.4, 3.0]Rs with a step of 0.1Rs, and the Ri within the interval [1.3, 2.8]Rs with the same step size. The study is repeated for 12 coronal holes of different latitudinal position and geometry. We compare the modelled coronal holes with boundaries obtained by remote sensing EUV observations using the CATCH tool (Collection of Analysis Tools for Coronal Holes). Preliminary results of the study indicate that a previously defined pair of PFSS and SCS radii results in underestimated coronal hole sizes. It also indicates that different radii sets give better results for different types of coronal holes. Title: ICMEs Propagating Towards Mars Observed in Heliospheric Imagers and their Associated Forbush Decreases at MSL/RAD Authors: von Forstner, Johan; Guo, Jingnan; Wimmer-Schweingruber, Robert F.; Temmer, Manuela; Dumbović, Mateja; Veronig, Astrid; Möstl, Christian; Hassler, Donald M.; Zeitlin, Cary J.; Ehresmann, Bent Bibcode: 2019EGUGA..21.8305V Altcode: The Radiation Assessment Detector (RAD) onboard the Mars Science Laboratory (MSL) mission's Curiosity rover has been measuring galactic cosmic rays (GCR) as well as solar energetic particles (SEP) on the surface of Mars for more than 6 years since its landing in August 2012 and in interplanetary space during its 8-month cruise to Mars between 2011 and 2012. The observations include a large number of Forbush decreases (FD) caused by interplanetary coronal mass ejections (ICMEs) and their associated shocks passing MSL. Our previous work (Freiherr von Forstner et al. 2018, JGR: Space Physics) studied 15 ICME events close to oppositions of Mars as seen from Earth or the STEREO A and B spacecraft, where in situ Forbush decrease observations at both locations could be used to derive the propagation time of the ICME from 1 AU to Mars. We found that on average, ICMEs in our sample continued to decelerate beyond 1 AU. We now investigate a different constellation where MSL/RAD Forbush decrease measurements are combined with remote tracking of ICMEs using the STEREO Heliospheric Imager (HI) telescopes. A large catalog of such remote observations was created by the HELCATS project (Möstl et al. 2017, Space Weather), not only including ICMEs propagating towards Earth, but also some that passed Mars. This allows to enlarge our sample for a statistical study of ICMEs at Mars. We associate STEREO-HI observations from the catalog with corresponding FDs at MSL/RAD and study the accuracy when predicting the arrival of an ICME at Mars using common models applied to HI data. Based on the catalogue of events built using this method, we also investigate the properties of the corresponding Forbush decreases at RAD, such as their magnitude, steepness and duration. We find both correlations between the parameters themselves as well as possible relations to the ICME properties (derived from HI data). These data are also compared to findings from previous studies using Earth-based observations. Title: Benchmarking CME Arrival Time and Impact: Progress on Metadata, Metrics, and Events Authors: Verbeke, C.; Mays, M. L.; Temmer, M.; Bingham, S.; Steenburgh, R.; Dumbović, M.; Núñez, M.; Jian, L. K.; Hess, P.; Wiegand, C.; Taktakishvili, A.; Andries, J. Bibcode: 2019SpWea..17....6V Altcode: 2018arXiv181110695V Accurate forecasting of the arrival time and subsequent geomagnetic impacts of coronal mass ejections (CMEs) at Earth is an important objective for space weather forecasting agencies. Recently, the CME Arrival and Impact working team has made significant progress toward defining community-agreed metrics and validation methods to assess the current state of CME modeling capabilities. This will allow the community to quantify our current capabilities and track progress in models over time. First, it is crucial that the community focuses on the collection of the necessary metadata for transparency and reproducibility of results. Concerning CME arrival and impact we have identified six different metadata types: 3-D CME measurement, model description, model input, CME (non)arrival observation, model output data, and metrics and validation methods. Second, the working team has also identified a validation time period, where all events within the following two periods will be considered: 1 January 2011 to 31 December 2012 and January 2015 to 31 December 2015. Those two periods amount to a total of about 100 hit events at Earth and a large amount of misses. Considering a time period will remove any bias in selecting events and the event set will represent a sample set that will not be biased by user selection. Lastly, we have defined the basic metrics and skill scores that the CME Arrival and Impact working team will focus on. Title: Genesis and Impulsive Evolution of the 2017 September 10 Coronal Mass Ejection Authors: Veronig, Astrid M.; Podladchikova, Tatiana; Dissauer, Karin; Temmer, Manuela; Seaton, Daniel B.; Long, David; Guo, Jingnan; Vršnak, Bojan; Harra, Louise; Kliem, Bernhard Bibcode: 2018ApJ...868..107V Altcode: 2018arXiv181009320V The X8.2 event of 2017 September 10 provides unique observations to study the genesis, magnetic morphology, and impulsive dynamics of a very fast coronal mass ejection (CME). Combining GOES-16/SUVI and SDO/AIA EUV imagery, we identify a hot (T ≈ 10-15 MK) bright rim around a quickly expanding cavity, embedded inside a much larger CME shell (T ≈ 1-2 MK). The CME shell develops from a dense set of large AR loops (≳0.5R s ) and seamlessly evolves into the CME front observed in LASCO C2. The strong lateral overexpansion of the CME shell acts as a piston initiating the fast EUV wave. The hot cavity rim is demonstrated to be a manifestation of the dominantly poloidal flux and frozen-in plasma added to the rising flux rope by magnetic reconnection in the current sheet beneath. The same structure is later observed as the core of the white-light CME, challenging the traditional interpretation of the CME three-part morphology. The large amount of added magnetic flux suggested by these observations explains the extreme accelerations of the radial and lateral expansion of the CME shell and cavity, all reaching values of 5-10 km s-2. The acceleration peaks occur simultaneously with the first RHESSI 100-300 keV hard X-ray burst of the associated flare, further underlining the importance of the reconnection process for the impulsive CME evolution. Finally, the much higher radial propagation speed of the flux rope in relation to the CME shell causes a distinct deformation of the white-light CME front and shock. Title: CME-driven Shock and Type II Solar Radio Burst Band Splitting Authors: Chrysaphi, Nicolina; Kontar, Eduard P.; Holman, Gordon D.; Temmer, Manuela Bibcode: 2018ApJ...868...79C Altcode: 2018arXiv181008026C Coronal mass ejections (CMEs) are believed to be effective in producing shocks in the solar corona and interplanetary space. One of the important signatures of shocks and shock acceleration are Type II solar radio bursts that drift with the shock speed and produce bands of fundamental and higher harmonic plasma radio emission. An intriguing aspect of Type II radio bursts is the occasional split of a harmonic band into thinner lanes, known as band splitting. Here we report a detailed imaging and spectroscopic observation of a CME-driven shock producing band splitting in a Type II burst. Using LOFAR, we examine the spatial and temporal relation of the Type II burst to the associated CME event, use source imaging to calculate the apparent coronal density, and demonstrate how source imaging can be used to estimate projection effects. We consider two widely accepted band-splitting models that make opposing predictions regarding the locations of the true emission sources with respect to the shock front. Our observations suggest that the locations of the upper and lower subband sources are spatially separated by ∼0.2 ± 0.05 R ⊙. However, we quantitatively show, for the first time, that such separation is consistent with radio-wave scattering of plasma radio emission from a single region, implying that the split-band Type II sources could originate from nearly cospatial locations. Considering the effects of scattering, the observations provide supporting evidence for the model that interprets the band splitting as emission originating in the upstream and downstream regions of the shock front, two virtually cospatial areas. Title: Coronal holes detection using supervised classification Authors: Delouille, Veronique; Hofmeister, Stefan; Reiss, Martin; Mampaey, Benjamin; Temmer, Manuela; Veronig, Astrid Bibcode: 2018csc..confE..93D Altcode: We demonstrate the use of machine learning algorithms in combination with segmentation techniques in order to distinguish coronal holes and filaments in solar EUV images. We used the Spatial Possibilistic Clustering Algorithm (SPoCA) to prepare data sets of manually labeled coronal hole and filament channel regions present on the Sun during the time range 2010-2016. By mapping the extracted regions from EUV observations onto HMI line-of-sight magnetograms we also include their magnetic characteristics. We computed average latitude, area, shape measures from the segmented binary maps as well as first order, and second order texture statistics from the segmented regions in the EUV images and magnetograms. These attributes were used for data mining investigations to identify the most performant rule to differentiate between coronal holes and filament channels, taking into account the imbalance in our dataset which contains one filament channel for 15 coronal holes. We tested classifiers such as Support Vector Machine, Linear Support Vector Machine, Decision Tree, k-Nearest Neighbors, as well as ensemble classifier based on Decision Trees. Best performance in terms of True Skill Statistics are obtained with cost-sensitive learning, Support Vector Machine classifiers, and when HMI attributes are included in the dataset. Title: The photospheric structure of coronal holes: magnetic elements Authors: Hofmeister, Stefan; Utz, Dominik; Heinemann, Stephan; Veronig, Astrid; Temmer, Manuela Bibcode: 2018csc..confE.129H Altcode: Coronal holes attracted recently more attention by the scientific community as they represent the source region for the fast solar wind which is ifself an important ingredient in understanding the space environment and space weather. Nevertheless, our knowledge about the detailed magnetic field structure below coronal holes is quite limited, maybe since such a research would necessarily involve the high atmospheric and photospheric community. In this contribution we would like to bridge this gap and investigate in detail the magnetic field distribution below coronal holes and its relationship to the large-scale coronal hole topology. To do so, we investigate the distribution and properties of photospheric magnetic elements below 106 low and medium latitude coronal holes using SDO/HMI line-of-sight magnetogram data from 2010 to 2016, and relate them to the overall properties of the coronal holes. Since magnetic elements produce clearly visible photospheric structures, they can be well observed and give us valuable insights into the structure of coronal holes. We find that the distribution of the magnetic flux of magnetic elements follows an exponential function. The area and flux of magnetic elements are strongly related to each other by a power law with an exponent of 1.25. The larger magnetic elements are located at the edges of the magnetic network and seem to be the "core" structure of coronal holes. They have lifetimes > 4 days, i.e., longer than the timescale of the supergranulation. Further, they contain up to 50 magnetic bright points as observed by Hinode/SOT in the G-Band, meaning that the large magnetic elements are large clusters of individual magnetic elements. The mean magnetic field density of the overall coronal holes and thus their unbalanced magnetic flux is determined by their percentage coverage with magnetic elements at cc=0.98. Since magnetic elements are the foot points of magnetic funnels and thus the small-scale source regions of high-speed solar wind streams, the dependence of the coverage with magnetic elements on the strength of coronal holes also explains the dependence of the plasma density of high-speed streams near the Sun to the strength of its source coronal hole. The rotation rates of the magnetic elements match the rotation rate of the coronal hole and is surprisingly similar to the differential rotation rate of active regions at low- and medium latitudes, suggesting they are rooted at similar deep layers. This also means that coronal holes do not show an abnormal rotation rate as suggested by various authors. Finally, by projecting the magnetic elements to AIA-171 and 193 filtergrams, we surprisingly find that the magnetic elements are not located in the darkest regions of coronal holes. Therefore, the vertical plasma outflow from magnetic funnels is probably not the primary reason why coronal holes appear as dark patches in EUV images. We conclude that magnetic elements are the basic building blocks of coronal holes which completely determine their magnetic properties. Title: Evolution of flux rope, CME and associated EUV wave in the 10-Sep-2018 X8.2 event Authors: Podladchikova, Tatiana; Veronig, Astrid M.; Dissauer, Karin; Temmer, Manuela; Seaton, Daniel B.; Long, David; Guo, Jingnan; Vršnak, Bojan; Harra, Louise; Kliem, Bernhard Bibcode: 2018csc..confE..38P Altcode: We combine the high-cadence and large field-of-view EUV imagery of the Atmospheric Imaging Assembly (AIA) onboard SDO and the Solar Ultraviolet Imager (SUVI) onboard GOES-16 to study the origin and impulsive evolution of the fast CME that originated in the September 10th 2017 X8.2 event as well as the initiation of the associated EUV wave. In the LASCO field-of-view, the CME reveals speeds >3000 km/s. In the low-to-mid corona, it shows a distinct bubble in the EUV imagery that reveals a significant lateral overexpansion. In addition, is also shows a distinct expanding cavity that is interpreted as manifestation of the flux rope driving the eruption. We present a method to automatically identify and segment the CME bubble in SUVI images and to derive its radial and lateral evolution up to about 2 solar radii, in terms of velocity and acceleration. These measurements are set into context with the evolution of the embedded flux rope/cavity observed by AIA. The observations show clear signatures of new poloidal flux added to the flux rope by magnetic reconnection in the current sheet beneath the eruptive structure, which is important for the high accelerations observed in this event. The radial propagation of the CME shell revealed a peak value of the acceleration of about 5.3 km/s2, whereas the lateral expansion reached a peak value of 10.1 km/s2, which is the largest value reported so far. The flux rope/cavity reveals a radial acceleration of 6.7 km/s2 and lateral acceleration of 5.3 km/s2. We note that at this early evolution phase, the speed of the cavity/flux rope is higher than that of the CME bubble (front). The EUV wave associated with this eruption was observed by AIA, SUVI and STEREO-A EUVI, which had a separation angle with Earth of 128°, and the common field of view of the spacecraft was 52°. AIA and SUVI images above the solar limb reveal the initiation of the EUV wave by the accelerating flanks of the CME bubble, followed by detachment and propagation of the wave with a speed of 1100 km/s. The EUV wave shows a global propagation over the full hemisphere visible to Earth view as well as into the STEREO-A field-of-view. We study the propagation and kinematics of the direct as well as the various reflected and refracted EUV wave components on the solar sphere, finding speeds in the range from 370 to 1010 km/s. Finally, we note that this EUV wave is also distinct as it reveals propagation and transmission through the polar coronal holes. Title: Studying the dynamics of coronal dimmings and their relationship to flares and coronal mass ejections Authors: Dissauer, Karin; Veronig, Astrid M.; Temmer, Manuela; Podladchikova, Tatiana; Vanninathan, Kamalam Bibcode: 2018csc..confE..26D Altcode: Coronal dimmings are observed as localized regions of reduced emission in the EUV and soft X-rays, interpreted as density depletions due to mass loss during the CME expansion. They contain crucial information on the evolution and early propagation phase of CMEs low in the corona. For a set of 62 dimming events, characteristic parameters, describing their dynamics, morphology, magnetic properties and the brightness evolution are derived, statistically analyzed and compared with basic flare and CME quantities. We use optimized multi-point observations, where the on-disk dimming evolution is studied in high-cadence SDO/AIA filtergrams and SDO/HMI line-of-sight magnetograms, while STEREO/EUVI, COR1 and COR2 data is used to measure the associated CME kinematics close to the limb with low projection effects. For 60% of the events we identified core dimmings, i.e. potential footpoints of the erupting CME structure. These regions contain 20% of the magnetic flux covering only 5% of the total dimming area. The majority of the total dimming area consists of secondary dimmings mapping overlying fields that are stretched during the eruption and closed down by magnetic reconnection, thus adding flux to the erupting structure via magnetic reconnection. This interpretation is supported by the high correlation between the magnetic fluxes of secondary dimmings and flare reconnection fluxes (c=0.63±0.08), the balance between positive and negative magnetic fluxes (c=0.83±0.04) within the total dimmings and the fact that for strong flares (>M1.0) the flare reconnection and secondary dimming fluxes are roughly equal. The area of the total dimming, i.e. including both core and secondary dimmmings, its total brightness and the total unsigned magnetic flux show the highest correlations with the flare fluence (c>0.7) and the CME mass (c>0.6). Their corresponding time derivatives, describing the dimming dynamics, strongly correlate with the GOES flare class (c>0.6). Events where high-cadence observations from STEREO are available show a moderate correlation between the area growth rate of the dimming and the maximum speed of the CME. Title: Multiple Satellite Analysis of the Earth's Thermosphere and Interplanetary Magnetic Field Variations Due to ICME/CIR Events During 2003-2015 Authors: Krauss, S.; Temmer, M.; Vennerstrom, S. Bibcode: 2018JGRA..123.8884K Altcode: 2018arXiv181102999K We present a refined statistical analysis based on interplanetary coronal mass ejections (ICMEs) as well as corotating interaction regions (CIRs) for the time period 2003-2015 to estimate the impact of different solar wind types on the geomagnetic activity and the neutral density in the Earth's thermosphere. For the time-based delimitation of the events, we rely on the catalog maintained by Richardson and Cane and the corotating interaction region lists provided by S. Vennerstrom and Jian et al. (2011, https://doi.org/10.1007/s11207-011-9737-2). These archives are based on in situ measurements from the Advanced Composition Explorer and/or the Wind spacecraft. On this basis, we thoroughly investigated 196 Earth-directed ICME and 195 CIR events. To verify the impact on the Earths thermosphere we determined neutral mass densities by using accelerometer measurements collected by the low-Earth-orbiting satellites Gravity Recovery and Climate Experiment and Challenging Minisatellite Payload. Subsequently, the atmospheric densities are related to characteristic ICME parameters. In this process a new calibration method has been examined. Since increased solar activity may lead to a decrease of the satellites orbital altitude we additionally assessed the orbital decay for each of the events and satellites. The influence of CIR events is in the same range of magnitude as the majority of the ICMEs (186 out of 196). Even though, the extended investigation period between 2011 and 2015 has a lack of extreme solar events the combined analysis reveals comparable correlation coefficients between the neutral densities and the various ICME and geomagnetic parameters (mostly >0.85). The evaluation of orbit decay rates at different altitudes revealed a high dependency on the satellite actual altitude. Title: Hard X-ray Diagnostic of Proton Producing Solar Flares Compared to Other Emission Signatures Authors: Miteva, Rositsa; Koleva, Kostadinka; Dechev, Momchil; Veronig, Astrid; Kozarev, Kamen; Temmer, Manuela; Dissauer, Karin; Duchlev, Peter Bibcode: 2018PASRB..18..117M Altcode: We present results on the correlation analysis between the peak intensity of the in situ proton events from SOHO/ERNE instrument and the properties of their solar origin, solar flares and coronal mass ejections (CMEs). Starting at the RHESSI mission launch after 2002, 70 flares well-observed in hard X-rays (HXRs) that are also accompanied with in situ proton events are selected. In addition to HXRs, flare emission at several other wavelengths, namely in the soft X-ray (SXR), ultraviolet (UV) and microwave (MW), is used. We calculated Pearson correlation coefficients between the proton peak intensities from one side, and, from another, the peak flare flux at various wavelengths or the speed of the accompanied CME. We obtain the highest correlations with the CME speed, with the SXR flare class and with MWs, lower ones with the SXR derivative, UV and 12-50 keV HXRs and the lowest correlation coefficients are obtained with the 50-300 keV HXRs. Possible interpretations are discussed. Title: Three-phase Evolution of a Coronal Hole. II. The Magnetic Field Authors: Heinemann, Stephan G.; Hofmeister, Stefan J.; Veronig, Astrid M.; Temmer, Manuela Bibcode: 2018ApJ...863...29H Altcode: 2018arXiv180610052H We investigate the magnetic characteristics of a persistent coronal hole (CH) extracted from EUV imagery using Heliospheric and Magnetic Imager filtergrams over the period 2012 February-October. The magnetic field, its distribution, and the magnetic fine structure in the form of flux tubes (FTs) are analyzed in different evolutionary states of the CH. We find a strong linear correlation between the magnetic properties (e.g., signed/unsigned magnetic field strength) and the area of the CH. As such, the evolutionary pattern in the magnetic field clearly follows a three-phase evolution (growing, maximum, and decaying) as found from EUV data (Part I). This evolutionary process is most likely driven by strong FTs with a mean magnetic field strength exceeding 50 G. During the maximum phase they entail up to 72% of the total signed magnetic flux of the CH, but only cover up to 3.9% of the total CH area, whereas during the growing and decaying phases, strong FTs entail 54%-60% of the signed magnetic flux and cover around 1%-2% of the CH’s total area. We conclude that small-scale structures of strong unipolar magnetic field are the fundamental building blocks of a CH and govern its evolution. Title: Filament Eruptions Associated with Flares, Coronal Mass Ejections and Solar Energetic Particle Events Authors: Koleva, K.; Duchlev, P.; Dechev, M.; Miteva, R.; Kozarev, K.; Veronig, A.; Temmer, M. Bibcode: 2018simi.conf...19K Altcode: We present analysis of three cases of filament eruptions (FEs) that occurred on 04 Aug 2011, 09 Nov 2011 and 05 Apr 2012 and their associations with flares as sources of solar energetic particles (SEPs) and coronal mass ejections. The associated FEs and SEP-related solar flares were selected by simultaneous observations in X-ray, EUV and radio wavelengths. Title: Statistics of Coronal Dimmings Associated with Coronal Mass Ejections. I. Characteristic Dimming Properties and Flare Association Authors: Dissauer, K.; Veronig, A. M.; Temmer, M.; Podladchikova, T.; Vanninathan, K. Bibcode: 2018ApJ...863..169D Altcode: 2018arXiv180705056D Coronal dimmings, localized regions of reduced emission in the extreme-ultraviolet and soft X-rays (SXRs), are interpreted as density depletions due to mass loss during the coronal mass ejection (CME) expansion. They contain crucial information on the early evolution of CMEs low in the corona. For 62 dimming events, characteristic parameters are derived, statistically analyzed, and compared with basic flare quantities. On average, coronal dimmings have a size of 2.15 × 1010 km2, contain a total unsigned magnetic flux of 1.75 × 1021 Mx, and show a total brightness decrease of -1.91 × 106 DN, which results in a relative decrease of ∼60% compared to the pre-eruption intensity level. Their main evacuation phase lasts for ∼50 minutes. The dimming area, the total dimming brightness, and the total unsigned magnetic flux show the highest correlation with the flare SXR fluence (c ≳ 0.7). Their corresponding time derivatives, describing the dimming dynamics, strongly correlate with the GOES flare class (c ≳ 0.6). For 60% of the events we identified core dimmings, i.e., signatures of an erupting flux rope. They contain 20% of the magnetic flux covering only 5% of the total dimming area. Secondary dimmings map overlying fields that are stretched during the eruption and closed down by magnetic reconnection, thus adding flux to the erupting flux rope via magnetic reconnection. This interpretation is supported by the strong correlation between the magnetic fluxes of secondary dimmings and flare reconnection fluxes (c = 0.63 ± 0.08), the balance between positive and negative magnetic fluxes (c = 0.83 ± 0.04) within the total dimmings, and the fact that for strong flares (>M1.0) the reconnection and secondary dimming fluxes are roughly equal. Title: Dynamcis and magnetic properties in coronal holes using high-resolution multi-instrument solar observations Authors: Krikova, K.; Utz, D.; Veronig, A.; Gömöry, P.; Hofmeister, S.; Temmer, M. Bibcode: 2018simi.conf...31K Altcode: Using high-resolution solar observations from the Hinode Instruments SOT/SP, EIS and XRT as well as IRIS from a coronal hole on the 26th of September 2017, we are investigating the dynamics within the coronal hole visible on the specified date. Further satellite data support is given by full disc images from SDO with the AIA and HMI instruments. EIS and IRIS data provide us with crucial information about the plasma and energy flow from the Sun's chromosphere into the corona using the EUV and UV spectra and images. Investigating the magnetic configuration as well as the dynamics and changes within the coronal hole by using the SOT/SP data will give us additional crucial insights about the physical processes leading to the corresponding changes in the higher atmosphere. We compare the Hinode data with AIA and HMI data to get a firm comprehensive picture about the connection from high resolved photospheric fields and its dynamics within the higher layer. Within the timeframe of the analysed EIS dataset two microflare events associated with a solar jet were captured, originating inside the coronal hole under investigation. We believe that it is totally worthwhile to study these features in full detail as not so much attention was paid to high energy processes within coronal holes and their basic relationship to the harboring coronal hole and they show surprisingly high downflows in the Fe XII iron line (up to 140 km/s). In the current proceeding we will outline the state of the art of this investigation and give an overview of the further steps necessary. The mentioned data were obtained during a recent GREGOR campaign with the joint support of IRIS and Hinode (HOP 338). Title: Modeling the Evolution and Propagation of 10 September 2017 CMEs and SEPs Arriving at Mars Constrained by Remote Sensing and In Situ Measurement Authors: Guo, Jingnan; Dumbović, Mateja; Wimmer-Schweingruber, Robert F.; Temmer, Manuela; Lohf, Henning; Wang, Yuming; Veronig, Astrid; Hassler, Donald M.; Mays, Leila M.; Zeitlin, Cary; Ehresmann, Bent; Witasse, Olivier; Freiherr von Forstner, Johan L.; Heber, Bernd; Holmström, Mats; Posner, Arik Bibcode: 2018SpWea..16.1156G Altcode: 2018arXiv180300461G On 10 September 2017, solar energetic particles originating from the active region 12673 produced a ground level enhancement at Earth. The ground level enhancement on the surface of Mars, 160 longitudinally east of Earth, observed by the Radiation Assessment Detector (RAD) was the largest since the landing of the Curiosity rover in August 2012. Based on multipoint coronagraph images and the Graduated Cylindrical Shell model, we identify the initial 3-D kinematics of an extremely fast coronal mass ejection (CME) and its shock front, as well as another two CMEs launched hours earlier with moderate speeds. The three CMEs interacted as they propagated outward into the heliosphere and merged into a complex interplanetary CME (ICME). The arrival of the shock and ICME at Mars caused a very significant Forbush decrease seen by RAD only a few hours later than that at Earth, which was about 0.5 AU closer to the Sun. We investigate the propagation of the three CMEs and the merged ICME together with the shock, using the drag-based model and the WSA-ENLIL plus cone model constrained by the in situ observations. The synergistic study of the ICME and solar energetic particle arrivals at Earth and Mars suggests that to better predict potentially hazardous space weather impacts at Earth and other heliospheric locations for human exploration missions, it is essential to analyze (1) the eruption of the flare and CME at the Sun, (2) the CME kinematics, especially during their interactions, and (3) the spatially and temporally varying heliospheric conditions, such as the evolution and propagation of the stream interaction regions. Title: What can we learn from coronal dimmings about the early evolution of Earth-directed CMEs? Authors: Dissauer, Karin; Podladchikova, Tatiana; Vanninathan, Kamalam; Veronig, Astrid; Temmer, Manuela Bibcode: 2018cosp...42E.846D Altcode: Earth-directed coronal mass ejections (CMEs) are the main drivers for severe space weather events affecting the near-Earth environment. However, they allow the least accurate measurements of their properties due to strong projection effects and especially their early evolution is not well observed with traditional coronagraphs.The most distinct phenomena associated with CMEs are coronal dimmings, i.e. localized regions of reduced emission in the extreme-ultraviolet (EUV) and soft X-rays low in the corona. They are interpreted as density depletions due to mass loss or rapid expansion of the overlying corona during the CME lift off.We extract characteristic parameters describing the dynamics, morphology, magnetic properties and the brightness evolution of coronal dimming regions in order to obtain additional information on the initiation and early evolution of Earth-directed CMEs. To this aim, we developed an automatic dimming detection algorithm (based on logarithmic base-ratio images) that allows us also to distinguish between core and secondary dimming regions. Using this newly developed method, we extract the physical properties of 76 coronal dimming events in optimized multi-point observations and compare them with characteristic parameters describing their corresponding CMEs. The on-disk dimming evolution is studied using the high-cadence, multi-wavelengths data of SDO/AIA and the line-of-sight (LOS) magnetograms of SDO/HMI, while STEREO/EUVI, COR1 and COR2 data is used to measure the associated CME close to the limb with low projection effects.The impulsive phase of the dimming (i.e. main expansion phase of its area) starts co-temporal with the onset of the CME and the associated flare and the overall dimming region expands around locations that are identified as core dimming regions. On average this main evacuation phase lasts for about 50 minutes. For the majority of events, the total unsigned magnetic flux involved in the dimming regions is balanced and for selected events up to 30% of this flux results from the localized core dimming regions covering only ∼10% of the total dimming area. The size of the total dimming region, the total unsigned magnetic flux, as well as its intensity decrease are strongly correlated with the CME mass. Events where high-cadence observations from STEREO are available show in addition also a moderate correlations between the growth rate of the dimming and the maximum speed of the CME. Title: The September 2017 events and their imprints at Earth, Mars and STEREO-A Authors: Guo, Jingnan; Wang, Yuming; Mays, M. Leila; Heber, Bernd; Holmstroem, Mats; Ehresmann, Bent; Olivier Witasse, .; Zeitlin, Cary; Taut, Andreas; Veronig, Astrid; Wimmer-Schweingruber, Robert; Dumbovic, Mateja; Lohf, Henning; Temmer, Manuela; Hassler, Donald M.; von Forstner, Johan Lauritz Freiherr Bibcode: 2018cosp...42E1321G Altcode: During the declining phase of the current solar cycle, heliospheric activity has suddenly and drastically increased starting from a simple sunspot in Active Region (AR) 2673, which transformed into a complex region with three X-class flares accompanied by several Earth-directed Coronal Mass Ejections (CME) from 4th to 6th of September. Only a few days later, on 10th September, the same AR 2673 produced solar energetic particles (SEPs) which were registered as a ground level enhancement (GLE) at Earth and the biggest GLE on the surface of Mars as observed by the Radiation Assessment Detector (RAD) since the landing of the Curiosity rover in August 2012. Both Earth and Mars saw an impulsive and intense enhancement of the accelerated protons with energies larger than hundreds of MeV whereas STEREO-A, despite being at the back side of the event, detected gradually increasing fluxes of particles transported there across the heliospheric magnetic field. These high energy particles were mainly accelerated by the flares and shocks which were associated with three consecutive CMEs launched on 9th and 10th of September. Based on STEREO-A and SOHO coronograph images, we identified the initial three-dimensional kinematics of the three CMEs using the Graduated Cylindrical Shell (GCS) model. The first two CMEs had moderate launch speeds while the last one was extremely fast (larger than 2500 km/s at 20 solar radii). These three CMEs interacted as they propagated outwards into the heliosphere and the resulting complex interplanetary CME (ICME) together with its associated shock was highly likely related to the effective acceleration of particles at such high energies causing GLE at both Earth and Mars. The arrival of the ICME at Mars caused a very significant Forbush decrease seen by the Radiation Assessment Detector (RAD) on the surface of Mars and the arrival time is only a few hours later than that at Earth which is about 0.5 AU closer to the Sun than Mars. We investigated the interaction of three CMEs and propagation of the consequent ICME using the Drag Based Model (DBM) as well as the WSA-ENLIL plus cone model and the simulated results are compared with in-situ measurements at both Earth and Mars. The comparison shows that in order to better predict the ICME arrival and its potential space weather impact at Earth and other heliospheric locations, it is essential to 1) analyze the evolution of the ICME kinematics, especially during interactions of different CMEs and 2) better understand the spatially and temporally varying interplanetary conditions of the heliosphere. Title: Development of adaptive Kalman filter for solar wind forecast Authors: Podladchikova, Tatiana; Veronig, Astrid; Temmer, Manuela; Hofmeister, Stefan Bibcode: 2018cosp...42E2698P Altcode: Accurate solar wind modeling is important for predicting the arrival and geomagnetic response of high-speed solar wind streams as well as for modeling the transit of coronal mass ejections in interplanetary space and their impact at Earth. Data assimilation techniques combining the strength of models and observations provide a very useful tool for accurate solar wind forecasts. We develop a method to predict the solar wind speed at Earth 1-day ahead by using coronal hole areas derived from SDO AIA images in combination with in situ solar wind plasma and field data (speed, density, and magnetic field magnitude) from ACE and Wind spacecraft. To forecast the solar wind speed, we form a multidimensional linear regression model relating the solar wind speed one day ahead with the fractional coronal hole area observed three days before the current moment, as well as proton density, magnetic field magnitude, and solar wind speed at the current moment. One of the major concerns with such data assimilation scheme is that the regression coefficients do not remain constant and are time-varying. To avoid the fitting of regression coefficients to a particular situation, that can be changed in future, we develop an adaptive Kalman filter to create a dynamic linear regression for the 1-day ahead prediction of the solar wind speed. Testing the developed forecasting technique for the period 2010-2017, we obtain a correlation coefficient between the predicted and observed solar wind speed of 0.93, with an RMS error of prediction of 33 km/s. These results demonstrate that the proposed adaptive Kalman filter method significantly improves the quality of the solar wind forecasts and can be applied for reliable real-time warnings of the space weather conditions in the near-Earth environment. Title: CME acceleration and EUV wave kinematics for September 10th 2017 event Authors: Podladchikova, Tatiana; Dissauer, Karin; Veronig, Astrid; Temmer, Manuela; Seaton, Daniel Bibcode: 2018cosp...42E2697P Altcode: On September 10th 2017 a large solar eruption, accompanied by an X8.2 solar flare, from NOAA active region 12673 was observed on the Sun's western limb by the new Solar Ultraviolet Imager (SUVI) on the GOES-16 spacecraft. We present a method to identify the CME bubble shape and to determine its radial and lateral acceleration. The large field of view of SUVI allows us to study the early impulsive CME acceleration up to 2 solar radii. The CME bubble reveals a fast evolution and strong overexpansion. The radial propagation of the CME revealed a peak value of the acceleration of about 4.8 km/s^{2}, whereas the lateral expansion reached a peak value of 8.9 km/s^{2}. The EUV wave associated with this eruption was observed by SUVI and STEREO-A, which had a separation angle with Earth of 128°, and the common field of view of both spacecraft was 52°. SUVI images above the solar limb reveal the initiation of the EUV wave by the accelerating flanks of the CME bubble, followed by detachment and propagation of the wave with a speed of 1100 km/s. Above the limb, the wave front can be observed as high as 0.7 solar radii. The EUV wave shows a global propagation over the full SUVI disk as well as into the STEREO-A field-of-view, and can be followed up to distances of about 1727 Mm from the source region. We study the propagation and kinematics of the direct as well as the various reflected and refracted EUV wave components on the solar sphere, finding speeds in the range from 370 to 1010 km/s. Finally, we note that this EUV wave is also distinct as it reveals propagation and transmission through a polar coronal hole. Title: Coronal mass ejections and space weather effects Authors: Temmer, Manuela Bibcode: 2018cosp...42E3354T Altcode: Earth-directed coronal mass ejections (CMEs), with their embedded magnetic fields and shocks ahead, compress and reconnect with the Earth's magnetic field and are the main drivers of strong geomagnetic storms. The impact of strong events may endanger critical ground-based infrastructure like power grids or disrupt communication and navigation systems. Due to such Space Weather effects, CMEs and related phenomena are an area of intense research interest. Important scientific knowledge could be achieved by closely monitoring and investigating the Sun-to-Earth "chain of action" of solar activity (evolution of surface magnetic fields, flares and CMEs), measurements of near-Earth space (in-situ plasma and magnetic field, energetic particles) and geomagnetic activity (response of the magnetosphere and different atmospheric layers down to ground-induced currents). This overview talk covers and discusses our recent understanding of the physical processes about the initiation and propagation of CMEs, their interaction with the solar wind and other ejecta, and consequences for Space Weather. Title: Three-phase Evolution of a Coronal Hole. I. 360° Remote Sensing and In Situ Observations Authors: Heinemann, Stephan G.; Temmer, Manuela; Hofmeister, Stefan J.; Veronig, Astrid M.; Vennerstrøm, Susanne Bibcode: 2018ApJ...861..151H Altcode: 2018arXiv180609495H We investigate the evolution of a well-observed, long-lived, low-latitude coronal hole (CH) over 10 solar rotations in the year 2012. By combining extreme ultraviolet (EUV) imagery from the Solar TErrestrial RElations Observatories (STEREO-A/B) and the Solar Dynamics Observatory (SDO), we are able to track and study the entire evolution of the CH having a continuous 360° coverage of the Sun. The remote sensing data are investigated together with in situ solar wind plasma and magnetic field measurements from STEREO-A/B, the Advanced Composition Explorer (ACE), and WIND. From this, we obtain how different evolutionary states of the CH as observed in the solar atmosphere (changes in EUV intensity and area) affect the properties of the associated high-speed stream measured at 1 au. Most distinctly pronounced for the CH area, three development phases are derived: (a) growing, (b) maximum, and (c) decaying phase. During these phases the CH area (a) increases over a duration of around three months from about 1 · 1010 km2 to 6 · 1010 km2, (b) keeps a rather constant area for about one month of >9 · 1010 km2, and (c) finally decreases in the following three months below 1 · 1010 km2 until the CH cannot be identified anymore. The three phases manifest themselves also in the EUV intensity and in in situ measured solar wind proton bulk velocity. Interestingly, the three phases are related to a different range in solar wind speed variations, and we find for the growing phase a range of 460-600 km s-1, for the maximum phase 600-720 km s-1, and for the decaying phase a more irregular behavior connected to slow and fast solar wind speeds of 350-550 km s-1. Title: Observations of the solar chromosphere with ALMA and comparison with theoretical models Authors: Brajsa, Roman; Sudar, Davor; Skokic, Ivica; Benz, Arnold O.; Kuhar, Matej; Kobelski, Adam; Wedemeyer, Sven; White, Stephen M.; Ludwig, Hans-G.; Temmer, Manuela; Saar, Steven H.; Selhorst, Caius L. Bibcode: 2018csss.confE..37B Altcode: 2018arXiv181207293B In this work we use solar observations with the ALMA radio telescope at the wavelength of 1.21 mm. The aim of the analysisis to improve understanding of the solar chromosphere, a dynamic layer in the solar atmosphere between the photosphere andcorona. The study has an observational and a modeling part. In the observational part full-disc solar images are analyzed.Based on a modied FAL atmospheric model, radiation models for various observed solar structures are developed. Finally, theobservational and modeling results are compared and discussed. Title: Ensemble Prediction of a Halo Coronal Mass Ejection Using Heliospheric Imagers Authors: Amerstorfer, T.; Möstl, C.; Hess, P.; Temmer, M.; Mays, M. L.; Reiss, M. A.; Lowrance, P.; Bourdin, P. -A. Bibcode: 2018SpWea..16..784A Altcode: 2017arXiv171200218A The Solar TErrestrial RElations Observatory (STEREO) and its heliospheric imagers (HIs) have provided us the possibility to enhance our understanding of the interplanetary propagation of coronal mass ejections (CMEs). HI-based methods are able to forecast arrival times and speeds at any target and use the advantage of tracing a CME's path of propagation up to 1 AU and beyond. In our study, we use the ELEvoHI model for CME arrival prediction together with an ensemble approach to derive uncertainties in the modeled arrival time and impact speed. The CME from 3 November 2010 is analyzed by performing 339 model runs that are compared to in situ measurements from lined-up spacecraft MErcury Surface, Space ENvironment, GEochemistry, and Ranging and STEREO-B. Remote data from STEREO-B showed the CME as halo event, which is comparable to an HI observer situated at L1 and observing an Earth-directed CME. A promising and easy approach is found by using the frequency distributions of four ELEvoHI output parameters, drag parameter, background solar wind speed, initial distance, and speed. In this case study, the most frequent values of these outputs lead to the predictions with the smallest errors. Restricting the ensemble to those runs, we are able to reduce the mean absolute arrival time error from 3.5 ± 2.6 to 1.6 ± 1.1 hr at 1 AU. Our study suggests that L1 may provide a sufficient vantage point for an Earth-directed CME, when observed by HI, and that ensemble modeling could be a feasible approach to use ELEvoHI operationally. Title: Forbush decrease model for expanding CMEs (ForbMod) Authors: Dumbovic, Mateja; Möstl, Christian; Guo, Jingnan; Heber, Bernd; Vrsnak, Bojan; Temmer, Manuela Bibcode: 2018cosp...42E.917D Altcode: Forbush decreases (FDs) can be used as one of the "signatures" of an ICME passage. An analytical diffusion-expansion FD model (ForbMod) was developed that is based on the widely used approach of an initially empty, closed magnetic structure (i.e. flux rope) that fills up slowly with particles by diffusion perpendicular to the magnetic field of the flux rope. In our approach the FD amplitude is not only determined by the diffusion process but also by the expansion of the flux rope. While the first process leads to a smaller amplitude the second one leads again to a larger effect. Remote CME observations and 3D reconstruction is used to constrain initial and boundary conditions. CME evolutionary properties are taken into account by incorporating the flux rope expansion. Several options of flux rope expansion are regarded as competing mechanism to diffusion, which can lead to different FD characteristics, and forward modelling is used to analyse flux rope expansion and further constrain the model. In testing the model, a number of spacecraft and planetary observation is utilised, including those by the Radiation Assessment Detector aboard the Mars Rover Curiosity. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk_odowska-Curie grant agreement No 745782. Title: Modeling the evolution and propagation of the 2017 September 9th and 10th CMEs and SEPs arriving at Mars constrained by remote-sensing and in-situ measurement Authors: Guo, Jingnan; Dumbović, Mateja; Wimmer-Schweingruber, Robert F.; Temmer, Manuela; Lohf, Henning; Wang, Yuming; Veronig, Astrid; Hassler, Donald M.; Mays, Leila M.; Zeitlin, Cary; Ehresmann, Bent; Witasse, Olivier; von Forstner, Johan L. Freiherr; Heber, Bernd; Holmström, Mats; Posner, Arik Bibcode: 2018shin.confE..84G Altcode: On 2017-09-10, solar energetic particles (SEPs) originating from the active region 12673 were registered as a ground level enhancement (GLE) at Earth and the biggest GLE on the surface of Mars as observed by the Radiation Assessment Detector (RAD) since the landing of the Curiosity rover in August 2012. Based on multi-point coronagraph im- Title: Ideas and plans for ISWAT clusters focused on propagation of transients through evolving ambient heliosphere and input to geospace Authors: Temmer, Manuela Bibcode: 2018cosp...42E3353T Altcode: Space Weather is an important issue of global matter, but needs coordinated efforts. Many international groups perform research on the propagation of transients and based on that develop Space Weather forecasting services. In order to avoid duplication and to efficiently improve the performance of currently available models, they need to become better visible and to undergo scientific peer-review qualification. iSWAT is an international, community driven effort and provides the required platform to challenge propagation models and to exchange experience with peers. iSWAT is also a network that fosters collaboration among interdisciplinary group members, like from geospace, that are potential users of propagation models. Coordinated international cooperation will offer new perspectives and will make models more efficient and progress them efficiently towards operational tools. Operational tools are not only meant to be used by (industrial) end-users, but particularly by peers in order to get a more complete understanding of the physical processes underlying CME propagation. Title: Drag-based ensemble model (DBEM) Authors: Dumbovic, Mateja; Möstl, Christian; Mays, M. Leila; Vrsnak, Bojan; Veronig, Astrid; Salogovic, Jara; Piantschitsch, Isabell; Amerstorfer, Tanja; Temmer, Manuela; Sudar, Davor Bibcode: 2018cosp...42E.918D Altcode: The drag-based model (DBM) for heliospheric propagation of ICMEs is a widely used simple analytical model which can predict ICME arrival time and speed at a given heliospheric distance (Vr_nak et al., 2013, SolPhys). It is based on the assumption that the heliospheric propagation of ICMEs, is solely under the influence of MHD drag, where ICME propagation is determined based on CME properties as well as the properties of the ambient solar wind. The current version of the DBM is operational as part of ESA's SSA programme (http://swe.ssa.esa.int/web/guest/graz-dbm-federated). The DBM takes into account the ICME geometry to track the whole leading edge of an ICME, it can estimate whether or not an ICME will reach the observer and calculate the transit time and impact speed. To estimate the uncertainty for a single event, Drag-Based Ensemble Model (DBEM) was developed (Dumbovic et al., 2018, ApJ) which utilizes an ensemble of the observation-based CME input and synthetic values of the ambient solar wind speed and drag parameter. Using multiple runs with different input parameters, distributions of predicted arrival times and speeds are obtained allowing to forecast the confidence in the likelihood of the ICME arrival. The DBEM was further developed to an on-line application to provide the real-time CME forecast, which is currently in a test phase, and will soon be a part of ESA-SSA Heliospheric Weather Expert Service Group (http://swe.ssa.esa.int/heliospheric-weather). We test the model and the on-line application using observations and compare the performance with other CME propagation models. Title: Predicting a CME arrival as observed from L1 by heliospheric imagers using ELEvoHI Authors: Amerstorfer, Tanja; Moestl, Christian; Mays, M. Leila; Hess, Phillip; Temmer, Manuela; Reiss, Martin Bibcode: 2018cosp...42E..85A Altcode: The Lagrangian point L5 is expected to be an ideal location for a future operational space weather observatory, already indicated by The Solar TErrestrial RElations Observatory (STEREO). STEREO has improved our understanding on the interplanetary (IP) evolution of coronal mass ejections (CMEs). Especially the wide-angle heliospheric imagers (HI) facilitated the development of a variety of methods for analyzing the evolution of CMEs through IP space. In this study, we present an ensemble forecast based on 339 model runs using the HI-based CME prediction tool ELEvoHI and test if an HI observer located at L1 may be an appropriate alternative (or supplement) to an L5 HI observatory. ELEvoHI, the ELlipse Evolution model (ELEvo) based on HI observations uses the benefits of different methods and observations. It provides the possibility to adjust the CME frontal shape (angular width, ellipse aspect ratio) and the direction of motion for each CME event individually. This information can be gained from Graduated Cylindrical Shell (GCS) flux-rope fitting within coronagraph images. Using the ELlipse Conversion (ELCon) method, the observed HI elongation angle is converted into a unit of distance, which reveals the kinematics (including the initial time, distance and speed) of the event. After fitting the time-distance profile of the CME using the drag-based equation of motion, where real-time in situ solar wind speed from 1 AU is used as additional input, we obtain all input parameters needed to run a forecast using the ELEvo model and to predict arrival times and speeds at any target of interest in IP space. Here, we present a test on a slow CME event of 3 November 2010, in situ detected by the lined-up spacecraft MESSENGER and STEREO-B and remotely observed by STEREO-B/HI, i.e. it was a halo CME for STEREO-B. These conditions simulate an Earth-directed CME observed by HI located at L1. Our study suggests that L1 may provide a sufficient vantage point for an Earth-directed CME, when observed by HI, and that ensemble modeling could be a feasible approach to use ELEvoHI operationally. Title: An Analytical Diffusion-Expansion Model for Forbush Decreases Caused by Flux Ropes Authors: Dumbović, Mateja; Heber, Bernd; Vršnak, Bojan; Temmer, Manuela; Kirin, Anamarija Bibcode: 2018ApJ...860...71D Altcode: 2018arXiv180500916D We present an analytical diffusion-expansion Forbush decrease (FD) model ForbMod, which is based on the widely used approach of an initially empty, closed magnetic structure (i.e., flux rope) that fills up slowly with particles by perpendicular diffusion. The model is restricted to explaining only the depression caused by the magnetic structure of the interplanetary coronal mass ejection (ICME). We use remote CME observations and a 3D reconstruction method (the graduated cylindrical shell method) to constrain initial boundary conditions of the FD model and take into account CME evolutionary properties by incorporating flux rope expansion. Several flux rope expansion modes are considered, which can lead to different FD characteristics. In general, the model is qualitatively in agreement with observations, whereas quantitative agreement depends on the diffusion coefficient and the expansion properties (interplay of the diffusion and expansion). A case study was performed to explain the FD observed on 2014 May 30. The observed FD was fitted quite well by ForbMod for all expansion modes using only the diffusion coefficient as a free parameter, where the diffusion parameter was found to correspond to an expected range of values. Our study shows that, in general, the model is able to explain the global properties of an FD caused by a flux rope and can thus be used to help understand the underlying physics in case studies. Title: An Event-Based Verification Scheme for the Real-Time Flare Detection System at Kanzelhöhe Observatory Authors: Pötzi, W.; Veronig, A. M.; Temmer, M. Bibcode: 2018SoPh..293...94P Altcode: In the framework of the Space Situational Awareness program of the European Space Agency (ESA/SSA), an automatic flare detection system was developed at Kanzelhöhe Observatory (KSO). The system has been in operation since mid-2013. The event detection algorithm was upgraded in September 2017. All data back to 2014 was reprocessed using the new algorithm. In order to evaluate both algorithms, we apply verification measures that are commonly used for forecast validation. In order to overcome the problem of rare events, which biases the verification measures, we introduce a new event-based method. We divide the timeline of the Hα observations into positive events (flaring period) and negative events (quiet period), independent of the length of each event. In total, 329 positive and negative events were detected between 2014 and 2016. The hit rate for the new algorithm reached 96% (just five events were missed) and a false-alarm ratio of 17%. This is a significant improvement of the algorithm, as the original system had a hit rate of 85% and a false-alarm ratio of 33%. The true skill score and the Heidke skill score both reach values of 0.8 for the new algorithm; originally, they were at 0.5. The mean flare positions are accurate within ±1 heliographic degree for both algorithms, and the peak times improve from a mean difference of 1.7 ±2.9 minutes to 1.3 ±2.3 minutes. The flare start times that had been systematically late by about 3 minutes as determined by the original algorithm, now match the visual inspection within −0.47 ±4.10 minutes. Title: "Chapter 15 - Coronal Holes Detection Using Supervised Classification Authors: Delouille, Véronique; Hofmeister, Stefan J.; Reiss, Martin A.; Mampaey, Benjamin; Temmer, Manuela; Veronig, Astrid Bibcode: 2018mlts.book..365D Altcode: We demonstrate the use of machine learning algorithms in combination with segmentation techniques in order to distinguish coronal holes and filaments in solar extreme ultraviolet (EUV) images recorded by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. We used the Spatial Possibilistic Clustering Algorithm to prepare datasets of manually labeled coronal hole and filament channel regions present on the Sun during the time range 2010-16. By mapping the extracted regions from EUV observations onto Helioseismic and Magnetic Imager (HMI) line-of-sight magnetograms, we also include their magnetic characteristics. We computed average latitude, area, and shape measures from the segmented binary maps, as well as first-order and second-order texture statistics from the segmented regions in the EUV images and magnetograms. These attributes were used for data-mining investigations to identify the best rule for differentiating between coronal holes and filame!

nt channels, taking into account the imbalance in our dataset, which contains 1 filament channel for 15 coronal holes. We tested classifiers such as support vector machine (SVM), linear SVM, decision tree, k-nearest neighbors, as well as an ensemble classifier based on decision trees. The best performance in terms of true skill statistics is obtained with cost-sensitive learning, SVM classifiers, and when HMI attributes are included in the dataset. Title: A Comparative Study between a Failed and a Successful Eruption Initiated from the Same Polarity Inversion Line in AR 11387 Authors: Liu, Lijuan; Wang, Yuming; Zhou, Zhenjun; Dissauer, Karin; Temmer, Manuela; Cui, Jun Bibcode: 2018ApJ...858..121L Altcode: 2018arXiv180400867L In this paper, we analyzed a failed and a successful eruption that initiated from the same polarity inversion line within NOAA AR 11387 on 2011 December 25. They both started from a reconnection between sheared arcades, with distinct pre-eruption conditions and eruption details: before the failed one, the magnetic fields of the core region had a weaker non-potentiality; the external fields had a similar critical height for torus instability, and a similar local torus-stable region, but a larger magnetic flux ratio (of low corona and near-surface region) compared to the successful one. During the failed eruption, a smaller Lorentz force impulse was exerted on the outward ejecta; the ejecta had a much slower rising speed. Factors that might lead to the initiation of the failed eruption are identified: (1) a weaker non-potentiality of the core region, and a smaller Lorentz force impulse gave the ejecta a small momentum; (2) the large flux ratio, and the local torus-stable region in the corona provided strong confinements that made the erupting structure regain an equilibrium state. Title: Long-lasting injection of solar energetic electrons into the heliosphere Authors: Dresing, N.; Gómez-Herrero, R.; Heber, B.; Klassen, A.; Temmer, M.; Veronig, A. Bibcode: 2018A&A...613A..21D Altcode: 2018arXiv180204722D Context. The main sources of solar energetic particle (SEP) events are solar flares and shocks driven by coronal mass ejections (CMEs). While it is generally accepted that energetic protons can be accelerated by shocks, whether or not these shocks can also efficiently accelerate solar energetic electrons is still debated. In this study we present observations of the extremely widespread SEP event of 26 Dec 2013 To the knowledge of the authors, this is the widest longitudinal SEP distribution ever observed together with unusually long-lasting energetic electron anisotropies at all observer positions. Further striking features of the event are long-lasting SEP intensity increases, two distinct SEP components with the second component mainly consisting of high-energy particles, a complex associated coronal activity including a pronounced signature of a shock in radio type-II observations, and the interaction of two CMEs early in the event.
Aims: The observations require a prolonged injection scenario not only for protons but also for electrons. We therefore analyze the data comprehensively to characterize the possible role of the shock for the electron event.
Methods: Remote-sensing observations of the complex solar activity are combined with in situ measurements of the particle event. We also apply a graduated cylindrical shell (GCS) model to the coronagraph observations of the two associated CMEs to analyze their interaction.
Results: We find that the shock alone is likely not responsible for this extremely wide SEP event. Therefore we propose a scenario of trapped energetic particles inside the CME-CME interaction region which undergo further acceleration due to the shock propagating through this region, stochastic acceleration, or ongoing reconnection processes inside the interaction region. The origin of the second component of the SEP event is likely caused by a sudden opening of the particle trap. Title: STEREO-A persistence model for solar wind speed forecasting and uncertainty assessment from the evolution of coronal holes Authors: Temmer, Manuela; Hinterreiter, Jürgen; Reiss, Martin Bibcode: 2018EGUGA..20.3996T Altcode: We present the concept of a persistence model to forecast the solar wind speed at 1 AU, using the advantage of multi-viewpoint satellite data. The model is based on STEREO in-situ measurements for satellite positions eastward of Earth, shifted forward by a variable time span according to the angle of the STEREO spacecraft with Earth ( 2-10 days). The STEREO persistence model is applied on the time range 2008-2012 (STEREO-B) and 2017 (STEREO-A) and compared to a recurrence model based on ACE data forward shifted by a full rotation. In addition, the STEREO persistence model is modified by assessing the speed uncertainties that are caused by the evolution of coronal holes (CH). We derive the information on CH evolution by comparing CH areas extracted in EUV data from STEREO and Earth perspective. Compared to an ACE based persistence model, the performance of the new STEREO+CH persistence model which takes into account the evolution of coronal holes, is able to reduce the number of missed high-speed streams by about 23%, the false alarms by about 19%, and to increase the hit rate by about 12%. Title: Using Forbush decreases to derive the transit time of ICMEs propagating from 1 AU to Mars Authors: von Forstner, Johan; Guo, Jingnan; Wimmer-Schweingruber, Robert F.; Hassler, Donald M.; Temmer, Manuela; Dumbović, Mateja; Jian, Lan K.; Appel, Jan K.; Čalogović, Jaša; Ehresmann, Bent; Heber, Bernd; Lohf, Henning; Posner, Arik; Vršnak, Bojan; Zeitlin, Cary J. Bibcode: 2018EGUGA..20.9306V Altcode: The propagation of 15 interplanetary coronal mass ejections (ICMEs) from Earth's orbit (1 AU) to Mars (∼1.5 AU) has been studied with their propagation speed estimated from both measurements and simulations. The enhancement of magnetic fields related to ICMEs and their shock fronts cause the so-called Forbush decrease, which can be detected as a reduction of galactic cosmic ray (GCR) intensity measured on-ground or on a spacecraft. This effect can be used to detect the passage of ICMEs at various locations in the heliosphere, for example at Earth (using neutron monitors), the STEREO A and B spacecraft (HET) as well the on the surface of Mars using the Radiation Assessment Detector (RAD) instrument on the Mars Science Laboratory (MSL) rover. A set of ICME events has been selected during the periods when Earth (or STEREO A or B) and Mars locations were nearly aligned on the same side of the Sun in the ecliptic plane (so-called opposition phase). Such lineups allow us to estimate the ICMEs' transit times between 1 and 1.5 AU by determining the time delay between the corresponding Forbush decreases measured at each location. We investigate the evolution of the ICME propagation speeds before and after passing Earth's orbit and find that their deceleration due to interaction with the ambient solar wind may continue beyond 1 AU. We also find a substantial variance of the speed evolution among different events revealing the dynamic and diverse nature of eruptive solar events. Furthermore, the results are compared to simulation data obtained from two CME propagation models, namely the Drag-Based Model and ENLIL plus cone model. Title: Forbush decrease model for expanding CMEs (ForbMod) Authors: Dumbovic, Mateja; Temmer, Manuela; Guo, Jingnan; Heber, Bernd; Möstl, Christian; Vrsnak, Bojan Bibcode: 2018EGUGA..2015396D Altcode: The Project ForbMod aims to unravel how galactic cosmic rays are influenced by solar storms in the inner solar system (Sun to Mars) by developing a new model and utilizing a number of spacecraft and planetary observation, including those by the Radiation Assessment Detector aboard the Mars Rover Curiosity. The project focuses on Forbush decreases (FDs) in the galactic cosmic ray flux, which can be used as one of the "signatures" of an ICME passage. An analytical diffusion-expansion FD model was developed that is based on the widely used approach of an initially empty, closed magnetic structure (i.e. flux rope) that fills up slowly with particles by perpendicular diffusion. Remote CME observations and 3D reconstruction is used to constrain initial and boundary conditions. CME evolutionary properties are taken into account by incorporating the flux rope expansion. Several options of flux rope expansion are regarded as competing mechanism to diffusion, which can lead to different FD characteristics. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 745782. Title: Validation of the background solar wind modeled by EUHFORIA Authors: Hinterreiter, Jürgen; Temmer, Manuela; Verbeke, Christine; Poedts, Stefaan; Pomoell, Jens; Magdalenic, Jasmina; Scolini, Camilla; Rodriguez, Luciano; Kilpua, Emili; Asvestari, Eleanna Bibcode: 2018EGUGA..20.6533H Altcode: Nowadays, forecasting the arrival time and the geo-effectiveness of CMEs and the fast solar wind has become of increasing importance. For that reason, knowledge of the structure and propagation of the background solar wind is essential. The testing and validation of the performance of solar wind models is therefore important to assess their reliability and to further improve the models. This is done for the EUHFORIA (EUropean Heliospheric FORecasting Information Asset) model within the CCSOM (Constraining CMEs and Shocks by Observations and Modelling throughout the inner heliosphere) project [http://sidc.be/ccsom/]. We validate the modeled background solar wind by comparing the results to in-situ measurements, in order to make EUHFORIA ready for scientific exploitation and operational space weather purposes. For this several established test methods are applied on i) continuous variables of the solar wind plasma and magnetic field parameters (speed, density, pressure, Bz), and ii) binary variables based on specific events such as the arrival time and impact speed of solar wind high speed streams (HSS). We present first statistical results covering times of low (2008) and high (2012) solar activity. Title: The 3-Phase evolution of a long-lived low-latitude coronal hole. Authors: Heinemann, Stephan; Temmer, Manuela; Hofmeister, Stefan; Veronig, Astrid; Vennerstrom, Susanne Bibcode: 2018EGUGA..20.6670H Altcode: High speed solar wind streams (HSS) emanating from coronal holes, and associated stream interaction regions, may cause geomagnetic storms and deflect coronal mass ejections propagation in interplanetary space. By understanding the evolution and the relations between coronal holes and solar wind parameters, we increase our knowledge for improving space weather forecasts. We investigate the evolution of a persistent coronal hole using EUV data from STEREO-A/B and SDO over the timerange February 2012 -October 2012. Combined STEREO-SDO data enable a continuous observation of the CH covering 360° degrees over several rotations. Together with magnetic field measurements from SDO filtergrams and in-situ solar wind observations, we analyze during different evolutionary states of the CH, the solar surface properties of the CH (intensity, area, shape, magnetic flux) and its effects at 1AU (solar wind speed). As a result we find an evolutionary pattern in most parameters, clearly showing a three-phase evolution (growing, maximum and decaying phase). Title: Hard X-ray, EUV, and radio signatures in relation to solar energetic particles Authors: Koleva, Kostadinka; Miteva, Rositsa; Dechev, Momchil; Kozarev, Kamen; Veronig, Astrid; Temmer, Manuela Bibcode: 2018EGUGA..20.7408K Altcode: In this report we present analysis of well-observed electromagnetic signatures related to solar energetic particles (SEPs). We selected cases with simultaneous observations in hard X-ray, EUV and radio wavelengths of the SEP-related solar flares and analyzed the properties of the emission (light curves, spectrum and temporal evolution). The non-thermal potential of solar flares is tested in terms of correlation studies between the particle intensities (protons and electrons) and the flare flux at various wavelengths. The results are compared with the outcomes when using GOES soft X-ray flare class. The solar origin of SEP events in terms of solar flares is discussed. Title: The September 2017 events and their imprints at Earth and Mars Authors: Guo, Jingnan; Mays, Leila; Dumbovic, Mateja; Temmer, Manuela; Veronig, Astrid; Wimmer-Schweingruber, Robert; von Forstner, Johan Freiherr; Hassler, Donald; Heber, Bernd; Zeitlin, Cary; Ehresmann, Bent; Witasse, Oliver Bibcode: 2018EGUGA..2015655G Altcode: During the declining phase of the current quiet solar cycle, heliospheric activity has suddenly and drastically increased starting from a simple sunspot in Active Region (AR) 2673, which transformed into a complex region with three X-flares accompanied by several Earth-directed Coronal Mass Ejections (CME) from 4th to 6th of September. Four days later, on 10th September, the same AR produced solar energetic particles (SEPs) which were registered as a ground level enhancement (GLE) at Earth and the biggest GLE on the surface of Mars as observed by the Radiation Assessment Detector (RAD) since the landing of the Curiosity rover in August 2012. Both Earth and Mars saw an impulsive and intense enhancement of the accelerated protons with energies larger than hundreds of MeV whereas STEREO-A, despite being at the back-side of the event, detected gradually increasing fluxes of particles transported there across the heliospheric magnetic field. Such high energetic particles were mainly accelerated by shocks associated with the CMEs also launched on 10th of September. Three CMEs with similar longitudinal launch directions (between Earth and Mars with the central axis approximately 100 degrees from Earth and 40-50 degrees from Mars) can be identified based on STEREO-A and SOHO LASCO chronograph images. The first two had moderate launch speed while the last one had an extremely fast launch speed ( 2500 km/s). The merging and interactions of the three CMEs into an interplanetary CME (ICME) were very complex through the inner heliosphere and caused a very significant Forbush decrease at Mars three days later, even before the enhanced particle flux recovered to quiet-time level. The arrival of the ICME at Mars is only a few hours later than that at Earth, despite Mars being 0.5 AU further away from the Sun than Earth. This timing difference between the ICME arrival at Earth and Mars is likely due to (1) the earlier ICMEs from 4th and 6th which have considerably changed the interplanetary conditions and (2) the interaction of the ICME with a High Speed Stream structure passing by Mars. The 3D launch geometry and direction of the CMEs has been reconstructed based on the Graduated Cylindrical Shell (GCS) model and the subsequent ICME propagation has been performed using the WSA-ENLIL plus cone model, as well as the Drag Based Model (DBM) and CDPP propagation tool. Such modeled ICME arrivals at Earth and Mars are compared with in-situ measurements and the comparison shows that it is essential to consider the interactions of different CMEs as well as the spatially and temporally varying interplanetary conditions in order to better predict the ICME arrival at Earth and other planets. Title: Combining remote-sensing image data with in-situ measurements supported by modeling for Earth-affecting CME events Authors: Temmer, Manuela; Thalmann, Julia; Dissauer, Karin; Veronig, Astrid; Tschernitz, Johannes; Hinterreiter, Jürgen; Rodriguez, Luciano Bibcode: 2018EGUGA..20.3999T Altcode: We analyze the well observed flare-CME event from October 1, 2011 and cover the complete chain of action - from the Sun to Earth. We study in detail the solar surface and atmosphere (SDO and ground-based instruments) associated to the flare/CME and also track the off-limb CME signatures in interplanetary space (STEREO-SoHO). This is complemented by surface magnetic field information and 3D coronal magnetic field modeling. From in-situ measurements (Wind), we extract the corresponding ICME characteristics. Results show that the flare reconnection flux is most probably a lower limit for estimating the magnetic flux within the flux rope as 1) magnetic reconnection processes were already ongoing before the start of the impulsive flare phase and 2) the dimming flux increased by more than 25% after the end of the flare, indicating that magnetic flux was still added to the flux rope after eruption. When comparing this to the in-situ axial magnetic flux of the magnetic cloud, we find that it is reduced by at least 75%, referring to substantial erosion in interplanetary space. Careful inspection of on-disk features associated with CMEs are essential for interpreting such scenarios. Title: Case study of July 2017 CMEs using modelling and multi-spacecraft observational approach Authors: Dumbovic, Mateja; Guo, Jingnan; Temmer, Manuela Bibcode: 2018EGUGA..2015713D Altcode: We present the analysis of several CMEs that erupted mid-July 2017 from the same source region on the back side of the Sun as viewed from Earth. In our analysis, we use multi-instrument and multi-spacecraft measurements as well as different modeling approaches. We perform a 3D reconstruction of each CME, to find their respective directions, geometry and kinematics. We employ WSA/ENLIL simulations and DBM propagation model to better understand their interplanetary evolution and associate them to signatures observed at STEREO-A and Mars. At Mars, a two-step Forbush decrease is observed with MSL/RAD July 24 2017. With the amplitude of more than 15% this is one of the largest Forbush decreases detected at Mars. At STEREO-A in situ ICME signatures are observed July 24/25 2017. This ICME shows a remarkably high magnetic field strength of 60 nT, probably related to the inability to expand due to interaction. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 745782. Title: Tracking and validating ICMEs propagating towards Mars using STEREO Heliospheric Imagers combined with Forbush decreases detected by MSL/RAD Authors: von Forstner, Johan; Guo, Jingnan; Temmer, Manuela; Dumbović, Mateja; Hassler, Donald M. Bibcode: 2018EGUGA..2014376V Altcode: The enhancement of magnetic fields related to ICMEs and their shock fronts cause the so-called Forbush decrease, which can be detected as a reduction of galactic cosmic ray intensity (GCR) measured on-ground or on a spacecraft. Forbush decreases observed by the Radiation Assessment Detector (RAD) instrument onboard Mars Science Laboratory (MSL) on the surface of Mars as well as during its flight to Mars in 2011-2012 can be combined with observations at Earth and the two STEREO spacecraft to study the propagation of ICMEs up to Earth orbit and beyond to Mars. Our previous work (Freiherr von Forstner et al. 2017, JGR: Space Physics) considered the case where Earth (or STEREO A or B) and Mars were nearly forming a straight line with the Sun so that ICMEs can be observed in situ at both locations. We now also study periods where one or both of the STEREO spacecraft are positioned suitably to remotely track ICMEs directed towards Mars continuously with their coronagraph and heliospheric imaging instruments and compare the arrival signatures with the in situ detection of the Forbush decrease by MSL/RAD. By studying additional events in periods with this constellation, we enhance our investigation of the evolution of ICME propagation speeds through the inner heliosphere up to Mars. Title: Plasma Diagnostics of Coronal Dimming Events Authors: Vanninathan, Kamalam; Veronig, Astrid M.; Dissauer, Karin; Temmer, Manuela Bibcode: 2018ApJ...857...62V Altcode: 2018arXiv180206152V Coronal mass ejections are often associated with coronal dimmings, i.e., transient dark regions that are most distinctly observed in Extreme Ultra-violet wavelengths. Using Atmospheric Imaging Assembly (AIA) data, we apply Differential Emission Measure diagnostics to study the plasma characteristics of six coronal dimming events. In the core dimming region, we find a steep and impulsive decrease of density with values up to 50%-70%. Five of the events also reveal an associated drop in temperature of 5%-25%. The secondary dimming regions also show a distinct decrease in density, but less strong, decreasing by 10%-45%. In both the core and the secondary dimming the density changes are much larger than the temperature changes, confirming that the dimming regions are mainly caused by plasma evacuation. In the core dimming, the plasma density reduces rapidly within the first 20-30 minutes after the flare start and does not recover for at least 10 hr later, whereas the secondary dimming tends to be more gradual and starts to replenish after 1-2 hr. The pre-event temperatures are higher in the core dimming (1.7-2.6 MK) than in the secondary dimming regions (1.6-2.0 MK). Both core and secondary dimmings are best observed in the AIA 211 and 193 Å filters. These findings suggest that the core dimming corresponds to the footpoints of the erupting flux rope rooted in the AR, while the secondary dimming represents plasma from overlying coronal structures that expand during the CME eruption. Title: Coronal hole evolution from multi-viewpoint data as input for a STEREO solar wind speed persistence model Authors: Temmer, Manuela; Hinterreiter, Jürgen; Reiss, Martin A. Bibcode: 2018JSWSC...8A..18T Altcode: 2018arXiv180110213T We present a concept study of a solar wind forecasting method for Earth, based on persistence modeling from STEREO in situ measurements combined with multi-viewpoint EUV observational data. By comparing the fractional areas of coronal holes (CHs) extracted from EUV data of STEREO and SoHO/SDO, we perform an uncertainty assessment derived from changes in the CHs and apply those changes to the predicted solar wind speed profile at 1 AU. We evaluate the method for the time period 2008-2012, and compare the results to a persistence model based on ACE in situ measurements and to the STEREO persistence model without implementing the information on CH evolution. Compared to an ACE based persistence model, the performance of the STEREO persistence model which takes into account the evolution of CHs, is able to increase the number of correctly predicted high-speed streams by about 12%, and to decrease the number of missed streams by about 23%, and the number of false alarms by about 19%. However, the added information on CH evolution is not able to deliver more accurate speed values for the forecast than using the STEREO persistence model without CH information which performs better than an ACE based persistence model. Investigating the CH evolution between STEREO and Earth view for varying separation angles over ∼25-140° East of Earth, we derive some relation between expanding CHs and increasing solar wind speed, but a less clear relation for decaying CHs and decreasing solar wind speed. This fact most likely prevents the method from making more precise forecasts. The obtained results support a future L5 mission and show the importance and valuable contribution using multi-viewpoint data. Title: The Dependence of the Peak Velocity of High-Speed Solar Wind Streams as Measured in the Ecliptic by ACE and the STEREO satellites on the Area and Co-latitude of Their Solar Source Coronal Holes Authors: Hofmeister, Stefan J.; Veronig, Astrid; Temmer, Manuela; Vennerstrom, Susanne; Heber, Bernd; Vršnak, Bojan Bibcode: 2018JGRA..123.1738H Altcode: 2018arXiv180409579H We study the properties of 115 coronal holes in the time range from August 2010 to March 2017, the peak velocities of the corresponding high-speed streams as measured in the ecliptic at 1 AU, and the corresponding changes of the Kp index as marker of their geoeffectiveness. We find that the peak velocities of high-speed streams depend strongly on both the areas and the co-latitudes of their solar source coronal holes with regard to the heliospheric latitude of the satellites. Therefore, the co-latitude of their source coronal hole is an important parameter for the prediction of the high-speed stream properties near the Earth. We derive the largest solar wind peak velocities normalized to the coronal hole areas for coronal holes located near the solar equator and that they linearly decrease with increasing latitudes of the coronal holes. For coronal holes located at latitudes ≳60°, they turn statistically to zero, indicating that the associated high-speed streams have a high chance to miss the Earth. Similarly, the Kp index per coronal hole area is highest for the coronal holes located near the solar equator and strongly decreases with increasing latitudes of the coronal holes. We interpret these results as an effect of the three-dimensional propagation of high-speed streams in the heliosphere; that is, high-speed streams arising from coronal holes near the solar equator propagate in direction toward and directly hit the Earth, whereas solar wind streams arising from coronal holes at higher solar latitudes only graze or even miss the Earth. Title: On the Detection of Coronal Dimmings and the Extraction of Their Characteristic Properties Authors: Dissauer, K.; Veronig, A. M.; Temmer, M.; Podladchikova, T.; Vanninathan, K. Bibcode: 2018ApJ...855..137D Altcode: 2018arXiv180203185D Coronal dimmings are distinct phenomena associated with coronal mass ejections (CMEs). The study of coronal dimmings and the extraction of their characteristic parameters help us to obtain additional information regarding CMEs, especially on the initiation and early evolution of Earth-directed CMEs. We present a new approach to detect coronal dimming regions based on a thresholding technique applied on logarithmic base-ratio images. Characteristic dimming parameters describing the dynamics, morphology, magnetic properties, and the brightness of coronal dimming regions are extracted by cumulatively summing newly dimmed pixels over time. It is also demonstrated how core dimming regions are identified as a subset of the overall identified dimming region. We successfully apply our method to two well-observed coronal dimming events. For both events, the core dimming regions are identified and the spatial evolution of the dimming area reveals the expansion of the dimming region around these footpoints. We also show that in the early impulsive phase of the dimming expansion the total unsigned magnetic flux involved in the dimming regions is balanced and that up to 30% of this flux results from the localized core dimming regions. Furthermore, the onset in the profile of the area growth rate is cotemporal with the start of the associated flares and in one case also with the fast rise of the CME, indicating a strong relationship of coronal dimmings with both flares and CMEs. Title: The Drag-based Ensemble Model (DBEM) for Coronal Mass Ejection Propagation Authors: Dumbović, Mateja; Čalogović, Jaša; Vršnak, Bojan; Temmer, Manuela; Mays, M. Leila; Veronig, Astrid; Piantschitsch, Isabell Bibcode: 2018ApJ...854..180D Altcode: 2018arXiv180107473D The drag-based model for heliospheric propagation of coronal mass ejections (CMEs) is a widely used analytical model that can predict CME arrival time and speed at a given heliospheric location. It is based on the assumption that the propagation of CMEs in interplanetary space is solely under the influence of magnetohydrodynamical drag, where CME propagation is determined based on CME initial properties as well as the properties of the ambient solar wind. We present an upgraded version, the drag-based ensemble model (DBEM), that covers ensemble modeling to produce a distribution of possible ICME arrival times and speeds. Multiple runs using uncertainty ranges for the input values can be performed in almost real-time, within a few minutes. This allows us to define the most likely ICME arrival times and speeds, quantify prediction uncertainties, and determine forecast confidence. The performance of the DBEM is evaluated and compared to that of ensemble WSA-ENLIL+Cone model (ENLIL) using the same sample of events. It is found that the mean error is ME = -9.7 hr, mean absolute error MAE = 14.3 hr, and root mean square error RMSE = 16.7 hr, which is somewhat higher than, but comparable to ENLIL errors (ME = -6.1 hr, MAE = 12.8 hr and RMSE = 14.4 hr). Overall, DBEM and ENLIL show a similar performance. Furthermore, we find that in both models fast CMEs are predicted to arrive earlier than observed, most likely owing to the physical limitations of models, but possibly also related to an overestimation of the CME initial speed for fast CMEs. Title: A comparison of solar ALMA observations and model based predictions of the brightness temperature Authors: Brajša, R.; Kuhar, M.; Benz, A. O.; Skokić, I.; Sudar, D.; Wedemeyer, S.; Báarta, M.; De Pontieu, B.; Kim, S.; Kobelski, A.; Shimojo, M.; White, S.; Yagoubov, P.; Yan, Y.; Ludwig, H. G.; Temmer, M.; Saar, S. H.; Selhorst, C. L.; Beuc, R. Bibcode: 2018CEAB...42....1B Altcode: The new facility Atacama Large Millimeter/submillimeter Array (ALMA) is capable of observing the Sun in the wavelength range from 0.3 mm to 10 mm with an unprecedented spatial, temporal and spectral resolution. The first aim of the present work is to identify different structures in the solar atmosphere (quiet Sun, active regions, filaments on the disc, and coronal holes) in a full disc solar ALMA image at 1.21 mm obtained on December 18, 2015 during a CSV-EOC campaign. It is compared with full disc solar images from the same day in the Hα line (Cerro Tololo Observatory, NISP), and at three EUV wavelengths (30.4 nm, 21.1 nm, 17.1 nm; a composite SDO image). Positions of the quiet Sun areas, active regions, filaments on the disc, and coronal holes are identified in the ALMA image. To interpret solar observations with ALMA it is important to compare the measured and calculated intensities of various solar structures. So, the second aim of this work is to calculate the intensity (brightness temperature) for those structures (quiet Sun, active regions, filaments on the disc, and coronal holes) for a broad wavelength range (from 0.3 mm to 10 mm), closely related to that of the ALMA, and to compare the results with available ALMA observations. Thermal bremsstrahlung is the dominant radiation mechanism for explanation of the observed phenomena. A procedure for calculating the brightness temperature for a given wavelength and model atmosphere, which integrates the radiative transfer equation for thermal bremsstrahlung, is used. At the wavelength of 1.21 mm active regions appear as bright areas, while filaments on the disc and coronal holes are not discernible from the quiet Sun background. The models generally agree with the observed results: Active regions are bright primarily due to higher densities, filaments can appear bright, dark or not at all and coronal holes cannot be easily identified. Title: Small-scale dynamcis in a coronal-hole related to microflaring events Authors: Krikova, K.; Utz, D.; Veronig, A.; Hofmeister, S.; Temmer, M.; Gömöry, P.; Holzknecht, L. Bibcode: 2018CEAB...42....8K Altcode: Using high-resolution solar imagery and spectroscopy from the Hinode EIS and SDO instruments, we investigate the dynamics within a coronal hole observed on the 26th September 2017. Further data is given by full disc images from SDO with the AIA and HMI instruments. EIS spectra provide us with crucial information about the plasma and energy flows from the Sun's chromosphere into the corona. Within the timeframe of the analysed EIS dataset two microflares associated with a jet-like event were captured, originating inside the coronal hole under investigation. These two microflare events were analysed in the study at hand in detail. Such recurring solar transient events could contribute to the mass and energy input into the solar corona and also to the solar wind. Our analysis shows that microflare temperatures can reach up to 3 MK with a hot component close to the reconnection site. Moreover an enhanced density at the microflare region was found. The obtained EIS ion line ratios suggest a density of up to 2.9 \cdot 10^{10} cm^{-3}. Title: 3D reconstruction and interplanetary expansion of the 2010 April 3^{rd} CME Authors: Rodari, M.; Dumbović, M.; Temmer, M.; Holzknecht, L.; Veronig, A. Bibcode: 2018CEAB...42...11R Altcode: 2019arXiv190405611R We analyse the 2010 April 3^{rd} CME using spacecraft coronagraphic images at different vantage points (SOHO, STEREO-A and STEREO-B). We perform a 3D reconstruction of both the flux rope and shock using the Graduated Cylindrical Shell (GCS) model to calculate CME kinematic and morphologic parameters (e.g. velocity, acceleration, radius). The obtained results are fitted with empirical models describing the expansion of the CME radius in the heliosphere and compared with in situ measurements from Wind spacecraft: the CME is found to expand linearly towards Earth. Finally, we relate the event with decreases in the Galactic Cosmic Ray (GCR) Flux, known as Forbush decreases (FD), detected by EPHIN instrument onboard SOHO spacecraft. We use the analytical diffusion-expansion model (ForbMod) to calculate the magnetic field power law index, obtaining a value of ∼1.6, thus estimating a starting magnetic field of ∼0.01 G and an axial magnetic flux of ∼5 \cdot 10^{20} Mx at 15.6 R_⊙. Title: Using Forbush Decreases to Derive the Transit Time of ICMEs Propagating from 1 AU to Mars Authors: Freiherr von Forstner, Johan L.; Guo, Jingnan; Wimmer-Schweingruber, Robert F.; Hassler, Donald M.; Temmer, Manuela; Dumbović, Mateja; Jian, Lan K.; Appel, Jan K.; Čalogović, Jaša.; Ehresmann, Bent; Heber, Bernd; Lohf, Henning; Posner, Arik; Steigies, Christian T.; Vršnak, Bojan; Zeitlin, Cary J. Bibcode: 2018JGRA..123...39F Altcode: 2017arXiv171207301V The propagation of 15 interplanetary coronal mass ejections (ICMEs) from Earth's orbit (1 AU) to Mars (∼1.5 AU) has been studied with their propagation speed estimated from both measurements and simulations. The enhancement of magnetic fields related to ICMEs and their shock fronts causes the so-called Forbush decrease, which can be detected as a reduction of galactic cosmic rays measured on ground. We have used galactic cosmic ray (GCR) data from in situ measurements at Earth, from both STEREO A and STEREO B as well as GCR measurements by the Radiation Assessment Detector (RAD) instrument on board Mars Science Laboratory on the surface of Mars. A set of ICME events has been selected during the periods when Earth (or STEREO A or STEREO B) and Mars locations were nearly aligned on the same side of the Sun in the ecliptic plane (so-called opposition phase). Such lineups allow us to estimate the ICMEs' transit times between 1 and 1.5 AU by estimating the delay time of the corresponding Forbush decreases measured at each location. We investigate the evolution of their propagation speeds before and after passing Earth's orbit and find that the deceleration of ICMEs due to their interaction with the ambient solar wind may continue beyond 1 AU. We also find a substantial variance of the speed evolution among different events revealing the dynamic and diverse nature of eruptive solar events. Furthermore, the results are compared to simulation data obtained from two CME propagation models, namely the Drag-Based Model and ENLIL plus cone model. Title: CME volume calculation from 3D GCS reconstruction Authors: Holzknecht, L.; Temmer, M.; Dumbović, M.; Wellenzohn, S.; Krikova, K.; Heinemann, S. G.; Rodari, M.; Vršnak, B.; Veronig, A. M. Bibcode: 2018CEAB...42....3H Altcode: 2019arXiv190411418H The mass evolution of a coronal mass ejection (CME) is an important parameter characterizing the drag force acting on a CME as it propagates through interplanetary space. Spacecraft measure in-situ plasma densities of CMEs during crossing events, but for investigating the mass evolution, we also need to know the CME geometry, more specific, its volume. Having derived the CME volume and mass from remote sensing data using 3D reconstructed CME geometry, we can calculate the CME density and compare it with in-situ proton density measurements near Earth. From that we may draw important conclusions on a possible mass increase as the CME interacts with the ambient solar wind in the heliosphere. In this paper we will describe in detail the method for deriving the CME volume using the graduated cylindrical shell (GCS) model tep[][see \ref{fig:GCSModel}]{thernisien06,thernisien09}. We show that, assuming self-similar expansion, one can derive the volume of the CME from two GCS parameters and that it furthermore can be expressed as a function of distance. Title: Plasma Diagnostics of Coronal Dimming Regions and Relation to Characteristic CME Parameters Authors: Veronig, A.; Vanninathan, K.; Dissauer, K.; Temmer, M. Bibcode: 2017AGUFMSH52B..08V Altcode: Coronal Mass Ejections (CMEs) are often associated with coronal dimmings, i.e. transient dark regions in the solar corona that are most prominently observed at Extreme Ultra-violet (EUV) wavelengths. Coronal dimmings are thought to be a result of the evacuation of mass related to the erupting CME structure. Using data from the six EUV channels of the Atmospheric Imaging Assembly (AIA) onboard SDO, we apply Differential Emission Measure (DEM) diagnostics, to study the plasma characteristics of on-disk coronal dimming regions. We analysed in detail seven coronal dimming events associated with CMEs distributed over a speed range from 300 to 1250 km/s. We derived the weighted emission measure, density and temperature as a function of time for both the core and the secondary dimming regions. In the core dimming regions, the plasma parameters reached a minimum within about 30 min after the CME onset, whereas the secondary dimming regions tend to show a more gradual evolution. For most of the events, the values of these parameters remained low within the core dimming region for the entire duration of this study ( 10 hrs after the flare) while the secondary dimming region showed a gradual increase after 1-2 hrs indicating refilling of these regions with plasma. The emission measure decrease in the core dimming region was found to lie in the range from 60-90%, the density decrease from 35-70% and the temperature decrease from 5-30%. In the secondary dimming region, the decreases of the plasma parameters derived are smaller. In addition, we performed a statistical analysis of 76 dimming events during the time range 2010 - 2012, which were observed on-disk by SDO and close to the limb by at least one of the two STEREO spacecraft. Characteristic parameters of the early CME dynamics (initial velocity, peak acceleration, mass and initiation height) are derived and compared with decisive coronal dimming parameters like the magnetic flux involved, the area, the area growth rate and the intensity drop in the dimming region. The findings of our study are discussed with respect to the different coronal structures involved in the dimming regions and how they relate to decisive parameters of the CME. Title: Long-lasting solar energetic electron injection during the 26 Dec 2013 widespread SEP event Authors: Dresing, N.; Klassen, A.; Temmer, M.; Gomez-Herrero, R.; Heber, B.; Veronig, A. Bibcode: 2017AGUFMSH33C..03D Altcode: The solar energetic particle (SEP) event on 26 Dec 2013 was detected all around the Sun by the two STEREO spacecraft and close-to-Earth observers. While the two STEREOs were separated by 59 degrees and situated at the front side of the associated large coronal event, it was a backside-event for Earth. Nevertheless, significant and long-lasting solar energetic electron anisotropies together with long rise times were observed at all three viewpoints, pointing to an extended electron injection. Although the CME-driven shock appears to account for the SEP event at a first glance a more detailed view reveals a more complex scenario: A CME-CME interaction takes place during the very early phase of the SEP event. Furthermore, four hours after the onset of the event, a second component is measured at all three viewpoints on top of the first SEP increase, mainly consisting of high energy particles. We find that the CME-driven shock alone can hardly account for the observed SEP event in total but a trapping scenario together with ongoing particle acceleration is more likely. Title: Multi-spacecraft observations of ICMEs propagating beyond Earth orbit during MSL/RAD flight and surface phases Authors: von Forstner, J.; Guo, J.; Wimmer-Schweingruber, R. F.; Hassler, D.; Temmer, M.; Vrsnak, B.; Čalogović, J.; Dumbovic, M.; Lohf, H.; Appel, J. K.; Heber, B.; Steigies, C. T.; Zeitlin, C.; Ehresmann, B.; Jian, L. K.; Boehm, E.; Boettcher, S. I.; Burmeister, S.; Martin-Garcia, C.; Brinza, D. E.; Posner, A.; Reitz, G.; Matthiae, D.; Rafkin, S. C.; weigle, G., II; Cucinotta, F. Bibcode: 2017AGUFMSH53A2543V Altcode: The propagation of interplanetary coronal mass ejections (ICMEs) between Earth's orbit (1 AU) and Mars ( 1.5 AU) has been studied with their propagation speed estimated from both measurements and simulations. The enhancement of the magnetic fields related to ICMEs and their shock fronts cause so-called Forbush decreases, which can be detected as a reduction of galactic cosmic rays measured on-ground or on a spacecraft. We have used galactic cosmic ray (GCR) data from in-situ measurements at Earth, from both STEREO A and B as well as the GCR measurement by the Radiation Assessment Detector (RAD) instrument onboard Mars Science Laboratory (MSL) on the surface of Mars as well as during its flight to Mars in 2011-2012. A set of ICME events has been selected during the periods when Earth (or STEREO A or B) and MSL locations were nearly aligned on the same side of the Sun in the ecliptic plane (so-called opposition phase). Such lineups allow us to estimate the ICMEs' transit times between 1 AU and the MSL location by estimating the delay time of the corresponding Forbush decreases measured at each location. We investigate the evolution of their propagation speeds after passing Earth's orbit and find that the deceleration of ICMEs due to their interaction with the ambient solar wind continues beyond 1 AU. The results are compared to simulation data obtained from two CME propagation models, namely the Drag-Based Model (DBM) and the WSA-ENLIL plus cone model. Title: The Analytical Diffusion-Expansion Model for Forbush Decreases Caused by Flux Ropes Authors: Dumbovic, M.; Temmer, M. Bibcode: 2017AGUFMSH13C2492D Altcode: Identification and tracking of interplanetary coronal mass ejections (ICMEs) throughout the heliosphere is a growingly important aspect of space weather research. One of the "signatures" of ICME passage is the corresponding Forbush decrease (FD), a short term decrease in the galactic cosmic ray flux. These depressions are observed at the surface of the Earth for over 50 years, by several spacecraft in interplanetary space in the past couple of decades, and recently also on Mars' surface with Curiosity rover. In order to use FDs as ICME signatures efficiently, it is important to model ICME interaction with energetic particles by taking into account ICME evolution and constraining the model with observational data. We present an analytical diffusion-expansion FD model ForbMod which is based on the widely used approach of the initially empty, closed magnetic structure (i.e. flux rope) which fills up slowly with particles by perpendicular diffusion. The model is restricted to explain only the depression caused by the magnetic structure of the ICME and not of the associated shock. We use remote CME observations and a 3D reconstruction method (the Graduated Cylindrical Shell method) to constrain initial and boundary conditions of the FD model and take into account CME evolutionary properties by incorporating flux rope expansion. Several options of flux rope expansion are regarded as the competing mechanism to diffusion which can lead to different FD characteristics. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 745782. Title: Presentation of the project "An investigation of the early stages of solar eruptions - from remote observations to energetic particles" Authors: Kozarev, Kamen; Veronig, Astrid; Duchlev, Peter; Koleva, Kostadinka; Dechev, Momchil; Miteva, Rositsa; Temmer, Manuela; Dissauer, Karin Bibcode: 2017ses..conf...63K Altcode: Coronal mass ejections (CMEs), one of the most energetic manifestations of solar activity, are complex events, which combine multiple related phenomena occurring on the solar surface, in the extended solar atmosphere (corona), as well as in interplanetary space. We present here an outline of a new collaborative project between scientists from the Bulgarian Academy of Sciences (BAS), Bulgaria and the University of Graz, Austria. The goal of the this research project is to answer the following questions: 1) What are the properties of erupting filaments, CMEs, and CME-driven shock waves near the Sun, and of associated solar energetic particle (SEP) fluxes in interplanetary space? 2) How are these properties related to the coronal acceleration of SEPs? To achieve the scientific goals of this project, we will use remote solar observations with high spatial and temporal resolution to characterize the early stages of coronal eruption events in a systematic way - studying the pre-eruptive behavior of filaments and flares during energy build-up, the kinematics and morphology of CMEs and compressive shock waves, and the signatures of high energy non-thermal particles in both remote and in situ observations. Title: The Causes of Quasi-homologous CMEs Authors: Liu, Lijuan; Wang, Yuming; Liu, Rui; Zhou, Zhenjun; Temmer, M.; Thalmann, J. K.; Liu, Jiajia; Liu, Kai; Shen, Chenglong; Zhang, Quanhao; Veronig, A. M. Bibcode: 2017ApJ...844..141L Altcode: 2017arXiv170608878L In this paper, we identified the magnetic source locations of 142 quasi-homologous (QH) coronal mass ejections (CMEs), of which 121 are from solar cycle (SC) 23 and 21 from SC 24. Among those CMEs, 63% originated from the same source location as their predecessor (defined as S-type), while 37% originated from a different location within the same active region as their predecessor (defined as D-type). Their distinctly different waiting time distributions, peaking around 7.5 and 1.5 hr for S- and D-type CMEs, suggest that they might involve different physical mechanisms with different characteristic timescales. Through detailed analysis based on nonlinear force-free coronal magnetic field modeling of two exemplary cases, we propose that the S-type QH CMES might involve a recurring energy release process from the same source location (by magnetic free energy replenishment), whereas the D-type QH CMEs can happen when a flux tube system is disturbed by a nearby CME. Title: Erratum: “The Confined X-class Flares of Solar Active Region 2192” (2015, ApJL, 801, L23) Authors: Thalmann, J. K.; Su, Y.; Temmer, M.; Veronig, A. M. Bibcode: 2017ApJ...844L..27T Altcode: No abstract at ADS Title: On Flare-CME Characteristics from Sun to Earth Combining Remote-Sensing Image Data with In Situ Measurements Supported by Modeling Authors: Temmer, Manuela; Thalmann, Julia K.; Dissauer, Karin; Veronig, Astrid M.; Tschernitz, Johannes; Hinterreiter, Jürgen; Rodriguez, Luciano Bibcode: 2017SoPh..292...93T Altcode: 2017arXiv170300694T We analyze the well-observed flare and coronal mass ejection (CME) from 1 October 2011 (SOL2011-10-01T09:18) covering the complete chain of effects - from Sun to Earth - to better understand the dynamic evolution of the CME and its embedded magnetic field. We study in detail the solar surface and atmosphere associated with the flare and CME using the Solar Dynamics Observatory (SDO) and ground-based instruments. We also track the CME signature off-limb with combined extreme ultraviolet (EUV) and white-light data from the Solar Terrestrial Relations Observatory (STEREO). By applying the graduated cylindrical shell (GCS) reconstruction method and total mass to stereoscopic STEREO-SOHO (Solar and Heliospheric Observatory) coronagraph data, we track the temporal and spatial evolution of the CME in the interplanetary space and derive its geometry and 3D mass. We combine the GCS and Lundquist model results to derive the axial flux and helicity of the magnetic cloud (MC) from in situ measurements from Wind. This is compared to nonlinear force-free (NLFF) model results, as well as to the reconnected magnetic flux derived from the flare ribbons (flare reconnection flux) and the magnetic flux encompassed by the associated dimming (dimming flux). We find that magnetic reconnection processes were already ongoing before the start of the impulsive flare phase, adding magnetic flux to the flux rope before its final eruption. The dimming flux increases by more than 25% after the end of the flare, indicating that magnetic flux is still added to the flux rope after eruption. Hence, the derived flare reconnection flux is most probably a lower limit for estimating the magnetic flux within the flux rope. We find that the magnetic helicity and axial magnetic flux are lower in the interplanetary space by ∼ 50% and 75%, respectively, possibly indicating an erosion process. A CME mass increase of 10% is observed over a range of ∼4 -20 R⊙. The temporal evolution of the CME-associated core-dimming regions supports the scenario that fast outflows might supply additional mass to the rear part of the CME. Title: Sunward-propagating Solar Energetic Electrons inside Multiple Interplanetary Flux Ropes Authors: Gómez-Herrero, Raúl; Dresing, Nina; Klassen, Andreas; Heber, Bernd; Temmer, Manuela; Veronig, Astrid; Bučík, Radoslav; Hidalgo, Miguel A.; Carcaboso, Fernando; Blanco, Juan J.; Lario, David Bibcode: 2017ApJ...840...85G Altcode: On 2013 December 2 and 3, the SEPT and STE instruments on board STEREO-A observed two solar energetic electron events with unusual sunward-directed fluxes. Both events occurred during a time interval showing typical signatures of interplanetary coronal mass ejections (ICMEs). The electron timing and anisotropies, combined with extreme-ultraviolet solar imaging and radio wave spectral observations, are used to confirm the solar origin and the injection times of the energetic electrons. The solar source of the ICME is investigated using remote-sensing observations and a three-dimensional reconstruction technique. In situ plasma and magnetic field data combined with energetic electron observations and a flux-rope model are used to determine the ICME magnetic topology and the interplanetary electron propagation path from the Sun to 1 au. Two consecutive flux ropes crossed the STEREO-A location and each electron event occurred inside a different flux rope. In both cases, the electrons traveled from the solar source to 1 au along the longest legs of the flux ropes still connected to the Sun. During the December 2 event, energetic electrons propagated along the magnetic field, while during the December 3 event they were propagating against the field. As found by previous studies, the energetic electron propagation times are consistent with a low number of field line rotations N < 5 of the flux rope between the Sun and 1 au. The flux rope model used in this work suggests an even lower number of rotations. Title: The February 15 2011 CME-CME interaction and possibly associated radio emission Authors: Magdalenic, Jasmina; Temmer, Manuela; Krupar, Vratislav; Marque, Christophe; Veronig, Astrid; Eastwood, Jonathan Bibcode: 2017EGUGA..19.9850M Altcode: On February 15, 2011 a particular, continuum-like radio emission was observed by STEREO WAVES and WIND WAVES spacecraft. The radio event appeared to be associated with the complex interaction of two coronal mass ejections (CMEs) successively launched (February 14 and February 15) from the same active region. Although the CME-CME interaction was widely studied (e.g. Temmer et al., 2014, Maricic et al., 2014, Mishra & Srivastava, 2014) none of the analyses confirmed an association with the continuum-like radio emission. The usual method of establishing temporal coincidence of radio continuum and a CME-CME interaction is not applicable in this event due to a complex and long-lasting interaction of the CMEs. Therefore, we performed radio triangulation studies (see also Magdalenic et al., 2014) which provided us with the 3D source positions of the radio emission. Comparison of the positions of radio sources and the reconstructed positions of the interacting CMEs, shows that the source position of the continuum-like radio emission is about 0.5 AU away from the interacting CMEs. We can therefore concluded that, in this event, the continuum-like emission is not the radio signature of the CME-CME interaction. Title: The Interaction of Successive Coronal Mass Ejections: A Review Authors: Lugaz, Noé; Temmer, Manuela; Wang, Yuming; Farrugia, Charles J. Bibcode: 2017SoPh..292...64L Altcode: 2016arXiv161202398L We present a review of the different aspects associated with the interaction of successive coronal mass ejections (CMEs) in the corona and inner heliosphere, focusing on the initiation of series of CMEs, their interaction in the heliosphere, the particle acceleration associated with successive CMEs, and the effect of compound events on Earth's magnetosphere. The two main mechanisms resulting in the eruption of series of CMEs are sympathetic eruptions, when one eruption triggers another, and homologous eruptions, when a series of similar eruptions originates from one active region. CME - CME interaction may also be associated with two unrelated eruptions. The interaction of successive CMEs has been observed remotely in coronagraphs (with the Large Angle and Spectrometric Coronagraph Experiment - LASCO - since the early 2000s) and heliospheric imagers (since the late 2000s), and inferred from in situ measurements, starting with early measurements in the 1970s. The interaction of two or more CMEs is associated with complex phenomena, including magnetic reconnection, momentum exchange, the propagation of a fast magnetosonic shock through a magnetic ejecta, and changes in the CME expansion. The presence of a preceding CME a few hours before a fast eruption has been found to be connected with higher fluxes of solar energetic particles (SEPs), while CME - CME interaction occurring in the corona is often associated with unusual radio bursts, indicating electron acceleration. Higher suprathermal population, enhanced turbulence and wave activity, stronger shocks, and shock - shock or shock - CME interaction have been proposed as potential physical mechanisms to explain the observed associated SEP events. When measured in situ, CME - CME interaction may be associated with relatively well organized multiple-magnetic cloud events, instances of shocks propagating through a previous magnetic ejecta or more complex ejecta, when the characteristics of the individual eruptions cannot be easily distinguished. CME - CME interaction is associated with some of the most intense recorded geomagnetic storms. The compression of a CME by another and the propagation of a shock inside a magnetic ejecta can lead to extreme values of the southward magnetic field component, sometimes associated with high values of the dynamic pressure. This can result in intense geomagnetic storms, but can also trigger substorms and large earthward motions of the magnetopause, potentially associated with changes in the outer radiation belts. Future in situ measurements in the inner heliosphere by Solar Probe+ and Solar Orbiter may shed light on the evolution of CMEs as they interact, by providing opportunities for conjunction and evolutionary studies. Title: Understanding CMEs using plasma diagnostics of the related dimmings Authors: Vanninathan, Kamalam; Veronig, Astrid; Gomory, Peter; Dissauer, Karin; Temmer, Manuela; Hannah, Iain; Kontar, Eduard Bibcode: 2017EGUGA..19.1571V Altcode: Coronal Mass Ejections (CMEs) are often associated with dimmings that are well observed in Extreme Ultra-violet (EUV) wavelengths. Such dimmings are suggested to represent the evacuation of mass that is carried out by CMEs and are a unique and indirect means to study CME properties. While Earth-directed CMEs (on-disk CMEs) are difficult to observe due to the bright background solar disk and projection effects, their corresponding dimmings are clearly discernible and ideally suited for analysis. Using data from the 6 EUV channels of Solar Dynamics Observatory/Atmospheric Imaging Assembly for Differential Emission Measure (DEM) diagnostics, we determine the plasma characteristics of the dimming region. These data are well suited for this kind of study due to the good temperature ranges covered by the multiple passbands of the instrument. We analyse 7 on-disk and 5 off-limb events and derive the weighted density and temperature as a function of time, from the DEMs. From such an analysis we differentiate 2 types of dimming regions: core and secondary dimmings. Core dimmings often occur in pairs lying on either sides of the active region and in opposite polarity regions while the secondary dimming is more extended. In both the regions the derived plasma parameters reach a minimum within 30-60 min after the flare. For each event the core dimming region shows a higher decrease in density and temperature than the corresponding secondary dimming regions. The values of these parameters remains low within the core dimming region for the entire duration of this study ( 10 hrs after the flare) while the secondary dimming region starts to show a gradual increase after 1-2 hrs. We also use spectroscopic data from Hinode/Extreme-Ultraviolet Imaging Spectrometer to differentiate core and secondary dimming regions. We find that the Fe XIII 202 Å line shows double component profiles within the core dimming region with strong blueshifts of 100 km/s while the secondary dimming region has weak upflows of 10 km/s. We conclude that the core dimming region corresponds to footpoints of the erupting flux rope from where there is continuous strong upflowing plasma for at least 10 hrs after the flare, while the secondary dimming region begins to refill within 1-2 hrs. These measurements can be used to deduce information about the mass of on-disk CMEs where white light measurements can fail. We also confirm that the dimmings are mainly caused by density decrease and not temperature changes. DEM analysis is a strong tool to decipher CME properties from dimming regions. Title: Statistical analysis on how CME and SIR/CIR events effect the geomagnetic activity and the Earth's thermosphere Authors: Krauss, Sandro; Temmer, Manuela; Edl, Martina; Veronig, Astrid Bibcode: 2017EGUGA..1915251K Altcode: In order to estimate the impact of different types of solar wind on the geomagnetic activity and the neutral density in the Earth's thermosphere, we present a comprehensive statistical analysis based on interplanetary coronal mass ejections (ICME) covering the time range from July 2003 - 2016 and stream interaction as well as corotating interaction regions (SIR/CIR) from July 2003 - December 2009. In general, geomagnetic storms induced by CIR are characterized by lower energy input compared to ICME induced storms but a significantly longer duration time due to a long-term negative Bz component in the magnetic cloud region. Regarding the time of occurrence of ICME events, we rely on the catalogue maintained by Richardson and Cane. For the period of investigation more than 250 Earth-directed CME events are listed. All of them have been measured in situ by plasma and field instruments on board the ACE spacecraft. The arrival times of SIRs/CIRs are taken from the catalogue maintained by Lan Jian based on ACE and Wind in-situ measurements. From this list, we extracted 98 SIR/CIR events, from which the minimum Bz component is determined within a time window of 36 hours starting at the arrival of the SIR/CIR (same procedure as for ICMEs). Accordingly, the peak in Earth's neutral density is determined in the same time window. The densities itself are estimated by using accelerometer measurements collected by the Gravity Recovery And Climate Experiment (GRACE) satellites and subsequently related to various geomagnetic indices (e.g. SYM-H, Polar cap, a-indices, ...) as well as characteristic CME parameters like the impact speed, the southward magnetic field strength Bz and resultant derivatives. We find high correlations (cc=0.9) between the CME characteristic (except the impact speed) and the thermospheric density enhancements as well as with most of the geomagnetic indices. However, considering only weaker ICME events (Bz up to -20nT) a lower correlation must be conceded. The same holds true for SIR/CIR events, as both cover compressed sheath regions with turbulent magnetic field. The absolute density increases for SIR/CIR induced storms is in the order of 1.7E-12kg/m3 for Bz values ranging from -4 to -19nT, with a related correlation coefficient of -0.41. Title: Quantification of disturbance periods of solar wind speed in interplanetary space due to coronal mass ejections Authors: Temmer, Manuela; Reiss, Martin A.; Nikolic, Ljubomir; Hofmeister, Stefan J.; Veronig, Astrid M. Bibcode: 2017EGUGA..19.1940T Altcode: Interplanetary space is characteristically structured mainly by high-speed solar wind streams emanating from coronal holes and transient disturbances such as coronal mass ejections (CMEs). While high-speed solar wind streams pose a continuous outflow, CMEs abruptly disrupt the rather steady structure causing large deviations from the quiet solar wind conditions. We present a quantification of the duration of disturbed conditions (preconditioning) for interplanetary space caused by CMEs by investigating the plasma speed component of the solar wind and the impact of in situ detected CMEs (ICMEs), compared to different background solar wind models (ESWF, WSA, persistence model) for the time range 2011-2015. We obtain for periods within an ICME interval an increase of 18-32% above the expected quiet Sun background and for the period of 2 days after the ICME an increase of 9-24%. The total duration of enhanced deviations is about 3 and up to 6 days after the ICME start, which is much longer than the average duration of an ICME disturbance itself (about 1.3 days), concluding that interplanetary space needs about 2-5 days to recover from the impact of ICMEs. The obtained results have strong implications for studying CME propagation behavior and also for space weather forecasting. Title: Testing ElEvoHI on a multi-point in situ detected Coronal Mass Ejection Authors: Amerstorfer, Tanja; Möstl, Christian; Hess, Phillip; Mays, M. Leila; Temmer, Manuela Bibcode: 2017EGUGA..19.7675A Altcode: The Solar TErrestrial RElations Observatory (STEREO) has provided us a deep insight into the interplanetary propagation of coronal mass ejections (CMEs). Especially the wide-angle heliospheric imagers (HI) enabled the development of a multitude of methods for analyzing the evolution of CMEs through interplanetary (IP) space. Methods able to forecast arrival times and speeds at Earth (or other targets) use the advantage of following a CME's path of propagation up to 1 AU. However, these methods were not able to reduce today's errors in arrival time forecasts to less than ±6 hours, arrival speeds are mostly overestimated by some 100 km s-1. One reason for that is the assumption of constant propagation speed, which is clearly incorrect for most CMEs—especially for those being faster than the ambient solar wind. ElEvoHI, the Ellipse Evolution model (ElEvo) based on HI observations, is a new prediction tool, which uses the benefits of different methods and observations. It provides the possibility to adjust the CME frontal shape (angular width, ellipse aspect ratio) and the direction of motion for each CME event individually. This information can be gained from Graduated Cylindrical Shell (GCS) flux-rope fitting within coronagraph images. Using the Ellipse Conversion (ElCon) method, the observed HI elongation angle is converted into a unit of distance, which reveals the kinematics of the event. After fitting the time-distance profile of the CME using the drag-based equation of motion, where real-time in situ solar wind speed from 1 AU is used as additional input, we receive all input parameters needed to run a forecast using the ElEvo model and to predict arrival times and speeds at any target of interest in IP space. Here, we present a test on a slow CME event of 3 November 2010, in situ detected by the lined-up spacecraft MESSENGER and STEREO Behind. We gain the shape of the CME front from a cut of the 3D GCS CME shape with the ecliptic plane, resulting in an almost ideal ElEvoHI forecast of arrival time and speed at 1 AU. Title: Flare-CME characteristics from Sun to Earth combining observations and modeling Authors: Temmer, Manuela; Thalmann, Julia K.; Dissauer, Karin; Veronig, Astrid M.; Tschernitz, Johannes; Hinterreiter, Jürgen; Rodriguez, Luciano Bibcode: 2017EGUGA..19.1942T Altcode: We analyze the well observed flare-CME event from October 1, 2011 (SOL2011-10-01T09:18) covering the complete chain of action - from Sun to Earth - for a better understanding of the dynamic evolution of the CME and its embedded magnetic field. We study in detail the solar surface and atmosphere from SDO and ground-based instruments associated to the flare-CME and also track the CME signature offlimb from combined EUV and white-light data with STEREO. By applying 3D reconstruction techniques (GCS, total mass) to stereoscopic STEREO-SoHO coronagraph data, we track the temporal and spatial evolution of the CME in interplanetary space and derive its geometry and 3D-mass. We combine the GCS and Lundquist model results to derive the axial flux and helicity of the MC from in situ measurements (Wind). This is compared to nonlinear force-free (NLFF) model results as well as to the reconnected magnetic flux derived from the flare ribbons (flare reconnection flux) and the magnetic flux encompassed by the associated dimming (dimming flux). We find that magnetic reconnection processes were already ongoing before the start of the impulsive flare phase, adding magnetic flux to the flux rope before its final eruption. The dimming flux increases by more than 25% after the end of the flare, indicating that magnetic flux is still added to the flux rope after eruption. Hence, the derived flare reconnection flux is most probably a lower limit for estimating the magnetic flux within the flux rope. We obtain that the magnetic helicity and axial magnetic flux are reduced in interplanetary space by ∼50% and 75%, respectively, possibly indicating to an erosion process. A mass increase of 10% for the CME is observed over the distance range from about 4-20 Rs. The temporal evolution of the CME associated core dimming regions supports the scenario that fast outflows might supply additional mass to the rear part of the CME. Title: Preconditioning of Interplanetary Space Due to Transient CME Disturbances Authors: Temmer, M.; Reiss, M. A.; Nikolic, L.; Hofmeister, S. J.; Veronig, A. M. Bibcode: 2017ApJ...835..141T Altcode: 2016arXiv161206080T Interplanetary space is characteristically structured mainly by high-speed solar wind streams emanating from coronal holes and transient disturbances such as coronal mass ejections (CMEs). While high-speed solar wind streams pose a continuous outflow, CMEs abruptly disrupt the rather steady structure, causing large deviations from the quiet solar wind conditions. For the first time, we give a quantification of the duration of disturbed conditions (preconditioning) for interplanetary space caused by CMEs. To this aim, we investigate the plasma speed component of the solar wind and the impact of in situ detected interplanetary CMEs (ICMEs), compared to different background solar wind models (ESWF, WSA, persistence model) for the time range 2011-2015. We quantify in terms of standard error measures the deviations between modeled background solar wind speed and observed solar wind speed. Using the mean absolute error, we obtain an average deviation for quiet solar activity within a range of 75.1-83.1 km s-1. Compared to this baseline level, periods within the ICME interval showed an increase of 18%-32% above the expected background, and the period of two days after the ICME displayed an increase of 9%-24%. We obtain a total duration of enhanced deviations over about three and up to six days after the ICME start, which is much longer than the average duration of an ICME disturbance itself (∼1.3 days), concluding that interplanetary space needs ∼2-5 days to recover from the impact of ICMEs. The obtained results have strong implications for studying CME propagation behavior and also for space weather forecasting. Title: Characteristics of Low-latitude Coronal Holes near the Maximum of Solar Cycle 24 Authors: Hofmeister, Stefan J.; Veronig, Astrid; Reiss, Martin A.; Temmer, Manuela; Vennerstrom, Susanne; Vršnak, Bojan; Heber, Bernd Bibcode: 2017ApJ...835..268H Altcode: 2017arXiv170202050H We investigate the statistics of 288 low-latitude coronal holes extracted from SDO/AIA-193 filtergrams over the time range of 2011 January 01-2013 December 31. We analyze the distribution of characteristic coronal hole properties, such as the areas, mean AIA-193 intensities, and mean magnetic field densities, the local distribution of the SDO/AIA-193 intensity and the magnetic field within the coronal holes, and the distribution of magnetic flux tubes in coronal holes. We find that the mean magnetic field density of all coronal holes under study is 3.0 ± 1.6 G, and the percentaged unbalanced magnetic flux is 49 ± 16%. The mean magnetic field density, the mean unsigned magnetic field density, and the percentaged unbalanced magnetic flux of coronal holes depend strongly pairwise on each other, with correlation coefficients cc > 0.92. Furthermore, we find that the unbalanced magnetic flux of the coronal holes is predominantly concentrated in magnetic flux tubes: 38% (81%) of the unbalanced magnetic flux of coronal holes arises from only 1% (10%) of the coronal hole area, clustered in magnetic flux tubes with field strengths >50 G (10 G). The average magnetic field density and the unbalanced magnetic flux derived from the magnetic flux tubes correlate with the mean magnetic field density and the unbalanced magnetic flux of the overall coronal hole (cc > 0.93). These findings give evidence that the overall magnetic characteristics of coronal holes are governed by the characteristics of the magnetic flux tubes. Title: 70 Years of Sunspot Observations at the Kanzelhöhe Observatory: Systematic Study of Parameters Affecting the Derivation of the Relative Sunspot Number Authors: Pötzi, Werner; Veronig, Astrid M.; Temmer, Manuela; Baumgartner, Dietmar J.; Freislich, Heinrich; Strutzmann, Heinz Bibcode: 2016SoPh..291.3103P Altcode: 2016SoPh..tmp...43P; 2015arXiv151200270P The Kanzelhöhe Observatory (KSO) was founded during World War II by the Deutsche Luftwaffe (German Airforce) as one station of a network of observatories that were set up to provide information on solar activity in order to better assess the actual conditions of the Earth's ionosphere in terms of radio-wave propagation. Solar observations began in 1943 with photographs of the photosphere and drawings of sunspots, plage regions, and faculae, as well as patrol observations of the solar corona. At the beginning, all data were sent to Freiburg (Germany). After WW II, international cooperation was established and the data were sent to Zurich, Paris, Moscow, and Greenwich. Relative sunspot numbers have been derived since 1944. The agreement between relative sunspot numbers derived at KSO and the new International Sunspot Number (ISN) (SILSO World Data Center in International Sunspot Number Monthly Bulletin and online catalogue, 1945 - 2015) lies within ≈10 % . However, revisiting the historical data, we also find periods with larger deviations. The reasons for the deviations were twofold: On the one hand, a major instrumental change took place during which the instrument was relocated and modified. On the other hand, a period of frequent replacements of personnel caused significant deviations; this clearly shows the importance of experienced observers. In the long term, the instrumental improvements led to better image quality. Additionally, we find a long-term trend towards better seeing conditions that began in 2000. Title: Kinematical properties of coronal mass ejections Authors: Temmer, M. Bibcode: 2016AN....337.1010T Altcode: 2016arXiv160301398T Coronal mass ejections (CMEs) are the most dynamic phenomena in our solar system. They abruptly disrupt the continuous outflow of solar wind by expelling huge clouds of magnetized plasma into interplanetary space with velocities enabling to cross the Sun-Earth distance within a few days. Earth-directed CMEs may cause severe geomagnetic storms when their embedded magnetic fields and the shocks ahead compress and reconnect with the Earth's magnetic field. The transit times and impacts in detail depend on the initial CME velocity, size, and mass, as well as on the conditions and coupling processes with the ambient solar wind flow in interplanetary space. The observed CME parameters may be severely affected by projection effects and the constant changing environmental conditions are hard to derive. This makes it difficult to fully understand the physics behind CME evolution, preventing to do a reliable forecast of Earth-directed events. This short review focusing on observational data, shows recent methods which were developed to derive the CME kinematical profile for the entire Sun-Earth distance range as well as studies which were performed to shed light on the physical processes that CMEs encounter when propagating from Sun to Earth. Title: Projection Effects in Coronal Dimmings and Associated EUV Wave Event Authors: Dissauer, K.; Temmer, M.; Veronig, A. M.; Vanninathan, K.; Magdalenić, J. Bibcode: 2016ApJ...830...92D Altcode: 2016arXiv160705961D We investigate the high-speed (v > 1000 km s-1) extreme-ultraviolet (EUV) wave associated with an X1.2 flare and coronal mass ejection (CME) from NOAA active region 11283 on 2011 September 6 (SOL2011-09-06T22:12). This EUV wave features peculiar on-disk signatures in particular, we observe an intermittent “disappearance” of the front for 120 s in Solar Dynamics Observatory (SDO)/AIA 171, 193, 211 Å data, whereas the 335 Å filter, sensitive to hotter plasmas (T ∼ 2.5 MK), shows a continuous evolution of the wave front. The eruption was also accompanied by localized coronal dimming regions. We exploit the multi-point quadrature position of SDO and STEREO-A, to make a thorough analysis of the EUV wave evolution, with respect to its kinematics and amplitude evolution and reconstruct the SDO line-of-sight (LOS) direction of the identified coronal dimming regions in STEREO-A. We show that the observed intensities of the dimming regions in SDO/AIA depend on the structures that are lying along their LOS and are the combination of their individual intensities, e.g., the expanding CME body, the enhanced EUV wave, and the CME front. In this context, we conclude that the intermittent disappearance of the EUV wave in the AIA 171, 193, and 211 Å filters, which are channels sensitive to plasma with temperatures below ∼2 MK is also caused by such LOS integration effects. These observations clearly demonstrate that single-view image data provide us with limited insight to correctly interpret coronal features. Title: A small mission concept to the Sun-Earth Lagrangian L5 point for innovative solar, heliospheric and space weather science Authors: Lavraud, B.; Liu, Y.; Segura, K.; He, J.; Qin, G.; Temmer, M.; Vial, J. -C.; Xiong, M.; Davies, J. A.; Rouillard, A. P.; Pinto, R.; Auchère, F.; Harrison, R. A.; Eyles, C.; Gan, W.; Lamy, P.; Xia, L.; Eastwood, J. P.; Kong, L.; Wang, J.; Wimmer-Schweingruber, R. F.; Zhang, S.; Zong, Q.; Soucek, J.; An, J.; Prech, L.; Zhang, A.; Rochus, P.; Bothmer, V.; Janvier, M.; Maksimovic, M.; Escoubet, C. P.; Kilpua, E. K. J.; Tappin, J.; Vainio, R.; Poedts, S.; Dunlop, M. W.; Savani, N.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard, T.; DeForest, C.; Webb, D.; Lugaz, N.; Fuselier, S. A.; Dalmasse, K.; Tallineau, J.; Vranken, D.; Fernández, J. G. Bibcode: 2016JASTP.146..171L Altcode: We present a concept for a small mission to the Sun-Earth Lagrangian L5 point for innovative solar, heliospheric and space weather science. The proposed INvestigation of Solar-Terrestrial Activity aNd Transients (INSTANT) mission is designed to identify how solar coronal magnetic fields drive eruptions, mass transport and particle acceleration that impact the Earth and the heliosphere. INSTANT is the first mission designed to (1) obtain measurements of coronal magnetic fields from space and (2) determine coronal mass ejection (CME) kinematics with unparalleled accuracy. Thanks to innovative instrumentation at a vantage point that provides the most suitable perspective view of the Sun-Earth system, INSTANT would uniquely track the whole chain of fundamental processes driving space weather at Earth. We present the science requirements, payload and mission profile that fulfill ambitious science objectives within small mission programmatic boundary conditions. Title: Exceptions to the rule: the X-flares of AR 2192 Lacking Coronal Mass Ejections Authors: Thalmann, J. K.; Su, Y.; Temmer, M.; Veronig, A. M. Bibcode: 2016ASPC..504..203T Altcode: NOAA Active region (AR) 2192, that was present on the Sun in October 2014, was the largest region which occurred since November 1990 (see Figure 1). The huge size accompanied by a very high activity level, was quite unexpected as it appeared during the unusually weak solar cycle 24. Nevertheless, the AR turned out to be one of the most prolific flaring ARs of cycle 24. It produced in total 6 X, 29 M, 79 C flares during its disk passage from October 18-29, 2014 (see Figure 2). Surprisingly, all flares greater than GOES class M5 and X were confined, i.e. had no coronal mass ejections (CME) associated. All the flare events had some obvious similarity in morphology, as they were located in the core of the AR and revealed only minor separation motion away from the neutral line but a large initial separation of the conjugate flare ribbons. In the paper by Thalmann et al. (2015) we describe the series of flares and give details about the confined X1.6 flare event from October 22, 2014 as well as the single eruptive M4.0 flare event from October 24, 2014. The study of the X1.6 flare revealed a large initial separation of flare ribbons together with recurrent flare brightenings, which were related to two episodes of enhanced hard X-ray emission as derived from RHESSI observations. This suggests that magnetic field structures connected to specific regions were repeatedly involved in the process of reconnection and energy release. Opposite to the central location of the sequence of confined events within the AR, a single eruptive (M4.0) event occurred on the outskirt of the AR in the vicinity of open magnetic fields. Our investigations revealed a predominantly north-south oriented magnetic system of arcade fields overlying the AR that could have preserved the magnetic arcade to erupt, and consequently kept the energy release trapped in a localized volume of magnetic field high up in the corona (as supported by the absence of a lateral motion of the flare ribbons and the recurrent brightenings within them). We conclude that the background magnetic field configuration is an essential parameter for deriving the "eruptiveness" of flare events. Sun et al. (2015) supports this conclusion and derived for this AR a quite slow decay of the strength of the overlying magnetic field (decay index; see Török & Kliem 2005). Interestingly, our magnetic field modellings revealed no flux rope inherent to the AR, indicating that further investigations are needed. In a recent paper by Veronig $ Polanec (2015), who investigated in more detail the X-flares using also ground-based observations in Hα from Kanzelhöhe Observatory (Pötzi et al. 2015), it was shown that such confined events could be explained by the emerging-flux model, where newly emerging small flux tubes reconnect with pre-existing large coronal loops. Title: Coimbra Solar Physics Meeting: Ground-based Solar Observations in the Space Instrumentation Era Authors: Dorotovic, I.; Fischer, C. E.; Temmer, M. Bibcode: 2016ASPC..504.....D Altcode: No abstract at ADS Title: Projection effects in coronal dimmings and associated EUV wave event Authors: Dissauer, Karin; Temmer, Manuela; Veronig, Astrid; Vanninathan, Kamalam; Magdalenic, Jasmina Bibcode: 2016EGUGA..18.6857D Altcode: We investigate the high-speed (v > 1000 km s-1) extreme-ultraviolet (EUV) wave associated with an X1.2 flare and coronal mass ejection (CME) from NOAA active region 11283. This EUV wave features peculiar on-disk signatures, in particular we observe an intermittent "disappearance" of the front for 120 s in SDO/AIA 171, 193, 211 Å data, whereas the 335 Å filter, sensitive to hotter plasmas (T∼ 2.5 MK), shows a continuous evolution of the wave front. We exploit the multi-point quadrature position of SDO and STEREO-A, to make a thorough analysis of the EUV wave evolution, with respect to its kinematics and amplitude evolution. We identify on-disk coronal dimming regions in SDO/AIA, reminiscent of core dimmings, that have no corresponding on-disk dimming signatures in STEREO-A/EUVI. Reconstructing the SDO line-of-sight (LOS) direction in STEREO-A clearly shows that the observed SDO on-disk dimming areas are not the footprints of the erupting fluxrope but result from decreased emission from the expanding CME body integrated along the LOS. In this context, we conclude that the intermittent disappearance of the EUV wave in the AIA 171, 193, 211 Å filters, which are channels sensitive to plasma with temperatures below ∼ 2 MK is also caused by such LOS integration effects. These observations clearly demonstrate that single-view image data provide us with limited insight to correctly interpret coronal features. Title: Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare Authors: Gömöry, P.; Veronig, A. M.; Su, Y.; Temmer, M.; Thalmann, J. K. Bibcode: 2016A&A...588A...6G Altcode: 2016arXiv160202145G
Aims: We study the response of the solar atmosphere during a GOES M1.6 flare using spectroscopic and imaging observations. In particular, we examine the evolution of the mass flows and electron density together with the energy input derived from hard X-ray (HXR) in the context of chromospheric evaporation.
Methods: We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer in the Fe xiii 202.044 Å (log T = 6.2) and Fe xvi 262.980 Å (log T = 6.4) spectral lines to derive temporal variations of the line intensity, Doppler shifts, and electron density during the flare. We combined these data with HXR measurements acquired with RHESSI to derive the energy input to the lower atmosphere by flare-accelerated electrons.
Results: During the flare impulsive phase, we observe no significant flows in the cooler Fe xiii line but strong upflows, up to 80-150 km s-1, in the hotter Fe xvi line. The largest Doppler shifts observed in the Fe xvi line were co-temporal with the sharp intensity peak. The electron density obtained from a Fe xiii line pair ratio exhibited fast increase (within two minutes) from the pre-flare level of 5.01 × 109 cm-3 to 3.16 × 1010 cm-3 during the flare peak. The nonthermal energy flux density deposited from the coronal acceleration site to the lower atmospheric layers during the flare peak was found to be 1.34 × 1010 erg s-1 cm-2 for a low-energy cut-off that was estimated to be 16 keV. During the decline flare phase, we found a secondary intensity and density peak of lower amplitude that was preceded by upflows of ~15 km s-1 that were detected in both lines. The flare was also accompanied by a filament eruption that was partly captured by the EIS observations. We derived Doppler velocities of 250-300 km s-1 for the upflowing filament material.
Conclusions: The spectroscopic results for the flare peak are consistent with the scenario of explosive chromospheric evaporation, although a comparatively low value of the nonthermal energy flux density was determined for this phase of the flare. This outcome is discussed in the context of recent hydrodynamic simulations. It provides observational evidence that the response of the atmospheric plasma strongly depends on the properties of the electron beams responsible for the heating, in particular the steepness of the energy distribution. The secondary peak of line intensity and electron density detected during the decline phase is interpreted as a signature of flare loops being filled by expanding hot material that is due to chromospheric evaporation.

A movie is available at http://www.aanda.org Title: Space Weather and confined CME events Authors: Thalmann, Julia; Temmer, Manuela; Veronig, Astrid; Su, Yang Bibcode: 2016EGUGA..18.7517T Altcode: The unusually large NOAA active region (AR) 2192, observed in October and November 2014, was outstanding in its productivity of major flares (GOES class M5 and larger). During the time when the AR faced Earth, major Space Weather events would have been expected. However, none of the X-flares was associated to a coronal mass ejection. Observational evidence for the confinement of the flare are large initial separation of the flare ribbons, together with an almost absent growth in ribbon separation. The low dynamic of the ribbons also suggests a reconnection site high up in the corona. From NLFF modeling we show that the arcade overlying the AR had a predominantly north-south oriented magnetic system, which served as a strong, also lateral, confinement for the flares at the core of the active region. From the magnetic field modeling we derived the decay of the constraining background, and it was found that the overlying field was only slowly decaying with height. We conclude that observational data of the solar surface, especially of flare ribbon dynamics as well as magnetic field models support Space Weather predictions. Title: ENLIL Global Heliospheric Modeling as a Context For Multipoint Observations Authors: Mays, M. Leila; Odstrcil, Dusan; Luhmann, Janet; Bain, Hazel; Li, Yan; Schwadron, Nathan; Gorby, Matt; Thompson, Barbara; Jian, Lan; Möstl, Christian; Rouillard, Alexis; Davies, Jackie; Temmer, Manuela; Rastaetter, Lutz; Taktakishvili, Aleksandre; MacNeice, Peter; Kuznetsova, Maria Bibcode: 2016EGUGA..1811638M Altcode: We present heliospheric simulation case studies using recent enhancements to WSA--ENLIL+Cone (version 2.8) at the Community Coordinated Modeling Center (CCMC). The global 3D MHD ENLIL model provides a time-dependent description of the background solar wind plasma and magnetic field using a sequence of WSA coronal model maps as input at the inner boundary of 21.5 Rs. A homogeneous, over-pressured hydrodynamic plasma cloud is launched through the inner boundary of the heliospheric computational domain and into the background solar wind. Multipoint observations help constrain simulations and this modeling system provides global context and arrival times of the solar wind streams and CMEs at Earth, planets, and spacecraft. Additionally, one can extract the magnetic topologies of observer-connected magnetic field lines and all plasma and shock properties along those field lines. ENLIL "likelihood/all-clear" forecasting maps provide expected intensity, timing/duration of events at locations throughout the heliosphere with "possible SEP affected areas" color-coded based on shock strength. ENLIL simulations are also useful to drive SEP models such as the Solar Energetic Particle Model (SEPMOD) (Luhmann et al. 2007, 2010) and Energetic Particle Radiation Environment Module (EPREM) (Schwadron et al., 2010). SEPMOD injects protons onto a sequence observer field lines at intensities dependent on the connected shock source strength which are then integrated at the observer to approximate the proton flux. EPREM couples with MHD models such as ENLIL and computes energetic particle distributions based on the focused transport equation along a Lagrangian grid of nodes that propagate out with the solar wind. Studies have shown that accurate descriptions of the heliosphere, and hence modeled CME arrival times and SEPs, are achieved by ENLIL only when the background solar wind is well-reproduced and CME parameters are accurate. It is essential to include all of the relevant CMEs and allow enough time for the events to propagate and interact. In this presentation we demonstrate several event case studies of ENLIL simulations compared with multipoint observations, exploring the background solar wind and CME pre-conditioning, and including comparisons between ENLIL synthetic j-maps with observed STEREO/HI j-maps using catalogues from the HELCATS FP7 project. Title: Forecasting the Arrival of Coronal Mass Ejections: The Drag-Based Model Authors: Vršnak, B.; Temmer, M.; Zic, T.; Dumbović, M.; Čalogović, J. Bibcode: 2016ASPC..504..209V Altcode: Arrival-time predictions based on the numerical "WSA-ENLIL+Cone model" and the analytical "Drag-based model" (DBM) are analyzed, employing a sample of 50 well observed CMEs. The best match between the two models is obtained if the background solar-wind speed of w = 400 km s-1 is applied in DBM. It is also demonstrated that both models show similar prediction accuracy. Title: Impact of coronal mass ejections on the Earth's thermosphere and geoeffectiveness observed by ACE and GRACE: Statistical results Authors: Krauss, Sandro; Temmer, Manuela; Veronig, Astrid; Baur, Oliver Bibcode: 2016EGUGA..18.9350K Altcode: For the period July 2003 to August 2010, the interplanetary coronal mass ejection (ICME) catalogue maintained by Richardson and Cane lists 106 Earth-directed events, which have been measured in situ by plasma and field instruments on board the ACE satellite. We present a statistical investigation of the Earth's thermospheric neutral density response by means of accelerometer measurements collected by the Gravity Recovery And Climate Experiment (GRACE) satellites, which are available for 104 ICMEs in the data set. We relate the thermospheric density increase to various geomagnetic indices (e.g. Dst, AE, Kp, a-indices, ...) and characteristic ICME parameters (impact speed, southward magnetic field strength Bz). We find high correlations between the ICME Bz and thermospheric density enhancements as well as with most of the geomagnetic indices. Separating the response for the shock-sheath region and the magnetic structure of the ICME, we find for instance that the Dst and SYM-H indices reveal a tighter relation to the Bz minimum in the magnetic structure of the ICME, whereas the polar cap indices show higher correlations with the Bz minimum in the shock-sheath region. These results are expected to further stimulate progress in space weather understanding and applications regarding satellite operations. Title: Injection of solar energetic particles into both loop legs of a magnetic cloud Authors: Dresing, N.; Gómez-Herrero, R.; Heber, B.; Hidalgo, M. A.; Klassen, A.; Temmer, M.; Veronig, A. Bibcode: 2016A&A...586A..55D Altcode: 2016arXiv160100491D Context. Each of the two Solar TErrestrial RElations Observatory (STEREO) spacecraft carries a Solar Electron and Proton Telescope (SEPT) which measures electrons and protons. Anisotropy observations are provided in four viewing directions: along the nominal magnetic field Parker spiral in the ecliptic towards the Sun (SUN) and away from the Sun (Anti-Sun/ASUN), and towards the north (NORTH) and south (SOUTH). The solar energetic particle (SEP) event on 7 November 2013 was observed by both STEREO spacecraft, which were longitudinally separated by 68° at that time. While STEREO A observed the expected characteristics of an SEP event at a well-connected position, STEREO B detected a very anisotropic bi-directional distribution of near-relativistic electrons and was situated inside a magnetic-cloud-like structure during the early phase of the event.
Aims: We examine the source of the bi-directional SEP distribution at STEREO B. On the one hand this distribution could be caused by a double injection into both loop legs of the magnetic cloud (MC). On the other hand, a mirroring scenario where the incident beam is reflected in the opposite loop leg could be the reason. Furthermore, the energetic electron observations are used to probe the magnetic structure inside the magnetic cloud.
Methods: We investigate in situ plasma and magnetic field observations and show that STEREO B was embedded in an MC-like structure ejected three days earlier on 4 November from the same active region. We apply a Graduated Cylindrical Shell (GCS) model to the coronagraph observations from three viewpoints as well as the Global Magnetic Cloud (GMC) model to the in situ measurements at STEREO B to determine the orientation and topology of the MC close to the Sun and at 1 AU. We also estimate the path lengths of the electrons propagating through the MC to estimate the amount of magnetic field line winding inside the structure.
Results: The relative intensity and timing of the energetic electron increases in the different SEPT telescopes at STEREO B strongly suggest that the bi-directional electron distribution is formed by SEP injections in both loop legs of the MC separately instead of by mirroring farther away beyond the STEREO orbit. Observations by the Nançay Radioheliograph (NRH) of two distinct radio sources during the SEP injection further support the above scenario. The determined electron path lengths are around 50% longer than the estimated lengths of the loop legs of the MC itself (based on the GCS model) suggesting that the amount of field line winding is moderate. Title: 70 Years of Sunspot Observations at Kanzelhoehe Observatory Authors: Pötzi, W.; Veronig, A.; Temmer, M.; Baumgartner, D. J.; Freislich, H.; Strutzmann, H. Bibcode: 2016CEAB...40..143P Altcode: During World War II the German Airforce established a network of observatories, among them the Kanzelhöhe Observatory (KSO), which would provide information on solar activity in order to investigate the conditions of the Earth's ionosphere in terms of radio-wave propagation. Solar observations began already in 1943 with photographs of the photosphere and drawings of sunspots, plage regions and faculae, as well as patrol observations of the solar corona. Since 1944 relative sunspot numbers were derived, these relative numbers agree with the new International Sunspot Number tep[ISN,][]{SIDC,Clette2014} within ≈ 10%. However, revisiting the historical data, we also find periods with larger deviations. There were two main reasons for these deviations. On the one hand major instrumental changes took place and the instrument was relocated to another observation tower. On the other hand there were periods of frequent replacements of personnel. In the long term, the instrumental improvements led to better image quality, and a trend towards better seeing conditions since the year 2000 was found. Title: Formation of Coronal Large-Amplitude Waves and the Chromospheric Response Authors: Vršnak, B.; Žic, T.; Lulić, S.; Temmer, M.; Veronig, A. M. Bibcode: 2016SoPh..291...89V Altcode: 2015SoPh..tmp..175V An in-depth analysis of numerical simulations is performed to obtain a deeper insight into the nature of various phenomena occurring in the solar atmosphere as a consequence of the eruption of unstable coronal structures. Although the simulations take into account only the most basic characteristics of a flux-rope eruption, the simulation analysis reveals important information on various eruption-related effects. It quantifies the relation between the eruption dynamics and the evolution of the large-amplitude coronal magnetohydrodynamic wave and the associated chromospheric downward-propagating perturbation. We show that the downward propagation of the chromospheric Moreton-wave disturbance can be approximated by a constant-amplitude switch-on shock that moves through a medium of rapidly decreasing Alfvén velocity. The presented analysis reveals the nature of secondary effects that are observed as coronal upflows, secondary shocks, various forms of wave-trains, delayed large-amplitude slow disturbances, transient coronal depletions, etc. We also show that the eruption can cause an observable Moreton wave and a secondary coronal front only if it is powerful enough and is preferably characterized by significant lateral expansion. In weaker eruptions, only the coronal and transition-region signatures of primary waves are expected to be observed. In powerful events, the primary wave moves at an Alfvén Mach number significantly larger than 1 and steepens into a shock that is due to the nonlinear evolution of the wavefront. After the eruption-driven phase, the perturbation evolves as a freely propagating simple wave, characterized by a significant deceleration, amplitude decrease, and wave-profile broadening. In weak events the coronal wave does not develop into a shock and propagates at a speed close to the ambient magnetosonic speed. Title: ALMA Observations of the Sun in Cycle 4 and Beyond Authors: Wedemeyer, S.; Fleck, B.; Battaglia, M.; Labrosse, N.; Fleishman, G.; Hudson, H.; Antolin, P.; Alissandrakis, C.; Ayres, T.; Ballester, J.; Bastian, T.; Black, J.; Benz, A.; Brajsa, R.; Carlsson, M.; Costa, J.; DePontieu, B.; Doyle, G.; Gimenez de Castro, G.; Gunár, S.; Harper, G.; Jafarzadeh, S.; Loukitcheva, M.; Nakariakov, V.; Oliver, R.; Schmieder, B.; Selhorst, C.; Shimojo, M.; Simões, P.; Soler, R.; Temmer, M.; Tiwari, S.; Van Doorsselaere, T.; Veronig, A.; White, S.; Yagoubov, P.; Zaqarashvili, T. Bibcode: 2016arXiv160100587W Altcode: This document was created by the Solar Simulations for the Atacama Large Millimeter Observatory Network (SSALMON) in preparation of the first regular observations of the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA), which are anticipated to start in ALMA Cycle 4 in October 2016. The science cases presented here demonstrate that a large number of scientifically highly interesting observations could be made already with the still limited solar observing modes foreseen for Cycle 4 and that ALMA has the potential to make important contributions to answering long-standing scientific questions in solar physics. With the proposal deadline for ALMA Cycle 4 in April 2016 and the Commissioning and Science Verification campaign in December 2015 in sight, several of the SSALMON Expert Teams composed strategic documents in which they outlined potential solar observations that could be feasible given the anticipated technical capabilities in Cycle 4. These documents have been combined and supplemented with an analysis, resulting in recommendations for solar observing with ALMA in Cycle 4. In addition, the detailed science cases also demonstrate the scientific priorities of the solar physics community and which capabilities are wanted for the next observing cycles. The work on this White Paper effort was coordinated in close cooperation with the two international solar ALMA development studies led by T. Bastian (NRAO, USA) and R. Brajsa, (ESO). This document will be further updated until the beginning of Cycle 4 in October 2016. In particular, we plan to adjust the technical capabilities of the solar observing modes once finally decided and to further demonstrate the feasibility and scientific potential of the included science cases by means of numerical simulations of the solar atmosphere and corresponding simulated ALMA observations. Title: The exceptional aspects of the confined X-class flares of solar active region 2192 Authors: Thalmann, Julia K.; Su, Yang; Temmer, Manuela; Veronig, Astrid M. Bibcode: 2016IAUS..320...60T Altcode: 2016arXiv160503712T During late October 2014, active region NOAA 2192 caused an unusual high level of solar activity, within an otherwise weak solar cycle. While crossing the solar disk, during a period of 11 days, it was the source of 114 flares of GOES class C1.0 and larger, including 29 M- and 6 X-flares. Surprisingly, none of the major flares (GOES class M5.0 and larger) was accompanied by a coronal mass ejection, contrary to statistical tendencies found in the past. From modeling the coronal magnetic field of NOAA 2192 and its surrounding, we suspect that the cause of the confined character of the flares is the strong surrounding and overlying large-scale magnetic field. Furthermore, we find evidence for multiple magnetic reconnection processes within a single flare, during which electrons were accelerated to unusual high energies. Title: STEREO Observations of an SEP Event Injected Into Both Loop Legs of a Magnetic Cloud Authors: Dresing, N.; Gomez-Herrero, R.; Heber, B.; Hidalgo, M. A. U.; Klassen, A.; Temmer, M.; Veronig, A. Bibcode: 2015AGUFMSH42A..06D Altcode: On 7 Nov 2013 STEREO B was embedded in a magnetic-cloud (MC) like structure when an SEP event occurred reaching both STEREO spacecraft. The bi-drectional near relativistic electron distribution observed by STEREO B reveals such timing and relative intensity characteristics suggesting that the SEPs were injected separately into both loop legs of the MC. Observations by the Nancay Radioheliograph (NRH) of two distinct radio sources at the same time further support the above scenario. In order to derive the 3D morphology and average speed of the CME close to the Sun, we use the graduated cylindrical shell model (GCS) which is applied to the white-light coronagraph observations by the STEREO spacecraft and SOHO. Furthermore, a global magnetic topology model for magnetic clouds is applied to the in-situ measurements of the magnetic field. Both models suggest that the MC is strongly inclined with respect to the ecliptic yielding a north/south orientation. The energetic electron observations are used to probe the structure of the magnetic cloud: We determine the electron path lengths along both loop legs of the structure to infer the amount of field line twist inside the MC. The resulting path lengths are around 50% longer than the estimated lengths of the loop legs of the MC itself suggesting that the amount of field line winding is moderate. Title: Low Solar Wind Density Causing the Fast Coronal Mass Ejection from 23 July 2012 Authors: Nitta, N.; Temmer, M. Bibcode: 2015AGUFMSH53A2458N Altcode: The fast coronal mass ejection (CME) from July 23, 2012 raised special attention due to its short propagation time of less than 21hrs from Sun to 1 AU. In-situ data from STEREO-A revealed the arrival of a fast forward shock having a velocity of more than 2200 km/s followed by a magnetic structure with a speed of almost 1900 km/s. We study the evolution of the CME in interplanetary (IP) space using the drag based model to reproduce the short propagation time and high impact speed as derived from in-situ data. We find that the ambient density must have been exceptionally low due to which the drag force is reduced such that the CME experienced almost no deceleration. The density is found to be rather low due to the weak solar activity and was lowered even more by a previous CME event. Title: Propagation of the 7 January 2014 CME and Resulting Geomagnetic Non-event Authors: Mays, M. L.; Thompson, B. J.; Jian, L. K.; Colaninno, R. C.; Odstrcil, D.; Möstl, C.; Temmer, M.; Savani, N. P.; Collinson, G.; Taktakishvili, A.; MacNeice, P. J.; Zheng, Y. Bibcode: 2015ApJ...812..145M Altcode: 2015arXiv150906477M On 2014 January 7 an X1.2 flare and coronal mass ejection (CME) with a radial speed ≈2500 km s-1 was observed from near an active region close to disk center. This led many forecasters to estimate a rapid arrival at Earth (≈36 hr) and predict a strong geomagnetic storm. However, only a glancing CME arrival was observed at Earth with a transit time of ≈49 hr and a K P geomagnetic index of only 3-. We study the interplanetary propagation of this CME using the ensemble Wang-Sheeley-Arge (WSA)-ENLIL+Cone model, that allows a sampling of CME parameter uncertainties. We explore a series of simulations to isolate the effects of the background solar wind solution, CME shape, tilt, location, size, and speed, and the results are compared with observed in situ arrivals at Venus, Earth, and Mars. Our results show that a tilted ellipsoid CME shape improves the initial real-time prediction to better reflect the observed in situ signatures and the geomagnetic storm strength. CME parameters from the Graduated Cylindrical Shell model used as input to WSA-ENLIL+Cone, along with a tilted ellipsoid cloud shape, improve the arrival-time error by 14.5, 18.7, 23.4 hr for Venus, Earth, and Mars respectively. These results highlight that CME orientation and directionality with respect to observatories play an important role in understanding the propagation of this CME, and for forecasting other glancing CME arrivals. This study also demonstrates the importance of three-dimensional CME fitting made possible by multiple viewpoint imaging. Title: Thermospheric and geomagnetic responses to interplanetary coronal mass ejections observed by ACE and GRACE: Statistical results Authors: Krauss, S.; Temmer, M.; Veronig, A.; Baur, O.; Lammer, H. Bibcode: 2015JGRA..120.8848K Altcode: 2015arXiv151003549K For the period July 2003 to August 2010, the interplanetary coronal mass ejection (ICME) catalogue maintained by Richardson and Cane lists 106 Earth-directed events, which have been measured in situ by plasma and field instruments on board the ACE satellite. We present a statistical investigation of the Earth's thermospheric neutral density response by means of accelerometer measurements collected by the Gravity Recovery And Climate Experiment (GRACE) satellites, which are available for 104 ICMEs in the data set, and its relation to various geomagnetic indices and characteristic ICME parameters such as the impact speed (vmax), southward magnetic field strength (Bz). The majority of ICMEs causes a distinct density enhancement in the thermosphere, with up to a factor of 8 compared to the preevent level. We find high correlations between ICME Bz and thermospheric density enhancements (≈0.9), while the correlation with the ICME impact speed is somewhat smaller (≈0.7). The geomagnetic indices revealing the highest correlations are Dst and SYM-H(≈0.9); the lowest correlations are obtained for Kp and AE (≈0.7), which show a nonlinear relation with the thermospheric density enhancements. Separating the response for the shock-sheath region and the magnetic structure of the ICME, we find that the Dst and SYM-H reveal a tighter relation to the Bz minimum in the magnetic structure of the ICME, whereas the polar cap indices show higher correlations with the Bz minimum in the shock-sheath region. Since the strength of the Bz component—either in the sheath or in the magnetic structure of the ICME—is highly correlated (≈0.9) with the neutral density enhancement, we discuss the possibility of satellite orbital decay estimates based on magnetic field measurements at L1, i.e., before the ICME hits the Earth magnetosphere. These results are expected to further stimulate progress in space weather understanding and applications regarding satellite operations. Title: The exceptional aspects of the confined X-Flares of Solar Active Region 2192 Authors: Thalmann, Julia K.; Su, Yang; Temmer, Manuela; Veronig, Astrid Bibcode: 2015IAUGA..2215645T Altcode: Active region NOAA 2192 showed an outstanding productivity of major (GOES class M5 and larger) two-ribbon flares lacking eruptive events. None of the X-flares was associated to a coronal mass ejection. The major confined flares on 2014 October 22 and 24 originated from the active-region core and were prohibited to develop an associated mass ejection due to the confinement of the overlying strong magnetic field. In contrast, the single eruptive M-flare on October 24 originated from the outer parts of the active region, in the neighborhood of open large-scale fields, which allowed for the observed mass ejection. Analysis of the spacial and temporal characteristics of the major confined flares revealed exceptional aspects, including a large initial separation of the confined flares' ribbons and an almost absent growth in ribbon separation, suggesting a reconnection site high up in the corona. Furthermore, detailed analysis of a confined X-flare on October 22 provides evidence that magnetic field structures were repeatedly involved in magnetic reconnection, that a large number of electrons was accelerated to non-thermal energies but that only a small fraction out of these accelerated electrons was accelerated to high energies. We conclude the latter due to the unusual steepness of the associated power law spectrum. Finally, we demonstrate that a considerable portion of the magnetic energy released during the X-flare was consumed by the non-thermal flare energy. Title: Improvements on coronal hole detection in SDO/AIA images using supervised classification Authors: Reiss, Martin A.; Hofmeister, Stefan J.; De Visscher, Ruben; Temmer, Manuela; Veronig, Astrid M.; Delouille, Véronique; Mampaey, Benjamin; Ahammer, Helmut Bibcode: 2015JSWSC...5A..23R Altcode: 2015arXiv150606623R We demonstrate the use of machine learning algorithms in combination with segmentation techniques in order to distinguish coronal holes and filaments in SDO/AIA EUV images of the Sun. Based on two coronal hole detection techniques (intensity-based thresholding, SPoCA), we prepared datasets of manually labeled coronal hole and filament channel regions present on the Sun during the time range 2011-2013. By mapping the extracted regions from EUV observations onto HMI line-of-sight magnetograms we also include their magnetic characteristics. We computed shape measures from the segmented binary maps as well as first order and second order texture statistics from the segmented regions in the EUV images and magnetograms. These attributes were used for data mining investigations to identify the most performant rule to differentiate between coronal holes and filament channels. We applied several classifiers, namely Support Vector Machine (SVM), Linear Support Vector Machine, Decision Tree, and Random Forest, and found that all classification rules achieve good results in general, with linear SVM providing the best performances (with a true skill statistic of ≈ 0.90). Additional information from magnetic field data systematically improves the performance across all four classifiers for the SPoCA detection. Since the calculation is inexpensive in computing time, this approach is well suited for applications on real-time data. This study demonstrates how a machine learning approach may help improve upon an unsupervised feature extraction method. Title: Heliospheric Propagation of Coronal Mass Ejections: Drag-based Model Fitting Authors: Žic, T.; Vršnak, B.; Temmer, M. Bibcode: 2015ApJS..218...32Z Altcode: 2015arXiv150608582Z The so-called drag-based model (DBM) simulates analytically the propagation of coronal mass ejections (CMEs) in interplanetary space and allows the prediction of their arrival times and impact speeds at any point in the heliosphere (“target”). The DBM is based on the assumption that beyond a distance of about 20 solar radii from the Sun, the dominant force acting on CMEs is the “aerodynamic” drag force. In the standard form of DBM, the user provisionally chooses values for the model input parameters, by which the kinematics of the CME over the entire Sun-“target” distance range is defined. The choice of model input parameters is usually based on several previously undertaken statistical studies. In other words, the model is used by ad hoc implementation of statistics-based values of the input parameters, which are not necessarily appropriate for the CME under study. Furthermore, such a procedure lacks quantitative information on how well the simulation reproduces the coronagraphically observed kinematics of the CME, and thus does not provide an estimate of the reliability of the arrival prediction. In this paper we advance the DBM by adopting it in a form that employs the CME observations over a given distance range to evaluate the most suitable model input parameters for a given CME by means of least-squares fitting. Furthermore, the new version of the model automatically responds to any significant change of the conditions in the ambient medium (solar wind speed, density, CME-CME interactions, etc.) by changing the model input parameters according to changes in the CME kinematics. The advanced DBM is shaped in a form that can be readily employed in an operational system for real-time space-weather forecasting by promptly adjusting to a successively expanding observational data set, thus providing a successively improving prediction of the CME arrival. Title: Strong coronal channelling and interplanetary evolution of a solar storm up to Earth and Mars Authors: Möstl, Christian; Rollett, Tanja; Frahm, Rudy A.; Liu, Ying D.; Long, David M.; Colaninno, Robin C.; Reiss, Martin A.; Temmer, Manuela; Farrugia, Charles J.; Posner, Arik; Dumbović, Mateja; Janvier, Miho; Démoulin, Pascal; Boakes, Peter; Devos, Andy; Kraaikamp, Emil; Mays, Mona L.; Vršnak, Bojan Bibcode: 2015NatCo...6.7135M Altcode: 2015arXiv150602842M; 2015NatCo...6E7135M The severe geomagnetic effects of solar storms or coronal mass ejections (CMEs) are to a large degree determined by their propagation direction with respect to Earth. There is a lack of understanding of the processes that determine their non-radial propagation. Here we present a synthesis of data from seven different space missions of a fast CME, which originated in an active region near the disk centre and, hence, a significant geomagnetic impact was forecasted. However, the CME is demonstrated to be channelled during eruption into a direction +37+/-10° (longitude) away from its source region, leading only to minimal geomagnetic effects. In situ observations near Earth and Mars confirm the channelled CME motion, and are consistent with an ellipse shape of the CME-driven shock provided by the new Ellipse Evolution model, presented here. The results enhance our understanding of CME propagation and shape, which can help to improve space weather forecasts. Title: Real-Time Solar Wind Prediction Based on SDO/AIA Coronal Hole Data Authors: Rotter, T.; Veronig, A. M.; Temmer, M.; Vršnak, B. Bibcode: 2015SoPh..290.1355R Altcode: 2015arXiv150106697R; 2015SoPh..tmp...37R We present an empirical model based on the visible area covered by coronal holes close to the central meridian with the aim to predict the solar wind speed at 1 AU with a lead time of up to four days in advance with a time resolution of one hour. Linear prediction functions are used to relate coronal hole areas to solar wind speed. The function parameters are automatically adapted by using the information from the previous three Carrington Rotations. Thus the algorithm automatically reacts to the changes of the solar wind speed during different phases of the solar cycle. The adaptive algorithm was applied to and tested on SDO/AIA-193 Å observations and ACE measurements during the years 2011 - 2013, covering 41 Carrington Rotations. The solar wind needs on average 4.02±0.5 days to reach Earth. The algorithm produces good predictions for the 156 solar wind high-speed streams peak amplitudes with correlation coefficients of cc≈0.60. For 80 % of the peaks, the predicted arrival matches the ACE in situ measurements within a time window of 0.5 days. The same algorithm, using linear predictions, was also applied to predict the magnetic field strength in wind streams originating from coronal hole areas, but it did not give reliable predictions (cc≈0.15). Title: Strong coronal deflection of a CME and its interplanetary evolution to Earth and Mars Authors: Möstl, Christian; Rollett, Tanja; Frahm, Rudy A.; Liu, Ying D.; Long, David M.; Colaninno, Robin C.; Reiss, Martin A.; Temmer, Manuela; Farrugia, Charles J.; Posner, Arik; Dumbovic, Mateja; Janvier, Miho; Demoulin, Pascal; Boakes, Peter; Devos, Andy; Kraaikamp, Emil; Mays, Mona L.; Vrsnak, Bojan Bibcode: 2015EGUGA..17.1366M Altcode: We discuss multipoint imaging and in situ observations of the coronal mass ejection (CME) on January 7 2014 which resulted in a major false alarm. While the source region was almost at disk center facing Earth, the eruption was strongly deflected in the corona, and in conjunction with its particular orientation this CME missed Earth almost entirely, leading to no significant geomagnetic effects. We demonstrate this by a synthesis of data from 7 different heliospheric and planetary space missions (STEREO-A/B, SOHO, SDO, Wind, Mars Express, Mars Science Laboratory). The CMEs ecliptic part was deflected by 37 ± 10° in heliospheric longitude, a value larger than previously thought. Multipoint in situ observations at Earth and Mars confirm the deflection, and are consistent with an elliptical interplanetary shock shape of aspect ratio 1.4 ± 0.4. We also discuss our new method, the Ellipse Evolution (ElEvo) model, which allows us to optimize the global shape of the CME shock with multipoint in situ observations of the interplanetary CME arrival. ElEvo, which is an extension to the Drag-Based-Model by Vrsnak et al., may also be used for real time space weather forecasting. The presented results enhance our understanding of CME deflection and shape, which are fundamental ingredients for improving space weather forecasts. Title: The Confined X-class Flares of Solar Active Region 2192 Authors: Thalmann, J. K.; Su, Y.; Temmer, M.; Veronig, A. M. Bibcode: 2015ApJ...801L..23T Altcode: 2015arXiv150205157T The unusually large active region (AR) NOAA 2192, observed in 2014 October, was outstanding in its productivity of major two-ribbon flares without coronal mass ejections. On a large scale, a predominantly north-south oriented magnetic system of arcade fields served as a strong top and lateral confinement for a series of large two-ribbon flares originating from the core of the AR. The large initial separation of the flare ribbons, together with an almost absent growth in ribbon separation, suggests a confined reconnection site high up in the corona. Based on a detailed analysis of the confined X1.6 flare on October 22, we show how exceptional the flaring of this AR was. We provide evidence for repeated energy release, indicating that the same magnetic field structures were repeatedly involved in magnetic reconnection. We find that a large number of electrons was accelerated to non-thermal energies, revealing a steep power-law spectrum, but that only a small fraction was accelerated to high energies. The total non-thermal energy in electrons derived (on the order of 1025 J) is considerably higher than that in eruptive flares of class X1, and corresponds to about 10% of the excess magnetic energy present in the active-region corona. Title: Interplanetary Propagation Behavior of the Fast Coronal Mass Ejection on 23 July 2012 Authors: Temmer, M.; Nitta, N. V. Bibcode: 2015SoPh..290..919T Altcode: 2015SoPh..tmp....2T; 2014arXiv1411.6559T The fast coronal mass ejection (CME) on 23 July 2012 caused attention because of its extremely short transit time from the Sun to 1 AU, which was shorter than 21 h. In situ data from STEREO-A revealed the arrival of a fast forward shock with a speed of more than 2200 km s−1 followed by a magnetic structure moving with almost 1900 km s−1. We investigate the propagation behavior of the CME shock and magnetic structure with the aim to reproduce the short transit time and high impact speed as derived from in situ data. We carefully measured the 3D kinematics of the CME using the graduated cylindrical shell model and obtained a maximum speed of 2580±280 km s−1 for the CME shock and 2270±420 km s−1 for its magnetic structure. Based on the 3D kinematics, the drag-based model (DBM) reproduces the observational data reasonably well. To successfully simulate the CME shock, the ambient flow speed needs to have an average value close to the slow solar wind speed (450 km s−1), and the initial shock speed at a distance of 30 R⊙ should not exceed ≈ 2300 km s−1, otherwise it would arrive much too early at STEREO-A. The model results indicate that an extremely small aerodynamic drag force is exerted on the shock, smaller by one order of magnitude than average. As a consequence, the CME hardly decelerates in interplanetary space and maintains its high initial speed. The low aerodynamic drag can only be reproduced when the density of the ambient solar wind flow, in which the fast CME propagates, is decreased to ρsw=1 - 2 cm−3 at the distance of 1 AU. This result is consistent with the preconditioning of interplanetary space by a previous CME. Title: Real-time Flare Detection in Ground-Based Hα Imaging at Kanzelhöhe Observatory Authors: Pötzi, W.; Veronig, A. M.; Riegler, G.; Amerstorfer, U.; Pock, T.; Temmer, M.; Polanec, W.; Baumgartner, D. J. Bibcode: 2015SoPh..290..951P Altcode: 2014arXiv1411.3896P; 2014SoPh..tmp..193P Kanzelhöhe Observatory (KSO) regularly performs high-cadence full-disk imaging of the solar chromosphere in the Hα and Ca II K spectral lines as well as in the solar photosphere in white light. In the frame of ESA's (European Space Agency) Space Situational Awareness (SSA) program, a new system for real-time Hα data provision and automatic flare detection was developed at KSO. The data and events detected are published in near real-time at ESA's SSA Space Weather portal (http://swe.ssa.esa.int/web/guest/kso-federated). In this article, we describe the Hα instrument, the image-recognition algorithms we developed, and the implementation into the KSO Hα observing system. We also present the evaluation results of the real-time data provision and flare detection for a period of five months. The Hα data provision worked in 99.96 % of the images, with a mean time lag of four seconds between image recording and online provision. Within the given criteria for the automatic image-recognition system (at least three Hα images are needed for a positive detection), all flares with an area ≥ 50 micro-hemispheres that were located within 60° of the solar center and occurred during the KSO observing times were detected, a number of 87 events in total. The automatically determined flare importance and brightness classes were correct in ∼ 85 %. The mean flare positions in heliographic longitude and latitude were correct to within ∼ 1°. The median of the absolute differences for the flare start and peak times from the automatic detections in comparison with the official NOAA (and KSO) visual flare reports were 3 min (1 min). Title: Initiation and Evolution of Global Coronal Waves Authors: Vršnak, B.; Muhr, N.; Žic, T.; Lulić, S.; Kienreich, I. W.; Temmer, M.; Veronig, A. M. Bibcode: 2015CEAB...39...65V Altcode: Some essential outcomes of a detailed analysis of the formation and evolution of the coronal EUV wave of 15 February 2011 are presented, focused on the relationship between the source region expansion, wave kinematics, and the evolution of the wave amplitude. The observations are explained in terms of the results of the numerical MHD simulations, providing new insights into the physical background of coronal waves, especially considering the nature of the relationship of the wave amplitude and propagation velocity in different phases of the wave evolution. Title: The real-time flare detection system at Kanzelhöhe Observatory Authors: Pötzi, W.; Veronig, A.; Riegler, G.; Amerstorfer, U.; Pock, TH.; Temmer, M.; Polanec, W.; Baumgartner, D. J. Bibcode: 2015CEAB...39..125P Altcode: Kanzelhöhe Observatory performs regular high-cadence full-disk observations of the solar chromosphere in the Hα and Ca II K spectral lines as well as the solar photosphere in white-light. In the frame of ESA's Space Situational Awareness (SSA) activities, a system for near real-time H-alpha image provision through the SSA Space Weather (SWE) portal (swe.ssa.esa.int) and for automatic alerting of flares and erupting filaments was developed. Image segmentation algorithms, for the automatic detection of solar filaments in real time H-alpha images have been developed and implemented at the Kanzelhöhe observing system. We present results of this system with respect to the automatic recognition and segmentation of flares on the Sun. Title: Forbush decreases associated to Stealth Coronal Mass Ejections Authors: Heber, B.; Wallmann, C.; Galsdorf, D.; Herbst K.; Kühl, P.; Dumbovic, M.; Vršnak, B.; Veronig, A.; Temmer, M.; Möstl, C.; Dalla, S. Bibcode: 2015CEAB...39...75H Altcode: Interplanetary coronal mass ejections (ICMEs) are structures in the solar wind that are the counterparts of coronal mass ejections (CMEs) at the Sun. It is commonly believed that enhanced magnetic fields in interplanetary shocks and solar ejecta as well as the increased turbulence in the solar wind sheath region are the cause of Forbush decreases (FDs) representing decreases of galactic cosmic ray (GCR) intensities. Recently, stealth CMEs i.e.~CMEs with no apparent solar surface association have become a subject in recent studies of solar activity. Whether all of such stealth CMEs can drive a FD is difficult to investigate on the basis of neutron monitor NM measurements because these measurements not only reflect the GCR intensity variation in interplanetary space but also the variation of the geomagnetic field as well as the conditions in the Earth atmosphere. Single detector counter from spacecraft instrumentation, here SOHO and Chandra EPHIN, exceed counting statistic of NMs allowing to determine intensity variation of less than 1 permil in interplanetary space on the basis of 30 minute count rate averages. Here we present the ongoing analysis of eleven stealth CMEs. Title: Instant: An Innovative L5 Small Mission Concept for Coordinated Science with Solar Orbiter and Solar Probe Plus Authors: Lavraud, B.; Liu, Y. D.; Harrison, R. A.; Liu, W.; Auchere, F.; Gan, W.; Lamy, P. L.; Xia, L.; Eastwood, J. P.; Wimmer-Schweingruber, R. F.; Zong, Q.; Rochus, P.; Maksimovic, M.; Temmer, M.; Escoubet, C. P.; Kilpua, E.; Rouillard, A. P.; Davies, J. A.; Vial, J. C.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard, T. A.; DeForest, C. E. Bibcode: 2014AGUFMSH21B4109L Altcode: We will present both the science objectives and related instrumentation of a small solar and heliospheric mission concept, INSTANT: INvestigation of Solar-Terrestrial Activity aNd Transients. It will be submitted as an opportunity to the upcoming ESA-China S-class mission call later this year. This concept was conceived to allow innovative measurements and unprecedented, early determination of key properties of Earthbound CMEs from the L5 vantage point. Innovative measurements will include magnetic field determination in the corona thanks to Hanle measurement in Lyman-α and polarized heliospheric imaging for accurate determination of CME trajectories. With complementary in situ measurements, it will uniquely permit solar storm science, solar storm surveillance, and synergy with Solar Orbiter and Solar Probe Plus (the ESA-China S2 mission launch is planned in 2021). Title: Statistical Analysis of Large-Scale EUV Waves Observed by STEREO/EUVI Authors: Muhr, N.; Veronig, A. M.; Kienreich, I. W.; Vršnak, B.; Temmer, M.; Bein, B. M. Bibcode: 2014SoPh..289.4563M Altcode: 2014arXiv1408.2513M; 2014SoPh..tmp..126M We statistically analyzed the kinematical evolution and wave pulse characteristics of 60 strong large-scale EUV wave events that occurred during January 2007 to February 2011 with the STEREO twin spacecraft. For the start velocity, the arithmetic mean is 312±115 km s−1 (within a range of 100 - 630 km s−1). For the mean (linear) velocity, the arithmetic mean is 254±76 km s−1 (within a range of 130 - 470 km s−1). 52 % of all waves under study show a distinct deceleration during their propagation (a≤−50 m s−2), the other 48 % are consistent with a constant speed within the uncertainties (−50≤a≤50 m s−2). The start velocity and the acceleration are strongly anticorrelated with c≈−0.8, i.e. initially faster events undergo stronger deceleration than slower events. The (smooth) transition between constant propagation for slow events and deceleration in faster events occurs at an EUV wave start-velocity of v≈230 km s−1, which corresponds well to the fast-mode speed in the quiet corona. These findings provide strong evidence that the EUV waves under study are indeed large-amplitude fast-mode MHD waves. This interpretation is also supported by the correlations obtained between the peak velocity and the peak amplitude, impulsiveness, and build-up time of the disturbance. We obtained the following association rates of EUV wave events with other solar phenomena: 95 % are associated with a coronal mass ejection (CME), 74 % to a solar flare, 15 % to interplanetary type II bursts, and 22 % to coronal type II bursts. These findings are consistent with the interpretation that the associated CMEs are the driving agents of the EUV waves. Title: Heliospheric Propagation of Coronal Mass Ejections: Comparison of Numerical WSA-ENLIL+Cone Model and Analytical Drag-based Model Authors: Vršnak, B.; Temmer, M.; Žic, T.; Taktakishvili, A.; Dumbović, M.; Möstl, C.; Veronig, A. M.; Mays, M. L.; Odstrčil, D. Bibcode: 2014ApJS..213...21V Altcode: Real-time forecasting of the arrival of coronal mass ejections (CMEs) at Earth, based on remote solar observations, is one of the central issues of space-weather research. In this paper, we compare arrival-time predictions calculated applying the numerical "WSA-ENLIL+Cone model" and the analytical "drag-based model" (DBM). Both models use coronagraphic observations of CMEs as input data, thus providing an early space-weather forecast two to four days before the arrival of the disturbance at the Earth, depending on the CME speed. It is shown that both methods give very similar results if the drag parameter Γ = 0.1 is used in DBM in combination with a background solar-wind speed of w = 400 km s-1. For this combination, the mean value of the difference between arrival times calculated by ENLIL and DBM is \overline{Δ }=0.09+/- 9.0 hr with an average of the absolute-value differences of \overline{\vert Δ \vert }=7.1 hr. Comparing the observed arrivals (O) with the calculated ones (C) for ENLIL gives O - C = -0.3 ± 16.9 hr and, analogously, O - C = +1.1 ± 19.1 hr for DBM. Applying Γ = 0.2 with w = 450 km s-1 in DBM, one finds O - C = -1.7 ± 18.3 hr, with an average of the absolute-value differences of 14.8 hr, which is similar to that for ENLIL, 14.1 hr. Finally, we demonstrate that the prediction accuracy significantly degrades with increasing solar activity. Title: Combined Multipoint Remote and in situ Observations of the Asymmetric Evolution of a Fast Solar Coronal Mass Ejection Authors: Rollett, T.; Möstl, C.; Temmer, M.; Frahm, R. A.; Davies, J. A.; Veronig, A. M.; Vršnak, B.; Amerstorfer, U. V.; Farrugia, C. J.; Žic, T.; Zhang, T. L. Bibcode: 2014ApJ...790L...6R Altcode: 2014arXiv1407.4687R We present an analysis of the fast coronal mass ejection (CME) of 2012 March 7, which was imaged by both STEREO spacecraft and observed in situ by MESSENGER, Venus Express, Wind, and Mars Express. Based on detected arrivals at four different positions in interplanetary space, it was possible to strongly constrain the kinematics and the shape of the ejection. Using the white-light heliospheric imagery from STEREO-A and B, we derived two different kinematical profiles for the CME by applying the novel constrained self-similar expansion method. In addition, we used a drag-based model to investigate the influence of the ambient solar wind on the CME's propagation. We found that two preceding CMEs heading in different directions disturbed the overall shape of the CME and influenced its propagation behavior. While the Venus-directed segment underwent a gradual deceleration (from ~2700 km s-1 at 15 R ⊙ to ~1500 km s-1 at 154 R ⊙), the Earth-directed part showed an abrupt retardation below 35 R ⊙ (from ~1700 to ~900 km s-1). After that, it was propagating with a quasi-constant speed in the wake of a preceding event. Our results highlight the importance of studies concerning the unequal evolution of CMEs. Forecasting can only be improved if conditions in the solar wind are properly taken into account and if attention is also paid to large events preceding the one being studied. Title: Solar Energetic Particles and Associated EIT Disturbances in Solar Cycle 23 Authors: Miteva, R.; Klein, K. -L.; Kienreich, I.; Temmer, M.; Veronig, A.; Malandraki, O. E. Bibcode: 2014SoPh..289.2601M Altcode: 2014arXiv1402.1676M; 2014SoPh..tmp...37M We explore the link between solar energetic particles (SEPs) observed at 1 AU and large-scale disturbances propagating in the solar corona, named after the Extreme ultraviolet Imaging Telescope (EIT) as EIT waves, which trace the lateral expansion of a coronal mass ejection (CME). A comprehensive search for SOHO/EIT waves was carried out for 179 SEP events during Solar Cycle 23 (1997 - 2006). 87 % of the SEP events were found to be accompanied by EIT waves. In order to test if the EIT waves play a role in the SEP acceleration, we compared their extrapolated arrival time at the footpoint of the Parker spiral with the particle onset in the 26 eastern SEP events that had no direct magnetic connection to the Earth. We find that the onset of proton events was generally consistent with this scenario. However, in a number of cases the first near-relativistic electrons were detected too early. Furthermore, the electrons had in general only weakly anisotropic pitch-angle distributions. This poses a problem for the idea that the SEPs were accelerated by the EIT wave or in any other spatially confined region in the low corona. The presence of weak electron anisotropies in SEP events from the eastern hemisphere suggests that transport processes in interplanetary space, including cross-field diffusion, play a role in giving the SEPs access to a broad range of helio-longitudes. Title: ISEST Program: International Stud of Earth-affecting Solar Transients Authors: Zhang, Jie; Temmer, Manuela; Gopalswamy, Nat Bibcode: 2014shin.confE...7Z Altcode: A new international program: International Study of Earth-affecting Solar Transients (IEST), is introduced. This program is one of the four scientific elements supported by the VarSITI (Variability of the Sun and Its Terrestrial Impact) project, a five-year long international-cross-discipline-collaboration project from 2014-2018, sponsored by the SCOSTEP (Scientific Committee of Solar-Terrestrial Physics). The aim of ISEST is to understand the origin, propagation and evolution of solar transients, including CMEs, CIRs and SEPs, through the space between the Sun and the Earth, and improve the prediction capability for space weather. Particular emphasis will be placed on the weak solar activity prevailing in Solar Cycle 24 (MiniMax24). The ISEST program consists of six working groups, encompassing data analysis, theoretical interpretation, numerical modeling, B-south challenge, event campaign study, and long-term MiniMax24 campaign studies. It is anticipated that the ISEST will create a comprehensive online database of Earth-affecting solar transients contributed by both observers and modelers. By the end of the program It is expected that the space weather prediction using solar observations will be improved significantly. Title: Future mmVLBI Research with ALMA: A European vision Authors: Tilanus, R. P. J.; Krichbaum, T. P.; Zensus, J. A.; Baudry, A.; Bremer, M.; Falcke, H.; Giovannini, G.; Laing, R.; van Langevelde, H. J.; Vlemmings, W.; Abraham, Z.; Afonso, J.; Agudo, I.; Alberdi, A.; Alcolea, J.; Altamirano, D.; Asadi, S.; Assaf, K.; Augusto, P.; Baczko, A-K.; Boeck, M.; Boller, T.; Bondi, M.; Boone, F.; Bourda, G.; Brajsa, R.; Brand, J.; Britzen, S.; Bujarrabal, V.; Cales, S.; Casadio, C.; Casasola, V.; Castangia, P.; Cernicharo, J.; Charlot, P.; Chemin, L.; Clenet, Y.; Colomer, F.; Combes, F.; Cordes, J.; Coriat, M.; Cross, N.; D'Ammando, F.; Dallacasa, D.; Desmurs, J-F.; Eatough, R.; Eckart, A.; Eisenacher, D.; Etoka, S.; Felix, M.; Fender, R.; Ferreira, M.; Freeland, E.; Frey, S.; Fromm, C.; Fuhrmann, L.; Gabanyi, K.; Galvan-Madrid, R.; Giroletti, M.; Goddi, C.; Gomez, J.; Gourgoulhon, E.; Gray, M.; di Gregorio, I.; Greimel, R.; Grosso, N.; Guirado, J.; Hada, K.; Hanslmeier, A.; Henkel, C.; Herpin, F.; Hess, P.; Hodgson, J.; Horns, D.; Humphreys, E.; Hutawarakorn Kramer, B.; Ilyushin, V.; Impellizzeri, V.; Ivanov, V.; Julião, M.; Kadler, M.; Kerins, E.; Klaassen, P.; van 't Klooster, K.; Kording, E.; Kozlov, M.; Kramer, M.; Kreikenbohm, A.; Kurtanidze, O.; Lazio, J.; Leite, A.; Leitzinger, M.; Lepine, J.; Levshakov, S.; Lico, R.; Lindqvist, M.; Liuzzo, E.; Lobanov, A.; Lucas, P.; Mannheim, K.; Marcaide, J.; Markoff, S.; Martí-Vidal, I.; Martins, C.; Masetti, N.; Massardi, M.; Menten, K.; Messias, H.; Migliari, S.; Mignano, A.; Miller-Jones, J.; Minniti, D.; Molaro, P.; Molina, S.; Monteiro, A.; Moscadelli, L.; Mueller, C.; Müller, A.; Muller, S.; Niederhofer, F.; Odert, P.; Olofsson, H.; Orienti, M.; Paladino, R.; Panessa, F.; Paragi, Z.; Paumard, T.; Pedrosa, P.; Pérez-Torres, M.; Perrin, G.; Perucho, M.; Porquet, D.; Prandoni, I.; Ransom, S.; Reimers, D.; Rejkuba, M.; Rezzolla, L.; Richards, A.; Ros, E.; Roy, A.; Rushton, A.; Savolainen, T.; Schulz, R.; Silva, M.; Sivakoff, G.; Soria-Ruiz, R.; Soria, R.; Spaans, M.; Spencer, R.; Stappers, B.; Surcis, G.; Tarchi, A.; Temmer, M.; Thompson, M.; Torrelles, J.; Truestedt, J.; Tudose, V.; Venturi, T.; Verbiest, J.; Vieira, J.; Vielzeuf, P.; Vincent, F.; Wex, N.; Wiik, K.; Wiklind, T.; Wilms, J.; Zackrisson, E.; Zechlin, H. Bibcode: 2014arXiv1406.4650T Altcode: Very long baseline interferometry at millimetre/submillimetre wavelengths (mmVLBI) offers the highest achievable spatial resolution at any wavelength in astronomy. The anticipated inclusion of ALMA as a phased array into a global VLBI network will bring unprecedented sensitivity and a transformational leap in capabilities for mmVLBI. Building on years of pioneering efforts in the US and Europe the ongoing ALMA Phasing Project (APP), a US-led international collaboration with MPIfR-led European contributions, is expected to deliver a beamformer and VLBI capability to ALMA by the end of 2014 (APP: Fish et al. 2013, arXiv:1309.3519). This report focuses on the future use of mmVLBI by the international users community from a European viewpoint. Firstly, it highlights the intense science interest in Europe in future mmVLBI observations as compiled from the responses to a general call to the European community for future research projects. A wide range of research is presented that includes, amongst others: - Imaging the event horizon of the black hole at the centre of the Galaxy - Testing the theory of General Relativity an/or searching for alternative theories - Studying the origin of AGN jets and jet formation - Cosmological evolution of galaxies and BHs, AGN feedback - Masers in the Milky Way (in stars and star-forming regions) - Extragalactic emission lines and astro-chemistry - Redshifted absorption lines in distant galaxies and study of the ISM and circumnuclear gas - Pulsars, neutron stars, X-ray binaries - Testing cosmology - Testing fundamental physical constants Title: Connecting Speeds, Directions and Arrival Times of 22 Coronal Mass Ejections from the Sun to 1 AU Authors: Möstl, C.; Amla, K.; Hall, J. R.; Liewer, P. C.; De Jong, E. M.; Colaninno, R. C.; Veronig, A. M.; Rollett, T.; Temmer, M.; Peinhart, V.; Davies, J. A.; Lugaz, N.; Liu, Y. D.; Farrugia, C. J.; Luhmann, J. G.; Vršnak, B.; Harrison, R. A.; Galvin, A. B. Bibcode: 2014ApJ...787..119M Altcode: 2014arXiv1404.3579M Forecasting the in situ properties of coronal mass ejections (CMEs) from remote images is expected to strongly enhance predictions of space weather and is of general interest for studying the interaction of CMEs with planetary environments. We study the feasibility of using a single heliospheric imager (HI) instrument, imaging the solar wind density from the Sun to 1 AU, for connecting remote images to in situ observations of CMEs. We compare the predictions of speed and arrival time for 22 CMEs (in 2008-2012) to the corresponding interplanetary coronal mass ejection (ICME) parameters at in situ observatories (STEREO PLASTIC/IMPACT, Wind SWE/MFI). The list consists of front- and backsided, slow and fast CMEs (up to 2700 km s-1). We track the CMEs to 34.9 ± 7.1 deg elongation from the Sun with J maps constructed using the SATPLOT tool, resulting in prediction lead times of -26.4 ± 15.3 hr. The geometrical models we use assume different CME front shapes (fixed-Φ, harmonic mean, self-similar expansion) and constant CME speed and direction. We find no significant superiority in the predictive capability of any of the three methods. The absolute difference between predicted and observed ICME arrival times is 8.1 ± 6.3 hr (rms value of 10.9 hr). Speeds are consistent to within 284 ± 288 km s-1. Empirical corrections to the predictions enhance their performance for the arrival times to 6.1 ± 5.0 hr (rms value of 7.9 hr), and for the speeds to 53 ± 50 km s-1. These results are important for Solar Orbiter and a space weather mission positioned away from the Sun-Earth line. Title: Morphology of an ICME-event derived by Multi-point in Situ and Heliospheric Imaging Data Authors: Rollett, Tanja; Möstl, Christian; Temmer, Manuela; Veronig, Astrid M.; Frahm, Rudy A.; Davies, Jackie A.; Vrsnak, Bojan; Farrugia, Charles J.; Amerstorfer, Ute V. Bibcode: 2014EGUGA..1610892R Altcode: We show the analysis of an outstanding fast interplanetary coronal mass ejection (ICME) of 07 March 2012, which has been observed stereoscopically from both STEREO spacecraft. Assuming self-similar expansion and constant direction of motion we derive the kinematical profiles for the eastern and the western part of the roughly Earth-directed ICME. As additional constraints we use the huge advantage of in situ measurements at various locations during the ICME's propagation, namely from Venus Express, Messenger, Wind and Mars Express. We found that the eastern part of the ICME had a much higher propagation speed than its western part. Using the drag-based model, a model for the propagation of ICMEs in the inner heliosphere, we analyzed the influence of the drag on both sides of the ICME due to the surrounding solar wind conditions. These different solar wind conditions could have been the reason for the differing velocities and therefore for a distortion of the ICME front. These studies are fundamental in order to deepen the understanding of ICME evolution and to enhance existing forecasting methods. Title: Connecting speeds, directions and arrival times of 22 coronal mass ejections from the Sun to 1 AU Authors: Möstl, Christian; Amla, Keshav; Hall, Jeff R.; Liewer, Paulett C.; DeJong, Eric M.; Colaninno, Robin C.; Veronig, Astrid M.; Rollett, Tanja; Temmer, Manuela; Peinhart, Vanessa; Davies, Jackie A.; Lugaz, Noé; Liu, Ying; Farrugia, Charles J.; Luhmann, Janet G.; Vrsnak, Bojan; Harrison, Richard A.; Galvin, Antoinette B. Bibcode: 2014EGUGA..16.1755M Altcode: Forecasting in situ properties of coronal mass ejections (CMEs) from remote images is expected to strongly enhance predictions of space weather, and is of general interest for studying the interaction of the solar wind with planetary environments. We study the feasibility of using a heliospheric imager (HI) instrument, which is able to image the solar wind density along the full Sun to 1 AU distance, for connecting remote images to in situ observations of CMEs. Such an instrument is currently in operation on each of the two STEREO spacecraft. We compare the predictions for speed and arrival time for 22 different CME events (between 2008-2012), each observed remotely by one STEREO spacecraft, to the interplanetary coronal mass ejection (ICME) speed and arrival time observed at in situ observatories (STEREO PLASTIC/IMPACT, Wind SWE/MFI). We use croissant modeling for STEREO/COR2, and with a single-spacecraft STEREO/HI instrument, we track each CME to 34.9 ± 7.1 degree elongation from the Sun with J-maps constructed with the SATPLOT tool. We then fit geometrical models to each track, assuming different CME front shapes (Fixed-Φ, Harmonic Mean, Self-Similar Expansion), and constant CME speed and direction. We find no significant preference in the predictive capability for any of the three geometrical modeling methods used on the full event list, consisting of front- and backsided, slow and fast CMEs (up to 2700 km s-1). The absolute difference between predicted and observed ICME arrival times is 8.1 ± 6.4 hours (rms value of 10.9h), and speeds are consistent within 284 ± 291 km s-1, including the geometric effects of CME apex or flank encounters. We derive new empirical corrections to the imaging results, enhancing the performance of the arrival time predictions to 6.1 ± 5.0 hours (rms value of 7.9h), and the speed predictions to 53 ± 50 km s-1, for this particular set of events. The prediction lead time is around 1 day (-26.4 ± 15.3h). CME directions given by the HI methods differ considerably, and biases are found on the order of 30-50 degree in heliospheric longitude, consistent with theoretical expectations. These results are of interest concerning future missions such as Solar Orbiter or a dedicated space weather mission positioned remotely from the Earth. Title: Comparative Study of MHD Modeling of the Background Solar Wind Authors: Gressl, C.; Veronig, A. M.; Temmer, M.; Odstrčil, D.; Linker, J. A.; Mikić, Z.; Riley, P. Bibcode: 2014SoPh..289.1783G Altcode: 2013arXiv1312.1220G Knowledge about the background solar wind plays a crucial role in the framework of space-weather forecasting. In-situ measurements of the background solar wind are only available for a few points in the heliosphere where spacecraft are located, therefore we have to rely on heliospheric models to derive the distribution of solar-wind parameters in interplanetary space. We test the performance of different solar-wind models, namely Magnetohydrodynamic Algorithm outside a Sphere/ENLIL (MAS/ENLIL), Wang-Sheeley-Arge/ENLIL (WSA/ENLIL), and MAS/MAS, by comparing model results with in-situ measurements from spacecraft located at 1 AU distance to the Sun (ACE, Wind). To exclude the influence of interplanetary coronal mass ejections (ICMEs), we chose the year 2007 as a time period with low solar activity for our comparison. We found that the general structure of the background solar wind is well reproduced by all models. The best model results were obtained for the parameter solar-wind speed. However, the predicted arrival times of high-speed solar-wind streams have typical uncertainties of the order of about one day. Comparison of model runs with synoptic magnetic maps from different observatories revealed that the choice of the synoptic map significantly affects the model performance. Title: Response of the Earth's thermosphere to interplanetary coronal mass ejections Authors: Krauss, S.; Temmer, M.; Lammer, H.; Veronig, A.; Baur, O.; Pfleger, M.; Boudjada, M. Y.; Leitzinger, M.; Besser, B. P. Bibcode: 2014EPSC....9..724K Altcode: In this contribution we address the Earth's thermospheric response to interplanetary coronal mass ejections. We investigate several ICME events by means of neutral density measurements from the low-Earth orbiting satellites GRACE. Furthermore we correlate these observations with data from the ACE satellite located at L1 upstream of the Earth. By analyzing the data, high correlations between the neutral density and various combinations of ICME parameters can be found. Title: Asymmetry in the CME-CME Interaction Process for the Events from 2011 February 14-15 Authors: Temmer, M.; Veronig, A. M.; Peinhart, V.; Vršnak, B. Bibcode: 2014ApJ...785...85T Altcode: 2014arXiv1402.6891T We present a detailed study of the interaction process of two coronal mass ejections (CMEs) successively launched on 2011 February 14 (CME1) and 2011 February 15 (CME2). Reconstructing the three-dimensional shape and evolution of the flux ropes, we verify that the two CMEs interact. The frontal structure of both CMEs, measured along different position angles (PAs) over the entire latitudinal extent, reveals differences in the kinematics for the interacting flanks and the apexes. The interaction process is strongly PA-dependent in terms of timing as well as kinematical evolution. The central interaction occurs along PA-100°, which shows the strongest changes in kinematics. During interaction, CME1 accelerates from ~400 km s-1 to ~700 km s-1 and CME2 decelerates from ~1300 km s-1 to ~600 km s-1. Our results indicate that a simplified scenario such as inelastic collision may not be sufficient to describe the CME-CME interaction. The magnetic field structures of the intertwining flux ropes and the momentum transfer due to shocks each play an important role in the interaction process. Title: Solar Magnetized Tornadoes: Rotational Motion in a Tornado-like Prominence Authors: Su, Yang; Gömöry, Peter; Veronig, Astrid; Temmer, Manuela; Wang, Tongjiang; Vanninathan, Kamalam; Gan, Weiqun; Li, YouPing Bibcode: 2014ApJ...785L...2S Altcode: 2013arXiv1312.5226S Su et al. proposed a new explanation for filament formation and eruption, where filament barbs are rotating magnetic structures driven by underlying vortices on the surface. Such structures have been noticed as tornado-like prominences when they appear above the limb. They may play a key role as the source of plasma and twist in filaments. However, no observations have successfully distinguished rotational motion of the magnetic structures in tornado-like prominences from other motions such as oscillation and counter-streaming plasma flows. Here we report evidence of rotational motions in a tornado-like prominence. The spectroscopic observations in two coronal lines were obtained from a specifically designed Hinode/EIS observing program. The data revealed the existence of both cold and million-degree-hot plasma in the prominence leg, supporting the so-called prominence-corona transition region. The opposite velocities at the two sides of the prominence and their persistent time evolution, together with the periodic motions evident in SDO/AIA dark structures, indicate a rotational motion of both cold and hot plasma with a speed of ~5 km s-1. Title: A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. II. CMEs, Shock Waves, and Drifting Radio Bursts Authors: Grechnev, V. V.; Uralov, A. M.; Chertok, I. M.; Slemzin, V. A.; Filippov, B. P.; Egorov, Y. I.; Fainshtein, V. G.; Afanasyev, A. N.; Prestage, N. P.; Temmer, M. Bibcode: 2014SoPh..289.1279G Altcode: 2013arXiv1308.3010G We continue our study (Grechnev et al., 2013, doi:10.1007/s11207-013-0316-6; Paper I) on the 18 November 2003 geoffective event. To understand possible impact on geospace of coronal transients observed on that day, we investigated their properties from solar near-surface manifestations in extreme ultraviolet, LASCO white-light images, and dynamic radio spectra. We reconcile near-surface activity with the expansion of coronal mass ejections (CMEs) and determine their orientation relative to the earthward direction. The kinematic measurements, dynamic radio spectra, and microwave and X-ray light curves all contribute to the overall picture of the complex event and confirm an additional eruption at 08:07 - 08:20 UT close to the solar disk center presumed in Paper I. Unusual characteristics of the ejection appear to match those expected for a source of the 20 November superstorm but make its detection in LASCO images hopeless. On the other hand, none of the CMEs observed by LASCO seem to be a promising candidate for a source of the superstorm being able to produce, at most, a glancing blow on the Earth's magnetosphere. Our analysis confirms free propagation of shock waves revealed in the event and reconciles their kinematics with "EUV waves" and dynamic radio spectra up to decameters. Title: A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. I. Unusual History of an Eruptive Filament Authors: Grechnev, V. V.; Uralov, A. M.; Slemzin, V. A.; Chertok, I. M.; Filippov, B. P.; Rudenko, G. V.; Temmer, M. Bibcode: 2014SoPh..289..289G Altcode: 2013arXiv1304.7950G This is the first of four companion papers, which comprehensively analyze a complex eruptive event of 18 November 2003 in active region (AR) 10501 and the causes of the largest Solar Cycle 23 geomagnetic storm on 20 November 2003. Analysis of a complete data set, not considered before, reveals a chain of eruptions to which hard X-ray and microwave bursts responded. A filament in AR 10501 was not a passive part of a larger flux rope, as usually considered. The filament erupted and gave origin to a coronal mass ejection (CME). The chain of events was as follows: i) a presumable eruption at 07:29 UT accompanied by a not reported M1.2 class flare probably associated with the onset of a first southeastern CME (CME1), which most likely is not responsible for the superstorm; ii) a confined eruption (without a CME) at 07:41 UT (M3.2 flare) that destabilized the large filament; iii) the filament acceleration around 07:56 UT; iv) the bifurcation of the eruptive filament that transformed into a large "cloud"; v) an M3.9 flare in AR 10501 associated to this transformation. The transformation of the filament could be due to the interaction of the eruptive filament with the magnetic field in the neighborhood of a null point, located at a height of about 100 Mm above the complex formed by ARs 10501, 10503, and their environment. The CORONAS-F/SPIRIT telescope observed the cloud in 304 Å as a large Y-shaped darkening, which moved from the bifurcation region across the solar disk to the limb. The masses and kinematics of the cloud and the filament were similar. Remnants of the filament were not clearly observed in the second southwestern CME (CME2), previously regarded as a source of the 20 November geomagnetic storm. These facts do not support a simple scenario, in which the interplanetary magnetic cloud is considered as a flux rope formed from a structure initially associated with the pre-eruption filament in AR 10501. Observations suggest a possible additional eruption above the bifurcation region close to solar disk center between 08:07 and 08:17 UT, which could be the source of the 20 November superstorm. Title: Kinematics of Interacting ICMEs and Related Forbush Decrease: Case Study Authors: Maričić, D.; Vršnak, B.; Dumbović, M.; Žic, T.; Roša, D.; Hržina, D.; Lulić, S.; Romštajn, I.; Bušić, I.; Salamon, K.; Temmer, M.; Rollett, T.; Veronig, A.; Bostanjyan, N.; Chilingarian, A.; Mailyan, B.; Arakelyan, K.; Hovhannisyan, A.; Mujić, N. Bibcode: 2014SoPh..289..351M Altcode: We study heliospheric propagation and some space weather aspects of three Earth-directed interplanetary coronal mass ejections (ICMEs), successively launched from the active region AR 11158 in the period 13 - 15 February 2011. From the analysis of the ICME kinematics, morphological evolution, and in situ observations, we infer that the three ICMEs interacted on their way to Earth, arriving together at 1 AU as a single interplanetary disturbance. Detailed analysis of the in situ data reveals complex internal structure of the disturbance, where signatures of the three initially independent ICMEs could be recognized. The analysis also reveals compression and heating of the middle ICME, as well as ongoing magnetic reconnection between the leading and the middle ICME. We present evidence showing that the propagation of these two, initially slower ICMEs, was boosted by the fastest, third ICME. Finally, we employ the ground-based cosmic ray observations, to show that this complex disturbance produced a single cosmic ray event, i.e., a simple Forbush decrease (FD). The results presented provide a better understanding of the ICME interactions and reveal effects that should be taken into account in forecasting of the arrival of such compound structures. Title: Identification of coronal holes and filament channels in SDO/AIA 193Å images via geometrical classification methods Authors: Reiss, M.; Temmer, M.; Rotter, T.; Hofmeister, S. J.; Veronig, A. M. Bibcode: 2014CEAB...38...95R Altcode: 2014arXiv1408.2777R In this study, we describe and evaluate shape measures for distinguishing between coronal holes and filament channels as observed in Extreme Ultraviolet (EUV) images of the Sun. For a set of well-observed coronal hole and filament channel regions extracted from SDO/AIA 193Å images we analyze their intrinsic morphology during the period 2011 to 2013, by using well known shape measures from the literature and newly developed geometrical classification methods. The results suggest an asymmetry in the morphology of filament channels giving support for the sheared arcade or weakly twisted flux rope model for filaments. We find that the proposed shape descriptors have the potential to reduce coronal hole classification errors and are eligible for screening techniques in order to improve the forecasting of solar wind high-speed streams from CH observations in solar EUV images. Title: Initiation of Coronal Mass Ejections by Sunspot Rotation Authors: Valori, G.; Török, T.; Temmer, M.; Veronig, A. M.; van Driel-Gesztelyi, L.; Vršnak, B. Bibcode: 2014IAUS..300..201V Altcode: We report observations of a filament eruption, two-ribbon flare, and coronal mass ejection (CME) that occurred in Active Region NOAA 10898 on 6 July 2006. The filament was located South of a strong sunspot that dominated the region. In the evolution leading up to the eruption, and for some time after it, a counter-clockwise rotation of the sunspot of about 30 degrees was observed. We suggest that the rotation triggered the eruption by progressively expanding the magnetic field above the filament. To test this scenario, we study the effect of twisting the initially potential field overlying a pre-existing flux rope, using three-dimensional zero-β MHD simulations. We consider a magnetic configuration whose photospheric flux distribution and coronal structure is guided by the observations and a potential field extrapolation. We find that the twisting leads to the expansion of the overlying field. As a consequence of the progressively reduced magnetic tension, the flux rope quasi-statically adapts to the changed environmental field, rising slowly. Once the tension is sufficiently reduced, a distinct second phase of evolution occurs where the flux rope enters an unstable regime characterized by a strong acceleration. Our simulation thus suggests a new mechanism for the triggering of eruptions in the vicinity of rotating sunspots. Title: The Wave-Driver System of the Off-Disk Coronal Wave of 17 January 2010 Authors: Temmer, M.; Vrsnak, B.; Veronig, A. M. Bibcode: 2013SoPh..287..441T Altcode: 2012arXiv1207.2857T; 2012SoPh..tmp..194T We study the 17 January 2010 flare-CME-wave event by using STEREO/SECCHI-EUVI and -COR1 data. The observational study is combined with an analytic model that simulates the evolution of the coronal wave phenomenon associated with the event. From EUV observations, the wave signature appears to be dome shaped having a component propagating on the solar surface (\overline{v}≈280~km s^{-1}) as well as one off-disk (\overline{v}≈ 600~km s^{-1}) away from the Sun. The off-disk dome of the wave consists of two enhancements in intensity, which conjointly develop and can be followed up to white-light coronagraph images. Applying an analytic model, we derive that these intensity variations belong to a wave-driver system with a weakly shocked wave, initially driven by expanding loops, which are indicative of the early evolution phase of the accompanying CME. We obtain the shock standoff distance between wave and driver from observations as well as from model results. The shock standoff distance close to the Sun (< 0.3 R⊙ above the solar surface) is found to rapidly increase with values of ≈ 0.03 - 0.09 R⊙, which gives evidence of an initial lateral (over)expansion of the CME. The kinematical evolution of the on-disk wave could be modeled using input parameters that require a more impulsive driver (duration t=90 s, acceleration a=1.7 km s−2) compared to the off-disk component (duration t=340 s, acceleration a=1.5 km s−2). Title: Initiation of Coronal Mass Ejections by Sunspot Rotation Authors: Török, T.; Temmer, M.; Valori, G.; Veronig, A. M.; van Driel-Gesztelyi, L.; Vršnak, B. Bibcode: 2013SoPh..286..453T Altcode: 2014arXiv1401.2922T We study a filament eruption, two-ribbon flare, and coronal mass ejection (CME) that occurred in NOAA Active Region 10898 on 6 July 2006. The filament was located South of a strong sunspot that dominated the region. In the evolution leading up to the eruption, and for some time after it, a counter-clockwise rotation of the sunspot of about 30 degrees was observed. We suggest that the rotation triggered the eruption by progressively expanding the magnetic field above the filament. To test this scenario, we study the effect of twisting the initially potential field overlying a pre-existing flux-rope, using three-dimensional zero-β MHD simulations. We first consider a relatively simple and symmetric system, and then study a more complex and asymmetric magnetic configuration, whose photospheric-flux distribution and coronal structure are guided by the observations and a potential field extrapolation. In both cases, we find that the twisting leads to the expansion of the overlying field. As a consequence of the progressively reduced magnetic tension, the flux-rope quasi-statically adapts to the changed environmental field, rising slowly. Once the tension is sufficiently reduced, a distinct second phase of evolution occurs where the flux-rope enters an unstable regime characterised by a strong acceleration. Our simulations thus suggest a new mechanism for the triggering of eruptions in the vicinity of rotating sunspots. Title: Formation of Coronal Shock Waves Authors: Lulić, S.; Vršnak, B.; Žic, T.; Kienreich, I. W.; Muhr, N.; Temmer, M.; Veronig, A. M. Bibcode: 2013SoPh..286..509L Altcode: 2013arXiv1303.2786L Magnetosonic wave formation driven by an expanding cylindrical piston is numerically simulated to obtain better physical insight into the initiation and evolution of large-scale coronal waves caused by coronal eruptions. Several very basic initial configurations are employed to analyze intrinsic characteristics of MHD wave formation that do not depend on specific properties of the environment. It turns out that these simple initial configurations result in piston/wave morphologies and kinematics that reproduce common characteristics of coronal waves. In the initial stage, the wave and the expanding source region cannot be clearly resolved; i.e. a certain time is needed before the wave detaches from the piston. Thereafter, it continues to travel as what is called a "simple wave." During the acceleration stage of the source region inflation, the wave is driven by the piston expansion, so its amplitude and phase-speed increase, whereas the wavefront profile steepens. At a given point, a discontinuity forms in the wavefront profile; i.e. the leading edge of the wave becomes shocked. The time/distance required for the shock formation is shorter for a more impulsive source-region expansion. After the piston stops, the wave amplitude and phase speed start to decrease. During the expansion, most of the source region becomes strongly rarefied, which reproduces the coronal dimming left behind the eruption. However, the density increases at the source-region boundary, and stays enhanced even after the expansion stops, which might explain stationary brightenings that are sometimes observed at the edges of the erupted coronal structure. Also, in the rear of the wave a weak density depletion develops, trailing the wave, which is sometimes observed as weak transient coronal dimming. Finally, we find a well-defined relationship between the impulsiveness of the source-region expansion and the wave amplitude and phase speed. The results for the cylindrical piston are also compared with the outcome for a planar wave that is formed by a one-dimensional piston, to find out how different geometries affect the evolution of the wave. Title: Imaging coronal magnetic-field reconnection in a solar flare Authors: Su, Yang; Veronig, Astrid M.; Holman, Gordon D.; Dennis, Brian R.; Wang, Tongjiang; Temmer, Manuela; Gan, Weiqun Bibcode: 2013NatPh...9..489S Altcode: 2013arXiv1307.4527S Magnetic-field reconnection is believed to play a fundamental role in magnetized plasma systems throughout the Universe, including planetary magnetospheres, magnetars and accretion disks around black holes. This letter presents extreme ultraviolet and X-ray observations of a solar flare showing magnetic reconnection with a level of clarity not previously achieved. The multi-wavelength extreme ultraviolet observations from SDO/AIA show inflowing cool loops and newly formed, outflowing hot loops, as predicted. RHESSI X-ray spectra and images simultaneously show the appearance of plasma heated to >10MK at the expected locations. These two data sets provide solid visual evidence of magnetic reconnection producing a solar flare, validating the basic physical mechanism of popular flare models. However, new features are also observed that need to be included in reconnection and flare studies, such as three-dimensional non-uniform, non-steady and asymmetric evolution. Title: Solar TErrestrial Relations Observatory-A (STEREO-A) and PRoject for On-Board Autonomy 2 (PROBA2) Quadrature Observations of Reflections of Three EUV Waves from a Coronal Hole Authors: Kienreich, I. W.; Muhr, N.; Veronig, A. M.; Berghmans, D.; De Groof, A.; Temmer, M.; Vršnak, B.; Seaton, D. B. Bibcode: 2013SoPh..286..201K Altcode: 2012SoPh..tmp..138K We investigate the interaction of three consecutive large-scale coronal waves with a polar coronal hole, simultaneously observed on-disk by the Solar TErrestrial Relations Observatory (STEREO)-A spacecraft and on the limb by the PRoject for On-Board Autonomy 2 (PROBA2) spacecraft on 27 January 2011. All three extreme ultraviolet (EUV) waves originate from the same active region, NOAA 11149, positioned at N30E15 in the STEREO-A field of view and on the limb in PROBA2. For the three primary EUV waves, we derive starting velocities in the range of ≈ 310 km s−1 for the weakest up to ≈ 500 km s−1 for the strongest event. Each large-scale wave is reflected at the border of the extended coronal hole at the southern polar region. The average velocities of the reflected waves are found to be smaller than the mean velocities of their associated direct waves. However, the kinematical study also reveals that in each case the ending velocity of the primary wave matches the initial velocity of the reflected wave. In all three events, the primary and reflected waves obey the Huygens-Fresnel principle, as the incident angle with ≈ 10° to the normal is of the same magnitude as the angle of reflection. The correlation between the speed and the strength of the primary EUV waves, the homologous appearance of both the primary and the reflected waves, and in particular the EUV wave reflections themselves suggest that the observed EUV transients are indeed nonlinear large-amplitude MHD waves. Title: Propagation of Interplanetary Coronal Mass Ejections: The Drag-Based Model Authors: Vršnak, B.; Žic, T.; Vrbanec, D.; Temmer, M.; Rollett, T.; Möstl, C.; Veronig, A.; Čalogović, J.; Dumbović, M.; Lulić, S.; Moon, Y. -J.; Shanmugaraju, A. Bibcode: 2013SoPh..285..295V Altcode: 2012SoPh..tmp..124V We present the "Drag-Based Model" (DBM) of heliospheric propagation of interplanetary coronal mass ejections (ICMEs). The DBM is based on the hypothesis that the driving Lorentz force, which launches a CME, ceases in the upper corona and that beyond a certain distance the dynamics becomes governed solely by the interaction of the ICME and the ambient solar wind. In particular, we consider the option where the drag acceleration has a quadratic dependence on the ICME relative speed, which is expected in a collisionless environment, where the drag is caused primarily by emission of magnetohydrodynamic (MHD) waves. In this paper we present the simplest version of DBM, where the equation of motion can be solved analytically, providing explicit solutions for the Sun-Earth ICME transit time and impact speed. This offers easy handling and straightforward application to real-time space-weather forecasting. Beside presenting the model itself, we perform an analysis of DBM performances, applying a statistical and case-study approach, which provides insight into the advantages and drawbacks of DBM. Finally, we present a public, DBM-based, online forecast tool. Title: Heliospheric Imaging of 3D Density Structures During the Multiple Coronal Mass Ejections of Late July to Early August 2010 Authors: Webb, D. F.; Möstl, C.; Jackson, B. V.; Bisi, M. M.; Howard, T. A.; Mulligan, T.; Jensen, E. A.; Jian, L. K.; Davies, J. A.; de Koning, C. A.; Liu, Y.; Temmer, M.; Clover, J. M.; Farrugia, C. J.; Harrison, R. A.; Nitta, N.; Odstrcil, D.; Tappin, S. J.; Yu, H. -S. Bibcode: 2013SoPh..285..317W Altcode: It is usually difficult to gain a consistent global understanding of a coronal mass ejection (CME) eruption and its propagation when only near-Sun imagery and the local measurements derived from single-spacecraft observations are available. Three-dimensional (3D) density reconstructions based on heliospheric imaging allow us to "fill in" the temporal and spatial gaps between the near-Sun and in situ data to provide a truly global picture of the propagation and interactions of the CME as it moves through the inner heliosphere. In recent years the heliospheric propagation of dense structures has been observed and measured by the heliospheric imagers of the Solar Mass Ejection Imager (SMEI) and on the twin Solar TErrestrial RElations Observatory (STEREO) spacecraft. We describe the use of several 3D reconstruction techniques based on these heliospheric imaging data sets to distinguish and track the propagation of multiple CMEs in the inner heliosphere during the very active period of solar activity in late July - early August 2010. We employ 3D reconstruction techniques used at the University of California, San Diego (UCSD) based on a kinematic solar wind model, and also the empirical Tappin-Howard model. We compare our results with those from other studies of this active period, in particular the heliospheric simulations made with the ENLIL model by Odstrcil et al. (J. Geophys. Res., 2013) and the in situ results from multiple spacecraft provided by Möstl et al. (Astrophys. J.758, 10 - 28, 2012). We find that the SMEI results in particular provide an overall context for the multiple-density flows associated with these CMEs. For the first time we are able to intercompare the 3D reconstructed densities with the timing and magnitude of in situ density structures at five spacecraft spread over 150° in ecliptic longitude and from 0.4 to 1 AU in radial distance. We also model the magnetic flux-rope structures at three spacecraft using both force-free and non-force-free modelling, and compare their timing and spatial structure with the reconstructed density flows. Title: The Height Evolution of the "True" Coronal Mass Ejection Mass derived from STEREO COR1 and COR2 Observations Authors: Bein, B. M.; Temmer, M.; Vourlidas, A.; Veronig, A. M.; Utz, D. Bibcode: 2013ApJ...768...31B Altcode: 2013arXiv1303.3372B Using combined STEREO-A and STEREO-B EUVI, COR1, and COR2 data, we derive deprojected coronal mass ejection (CME) kinematics and CME "true" mass evolutions for a sample of 25 events that occurred during 2007 December to 2011 April. We develop a fitting function to describe the CME mass evolution with height. The function considers both the effect of the coronagraph occulter, at the beginning of the CME evolution, and an actual mass increase. The latter becomes important at about 10-15 R ⊙ and is assumed to mostly contribute up to 20 R ⊙. The mass increase ranges from 2% to 6% per R ⊙ and is positively correlated to the total CME mass. Due to the combination of COR1 and COR2 mass measurements, we are able to estimate the "true" mass value for very low coronal heights (<3 R ⊙). Based on the deprojected CME kinematics and initial ejected masses, we derive the kinetic energies and propelling forces acting on the CME in the low corona (<3 R ⊙). The derived CME kinetic energies range between 1.0-66 × 1023 J, and the forces range between 2.2-510 × 1014 N. Title: 2.5D MHD Simulations of the Kelvin-Helmholtz Instability at CME-Boundaries in the Solar Corona Authors: Möstl, Ute; Temmer, Manuela; Veronig, Astrid Bibcode: 2013EGUGA..15.4171M Altcode: We discuss the observation of a coronal mass ejection (CME) by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory from 2011 February 24. This CME with an embedded filament shows periodic vortex-like structures at the northern side of the filament boundary with a wavelength of approximately 14.4 Mm and a propagation speed of about 310 ± 20 km/s. The morphological analysis hints at structures produced by the Kelvin-Helmholtz (KH) instability on the boundary of the filament. We conduct 2.5D numerical simulations of the KH instability, whose results yield qualitative as well as quantitative agreements with the observations. Furthermore, we study the absence of KH vortex-like structures on the southern side of the filament boundary and find that a magnetic field component parallel to the boundary with a strength of about 20% of the total magnetic field has stabilizing effects resulting in an asymmetric development of the instability. This work receives funding from the Austrian Science Fund (FWF): P21051-N16, V195-N16 and P24092-N16. Title: The Kanzelhöhe Observatory Authors: Pötzi, Werner; Temmer, Manuela; Veronig, Astrid; Hirtenfellner-Polanec, Wolfgang; Baumgartner, Dietmar Bibcode: 2013EGUGA..15.1459P Altcode: Kanzelhöhe Observatory (KSO; kso.ac.at) located in the South of Austria is part of the Institute of Physics of the University of Graz. Since the early 1940s, the Sun has been observed in various layers and wavelengths. Currently, KSO provides high-cadence full-disk observations of the solar disk in three wavelengths: H-alpha line, Ca II K line, white light. Real-time images are published online. For scientific use, the data is processed, and immediately available to the scientific community after each observing day via the Kanzelhöhe Online Data Archive archive (KODA; kanzelhohe.uni-graz.at). KSO is part of the Global H-Alpha Network and is also one of the contributing stations for the international sunspot number. In the frame of ESA's Space Situational Awareness program, methods are currently under development for near-real image recognition with respect to solar flares and filaments. These data products will give valuable complementary information for the solar sources of space weather. Title: Assessing the Constrained Harmonic Mean Method for Deriving the Kinematics of ICMEs with a Numerical Simulation Authors: Rollett, T.; Temmer, M.; Möstl, C.; Lugaz, N.; Veronig, A. M.; Möstl, U. V. Bibcode: 2013SoPh..283..541R Altcode: 2013arXiv1301.6945R In this study we use a numerical simulation of an artificial coronal mass ejection (CME) to validate a method for calculating propagation directions and kinematical profiles of interplanetary CMEs (ICMEs). In this method observations from heliospheric images are constrained with in-situ plasma and field data at 1 AU. These data are used to convert measured ICME elongations into distance by applying the harmonic mean approach, which assumes a spherical shape of the ICME front. We used synthetic white-light images, similar to those observed by STEREO-A/HI, for three different separation angles between remote and in-situ spacecraft of 30∘, 60∘, and 90∘. To validate the results of the method, the images were compared to the apex speed profile of the modeled ICME, as obtained from a top view. This profile reflects the "true" apex kinematics because it is not affected by scattering or projection effects. In this way it is possible to determine the accuracy of the method for revealing ICME propagation directions and kinematics. We found that the direction obtained by the constrained harmonic mean method is not very sensitive to the separation angle (30∘ sep: ϕ=W7; 60∘ sep: ϕ=W12; 90∘ sep: ϕ=W15; true dir.: E0/W0). For all three cases the derived kinematics agree relatively well with the real kinematics. The best consistency is obtained for the 30∘ case, while with growing separation angle the ICME speed at 1 AU is increasingly overestimated (30∘ sep: ΔVarr≈− 50 km s−1, 60∘ sep: ΔVarr≈+ 75 km s−1, 90∘ sep: ΔVarr≈+ 125 km s−1). Especially for future L4/L5 missions, the 60∘ separation case is highly interesting in order to improve space-weather forecasts. Title: Evolution of CMEs in the inner heliosphere - observations versus models Authors: Temmer, Manuela; Vrsnak, Bojan; Möstl, Christian; Veronig, Astrid; Rollett, Tanja; Bein, Bianca Bibcode: 2013EGUGA..15.1328T Altcode: With the SECCHI instrument suite aboard STEREO, coronal mass ejections (CMEs) can be observed from multiple vantage points during their entire propagation all the way from the Sun to 1 AU. The propagation behavior of CMEs in the interplanetary space is mainly influenced by the ambient solar wind flow. CMEs that are faster than the ambient solar wind get decelerated, whereas slower ones are accelerated until the CME speed is finally adjusted to the solar wind speed. On a statistical basis, empirical models taking into account the drag force acting on CMEs, are able to describe the observed kinematical behaviors. For several well observed events, we will present a comparative study showing the kinematical evolution of CMEs derived from remote sensing and in situ data, as well as from empirical models using 2D and 3D input parameters. From this we aim to obtain the distance regime at which the solar wind drag force is dominating the CME propagation. Title: Forecasting coronal mass ejections at 1 AU using Heliospheric Imagers Authors: Möstl, Christian; Amla, Keshav; Hall, Jeffrey R.; Liewer, Paulett C.; De Jong, Eric; Temmer, Manuela; Davies, Jackie A.; Lugaz, Noé; Rollett, Tanja; Veronig, Astrid M.; Farrugia, Charles J.; Liu, Ying; Luhmann, Janet G.; Galvin, Antoinette B.; Zhang, Tielong Bibcode: 2013EGUGA..15.1311M Altcode: We study the feasibility of using a Heliospheric Imager (HI) instrument, such as STEREO/HI, for operational space weather forecasting of interplanetary coronal mass ejections (ICMEs) at 1 AU. We compare the predictions for speed and arrival time for about 20 ICME events, each observed remotely by one STEREO spacecraft, to the speed and arrival time observed at various in situ observatories. We use geometrical modeling, which means we approximate the ICME fronts with various shapes (Fixed-Phi, Harmonic Mean, Self-Similar Expansion). These models are applied to the time-elongation functions extracted from STEREO/SECCHI images with the SolarSoft SATPLOT package. We use these techniques for a single-spacecraft HI observer, and consequently assume constant ICME speed and direction. Partly, the configuration mimics the situation of a single HI observatory parked at the L4 or L5 point in the Sun-Earth system. For assessing the accuracy of these predictions we look at plasma and magnetic field in situ data by Wind (MFI, SWE instruments) and STEREO-A/B (IMPACT, PLASTIC) around 1 AU. Wherever possible we include ICME arrivals in the inner heliosphere (< 1 AU), from the magnetic field data by Venus Express and MESSENGER. We also look at the ratio of prediction lead time to its accuracy, and see if there is a preferred value for the ICME width. Title: Radial evolution of magnetic cloud properties Authors: Rollett, Tanja; Veronig, Astrid M.; Leitner, Martin; Vrsnak, Bojan; Möstl, Christian; Farrugia, Charles J.; Temmer, Manuela Bibcode: 2013EGUGA..15.2710R Altcode: Magnetic clouds (MCs) are characterized as intervals of enhanced, smoothly rotating interplanetary magnetic field, low plasma beta and temperature in spacecraft in situ data and can be part of ICMEs. In this study we analyze the radial evolution of MCs using a sample of events detected by radial aligned spacecrafts at different heliocentric distances. The data-sets are fitted with a force-free, constant-alpha flux rope model. Using the outcome of this fitting model we calculate the estimated cross section diameter (assuming a cylindrical flux tube), the poloidal and the axial magnetic field, the current, the magnetic flux and the inductance. All these parameter are further studied as a function of heliocentric distance. Strong variations of the current or the magnetic flux could be a hint for magnetic reconnection between the MC and the solar wind. This work has received funding from the European Commission FP7 Project COMESEP (263252). Title: The Kelvin-Helmholtz Instability at Coronal Mass Ejection Boundaries in the Solar Corona: Observations and 2.5D MHD Simulations Authors: Möstl, U. V.; Temmer, M.; Veronig, A. M. Bibcode: 2013ApJ...766L..12M Altcode: 2013arXiv1304.5884M The Atmospheric Imaging Assembly on board the Solar Dynamics Observatory observed a coronal mass ejection with an embedded filament on 2011 February 24, revealing quasi-periodic vortex-like structures at the northern side of the filament boundary with a wavelength of approximately 14.4 Mm and a propagation speed of about 310 ± 20 km s-1. These structures could result from the Kelvin-Helmholtz instability occurring on the boundary. We perform 2.5D numerical simulations of the Kelvin-Helmholtz instability and compare the simulated characteristic properties of the instability with the observations, where we obtain qualitative as well as quantitative accordance. We study the absence of Kelvin-Helmholtz vortex-like structures on the southern side of the filament boundary and find that a magnetic field component parallel to the boundary with a strength of about 20% of the total magnetic field has stabilizing effects resulting in an asymmetric development of the instability. Title: The role of solar "tornadoes" and vortices in filament fromation and eruption Authors: Su, Yang; Wang, Tongjiang; Veronig, Astrid; Temmer, Manuela; Gan, Weiqun Bibcode: 2013enss.confE..51S Altcode: Solar magnetized "tornadoes" are rotating vertical magnetic structures in the corona probably driven by underlying vortex flows in the photosphere. They usually exist as a group and are related to filaments/prominences. Detailed case studies show that these tornadoes may play a distinct role in the supply of mass and twists to filaments. The findings could lead to a new explanation of filament formation and eruption. Title: Direct Observations of Coronal Magnetic Reconnection Authors: Su, Yang; Veronig, Astrid; Dennis, Brian R.; Holman, Gordon D.; Wang, Tongjiang; Temmer, Manuela; Gan, Weiqun Bibcode: 2013enss.confE..53S Altcode: Magnetic field reconnection is believed to play a fundamental role in magnetized plasma systems throughout the universe, but never before has it been so clearly demonstrated as in the EUV and X-ray movies of a GOES-C-class solar flare presented here. The multiwavelength EUV observations from SDO/AIA show the predicted inflowing cool loops and newly formed outflowing hot loops while simultaneous RHESSI X-ray spectra and images show the appearance of plasma heated to >10 MK at the expected locations. These two data sets provide solid visual evidence of magnetic reconnection producing a solar flare. The non-uniform, nonsteady, and asymmetric nature of the observed process, together with the measured reconnection rates, supports the so called flux-pile-up reconnection. These new features of plasma inflows should be included in reconnection and flare studies. Title: The Kanzelhöhe Online Data Archive Authors: Pötzi, W.; Hirtenfellner-Polanec, W.; Temmer, M. Bibcode: 2013CEAB...37..655P Altcode: The Kanzelhöhe Observatory provides high-cadence full-disk observations of solar activity phenomena like sunspots, flares and prominence eruptions on a regular basis. The data are available for download from the KODA (Kanzelhöhe Observatory Data Archive) which is freely accessible. The archive offers sunspot drawings back to 1950 and high cadence H-α data back to 1973. Images from other instruments, like white-light and CaIIK, are available since 2007 and 2010, respectively. In the following we describe how to access the archive and the format of the data. Title: Relation Between Coronal Hole Areas on the Sun and the Solar Wind Parameters at 1 AU Authors: Rotter, T.; Veronig, A. M.; Temmer, M.; Vršnak, B. Bibcode: 2012SoPh..281..793R Altcode: 2012SoPh..tmp..202R We analyze the relationship between the coronal hole (CH) characteristics on the Sun (area, position, and intensity levels) and the corresponding solar wind parameters (solar wind speed v, proton temperature T, proton density n, and magnetic field strength B) measured in situ at 1 AU with a 6-h time resolution. We developed a histogram-based intensity thresholding method to obtain fractional CH areas from SOHO/EIT 195 Å images. The algorithm was applied to 6-h cadence EIT 195 Å images for the year 2005, which were characterized by a low solar activity. In calculating well-defined peaks of the solar wind parameters corresponding to the peaks in CH area, we found that the solar wind speed v shows a high correlation with correlation coefficient cc=0.78, medium correlation for T and B with cc=0.41 and cc=0.41. No significant correlation was found with the proton density n. Applying an intensity-weighted CH area did not improve the relations, since the size and the mean intensity of the CH areas are not independent parameters but strongly correlated (cc=− 0.72). Comparison of the fractional CH areas derived from GOES/SXI and SOHO/EIT and the related solar wind predictions shows no systematic differences (cc=0.79). Title: Forecasting coronal mass ejections at 1 AU using Heliospheric Imagers Authors: Moestl, C.; Amla, K.; Temmer, M.; Hall, J. R.; Liewer, P. C.; De Jong, E. M.; Davies, J.; Lugaz, N.; Rollett, T.; Veronig, A.; Liu, Y.; Farrugia, C. J.; Luhmann, J. G.; Galvin, A. B.; Zhang, T. Bibcode: 2012AGUFMSH31A2208M Altcode: We study the feasibility of using a Heliospheric Imager (HI) instrument, such as STEREO/HI, for space weather forecasting of interplanetary coronal mass ejections (ICMEs) at 1 AU. We compare the predictions for speed and arrival time for ~15 ICME events, each observed remotely by one STEREO spacecraft, to the speed and arrival time observed at in situ observatories. We use three different models with varying ICME geometry, from point-like (Fixed-Phi) to a circle with a given width (Self-Similar-Expansion) to a very wide circle (Harmonic Mean). The models are fitted to density tracks on HI Jmaps with the SolarSoft SATPLOT tool. All these techniques assume constant ICME speed and direction. Partly, the configuration mimics the situation of a single HI observatory parked at the L4 or L5 point in the Sun-Earth system. We discuss problems associated with this study, such as CME-CME interactions leading to complicated Jmaps. For assessing the accuracy of these predictions we look at in situ data by Wind/ACE, STEREO-A/B, and Venus Express and MESSENGER. We also look at the ratio of prediction lead time to its accuracy, and see if there is a preferred value for the ICME width. Title: CMEs - interaction with the background solar wind and other CMEs Authors: Temmer, M. Bibcode: 2012AGUFMSH21C..01T Altcode: The propagation behavior of coronal mass ejections (CMEs) in the interplanetary space is mainly influenced by the ambient solar wind flow and can be expressed as drag force. CMEs that are faster than the ambient solar wind get decelerated, whereas slower ones are accelerated until the CME speed is finally adjusted to the solar wind speed. As solar activity is rising, active regions will emerge hosting enough energy to erupt in quick succession. CMEs heading into similar directions are expected to interact, which means (dramatic) changes in their kinematical behavior. With the SECCHI instrument suite aboard STEREO, CMEs can be observed during their entire propagation all the way from the Sun to 1 AU. Various 3D reconstruction techniques, developed over the recent years, are used to derive the propagation direction of CMEs which is essential to interpret the interaction/drag processes. The talk will summarize observations in EUV and white light, from the corona to the heliosphere, concerning the interaction of CMEs with the background solar wind and other CMEs. Title: Relation between the impulsive CME acceleration and the nonthermal flare characteristics Authors: Veronig, A. M.; Berkebile-Stoiser, S.; Bein, B. M.; Temmer, M. Bibcode: 2012AGUFMSH54A..03V Altcode: We investigate the relationship between the main acceleration phase of CMEs and the particle acceleration in the associated flares observed by RHESSI for a set of 37 impulsive flare-CME events. Both the CME peak velocity and peak acceleration yield distinct correlations with various parameters characterizing the flare-accelerated electron spectra. The highest correlation coefficient is obtained for the relation of the CME peak velocity and the total energy in accelerated electrons (c = 0.85), supporting the idea that the acceleration of the CME and the particle acceleration in the associated flare draw their energy from a common source, probably magnetic reconnection in the current sheet behind the erupting structure. In general, the CME peak velocity shows somewhat higher correlations with the non-thermal flare parameters than the CME peak acceleration, except for the spectral index of the accelerated electron spectrum, which yields a higher correlation with the CME peak acceleration (c = -0.6), indicating that the hardness of the flare-accelerated electron spectrum is tightly coupled to the impulsive acceleration process of the rising CME structure. We also obtained high correlations between the CME initiation height h0 and the non-thermal flare parameters, with the highest correlation of h0 to the spectral index δ of flare-accelerated electrons (c = 0.8). This means that CMEs erupting at low coronal heights, i.e., in regions of stronger magnetic fields, are accompanied by flares that are more efficient at accelerating electrons to high energies. In 80% of the events, the non-thermal flare emission starts after the CME acceleration (on average 6 min), which corresponds to a mean current sheet length at the onset of magnetic reconnection of 21 ± 7 Mm. The flare hard X-ray peaks are well synchronized with the peak of the CME acceleration profile, and in 75% of the cases they occur within ±5 minutes. Our findings provide strong evidence for the tight coupling between the CME dynamics and the particle acceleration in the associated flare in impulsive events, with the total energy in accelerated electrons being closely correlated with the peak velocity (and thus the kinetic energy) of the CME, whereas the number of electrons accelerated to high energies is decisively related to the CME peak acceleration and the height of the pre-eruptive structure. Title: Deep Solar Activity Minimum 2007-2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere Authors: Farrugia, C. J.; Harris, B. S.; Leitner, M.; Moestl, C.; Galvin, A. B.; Simunac, K.; Torbert, R. B.; Temmer, M.; Veronig, A.; Erkaev, N.; Szabo, A.; Ogilvie, K. W.; Luhmann, J. G.; Osherovich, V. Bibcode: 2012AGUFMSM41C2226F Altcode: We discuss the temporal variations and frequency distributions of solar wind and IMF parameters during the solar minimum of 2007-2009 from measurements returned by the IMPACT and PLASTIC instruments on STEREO-A. We find that the density and total field strength were significantly weaker than in the previous minimum. The Alfvén Mach number was higher than typical.This reflects the weakness of magnetohydrodynamic (MHD) forces, and has a direct effect on the solar wind-magnetosphere interactions. We then discuss two major aspects that this weak solar activity had on the magnetosphere, using data from textit{Wind} and ground-based observations: (a) the dayside contribution to the cross-polar cap potential (CPCP), and (b) the shapes of the magnetopause and bow shock. For (a) we find a low interplanetary electric field of 1.3 ± 0.9 mV m-1 and a CPCP of 37.3 ± 20.2 kV. The auroral activity is closely correlated to the prevalent stream-stream interactions. We suggest that the Alfvén wave trains in the fast streams and Kelvin-Helmholtz instability were the predominant agents mediating the transfer of solar wind momentum and energy to the magnetosphere during this three-year period. For (b) we determine 328 magnetopause and 271 bow shock crossings made by textit{Geotail, Cluster 1}, and the THEMIS B and C spacecraft during a three-month interval when the daily averages of the magnetic and kinetic energy densities attained their lowest value during the three years under survey. We use the same numerical approach as in Fairfield's (textit{J. Geophys. Res.} 76, 7600, 1971) empirical model and compare our findings with three magnetopause models. The stand-off distance of the subsolar magnetopause and bow shock were 11.8 RE and 14.35 RE, respectively. When comparing with Fairfield's (1971) classic result, we find that the subsolar magnetosheath is thinner by ∼1 RE. This is mainly due to the low dynamic pressure which results in a sunward shift of the magnetopause The magnetopause is more flared than in Fairfield's model. By contrast the bow shock is less flared, and the latter is the result of weaker MHD forces. Title: Validating a new method for deriving the kinematics of ICMEs with a numerical simulation Authors: Rollett, T.; Temmer, M.; Moestl, C.; Lugaz, N.; Veronig, A.; Moestl, U. V. Bibcode: 2012AGUFMSH31A2209R Altcode: Using a numerical simulation of a very wide coronal mass ejection (CME) we validate a method for calculating propagation directions and kinematical profiles of interplanetary CMEs (ICMEs). In this method observations from heliospheric images are constrained with the in-situ arrival time at 1 AU. This additional boundary condition is used to calculate the propagation direction and to convert measured ICME elongations into distance by applying the Harmonic Mean approach that assumes a spherical shape of the ICME front. We use synthetic white light images, similar as observed by STEREO-A/HI, for three different separation angles between remote and in-situ spacecraft, of 30°, 60° and 90°. For validation, the results of the method are compared to the "true" speed profile of the modeled ICME, as obtained from top view density images, for every separation case. In this way it is possible to determine the accuracy of the method for revealing ICME propagation directions and kinematics. We found that the direction yield by the constrained Harmonic Mean method is not very sensitive on the separation angle. For all three cases the derived kinematics are in a relatively good agreement with the real kinematics. The best consistency is obtained for the 30° case, while with growing separation the ICME speed at 1 AU is increasingly overestimated. Especially for future L4/L5 missions the 60° separation case is highly interesting in order to improve space weather forecasts. Title: The Deflection of CMEs During Instances of CME-CME Interactions Authors: Lugaz, N.; Farrugia, C. J.; Davies, J.; Moestl, C.; Temmer, M.; Davis, C. J.; Roussev, I. I. Bibcode: 2012AGUFMSH31A2211L Altcode: The interaction of successive coronal mass ejections (CMEs) can be directly imaged by remote-sensing instruments such as the HIs onboard STEREO and the resulting transients can be measured in situ by spacecraft such as STEREO-A, STEREO-B, ACE and Wind. Here, we present the analysis of two successive CMEs from May 2010, observed to interact within HI1 field-of-view. During the interaction, the second CME (CME2) is found to decelerate and the first CME (CME1) is found to get compressed. At 1 AU, Wind observed a single, typical magnetic cloud-like ejecta. By combining the different observations, we determine that this event shows a clear instance of the deflection of two CMEs due to their collision in the heliosphere, and we estimate the deflection of CME1 to be about 10 degrees in the longitudinal direction. The resulting ejecta at 1 AU has a duration in agreement with the previously proposed hypothesis that compressed CMEs may over-expand after the end of the interaction. We also discuss additional events of CME-CME interaction and relate the findings to previous simulation efforts. Title: The Deflection of the Two Interacting Coronal Mass Ejections of 2010 May 23-24 as Revealed by Combined in Situ Measurements and Heliospheric Imaging Authors: Lugaz, N.; Farrugia, C. J.; Davies, J. A.; Möstl, C.; Davis, C. J.; Roussev, I. I.; Temmer, M. Bibcode: 2012ApJ...759...68L Altcode: 2012arXiv1209.2359L In 2010 May 23-24, Solar Dynamics Observatory (SDO) observed the launch of two successive coronal mass ejections (CMEs), which were subsequently tracked by the SECCHI suite on board STEREO. Using the COR2 coronagraphs and the heliospheric imagers (HIs), the initial direction of both CMEs is determined to be slightly west of the Sun-Earth line. We derive the CME kinematics, including the evolution of the CME expansion until 0.4 AU. We find that, during the interaction, the second CME decelerates from a speed above 500 km s-1 to 380 km s-1, the speed of the leading edge of the first CME. STEREO observes a complex structure composed of two different bright tracks in HI2-A but only one bright track in HI2-B. In situ measurements from Wind show an "isolated" interplanetary CME, with the geometry of a flux rope preceded by a shock. Measurements in the sheath are consistent with draping around the transient. By combining remote-sensing and in situ measurements, we determine that this event shows a clear instance of deflection of two CMEs after their collision, and we estimate the deflection of the first CME to be about 10° toward the Sun-Earth line. The arrival time, arrival speed, and radius at Earth of the first CME are best predicted from remote-sensing observations taken before the collision of the CMEs. Due to the over-expansion of the CME after the collision, there are few, if any, signs of interaction in in situ measurements. This study illustrates that complex interactions during the Sun-to-Earth propagation may not be revealed by in situ measurements alone. Title: Deep Solar Activity Minimum 2007 - 2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere Authors: Farrugia, C. J.; Harris, B.; Leitner, M.; Möstl, C.; Galvin, A. B.; Simunac, K. D. C.; Torbert, R. B.; Temmer, M. B.; Veronig, A. M.; Erkaev, N. V.; Szabo, A.; Ogilvie, K. W.; Luhmann, J. G.; Osherovich, V. A. Bibcode: 2012SoPh..281..461F Altcode: 2012SoPh..tmp..222F We discuss the temporal variations and frequency distributions of solar wind and interplanetary magnetic field parameters during the solar minimum of 2007 - 2009 from measurements returned by the IMPACT and PLASTIC instruments on STEREO-A. We find that the density and total field strength were significantly weaker than in the previous minimum. The Alfvén Mach number was higher than typical. This reflects the weakness of magnetohydrodynamic (MHD) forces, and has a direct effect on the solar wind-magnetosphere interactions. We then discuss two major aspects that this weak solar activity had on the magnetosphere, using data from Wind and ground-based observations: i) the dayside contribution to the cross-polar cap potential (CPCP), and ii) the shapes of the magnetopause and bow shock. For i) we find a low interplanetary electric field of 1.3±0.9 mV m−1 and a CPCP of 37.3±20.2 kV. The auroral activity is closely correlated to the prevalent stream-stream interactions. We suggest that the Alfvén wave trains in the fast streams and Kelvin-Helmholtz instability were the predominant agents mediating the transfer of solar wind momentum and energy to the magnetosphere during this three-year period. For ii) we determine 328 magnetopause and 271 bow shock crossings made by Geotail, Cluster 1, and the THEMIS B and C spacecraft during a three-month interval when the daily averages of the magnetic and kinetic energy densities attained their lowest value during the three years under survey. We use the same numerical approach as in Fairfield's (J. Geophys. Res.76, 7600, 1971) empirical model and compare our findings with three magnetopause models. The stand-off distance of the subsolar magnetopause and bow shock were 11.8 RE and 14.35 RE, respectively. When comparing with Fairfield's (1971) classic result, we find that the subsolar magnetosheath is thinner by ∼1 RE. This is mainly due to the low dynamic pressure which results in a sunward shift of the magnetopause. The magnetopause is more flared than in Fairfield's model. By contrast the bow shock is less flared, and the latter is the result of weaker MHD forces. Title: Multi-point Shock and Flux Rope Analysis of Multiple Interplanetary Coronal Mass Ejections around 2010 August 1 in the Inner Heliosphere Authors: Möstl, C.; Farrugia, C. J.; Kilpua, E. K. J.; Jian, L. K.; Liu, Y.; Eastwood, J. P.; Harrison, R. A.; Webb, D. F.; Temmer, M.; Odstrcil, D.; Davies, J. A.; Rollett, T.; Luhmann, J. G.; Nitta, N.; Mulligan, T.; Jensen, E. A.; Forsyth, R.; Lavraud, B.; de Koning, C. A.; Veronig, A. M.; Galvin, A. B.; Zhang, T. L.; Anderson, B. J. Bibcode: 2012ApJ...758...10M Altcode: 2012arXiv1209.2866M We present multi-point in situ observations of a complex sequence of coronal mass ejections (CMEs) which may serve as a benchmark event for numerical and empirical space weather prediction models. On 2010 August 1, instruments on various space missions, Solar Dynamics Observatory/Solar and Heliospheric Observatory/Solar-TErrestrial-RElations-Observatory (SDO/SOHO/STEREO), monitored several CMEs originating within tens of degrees from the solar disk center. We compare their imprints on four widely separated locations, spanning 120° in heliospheric longitude, with radial distances from the Sun ranging from MESSENGER (0.38 AU) to Venus Express (VEX, at 0.72 AU) to Wind, ACE, and ARTEMIS near Earth and STEREO-B close to 1 AU. Calculating shock and flux rope parameters at each location points to a non-spherical shape of the shock, and shows the global configuration of the interplanetary coronal mass ejections (ICMEs), which have interacted, but do not seem to have merged. VEX and STEREO-B observed similar magnetic flux ropes (MFRs), in contrast to structures at Wind. The geomagnetic storm was intense, reaching two minima in the Dst index (≈ - 100 nT), and was caused by the sheath region behind the shock and one of two observed MFRs. MESSENGER received a glancing blow of the ICMEs, and the events missed STEREO-A entirely. The observations demonstrate how sympathetic solar eruptions may immerse at least 1/3 of the heliosphere in the ecliptic with their distinct plasma and magnetic field signatures. We also emphasize the difficulties in linking the local views derived from single-spacecraft observations to a consistent global picture, pointing to possible alterations from the classical picture of ICMEs. Title: Solar Magnetized "Tornadoes:" Relation to Filaments Authors: Su, Yang; Wang, Tongjiang; Veronig, Astrid; Temmer, Manuela; Gan, Weiqun Bibcode: 2012ApJ...756L..41S Altcode: 2012arXiv1208.0138S Solar magnetized "tornadoes," a phenomenon discovered in the solar atmosphere, appear as tornado-like structures in the corona but are rooted in the photosphere. Like other solar phenomena, solar tornadoes are a feature of magnetized plasma and therefore differ distinctly from terrestrial tornadoes. Here we report the first analysis of solar "tornadoes" (two papers which focused on different aspects of solar tornadoes were published in the Astrophysical Journal Letters and Nature, respectively, during the revision of this Letter). A detailed case study of two events indicates that they are rotating vertical magnetic structures probably driven by underlying vortex flows in the photosphere. They usually exist as a group and are related to filaments/prominences, another important solar phenomenon whose formation and eruption are still mysteries. Solar tornadoes may play a distinct role in the supply of mass and twists to filaments. These findings could lead to a new explanation of filament formation and eruption. Title: Impulsive Acceleration of Coronal Mass Ejections. II. Relation to Soft X-Ray Flares and Filament Eruptions Authors: Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.; Temmer, M.; Vršnak, B. Bibcode: 2012ApJ...755...44B Altcode: 2012arXiv1206.2144B Using high time cadence images from the STEREO EUVI, COR1, and COR2 instruments, we derived detailed kinematics of the main acceleration stage for a sample of 95 coronal mass ejections (CMEs) in comparison with associated flares and filament eruptions. We found that CMEs associated with flares reveal on average significantly higher peak accelerations and lower acceleration phase durations, initiation heights, and heights, at which they reach their peak velocities and peak accelerations. This means that CMEs that are associated with flares are characterized by higher and more impulsive accelerations and originate from lower in the corona where the magnetic field is stronger. For CMEs that are associated with filament eruptions we found only for the CME peak acceleration significantly lower values than for events that were not associated with filament eruptions. The flare rise time was found to be positively correlated with the CME acceleration duration and negatively correlated with the CME peak acceleration. For the majority of the events the CME acceleration starts before the flare onset (for 75% of the events) and the CME acceleration ends after the soft X-ray (SXR) peak time (for 77% of the events). In ~60% of the events, the time difference between the peak time of the flare SXR flux derivative and the peak time of the CME acceleration is smaller than ±5 minutes, which hints at a feedback relationship between the CME acceleration and the energy release in the associated flare due to magnetic reconnection. Title: Relation between the Coronal Mass Ejection Acceleration and the Non-thermal Flare Characteristics Authors: Berkebile-Stoiser, S.; Veronig, A. M.; Bein, B. M.; Temmer, M. Bibcode: 2012ApJ...753...88B Altcode: We investigate the relationship between the main acceleration phase of coronal mass ejections (CMEs) and the particle acceleration in the associated flares as evidenced in Reuven Ramaty High Energy Solar Spectroscopic Imager non-thermal X-rays for a set of 37 impulsive flare-CME events. Both the CME peak velocity and peak acceleration yield distinct correlations with various parameters characterizing the flare-accelerated electron spectra. The highest correlation coefficient is obtained for the relation of the CME peak velocity and the total energy in accelerated electrons (c = 0.85), supporting the idea that the acceleration of the CME and the particle acceleration in the associated flare draw their energy from a common source, probably magnetic reconnection in the current sheet behind the erupting structure. In general, the CME peak velocity shows somewhat higher correlations with the non-thermal flare parameters than the CME peak acceleration, except for the spectral index of the accelerated electron spectrum, which yields a higher correlation with the CME peak acceleration (c ≈ -0.6), indicating that the hardness of the flare-accelerated electron spectrum is tightly coupled to the impulsive acceleration process of the rising CME structure. We also obtained high correlations between the CME initiation height h 0 and the non-thermal flare parameters, with the highest correlation of h 0 to the spectral index δ of flare-accelerated electrons (c ≈ 0.8). This means that CMEs erupting at low coronal heights, i.e., in regions of stronger magnetic fields, are accompanied by flares that are more efficient at accelerating electrons to high energies. In the majority of events (~80%), the non-thermal flare emission starts after the CME acceleration, on average delayed by ≈6 minutes, in line with the standard flare model where the rising flux rope stretches the field lines underneath until magnetic reconnection sets in. We find that the current sheet length at the onset of magnetic reconnection is 21 ± 7 Mm. The flare hard X-ray peaks are well synchronized with the peak of the CME acceleration profile, and in 75% of the cases they occur within ±5 minutes. Our findings provide strong evidence for the tight coupling between the CME dynamics and the particle acceleration in the associated flare in impulsive events, with the total energy in accelerated electrons being closely correlated with the peak velocity (and thus the kinetic energy) of the CME, whereas the number of electrons accelerated to high energies is decisively related to the CME peak acceleration and the height of the pre-eruptive structure. Title: The Kelvin-Helmholtz Instability at CME-Boundaries in the Solar Corona: Observations and Preliminary 2.5D MHD Simulations Authors: Moestl, Ute Verena; Temmer, M.; Veronig, A. M. Bibcode: 2012shin.confE..85M Altcode: Just recently, the Solar Dynamics Observatory (SDO) observedfor the first time Kelvin-Helmholtz vortices at the boundary of acoronal mass ejection (CME). The importance of the Kelvin-Helmholtz instability might lie in its effect on the CME kinematics due to exerting a drag force via anomalous viscosity.We discuss the observation of a CME by SDO from February 24th2011. This event shows periodic vortex-like structures on the boundary to the filament. First analysis of these structures reveals a periodic appearance with a wavelength of approximately 14 Mm and a height of 3-4 Mm.Another striking feature of this observation is an apparent asymmetric evolution of the periodic structures on only one side of the boundary layer. This asymmetry is also seen in other observations. Such observed asymmetry could be due to different magnetic field directions, for example. We test this hypothesis and present results of preliminary 2.5D magnetohydrodynamic simulations of the February 24th 2011event using different input parameters for the plasma background. Our aim is to check if the observed structures can be produced by the Kelvin-Helmholtz instability and to investigate the effect of different magnetic field directions on the evolution of the instability. Title: Kinematics of Coronal Mass Ejections in the Inner Heliosphere Constrained with In Situ Signatures Authors: Rollett, Tanja; Möstl, Christian; Temmer, Manuela; Veronig, Astrid; Farrugia, Charles J. Bibcode: 2012shin.confE..80R Altcode: On the basis of the Harmonic Mean and Fixed-Phi methods we developed a new approach to derive kinematics and propagation directions of interplanetary coronal mass ejections (ICMEs). By combining remote observations performed by STEREO/HI with in situ measurements of the Wind and STEREO-B spacecraft at 1 AU, we make the derived kinematical ICME profiles as consistent as possible with in situ data. Within the limitations of the geometrical assumptions that are used for the shape of the ICME, the improved methods aim to isolate the kinematics from that part of the CME which is most probably directed towards the in situ spacecraft. The methods are applied and tested on observational data from well observed ICME events (1-6 June 2008, 13-18 February 2009). This work has received funding from the European Commission FP7 Project COMESEP (263252). Title: Multi-point shock and flux rope analysis of multiple ICMEs around 2010 August 1 in the inner heliosphere Authors: Moestl, Christian; Farrugia, C. J.; Kilpua, E. K. J.; Jian, L.; Liu, Y.; Jensen, L.; Mulligan, T.; Eastwood, J.; Rollett, T.; Temmer, M.; Luhmann, J. G.; Harrison, R.; Davies, J. A.; Webb, D.; Forsyth, R.; Lavraud, B.; Odstrcil, D.; de Koning, C. A.; Nitta, N.; Veronig, A. M.; Galvin, A. B.; Zhang, T. L. Bibcode: 2012shin.confE..77M Altcode: We present multi-point in situ observations of a complex sequence of coronal mass ejections which may serve as a benchmark event for numerical and empirical space weather prediction models. On 2010 August 1, instruments on various space missions (SDO/SOHO/STEREO) monitored repeated coronal mass ejections originating within tens of degrees from solar disk center. We compare their imprints on four widely separated locations, covering 120 degree in heliospheric longitude, with radial distances from the Sun ranging from MESSENGER (0.38 AU) to Venus Express (VEX, at 0.72 AU) to Wind, ACE and ARTEMIS near Earth and STEREO-B close to 1 AU. Calculating shock and flux rope parameters at each location points to a non-spherical shape of the shock, and shows the global configuration of the interplanetary coronal mass ejections (ICMEs), which have interacted but not merged, making individual identifications still possible. VEX and STEREO-B observed similar magnetic flux ropes, in contrast to the structures at Wind. The geomagnetic storm was moderate to major, reaching two minima in the Dst index, caused by the sheath region behind the shock and one of two observed magnetic flux ropes. MESSENGER received a glancing blow of the ICMEs, and the events missed STEREO-A entirely. The observations demonstrate how sympathetic solar eruptions may immerse at least 1/3 of the heliosphere in the ecliptic with their distinct plasma and magnetic field signatures and emphasize the difficulties in linking the local views derived from single-spacecraft observations to a consistent global picture, pointing to possible alterations from the classical picture of ICMEs. Title: Comparison of MHD Simulations of the Solar Wind with In-Situ Measurements Authors: Gressl, Corinna; Veronig, A. M.; Temmer, M.; Odstrcil, D. Bibcode: 2012shin.confE..31G Altcode: ENLIL is a time-dependent 3D MHD model to simulate the structure and evolution of the solar wind parameters in the inner and mid heliosphere. ENLIL can be coupled to the coronal models "Magnetohydrodynamics Around Sphere" (MAS) and "Wang-Sheeley-Arge" (WSA) which use synoptic magnetograms of the solar photosphere as input parameter. We tested the performance of the coupled models ENLIL/MAS and ENLIL/WSA by comparing the modeled solar wind speed, proton density, temperature, and radial and total magnetic field strength to in-situ measurements from Wind and ACE at 1 AU. For the comparison we chose the year 2005 as a time period with low solar activity. We requested model runs with the aim to produce a stationary solution of the background solar wind. All simulations were carried out by CCMC/NASA. For the analysis of the model results we extracted the data at the exact position of the spacecraft. We calculated correlation coefficients to quantify the agreement between model predictions and measurements. The accuracy of the predicted arrival times of solar wind structures was quantified by carrying out cross-correlations. The results show that ENLIL/MAS and ENLIL/WSA are able to simulate the general features of the background solar wind and to reproduce recurring structures in the heliosphere. The best results were obtained for the parameter solar wind speed. However, the predicted arrival times of high speed solar wind streams have typical uncertainties of the order of 1 - 1.5 days, and the absolute values of the magnetic field were systematically too low. The sector structure of the interplanetary magnetic field was well reproduced by both models. Title: CME acceleration and non-thermal flare characteristics Authors: Berkebile-Stoiser, S.; Veronig, A. M.; Bein, B. M.; Temmer, M. Bibcode: 2012arXiv1205.2539B Altcode: We investigate the relationship between the main acceleration phase of coronal mass ejections (CMEs) and the particle acceleration in the associated flares as evidenced in RHESSI non-thermal X-rays for a set of 37 impulsive flare-CME events. CME peak velocity and peak acceleration yield distinct correlations with various parameters characterizing the flare-accelerated electron spectra. The highest correlation coefficient is obtained for the relation of the CME peak velocity and the total energy in accelerated electrons (c = 0.85), supporting the idea that the acceleration of the CME and the particle acceleration in the associated flare draw their energy from a common source, probably magnetic reconnection in the current sheet behind the erupting structure. In general, the CME peak velocity shows somewhat higher correlations with the non-thermal flare parameters than the CME peak acceleration, except for the spectral index of the accelerated electron spectrum which yields a higher correlation with the CME peak acceleration (c = -0.6), indicating that the hardness of the flare-accelerated electron spectrum is tightly coupled to the impulsive acceleration process of the rising CME structure. We also obtained high correlations between the CME initiation height $h_0$ and the non-thermal flare parameters, with the highest correlation of $h_0$ to the spectral index of flare-accelerated electrons (c = 0.8). This means that CMEs erupting at low coronal heights, i.e.\ in regions of stronger magnetic fields, are accompanied with flares which are more efficient to accelerate electrons to high energies. In the majority of events (80%), the non-thermal flare emission starts after the CME acceleration (6 min), giving a current sheet length at the onset of magnetic reconnection of 21 \pm 7 Mm. The flare HXR peaks are well synchronized with the peak of the CME acceleration profile. Title: An Analysis of the Origin and Propagation of the Multiple Coronal Mass Ejections of 2010 August 1 Authors: Harrison, R. A.; Davies, J. A.; Möstl, C.; Liu, Y.; Temmer, M.; Bisi, M. M.; Eastwood, J. P.; de Koning, C. A.; Nitta, N.; Rollett, T.; Farrugia, C. J.; Forsyth, R. J.; Jackson, B. V.; Jensen, E. A.; Kilpua, E. K. J.; Odstrcil, D.; Webb, D. F. Bibcode: 2012ApJ...750...45H Altcode: On 2010 August 1, the northern solar hemisphere underwent significant activity that involved a complex set of active regions near central meridian with, nearby, two large prominences and other more distant active regions. This activity culminated in the eruption of four major coronal mass ejections (CMEs), effects of which were detected at Earth and other solar system bodies. Recognizing the unprecedented wealth of data from the wide range of spacecraft that were available—providing the potential for us to explore methods for CME identification and tracking, and to assess issues regarding onset and planetary impact—we present a comprehensive analysis of this sequence of CMEs. We show that, for three of the four major CMEs, onset is associated with prominence eruption, while the remaining CME appears to be closely associated with a flare. Using instrumentation on board the Solar Terrestrial Relations Observatory spacecraft, three of the CMEs could be tracked out to elongations beyond 50° their directions and speeds have been determined by various methods, not least to assess their potential for Earth impact. The analysis techniques that can be applied to the other CME, the first to erupt, are more limited since that CME was obscured by the subsequent, much faster event before it had propagated far from the Sun; we discuss the speculation that these two CMEs interact. The consistency of the results, derived from the wide variety of methods applied to such an extraordinarily complete data set, has allowed us to converge on robust interpretations of the CME onsets and their arrivals at 1 AU. Title: A Self-similar Expansion Model for Use in Solar Wind Transient Propagation Studies Authors: Davies, J. A.; Harrison, R. A.; Perry, C. H.; Möstl, C.; Lugaz, N.; Rollett, T.; Davis, C. J.; Crothers, S. R.; Temmer, M.; Eyles, C. J.; Savani, N. P. Bibcode: 2012ApJ...750...23D Altcode: Since the advent of wide-angle imaging of the inner heliosphere, a plethora of techniques have been developed to investigate the three-dimensional structure and kinematics of solar wind transients, such as coronal mass ejections, from their signatures in single- and multi-spacecraft imaging observations. These techniques, which range from the highly complex and computationally intensive to methods based on simple curve fitting, all have their inherent advantages and limitations. In the analysis of single-spacecraft imaging observations, much use has been made of the fixed phi fitting (FPF) and harmonic mean fitting (HMF) techniques, in which the solar wind transient is considered to be a radially propagating point source (fixed phi, FP, model) and a radially expanding circle anchored at Sun centre (harmonic mean, HM, model), respectively. Initially, we compare the radial speeds and propagation directions derived from application of the FPF and HMF techniques to a large set of STEREO/Heliospheric Imager (HI) observations. As the geometries on which these two techniques are founded constitute extreme descriptions of solar wind transients in terms of their extent along the line of sight, we describe a single-spacecraft fitting technique based on a more generalized model for which the FP and HM geometries form the limiting cases. In addition to providing estimates of a transient's speed and propagation direction, the self-similar expansion fitting (SSEF) technique provides, in theory, the capability to estimate the transient's angular extent in the plane orthogonal to the field of view. Using the HI observations, and also by performing a Monte Carlo simulation, we assess the potential of the SSEF technique. Title: STEREO-A and PROBA2 Quadrature Observations of Reflections of three EUV Waves from a Coronal Hole Authors: Kienreich, Ines Waltraud; Muhr, Nicole; Veronig, Astrid; Berghmans, David; de Groof, Anik; Temmer, Manuela; Vršnak, Bojan; Seaton, Dan Bibcode: 2012arXiv1204.6472K Altcode: 2012arXiv1204.6472W We investigate the interaction of three consecutive large-scale coronal waves with a polar coronal hole, simultaneously observed on-disk by the Solar TErrestrial Relations Observatory (STEREO)-A spacecraft and on the limb by the PRoject for On-Board Autonomy 2 (PROBA2) spacecraft on January 27, 2011. All three extreme-ultraviolet(EUV) waves originate from the same active region NOAA 11149 positioned at N30E15 in the STEREO-A field-of-view and on the limb in PROBA2. We derive for the three primary EUV waves start velocities in the range of ~310 km/s for the weakest up to ~500 km/s for the strongest event. Each large-scale wave is reflected at the border of the extended coronal hole at the southern polar region. The average velocities of the reflected waves are found to be smaller than the mean velocities of their associated direct waves. However, the kinematical study also reveals that in each case the end velocity of the primary wave matches the initial velocity of the reflected wave. In all three events the primary and reflected waves obey the Huygens-Fresnel principle, as the incident angle with ~10° to the normal is of the same size as the angle of reflection. The correlation between the speed and the strength of the primary EUV waves, the homologous appearance of both the primary and the reflected waves, and in particular the EUV wave reflections themselves implicate that the observed EUV transients are indeed nonlinear large-amplitude MHD waves. Title: The first STEREO multi-event: Numerical simulation of coronal mass ejections (CMEs) launched on August 1, 2010 Authors: Odstrcil, D.; de Koning, C. A.; Xie, H.; Moestl, C.; Temmer, M.; Jian, L.; Rouillard, A. P.; Davies, J. A.; Davis, C. J.; Harrison, R. Bibcode: 2012EGUGA..1414429O Altcode: On 2010-08-01 at least four coronal mass ejections (CMEs) were observed by the Heliospheric Imagers (HIs) onboard STEREO spacecraft. These events originated at different parts of the solar corona and generated complex scenario of four mutually interacting CMEs. Real-time prediction of the arrival times to Earth failed and it is difficult to associate features observed by HIs with their solar sources and impacts at spacecraft. We use the heliospheric code ENLIL to show the global solution for various scenarios using fitted CME parameters from coronagraph observations by different techniques. We present the temporal profiles and synthetic white-light images that enables direct comparison with in-situ and remote observations. These results show that in addition to multi-perspective coronagraph observations, heliospheric imagers and numerical simulations are needed to understand and predict the impact of complex heliospheric disturbances. Title: CME-CME interaction during the 2010 August 1 events Authors: Temmer, M.; Vrsnak, B.; Rollett, T.; Bein, B.; deKoning, C. A.; Liu, Y.; Bosman, E.; Davies, J. A.; Möstl, C.; Zic, T.; Veronig, A. M.; Bothmer, V.; Harrison, R.; Nitta, N.; Bisi, M.; Flor, O.; Eastwood, J.; Odstrcil, D.; Forsyth, R. Bibcode: 2012EGUGA..14.1677T Altcode: We study a CME-CME interaction that occurred during the 2010 August 1 events using STEREO/SECCHI data (COR and HI). The CMEs were Earth directed where clear signatures of magnetic flux ropes could be measured from in situ Wind data. To give evidence of the actual interaction we derive the direction of motion for both CMEs applying several independent methods. From this we obtain that both CMEs head into similar directions enabling us to actually observe the merging in the HI1 field-of-view (and rule out the possibility that this is just a line of sight effect). The full de-projected kinematics of the faster CME from Sun to Earth is derived when combining data points from remote observations with in situ parameters of the ICME measured at 1 AU. We study the evolution of the kinematical profile of the faster CME by applying a drag based model. Title: CME mass evolution derived from stereoscopic observations of STEREO/SECCHI instruments COR1 and COR2 Authors: Bein, B.; Temmer, M.; Vourlidas, A.; Veronig, A. Bibcode: 2012EGUGA..14.7174B Altcode: The STEREO mission consists of two nearly identical spacecraft STEREO-A and STEREO-B, which observe simultaneously the Sun from two different vantage points. We use observations from both coronagraphs, COR1 and COR2 of the SECCHI instrument suite aboard STEREO-A and STEREO-B, to derive the CME mass evolution for a height range from 1.4 to 15 RSun. Due to the fact that we have observations from two different vantage points, we measure not only the projected mass but can estimate the 'true' CME mass evolution with height. We developed a fit function, which considers the mass increase based on the geometry of the instrument (mass hidden behind the occulter) and a possible 'real' mass increase with height. The fit parameters are compared with characteristic CME quantities. Title: Deep Solar Activity Minimum 2007-2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere Authors: Farrugia, C. J.; Harris, B.; Leitner, M.; Möstl, C.; Galvin, A. B.; Simunac, K. D. C.; Torbert, R. B.; Temmer, M. B.; Veronig, A. M.; Erkaev, N. V.; Szabo, A.; Ogilvie, K. W.; Luhmann, J. G.; Osherovich, V. A. Bibcode: 2012EGUGA..14.6381F Altcode: We discuss the temporal variations and frequency distributions of solar wind and interplanetary magnetic field parameters during the solar minimum of 2007- 2009 from measurements returned by the IMPACT and PLASTIC instruments on STEREO-A. We find that the density and total field strength were considerably weaker than in the previous minimum. The Alfvén Mach number was higher than typical. This reflects the weakness of magnetohydrodynamic (MHD) forces, and has a direct effect on the solar wind-magnetosphere interactions. We then discuss two major aspects that this weak solar activity had on the magnetosphere using data from Wind and ground-based observations: (a) the level of solar wind driving and the associated dayside contribution to the crosspolar cap potential (CPCP), and (b) the shapes of the magnetopause and bow shock. For (a) we find very weak interplanetary electric field (V xBz = -0.05 ± 0.83 mV/m) and a CPCP of 36.6 ± 18.2 kV. The auroral activity is closely correlated to the prevalent stream-stream interactions.We argue that the Alfvén waves in the fast streams and Kelvin-Helmholtz instability were the predominant agents mediating the transfer of solar wind momentum and energy to the magnetosphere during this 3-year period. For (b) we determine 328 magnetopause and 271 bow shock crossings made by the Cluster 1, Themis B and C spacecraft during a 3-month interval when the daily averages of the magnetic and kinetic energy densities attained their lowest value during the 3 years under survey. We use the same numerical approach as in Fairfield's (1971) empirical model and compare our findings with his classic result. The stand-off distance of the subsolar magnetopause and bow shock were 11.8 RE and 14.35 RE, respectively, making the subsolar magnetosheath thinner by ≈ 1RE. This is mainly due to the low dynamic pressure which result in a sunward shift of the magnetopause The magnetopause is more flared than Fairfield's result. By contrast the bow shock is less flared, and the latter is the result of weaker MHD forces. Title: Characteristics of Kinematics of a Coronal Mass Ejection during the 2010 August 1 CME-CME Interaction Event Authors: Temmer, Manuela; Vršnak, Bojan; Rollett, Tanja; Bein, Bianca; de Koning, Curt A.; Liu, Ying; Bosman, Eckhard; Davies, Jackie A.; Möstl, Christian; Žic, Tomislav; Veronig, Astrid M.; Bothmer, Volker; Harrison, Richard; Nitta, Nariaki; Bisi, Mario; Flor, Olga; Eastwood, Jonathan; Odstrcil, Dusan; Forsyth, Robert Bibcode: 2012ApJ...749...57T Altcode: 2012arXiv1202.0629T We study the interaction of two successive coronal mass ejections (CMEs) during the 2010 August 1 events using STEREO/SECCHI COR and heliospheric imager (HI) data. We obtain the direction of motion for both CMEs by applying several independent reconstruction methods and find that the CMEs head in similar directions. This provides evidence that a full interaction takes place between the two CMEs that can be observed in the HI1 field of view. The full de-projected kinematics of the faster CME from Sun to Earth is derived by combining remote observations with in situ measurements of the CME at 1 AU. The speed profile of the faster CME (CME2; ~1200 km s-1) shows a strong deceleration over the distance range at which it reaches the slower, preceding CME (CME1; ~700 km s-1). By applying a drag-based model we are able to reproduce the kinematical profile of CME2, suggesting that CME1 represents a magnetohydrodynamic obstacle for CME2 and that, after the interaction, the merged entity propagates as a single structure in an ambient flow of speed and density typical for quiet solar wind conditions. Observational facts show that magnetic forces may contribute to the enhanced deceleration of CME2. We speculate that the increase in magnetic tension and pressure, when CME2 bends and compresses the magnetic field lines of CME1, increases the efficiency of drag. Title: Calculation of CME kinematics and propagation directions by constraining STEREO HI-images with in situ signatures at 1 AU Authors: Rollett, T.; Möstl, C.; Temmer, M.; Veronig, A. M.; Farrugia, C. J.; Biernat, H. K. Bibcode: 2012EGUGA..14.4778R Altcode: We present a new approach to combine remote observations and in situ measurements by STEREO/HI and Wind, respectively, to derive the kinematics and propagation directions of interplanetary coronal mass ejections (ICMEs). We use two methods, Fixed-Phi and Harmonic Mean, to convert ICME elongations into distance. The ICME direction is constrained such that the ICME distance-time and speed-time profiles are most consistent with in situ measurements of the arrival time and speed at 1 AU. These methods are applied to two ICME events of 02 - 06 June 2008 and 13 - 18 February 2009. Due to the geometrical assumptions HM delivers the propagation direction further away from the observing spacecraft with a mean difference of 25°. This work has received funding from the European Commission FP7 Project COMESEP (263252). Title: Constraining the Kinematics of Coronal Mass Ejections in the Inner Heliosphere with In-Situ Signatures Authors: Rollett, T.; Möstl, C.; Temmer, M.; Veronig, A. M.; Farrugia, C. J.; Biernat, H. K. Bibcode: 2012SoPh..276..293R Altcode: 2011SoPh..tmp..414R; 2011SoPh..tmp..412R; 2011arXiv1110.0300R We present a new approach to combine remote observations and in-situ data by STEREO/HI and Wind, respectively, to derive the kinematics and propagation directions of interplanetary coronal mass ejections (ICMEs). We use two methods, Fixed-ϕ (Fϕ) and Harmonic Mean (HM), to convert ICME elongations into distance, and constrain the ICME direction such that the ICME distance-time and velocity-time profiles are most consistent with in-situ measurements of the arrival time and velocity. The derived velocity-time functions from the Sun to 1 AU for the three events under study (1 - 6 June 2008, 13 - 18 February 2009, 3 - 5 April 2010) do not show strong differences for the two extreme geometrical assumptions of a wide ICME with a circular front (HM) or an ICME of small spatial extent in the ecliptic (Fϕ). Due to the geometrical assumptions, HM delivers the propagation direction further away from the observing spacecraft with a mean difference of ≈ 25°. Title: Interactions between Coronal Mass Ejections Viewed in Coordinated Imaging and in situ Observations Authors: Liu, Ying D.; Luhmann, Janet G.; Möstl, Christian; Martinez-Oliveros, Juan C.; Bale, Stuart D.; Lin, Robert P.; Harrison, Richard A.; Temmer, Manuela; Webb, David F.; Odstrcil, Dusan Bibcode: 2012ApJ...746L..15L Altcode: 2012arXiv1201.2968L The successive coronal mass ejections (CMEs) from 2010 July 30 to August 1 present us the first opportunity to study CME-CME interactions with unprecedented heliospheric imaging and in situ observations from multiple vantage points. We describe two cases of CME interactions: merging of two CMEs launched close in time and overtaking of a preceding CME by a shock wave. The first two CMEs on August 1 interact close to the Sun and form a merged front, which then overtakes the July 30 CME near 1 AU, as revealed by wide-angle imaging observations. Connections between imaging observations and in situ signatures at 1 AU suggest that the merged front is a shock wave, followed by two ejecta observed at Wind which seem to have already merged. In situ measurements show that the CME from July 30 is being overtaken by the shock at 1 AU and is significantly compressed, accelerated, and heated. The interaction between the preceding ejecta and shock also results in variations in the shock strength and structure on a global scale, as shown by widely separated in situ measurements from Wind and STEREO B. These results indicate important implications of CME-CME interactions for shock propagation, particle acceleration, and space weather forecasting. Title: Relation Between the 3D-Geometry of the Coronal Wave and Associated CME During the 26 April 2008 Event Authors: Temmer, M.; Veronig, A. M.; Gopalswamy, N.; Yashiro, S. Bibcode: 2012esrs.book..115T Altcode: We study the kinematical characteristics and 3D geometry of a large-scale coronal wave that occurred in association with the 26 April 2008 flare-CME event. The wave was observed with the EUVI instruments aboard both STEREO spacecraft (STEREO-A and STEREO-B) with a mean speed of ∼ 240 km s-1. The wave is more pronounced in the eastern propagation direction, and is thus, better observable in STEREO-B images. From STEREO-B observations we derive two separate initiation centers for the wave, and their locations fit with the coronal dimming regions. Assuming a simple geometry of the wave we reconstruct its 3D nature from combined STEREO-A and STEREO-B observations. We find that the wave structure is asymmetric with an inclination toward East. The associated CME has a deprojected speed of ∼ 750±50 km s-1, and it shows a non-radial outward motion toward the East with respect to the underlying source region location. Applying the forward fitting model developed by Thernisien, Howard, and Vourlidas (Astrophys. J. 652, 763, 2006), we derive the CME flux rope position on the solar surface to be close to the dimming regions. We conclude that the expanding flanks of the CME most likely drive and shape the coronal wave. Title: Plasma Diagnostics of an EIT Wave Observed by Hinode/EIS and SDO/AIA Authors: Veronig, A. M.; Gömöry, P.; Kienreich, I. W.; Muhr, N.; Vršnak, B.; Temmer, M.; Warren, H. P. Bibcode: 2011ApJ...743L..10V Altcode: 2011arXiv1111.3505V We present plasma diagnostics of an Extreme-Ultraviolet Imaging Telescope (EIT) wave observed with high cadence in Hinode/Extreme-Ultraviolet Imaging Spectrometer (EIS) sit-and-stare spectroscopy and Solar Dynamics Observatory/Atmospheric Imaging Assembly imagery obtained during the HOP-180 observing campaign on 2011 February 16. At the propagating EIT wave front, we observe downward plasma flows in the EIS Fe XII, Fe XIII, and Fe XVI spectral lines (log T ≈ 6.1-6.4) with line-of-sight (LOS) velocities up to 20 km s-1. These redshifts are followed by blueshifts with upward velocities up to -5 km s-1 indicating relaxation of the plasma behind the wave front. During the wave evolution, the downward velocity pulse steepens from a few km s-1 up to 20 km s-1 and subsequently decays, correlated with the relative changes of the line intensities. The expected increase of the plasma densities at the EIT wave front estimated from the observed intensity increase lies within the noise level of our density diagnostics from EIS Fe XIII 202/203 Å line ratios. No significant LOS plasma motions are observed in the He II line, suggesting that the wave pulse was not strong enough to perturb the underlying chromosphere. This is consistent with the finding that no Hα Moreton wave was associated with the event. The EIT wave propagating along the EIS slit reveals a strong deceleration of a ≈ -540 m s-2 and a start velocity of v 0 ≈ 590 km s-1. These findings are consistent with the passage of a coronal fast-mode MHD wave, pushing the plasma downward and compressing it at the coronal base. Title: Influence of the Ambient Solar Wind Flow on the Propagation Behavior of Interplanetary Coronal Mass Ejections Authors: Temmer, Manuela; Rollett, Tanja; Möstl, Christian; Veronig, Astrid M.; Vršnak, Bojan; Odstrčil, Dusan Bibcode: 2011ApJ...743..101T Altcode: 2011arXiv1110.0827T We study three coronal mass ejection (CME)/interplanetary coronal mass ejection (ICME) events (2008 June 1-6, 2009 February 13-18, and 2010 April 3-5) tracked from Sun to 1 AU in remote-sensing observations of Solar Terrestrial Relations Observatory Heliospheric Imagers and in situ plasma and magnetic field measurements. We focus on the ICME propagation in interplanetary (IP) space that is governed by two forces: the propelling Lorentz force and the drag force. We address the question: which heliospheric distance range does the drag become dominant and the CME adjust to the solar wind flow. To this end, we analyze speed differences between ICMEs and the ambient solar wind flow as a function of distance. The evolution of the ambient solar wind flow is derived from ENLIL three-dimensional MHD model runs using different solar wind models, namely, Wang-Sheeley-Arge and MHD-Around-A-Sphere. Comparing the measured CME kinematics with the solar wind models, we find that the CME speed becomes adjusted to the solar wind speed at very different heliospheric distances in the three events under study: from below 30 R ⊙, to beyond 1 AU, depending on the CME and ambient solar wind characteristics. ENLIL can be used to derive important information about the overall structure of the background solar wind, providing more reliable results during times of low solar activity than during times of high solar activity. The results from this study enable us to obtain greater insight into the forces acting on CMEs over the IP space distance range, which is an important prerequisite for predicting their 1 AU transit times. Title: Elliptical approximation for the fronts of ICMEs and application to STEREO events in August 2010 and February 2011 Authors: Moestl, C.; Davies, J. A.; Rollett, T.; Temmer, M.; Lugaz, N.; Farrugia, C. J.; Liu, Y.; Veronig, A. M. Bibcode: 2011AGUFMSH23C1971M Altcode: Geo-effective solar eruptions can now be followed continuously from the Sun to 1 AU from a viewpoint far away from the Sun-Earth line (with STEREO/SECCHI), thus making it possible to link solar, heliospheric and in situ observations unambiguously. A very basic problem is that only the elongation of the interplanetary coronal mass ejection's (ICME) density enhancements, and not the radial distances, are measured by an observer when the ICME is propagating at large angles to the Sun. Additionally, this is complicated by the effects of Thomson scattering. Nevertheless, the community has worked so far with increasingly realistic geometrical approximations to convert the observed elongations to radial distance, such as Point-P (a circle around the Sun), Fixed-Phi (a point), Harmonic Mean (a circle always attached to the Sun at one end), and Self-Similar Expansion (a circle with a given angular width). We add to this an analytical formula which is based on an elliptical geometry (abbreviated EL), with the assumption, similar to HM and SSE, that the observer looks along the tangent of the ellipse which approximates the ICME front. In this way we still ignore Thomson-scattering, but otherwise the free parameters direction, angular width and aspect ratio allow more freedom to derive ICME radial distances and speeds from heliospheric imager observations, which should improve the consistency with in situ ICME observations and the CME directions and speeds in coronagraphs. An application to combined STEREO heliospheric imager and multi-point in situ observations of the multiple ICME events on 1-4 August 2010 and 15-17 February 2011 is presented, and the possibility of using EL for real-time forecasts by means of inverse fitting and triangulation is discussed. Title: Propagation behavior of interplanetary CMEs: driving versus drag force Authors: Temmer, M.; Rollett, T.; Moestl, C.; Veronig, A. M.; Vrsnak, B. Bibcode: 2011AGUFMSH23C1968T Altcode: The evolution of coronal mass ejections (CMEs) is governed by the Lorentz and the drag force. Initially, the CME is launched and driven by the Lorentz force, whereas the drag force owing to the ambient solar wind controls the CME kinematics as it propagates into interplanetary (IP) space. The subject of the current study is to infer a heliospheric distance at which the drag force starts to prevail over the driving force. With the SECCHI instrument suite aboard STEREO, CMEs can be observed during their entire propagation all the way from Sun to 1 AU. In combination with in-situ measurements at 1 AU we are able to derive the direction and speed of a CME. This information is used as input to derive the kinematical behavior of well observed CME events in the IP distance regime, which is subsequently compared to the output from ENLIL (NASA/CCMC) MHD model runs for the ambient solar wind flow. Title: Interaction between Coronal Mass Ejections Viewed in Coordinated Imaging and In Situ Observations Authors: Liu, Y.; Luhmann, J. G.; Moestl, C.; Martinez Oliveros, J. C.; Harrison, R.; Temmer, M.; Bale, S.; Lin, R. P. Bibcode: 2011AGUFMSH23C1973L Altcode: Interaction between coronal mass ejections (CMEs), which is expected to be a frequent phenomenon, has important implications for both space weather and basic plasma physics. First, the interaction alters the global heliospheric configuration, which may lead to favorable conditions for geomagnetic storm generation. Second, the interaction implies significant energy and momentum transfer between the interacting CMEs where magnetic reconnection may take place. Third, in case a shock is driven by the trailing CME, interesting physical processes may occur when the shock is propagating through the preceding one, such as modifications in the shock strength, particle intensity and transport. There are successive CMEs on July 30 - August 1, 2011, which presents us the first opportunity to study CME-CME interaction with unprecedented heliospheric imaging and in situ observations from a fleet of spacecraft. The first two CMEs on August 1 interact close to the Sun and form a merged front, which then overtakes the July 30 CME near 1 AU, as revealed by wide-angle imaging observations. In situ measurements indicate that the first two CMEs on August 1 seem to have already merged at 0.7 and 1 AU, and at 1 AU their shock is propagating into the CME from July 30. We will report and discuss the CME-CME interaction signatures from the coordinated imaging and in situ observations in this presentation. Title: Validation of a New Method to Derive Sun-to-1 AU Kinematics of ICMEs with a Numerical Simulation Authors: Rollett, T.; Moestl, C.; Lugaz, N.; Temmer, M.; Veronig, A. M. Bibcode: 2011AGUFMSH23C1970R Altcode: The Heliospheric Imagers (HI) aboard the NASA STEREO mission offer the possibility to follow coronal mass ejections (CMEs) continuously on their way from close to the Sun up to ~ 1 AU. The interpretation of these images is challenging because line-of-sight as well as Thomson scattering effects influence the white-light signal. There are different methods to derive the velocity profiles and propagation directions of CMEs in the interplanetary space, e.g. Fixed-Φ (Kahler and Webb, 2007) and Harmonic Mean (Lugaz, Vourlidas and Roussev, 2009), which make the assumptions of a point like structure and a circle shaped front of the CME, respectively. These two approaches can be constrained using in situ measurements at 1 AU as shown in Rollett et al. (2011). To validate the applied methods, we perform the same procedures for a simulated CME as modeled in the space weather modeling framework (SWMF, Toth, et al., 2005). The measurements are outlined for synthetic HI images (Lugaz et al., 2005) at different observing points. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 263252 [COMESEP]. Title: The first STEREO multi-event: Numerical simulation of coronal mass ejections (CMEs) launched on August 1, 2010 Authors: Odstrcil, D.; de Koning, C. A.; Xie, H.; Moestl, C.; Temmer, M.; Jian, L.; Rouillard, A. P.; Davies, J. A.; Davis, C. J.; Harrison, R. Bibcode: 2011AGUFMSH32A..03O Altcode: On 2010-08-01 at least four coronal mass ejections (CMEs) were observed by the Heliospheric Imagers (HIs) onboard STEREO spacecraft. These events originated at different parts of the solar corona and generated complex scenario of four mutually interacting CMEs. Real-time prediction of the arrival times to Earth failed and it is difficult to associate features observed by HIs with their solar sources and impacts at spacecraft. We use the heliospheric code ENLIL to show the global solution for two scenarios using fitted CME parameters from coronagraph observations by two different techniques. We present the temporal profiles and synthetic white-light images that enables direct comparison with in-situ and remote observations. These results show that in addition to multi-perspective coronagraph observations, heliospheric imagers and numerical simulations are needed to understand and predict the impact of complex heliospheric disturbances. Title: Comparison between MHD modeled and in situ measured solar wind parameters Authors: Gressl, C.; Veronig, A. M.; Temmer, M.; Moestl, C. Bibcode: 2011AGUFMSH23C1977G Altcode: The numerical MHD model ENLIL enables us to simulate the solar wind conditions from Sun to 1 AU based on synoptic magnetograms over an entire Carrington rotation (runs are performed at the NASA/CCMC and are available on request under http://ccmc.gsfc.nasa.gov/). We use ENLIL for the inner-heliosphere coupled with the coronal model MAS (MHD-Around-A-Sphere) and the combined empirical and physics-based model WSA (Wang-Sheeley-Arge), respectively, to extract solar wind parameters at the distance of 1AU. The results from the simulation are compared to measured solar wind parameters at 1AU from ACE and Wind spacecraft. The study aims to test the accuracy and reliability for forecasting solar wind parameters like density, speed, temperature, and magnetic field from numerical models on time scales smaller than 1 day. Title: Arrival Time Calculation for Interplanetary Coronal Mass Ejections with Circular Fronts and Application to STEREO Observations of the 2009 February 13 Eruption Authors: Möstl, C.; Rollett, T.; Lugaz, N.; Farrugia, C. J.; Davies, J. A.; Temmer, M.; Veronig, A. M.; Harrison, R. A.; Crothers, S.; Luhmann, J. G.; Galvin, A. B.; Zhang, T. L.; Baumjohann, W.; Biernat, H. K. Bibcode: 2011ApJ...741...34M Altcode: 2011arXiv1108.0515M One of the goals of the NASA Solar TErestrial RElations Observatory (STEREO) mission is to study the feasibility of forecasting the direction, arrival time, and internal structure of solar coronal mass ejections (CMEs) from a vantage point outside the Sun-Earth line. Through a case study, we discuss the arrival time calculation of interplanetary CMEs (ICMEs) in the ecliptic plane using data from STEREO/SECCHI at large elongations from the Sun in combination with different geometric assumptions about the ICME front shape [fixed-Φ (FP): a point and harmonic mean (HM): a circle]. These forecasting techniques use single-spacecraft imaging data and are based on the assumption of constant velocity and direction. We show that for the slow (350 km s-1) ICME on 2009 February 13-18, observed at quadrature by the two STEREO spacecraft, the results for the arrival time given by the HM approximation are more accurate by 12 hr than those for FP in comparison to in situ observations of solar wind plasma and magnetic field parameters by STEREO/IMPACT/PLASTIC, and by 6 hr for the arrival time at Venus Express (MAG). We propose that the improvement is directly related to the ICME front shape being more accurately described by HM for an ICME with a low inclination of its symmetry axis to the ecliptic. In this case, the ICME has to be tracked to >30° elongation to obtain arrival time errors < ± 5 hr. A newly derived formula for calculating arrival times with the HM method is also useful for a triangulation technique assuming the same geometry. Title: Relation Between the 3D-Geometry of the Coronal Wave and Associated CME During the 26 April 2008 Event Authors: Temmer, M.; Veronig, A. M.; Gopalswamy, N.; Yashiro, S. Bibcode: 2011SoPh..273..421T Altcode: 2011SoPh..tmp...75T; 2011arXiv1103.0196T; 2011SoPh..tmp..227T; 2011SoPh..tmp..158T We study the kinematical characteristics and 3D geometry of a large-scale coronal wave that occurred in association with the 26 April 2008 flare-CME event. The wave was observed with the EUVI instruments aboard both STEREO spacecraft (STEREO-A and STEREO-B) with a mean speed of ∼ 240 km s−1. The wave is more pronounced in the eastern propagation direction, and is thus, better observable in STEREO-B images. From STEREO-B observations we derive two separate initiation centers for the wave, and their locations fit with the coronal dimming regions. Assuming a simple geometry of the wave we reconstruct its 3D nature from combined STEREO-A and STEREO-B observations. We find that the wave structure is asymmetric with an inclination toward East. The associated CME has a deprojected speed of ∼ 750±50 km s−1, and it shows a non-radial outward motion toward the East with respect to the underlying source region location. Applying the forward fitting model developed by Thernisien, Howard, and Vourlidas (Astrophys. J. 652, 763, 2006), we derive the CME flux rope position on the solar surface to be close to the dimming regions. We conclude that the expanding flanks of the CME most likely drive and shape the coronal wave. Title: Coronal Dimmings and the Early Phase of a CME Observed with STEREO and Hinode/EIS Authors: Miklenic, C.; Veronig, A. M.; Temmer, M.; Möstl, C.; Biernat, H. K. Bibcode: 2011SoPh..273..125M Altcode: 2011arXiv1110.0362M; 2011SoPh..tmp..350M We investigate the early phase of the 13 February 2009 coronal mass ejection (CME). Observations with the twin STEREO spacecraft in quadrature allow us to compare for the first time in one and the same event the temporal evolution of coronal EUV dimmings, observed simultaneously on-disk and above-the-limb. We find that these dimmings are synchronized and appear during the impulsive acceleration phase of the CME, with the highest EUV intensity drop occurring a few minutes after the maximum CME acceleration. During the propagation phase two confined, bipolar dimming regions, appearing near the footpoints of a pre-flare sigmoid structure, show an apparent migration away from the site of the CME-associated flare. Additionally, they rotate around the `center' of the flare site, i.e., the configuration of the dimmings exhibits the same `sheared-to-potential' evolution as the postflare loops. We conclude that the motion pattern of the twin dimmings reflects not only the eruption of the flux rope, but also the ensuing stretching of the overlying arcade. Finally, we find that: i) the global-scale dimmings, expanding from the source region of the eruption, propagate with a speed similar to that of the leaving CME front; ii) the mass loss occurs mainly during the period of strongest CME acceleration. Two hours after the eruption Hinode/EIS observations show no substantial plasma outflow, originating from the `open' field twin dimming regions. Title: The LSO/KSO Hα prominence catalogue: cross-calibration of data Authors: Rybák, J.; Gömöry, P.; Mačura, R.; Kučera, A.; Rušin, V.; Pötzi, W.; Baumgartner, D.; Hanslmeier, A.; Veronig, A.; Temmer, M. Bibcode: 2011CoSka..41..133R Altcode: We present work on the extension of the homogeneous prominence catalogue created for the epoch 1967 — 2009 at the Lomnicky Peak Observatory (LSO) by incorporating new data acquired at the Kanzelhöhe Observatory for Solar and Environmental Research (KSO). We use data of 20 Hα prominences observed almost simultaneously at both observatories during four days in August/September 2009 to analyze the significance of differences of the determined parameters used in the Hα prominence catalogue. A reduction of the data from KSO and adaptation of the resulting parameters to fit the parameters of the LSO catalogue confirm that no special homogenization is needed to create a common catalogue data set. Thus, we justified that the LSO catalogue could be extended onward in the future using a more comprehensive database of observations from KSO. Title: Analysis of Characteristic Parameters of Large-scale Coronal Waves Observed by the Solar-Terrestrial Relations Observatory/Extreme Ultraviolet Imager Authors: Muhr, N.; Veronig, A. M.; Kienreich, I. W.; Temmer, M.; Vršnak, B. Bibcode: 2011ApJ...739...89M Altcode: The kinematical evolution of four extreme ultraviolet waves, well observed by the Extreme Ultraviolet Imager on board the Solar-Terrestrial Relations Observatory (STEREO), is studied by visually tracking wave fronts as well as by a semi-automatized perturbation profile method, which leads to results matching each other within the error limits. The derived mean velocities of the events under study lie in the range of 220-350 km s-1. The fastest of the events (2007 May 19) reveals a significant deceleration of ≈ - 190 m s-2, while the others are consistent with a constant velocity during wave propagation. The evolution of maximum-intensity values reveals initial intensification of 20%-70% and decays to original levels within 40-60 minutes, while the widths at half-maximum and full-maximum of the perturbation profiles broaden by a factor of two to four. The integral below the perturbation profile remains basically constant in two cases, while it shows a decrease by a factor of three to four in the other two cases. From the peak perturbation amplitudes, we estimate the corresponding magnetosonic Mach numbers M ms, which range from 1.08-1.21. The perturbation profiles reveal three distinct features behind the propagating wave fronts: coronal dimmings, stationary brightenings, and rarefaction regions. All features appear after the wave passage and only slowly fade away. Our findings indicate that the events under study are weak-shock fast-mode magnetohydrodynamic waves initiated by the CME lateral expansion. Title: Propagation and impact of multiple coronal mass ejections events on August 1 2010 in the heliosphere Authors: Möstl, Christian; Farrugia, Charles J.; Harrison, Richard A.; Davies, J. A.; Kilpua, Emilia K. J.; Odstrcil, Dusan; Rollett, Tanja; Temmer, Manuela; Veronig, Astrid; Jian, Lan; Liu, Ying; Eastwood, Jonathan; Forsyth, Robert; Webb, David; Bisi, Mario M.; Jackson, Bernard V.; Mulligan, Tamitha; Jensen, Liz; Lavraud, Benoit; de Koning, Curt A.; Nitta, Nariaki; Luhmann, Janet; Galvin, Antoinette B.; Zhang, Tielong Bibcode: 2011sdmi.confE..69M Altcode: On August 1 2010 a large region of the solar northern hemisphere displayed major activity involving a complex set of central meridian and remote active regions, and two large prominence channels (Schrijver and Title, JGR, 2011). We witnessed the eruption of four coronal mass ejections (CMEs) which partly impacted Earth and lead to one of the first geomagnetic storms of the new solar cycle. We present an overview of the results of several analyses exploiting the extraordinary completeness of the imaging data (SDO/STEREO/SOHO) in combination with numerical simulations (ENLIL) and in situ observations. The imprints of the CMEs, including a prior event on July 30, were observed in situ in an almost laboratory-like configuration at 4 widely separated locations spanning over 120 degrees of heliospheric longitude (STEREO-B, Venus Express, ACE/Wind, ARTEMIS, and MESSENGER). The CME density enhancements could be followed with the STEREO-A/HI and Coriolis/SMEI instruments continuously from the Sun to 1 AU. Evidences of CME-CME interactions and resulting overlapping tracks in Jmaps make the analysis complex, but nevertheless we find robust interpretations for linking two magnetic flux ropes at Earth, one of them geo-effective and including elevated alpha particles related to possible filament material, to their solar counterparts. Additionally, we discuss the relationship between the in situ observations and the global picture given by the ENLIL model. Title: Solar wind high-speed streams and related geomagnetic activity in the declining phase of solar cycle 23 Authors: Verbanac, G.; Vršnak, B.; Živković, S.; Hojsak, T.; Veronig, A. M.; Temmer, M. Bibcode: 2011A&A...533A..49V Altcode: Context. Coronal holes (CHs) are the source of high-speed streams (HSSs) in the solar wind, whose interaction with the slow solar wind creates corotating interaction regions (CIRs) in the heliosphere.
Aims: We investigate the magnetospheric activity caused by CIR/HSS structures, focusing on the declining phase of the solar cycle 23 (years 2005 and 2006), when the occurrence rate of coronal mass ejections (CMEs) was low. We aim to (i) perform a systematic analysis of the relationship between the CH characteristics, basic parameters of HSS/CIRs, and the geomagnetic indices Dst, Ap and AE; (ii) study how the magnetospheric/ionospheric current systems behave when influenced by HSS/CIR; (iii) investigate if and how the evolution of the background solar wind from 2005 to 2006 affected the correlations between CH, CIR, and geomagnetic parameters.
Methods: The cross-correlation analysis was applied to the fractional CH area (CH) measured in the central meridian distance interval ± 10°, the solar wind velocity (V), the interplanetary magnetic field (B), and the geomagnetic indices Dst, Ap, and AE.
Results: The performed analysis shows that Ap and AE are better correlated with CH and solar wind parameters than Dst, and quantitatively demonstrates that the combination of solar wind parameters BV2 and BV plays the central role in the process of energy transfer from the solar wind to the magnetosphere.
Conclusions: We provide reliable relationships between CH properties, HSS/CIR parameters, and geomagnetic indices, which can be used in forecasting the geomagnetic activity in periods of low CME activity. Title: An Observational Overview of Solar Flares Authors: Fletcher, L.; Dennis, B. R.; Hudson, H. S.; Krucker, S.; Phillips, K.; Veronig, A.; Battaglia, M.; Bone, L.; Caspi, A.; Chen, Q.; Gallagher, P.; Grigis, P. T.; Ji, H.; Liu, W.; Milligan, R. O.; Temmer, M. Bibcode: 2011SSRv..159...19F Altcode: 2011SSRv..tmp..261F; 2011arXiv1109.5932F We present an overview of solar flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of solar flares is far from complete, so we conclude with a brief discussion of models, and a list of missing but important observations. Title: Impulsive Acceleration of Coronal Mass Ejections. I. Statistics and Coronal Mass Ejection Source Region Characteristics Authors: Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.; Temmer, M.; Muhr, N.; Kienreich, I.; Utz, D.; Vršnak, B. Bibcode: 2011ApJ...738..191B Altcode: 2011arXiv1108.0561B We use high time cadence images acquired by the STEREO EUVI and COR instruments to study the evolution of coronal mass ejections (CMEs) from their initiation through impulsive acceleration to the propagation phase. For a set of 95 CMEs we derived detailed height, velocity, and acceleration profiles and statistically analyzed characteristic CME parameters: peak acceleration, peak velocity, acceleration duration, initiation height, height at peak velocity, height at peak acceleration, and size of the CME source region. The CME peak accelerations we derived range from 20 to 6800 m s-2 and are inversely correlated with the acceleration duration and the height at peak acceleration. Seventy-four percent of the events reach their peak acceleration at heights below 0.5 R sun. CMEs that originate from compact sources low in the corona are more impulsive and reach higher peak accelerations at smaller heights. These findings can be explained by the Lorentz force, which drives the CME accelerations and decreases with height and CME size. Title: Analysis of characteristic parameters of large-scale coronal waves observed by STEREO/EUVI Authors: Muhr, N.; Veronig, A. M.; Kienreich, I. W.; Temmer, M.; Vrsnak, B. Bibcode: 2011arXiv1107.0921M Altcode: The kinematical evolution of four EUV waves, well observed by the Extreme UltraViolet Imager (EUVI) onboard the Solar-Terrestrial Relations Observatory (STEREO), is studied by visually tracking the wave fronts as well as by a semiautomatized perturbation profile method leading to results matching each other within the error limits. The derived mean velocities of the events under study lie in the range of 220-350 km/s. The fastest of the events (May 19, 2007) reveals a significant deceleration of \approx -190 m s-2 while the others are consistent with a constant velocity during the wave propagation. The evolution of the maximum intensity values reveals initial intensification by 20 up to 70%, and decays to original levels within 40-60 min, while the width at half maximum and full maximum of the perturbation profiles are broadening by a factor of 2 - 4. The integral below the perturbation profile remains basically constant in two cases, while it shows a decrease by a factor of 3 - 4 in the other two cases. From the peak perturbation amplitudes we estimate the corresponding magnetosonic Mach numbers Mms which are in the range of 1.08-1.21. The perturbation profiles reveal three distinct features behind the propagating wave fronts: coronal dimmings, stationary brightenings and rarefaction regions. All of them appear after the wave passage and are only slowly fading away. Our findings indicate that the events under study are weak shock fast-mode MHD waves initiated by the CME lateral expansion. Title: The Drag Based Model of ICME Propagation Authors: Dumbović, M.; Vršnak, B.; Žic, T.; Vrbanec, D.; Veronig, A.; Temmer, M.; Rollett, T.; Moestl, C.; Moon, Y. -J. Bibcode: 2011simi.confR...2D Altcode: One of central issues of space weather is the propagation of interplanetary coronal mass ejections (ICMEs). At the heliospheric distances beyond R=20 solar radii the "aerodynamic" drag is presumably the dominant force governing ICME propagation; therefore, a drag based model (DBM) was established, which can be used to forecast the ICME arrival at the Earth.

First, the model was tested on a sample of CMEs by combining remote observations of the CME take-off gained by the LASCO onboard SOHO, and in situ measurements from ACE and Wind satellites. The results of the DBM were compared to observational data and a fairly good agreement of the two was found. The model was then tested against STEREO observations. The ICME kinematics was inferred from STEREO observations by applying the Harmonic Mean method and compared to the DBM results. In this way we were able to reproduce the propagation of both slow and fast ICMEs, as well as to identify ICME-ICME interactions and a transition from fast-to-slow solar wind regimes. Finally, a statistical study was performed, where parameters were varied within a model in order to obtain optimal values, for which the average difference in the observed and calculated TT is zero (O-C=0) and the O-C scatter gets minimum. The source of the scatter in O–C values was investigated.

The research leading to the results presented in this paper has received funding from European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 218816. Title: Multiple, distant (40°) in situ observations of a magnetic cloud and a corotating interaction region complex Authors: Farrugia, C. J.; Berdichevsky, D. B.; Möstl, C.; Galvin, A. B.; Leitner, M.; Popecki, M. A.; Simunac, K. D. C.; Opitz, A.; Lavraud, B.; Ogilvie, K. W.; Veronig, A. M.; Temmer, M.; Luhmann, J. G.; Sauvaud, J. A. Bibcode: 2011JASTP..73.1254F Altcode: We report a comprehensive analysis of in situ observations made by Wind and the STEREO probes (STA, STB) of a complex interaction between a magnetic cloud (MC) and a corotating interaction region (CIR) occurring near the heliospheric current sheet (HCS) on November 19-21, 2007. The probes were separated by 0.7 AU (∼40∘) with a spread in heliographic latitudes (4.8,° 2.2,° and -0.4,° for STB, Wind and STA, respectively). We employ data from the MFI, SWE and 3DP instruments on Wind, and the PLASTIC and IMPACT suites on STEREO. STB, located east of Earth, observed a forward shock followed by signatures of a MC. The MC took the role of the HCS in that the polarity of the interplanetary magnetic field (IMF) on exit was the reverse of that on entry. A passage through a plasma sheet was observed. Along the Sun-Earth line Wind observed a stream interface (SI) between a forward and a reverse shock. A MC, compressed by the CIR, was entrained in this. STA, located 20° to the west of Earth, saw a MC which was not preceded by a shock. A SI trailed the transient. The shocks are examined using various methods and from this it is concluded that the forward shock at Wind—but not at STB—was driven by the MC. Examining the MC by Grad-Shafranov reconstruction, we find evidence of a double-flux rope structure at Wind and STA and possibly also at STB. The orientations are at variance with the notion of a large-scale flux tube being observed at the three spacecraft. We find consistency of this with the directional properties of the solar wind "strahl" electrons. We examine aspects of the geomagnetic response and find a double-dip storm corresponding to the two interplanetary triggers. The minimum Dst phase was prolonged and the geoeffects were intensified due to the interaction. We conclude that while the formation of compound streams is a common feature of interplanetary space, understanding their components when CIRs are involved is a complicated matter needing numerical simulations and/or more in situ observations for its complete elucidation. Title: Equatorial coronal holes, solar wind high-speed streams, and their geoeffectiveness Authors: Verbanac, G.; Vršnak, B.; Veronig, A.; Temmer, M. Bibcode: 2011A&A...526A..20V Altcode: Context. Solar wind high-speed streams (HSSs), originating in equatorial coronal holes (CHs), are the main driver of the geomagnetic activity in the late-declining phase of the solar cycle.
Aims: We analyze correlations between CH characteristics, HSSs parameters, and the geomagnetic activity indices, to establish empirical relationships that would provide forecasting of the solar wind characteristics, as well as the effect of HSSs on the geomagnetic activity in periods when the effect of coronal mass ejections is low.
Methods: We apply the cross-correlation analysis to the fractional CH area (CH) measured between central meridian distances ±10°, solar wind parameters (flow velocity V, proton density n, temperature T, and the magnetic field B), and the geomagnetic indices Dst and Ap.
Results: The cross-correlation analysis reveals a high degree of correlation between all studied parameters. In particular, we show that the Ap index is considerably more sensitive to HSS and CH characteristics than Dst. The Ap and Dst indices are most tightly correlated with the solar wind parameter BV2.
Conclusions: From the point of view of space weather, the most important result is that the established empirical relationships provide a few-days-in-advance forecasting of the HSS characteristics and the related geomagnetic activity at the six-hour resolution.

Appendices, Figs. 9-14, and table 4 are only available in electronic form at http://www.aanda.org Title: Case Study of Four Homologous Large-scale Coronal Waves Observed on 2010 April 28 and 29 Authors: Kienreich, I. W.; Veronig, A. M.; Muhr, N.; Temmer, M.; Vršnak, B.; Nitta, N. Bibcode: 2011ApJ...727L..43K Altcode: 2011arXiv1101.5232K On 2010 April 28 and 29, the Solar TErrestrial Relations Observatory B/Extreme Ultraviolet Imager observed four homologous large-scale coronal waves, the so-called EIT-waves, within 8 hr. All waves emerged from the same source active region, were accompanied by weak flares and faint coronal mass ejections, and propagated into the same direction at constant velocities in the range of ~220-340 km s-1. The last of these four coronal wave events was the strongest and fastest, with a velocity of 337 ± 31 km s-1 and a peak perturbation amplitude of ~1.24, corresponding to a magnetosonic Mach number of M ms ~ 1.09. The magnetosonic Mach numbers and velocities of the four waves are distinctly correlated, suggestive of the nonlinear fast-mode magnetosonic wave nature of the events. We also found a correlation between the magnetic energy buildup times and the velocity and magnetosonic Mach number. Title: Implementation of a Calcium telescope at Kanzelhöhe Observatory (KSO) Authors: Hirtenfellner-Polanec, W.; Temmer, M.; Pötzi, W.; Freislich, H.; Veronig, A. M.; Hanslmeier, A. Bibcode: 2011CEAB...35..205H Altcode: A new telescope is implemented at Kanzelhöhe Observatory in order to observe the chromosphere in the Ca II K line at 393.4 nm (FWHM 0.3 nm). The design of the new Ca camera system is very similar to the well established Kanzelhöhe Photosphere Digital Camera and the Hα system and allows obtaining automatically full disc Ca~II~K 2k×2k images time series with a cadence of a few seconds. The main purpose of this new instrument is a high precision full disc imaging of the chromosphere in order to observe flares, plages and the chromospheric network. The Ca emission is also an indicator for magnetic activity on the sun. Therefore the Ca data will be taken for analysing the variations in the structures of the magnetic field. Title: STEREO and Wind observations of a fast ICME flank triggering a prolonged geomagnetic storm on 5-7 April 2010 Authors: Möstl, C.; Temmer, M.; Rollett, T.; Farrugia, C. J.; Liu, Y.; Veronig, A. M.; Leitner, M.; Galvin, A. B.; Biernat, H. K. Bibcode: 2010GeoRL..3724103M Altcode: 2010arXiv1010.4150M On 5 April 2010 an interplanetary (IP) shock was detected by the Wind spacecraft ahead of Earth, followed by a fast (average speed 650 km/s) IP coronal mass ejection (ICME). During the subsequent moderate geomagnetic storm (minimum Dst = -72 nT, maximum Kp = 8-), communication with the Galaxy 15 satellite was lost. We link images from STEREO/ SECCHI to the near-Earth in situ observations and show that the ICME did not decelerate much between Sun and Earth. The ICME flank was responsible for a long storm growth phase. This type of glancing collision was for the first time directly observed with the STEREO Heliospheric Imagers. The magnetic cloud (MC) inside the ICME cannot be modeled with approaches assuming an invariant direction. These observations confirm the hypotheses that parts of ICMEs classified as (1) long-duration MCs or (2) magnetic-cloud-like (MCL) structures can be a consequence of a spacecraft trajectory through the ICME flank. Title: Application of data assimilation to solar wind forecasting models Authors: Innocenti, M.; Lapenta, G.; Vrsnak, B.; Temmer, M.; Veronig, A.; Bettarini, L.; Lee, E.; Markidis, S.; Skender, M.; Crespon, F.; Skandrani, C.; Soteria Space-Weather Forecast; Data Assimilation Team Bibcode: 2010AGUFMSM54A..08I Altcode: Data Assimilation through Kalman filtering [1,2] is a powerful statistical tool which allows to combine modeling and observations to increase the degree of knowledge of a given system. We apply this technique to the forecast of solar wind parameters (proton speed, proton temperature, absolute value of the magnetic field and proton density) at 1 AU, using the model described in [3] and ACE data as observations. The model, which relies on GOES 12 observations of the percentage of the meridional slice of the sun covered by coronal holes, grants 1-day and 6-hours in advance forecasts of the aforementioned quantities in quiet times (CMEs are not taken into account) during the declining phase of the solar cycle and is tailored for specific time intervals. We show that the application of data assimilation generally improves the quality of the forecasts during quiet times and, more notably, extends the periods of applicability of the model, which can now provide reliable forecasts also in presence of CMEs and for periods other than the ones it was designed for. Acknowledgement: The research leading to these results has received funding from the European Commission’s Seventh Framework Programme (FP7/2007-2013) under the grant agreement N. 218816 (SOTERIA project: http://www.soteria-space.eu). References: [1] R. Kalman, J. Basic Eng. 82, 35 (1960); [2] G. Welch and G. Bishop, Technical Report TR 95-041, University of North Carolina, Department of Computer Science (2001); [3] B. Vrsnak, M. Temmer, and A. Veronig, Solar Phys. 240, 315 (2007). Title: Multiple, Distant (40 deg) in situ Observations of a Magnetic Cloud and a Corotating Interaction Region Complex Authors: Farrugia, C. J.; Berdichevsky, D. B.; Moestl, C.; Galvin, A. B.; Leitner, M.; Popecki, M.; Simunac, K. D.; Opitz, A.; Lavraud, B.; Ogilvie, K.; Veronig, A.; Temmer, M.; Luhmann, J. G.; Sauvaud, J. Bibcode: 2010AGUFMSH51C1689F Altcode: We report a comprehensive analysis of in situ observations made by Wind and the STEREO probes (STA, STB) of a complex interaction between a magnetic cloud (MC) and a corotating interaction region (CIR) occurring near the heliospheric current sheet (HCS) on November 19-21, 2007. The probes were separated by 0.7 AU (~40 deg) with a spread in heliographic latitudes (4.8, 2.2, and -0.4 deg for STB, Wind and STA, respectively). We employ data from the MFI, SWE and 3DP instruments on Wind, and the PLASTIC and IMPACT suites on STEREO. STB, located east of Earth, observed a forward shock followed by signatures of a MC. The MC took the role of the HCS in that the polarity of the interplanetary magnetic field (IMF) on exit was the reverse of that on entry. A passage through a plasma sheet is observed. Along the Sun-Earth line Wind observed a stream interface (SI) between a forward and a reverse shock. A MC, compressed by the CIR, was entrained in this. STA, located 20 deg to the west of Earth, saw a MC which was not preceded by a shock. A SI trailed the transient. The shocks are examined using various methods and from this it is concluded that the forward shock at Wind - but not at STB - was driven by the MC. Examining the MC by Grad-Shafranov reconstruction, we find evidence of a double-flux rope structure at Wind and STA and possibly also at STB. The orientations are at variance with the notion of a large-scale flux tube being observed at the three spacecraft. We find consistency of this with the directional properties of the solar wind "strahl" electrons. We examine aspects of the geomagnetic response and find a double-dip storm corresponding to the two interplanetary triggers. The minimum Dst phase was prolonged and the geoffects were intensified due to the interaction. We conclude that while the formation of compound streams is a common feature of interplanetary space, understanding their components when CIRs are involved is a complicated matter needing numerical simulations and/or morein situ observations for its complete elucidation. Title: Propagation Directions and Kinematics of STEREO CME/ICMEs Events Authors: Rollett, T.; Moestl, C.; Temmer, M.; Veronig, A.; Lugaz, N.; Biernat, H. K. Bibcode: 2010AGUFMSH41A1775R Altcode: The Heliospheric Imagers on board the two STEREO twin satellites give us the possibilities to track Coronal Mass Ejections up to a distance of 1 AU. For events of our interest, remote sensing data as well as in situ measurements from the other STEREO spacecraft or Wind are available. The combination of both allows us to calculate a constant propagation direction in the ecliptic plane by using different methods (Fixed-Phi and the Harmonic Mean). These methods convert the measured elongation into distance by making different assumptions on the shape of the CME. With the combined data sets we can also derive the kinematics (distance-velocity plots) and try to crosscheck the results by taking care of the ambient solar wind. Moreover, we use inverse fitting methods for both the Fixed-Phi and Harmonic Mean approaches (which assume constant velocity) to fit our measurements and compare it to the results calculated by our combined method. Title: The CME/ICME relationship for the 3-5 April 2010 and Aug 1-4 2010 events Authors: Moestl, C.; Temmer, M.; Rollett, T.; Kilpua, E. K.; Farrugia, C. J.; Veronig, A.; Galvin, A. B.; Biernat, H. K. Bibcode: 2010AGUFMSH43C..07M Altcode: For two coronal mass ejections (CMEs) associated with interplanetary CMEs (ICMEs) causing moderate geomagnetic storms in 2010, we discuss properties such as interplanetary propagation, orientation and arrival time calculation. We study heliospheric images of the CMEs provided by STEREO / HI in combination with in situ observations by the Wind spacecraft near Earth. The 3-5 April 2010 event was the first fast (800 km/s) ICME including a magnetic cloud observed by both the STEREO/HI instruments and a near Earth spacecraft. During the subsequent geomagnetic storm (minimum Dst = -72 nT, maximum Kp = 8-), communication with the Galaxy 15 satellite was lost. Using forward modeling in combination with HI techniques and the in situ velocity, we show that the ICME did not decelerate much between Sun and Earth. Earth was not hit directly, but the ICME flank was responsible for a long storm growth phase. The magnetic cloud (MC) inside the ICME cannot be modeled with approaches assuming an invariant direction. These observations confirm the hypotheses that parts of ICMEs classified as (1) long-duration MCs or (2) magnetic-cloud-like (MCL) structures can be a consequence of a spacecraft trajectory through the ICME flank. The 1-4 Aug 2010 events consisted of several CMEs accompanied by multiple ICME signatures near Earth, responsible for a two-step geomagnetic storm. We discuss which of the ICMEs correspond to the flare/filaments/CMEs observed by STEREO/COR/HI and SDO HMI/AIA observed closer to the Sun. We apply reconstruction methods to estimate the local flux rope orientation and other properties. The ICME signatures are linked to HI observations of the CME fronts, which yields full CME kinematics between the Sun and Earth. STEREO Ahead HI1/2 images of the 3-5 April 2010 Earth-directed coronal mass ejection. Title: On the Origin of the Solar Moreton Wave of 2006 December 6 Authors: Balasubramaniam, K. S.; Cliver, E. W.; Pevtsov, A.; Temmer, M.; Henry, T. W.; Hudson, H. S.; Imada, S.; Ling, A. G.; Moore, R. L.; Muhr, N.; Neidig, D. F.; Petrie, G. J. D.; Veronig, A. M.; Vršnak, B.; White, S. M. Bibcode: 2010ApJ...723..587B Altcode: We analyzed ground- and space-based observations of the eruptive flare (3B/X6.5) and associated Moreton wave (~850 km s-1 ~270° azimuthal span) of 2006 December 6 to determine the wave driver—either flare pressure pulse (blast) or coronal mass ejection (CME). Kinematic analysis favors a CME driver of the wave, despite key gaps in coronal data. The CME scenario has a less constrained/smoother velocity versus time profile than is the case for the flare hypothesis and requires an acceleration rate more in accord with observations. The CME picture is based, in part, on the assumption that a strong and impulsive magnetic field change observed by a GONG magnetograph during the rapid rise phase of the flare corresponds to the main acceleration phase of the CME. The Moreton wave evolution tracks the inferred eruption of an extended coronal arcade, overlying a region of weak magnetic field to the west of the principal flare in NOAA active region 10930. Observations of Hα foot point brightenings, disturbance contours in off-band Hα images, and He I 10830 Å flare ribbons trace the eruption from 18:42 to 18:44 UT as it progressed southwest along the arcade. Hinode EIS observations show strong blueshifts at foot points of this arcade during the post-eruption phase, indicating mass outflow. At 18:45 UT, the Moreton wave exhibited two separate arcs (one off each flank of the tip of the arcade) that merged and coalesced by 18:47 UT to form a single smooth wave front, having its maximum amplitude in the southwest direction. We suggest that the erupting arcade (i.e., CME) expanded laterally to drive a coronal shock responsible for the Moreton wave. We attribute a darkening in Hα from a region underlying the arcade to absorption by faint unresolved post-eruption loops. Title: Multiwavelength Imaging and Spectroscopy of Chromospheric Evaporation in an M-class Solar Flare Authors: Veronig, A. M.; Rybák, J.; Gömöry, P.; Berkebile-Stoiser, S.; Temmer, M.; Otruba, W.; Vršnak, B.; Pötzi, W.; Baumgartner, D. Bibcode: 2010ApJ...719..655V Altcode: 2010arXiv1007.0930V We study spectroscopic observations of chromospheric evaporation mass flows in comparison with the energy input by electron beams derived from hard X-ray (HXR) data for the white-light M2.5 flare of 2006 July 6. The event was captured in high-cadence spectroscopic observing mode by SOHO/CDS combined with high-cadence imaging at various wavelengths in the visible, extreme ultraviolet, and X-ray domain during the joint observing campaign JOP171. During the flare peak, we observe downflows in the He I and O V lines formed in the chromosphere and transition region, respectively, and simultaneous upflows in the hot coronal Si XII line. The energy deposition rate by electron beams derived from RHESSI HXR observations is suggestive of explosive chromospheric evaporation, consistent with the observed plasma motions. However, for a later distinct X-ray burst, where the site of the strongest energy deposition is exactly located on the Coronal Diagnostics Spectrometer (CDS) slit, the situation is intriguing. The O V transition region line spectra show the evolution of double components, indicative of the superposition of a stationary plasma volume and upflowing plasma elements with high velocities (up to 280 km s-1) in single CDS pixels on the flare ribbon. However, the energy input by electrons during this period is too small to drive explosive chromospheric evaporation. These unexpected findings indicate that the flaring transition region is much more dynamic, complex, and fine structured than is captured in single-loop hydrodynamic simulations. Title: Statistical Properties of Flares and Sunspots over the Solar Cycle Authors: Temmer, M. Bibcode: 2010ASPC..428..161T Altcode: 2010arXiv1002.0413T The present paper reviews results derived from statistical studies of solar activity indices. The prolonged minimum phase of cycle 23 raised the question of peculiarities inherent in cycle 23. The most important solar activity index is the relative sunspot number and though most of the other indices are closely related, shifts are obtained between their peak activities of the order of 1-2 years. These shifts reveal a 22-year pattern which can be attributed to solar interior or dynamo related processes. The minimum phase of cycle 23 is not found to be exceptional. Investigating the relative sunspot numbers over the past 150 years, solar cycles of more prolonged minima are observed. Since 1920, solar activity has been quite high ("modern maximum") and cycle 23 might be the herald of the end of this phase. Title: First Observations of a Dome-shaped Large-scale Coronal Extreme-ultraviolet Wave Authors: Veronig, A. M.; Muhr, N.; Kienreich, I. W.; Temmer, M.; Vršnak, B. Bibcode: 2010ApJ...716L..57V Altcode: 2010arXiv1005.2060V We present first observations of a dome-shaped large-scale extreme-ultraviolet coronal wave, recorded by the Extreme Ultraviolet Imager instrument on board STEREO-B on 2010 January 17. The main arguments that the observed structure is the wave dome (and not the coronal mass ejection, CME) are (1) the spherical form and sharpness of the dome's outer edge and the erupting CME loops observed inside the dome; (2) the low-coronal wave signatures above the limb perfectly connecting to the on-disk signatures of the wave; (3) the lateral extent of the expanding dome which is much larger than that of the coronal dimming; and (4) the associated high-frequency type II burst indicating shock formation low in the corona. The velocity of the upward expansion of the wave dome (v ~ 650 km s-1) is larger than that of the lateral expansion of the wave (v ~ 280 km s-1), indicating that the upward dome expansion is driven all the time, and thus depends on the CME speed, whereas in the lateral direction it is freely propagating after the CME lateral expansion stops. We also examine the evolution of the perturbation characteristics: first the perturbation profile steepens and the amplitude increases. Thereafter, the amplitude decreases with r -2.5 ± 0.3, the width broadens, and the integral below the perturbation remains constant. Our findings are consistent with the spherical expansion and decay of a weakly shocked fast-mode MHD wave. Title: Four decades of geomagnetic and solar activity: 1960-2001 Authors: Verbanac, Giuli; Vršnak, Bojan; Temmer, Manuela; Mandea, Mioara; Korte, Monika Bibcode: 2010JASTP..72..607V Altcode: We analyze the relationship between some space weather indices (Dst, Ap, F10.7) and geomagnetic effects on the regional (European) scale, over the period 1960-2001. The remaining external field signal (RES) detected in the Northward magnetic component of the European observatory annual means are used as an indicator of the regional geomagnetic activity. Relationship RES-F10.7 suggests correction factors for getting the geomagnetic annual means of the Northern component less affected by the external sources. We have found some time lags among investigated parameters. These delays may suggest that the Ap responds to the solar activity in a differently than Dst and RES, Ap being more sensitive to the high-speed streams (HSS) and the Alfvenic waves present in HSS, while Dst and RES being more influenced by the coronal mass ejections activity (CME). Title: Calculating the propagation direction of coronal mass ejections by connecting in situ observations with heliospheric images Authors: Rollett, Tanja; Möstl, Christian; Temmer, Manuela; Veronig, Astrid; Biernat, Helfried K. Bibcode: 2010EGUGA..12.3468R Altcode: We determined the propagation direction of two coronal mass ejections by using data provided by the Heliospheric Imagers (HI) and the PLASTIC and IMPACT instruments onboard the two STEREO satellites. To facilitate the tracking of the CME's leading edge we made time-elongation plots (J-plots) for the investigated events and tracked the apparent leading edge therein several times in order to estimate the measurement error. For converting elongation to distance we compared several methods (Point-P, Fixed-Phi and their harmonic mean). To determine the direction of the CME's propagation in the ecliptic we connected the CME-track derived from HI J-plots with the measured in situ arrival time by modifying the propagation direction within the used model equations. The resulting directions and their errors are discussed with respect to the different assumptions used for each technique. Title: Combined STEREO/RHESSI Study of Coronal Mass Ejection Acceleration and Particle Acceleration in Solar Flares Authors: Temmer, M.; Veronig, A. M.; Kontar, E. P.; Krucker, S.; Vršnak, B. Bibcode: 2010ApJ...712.1410T Altcode: 2010arXiv1002.3080T Using the potential of two unprecedented missions, Solar Terrestrial Relations Observatory (STEREO) and Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), we study three well-observed fast coronal mass ejections (CMEs) that occurred close to the limb together with their associated high-energy flare emissions in terms of RHESSI hard X-ray (HXR) spectra and flux evolution. From STEREO/EUVI and STEREO/COR1 data, the full CME kinematics of the impulsive acceleration phase up to ~4 R sun is measured with a high time cadence of <=2.5 minutes. For deriving CME velocity and acceleration, we apply and test a new algorithm based on regularization methods. The CME maximum acceleration is achieved at heights h <= 0.4 R sun, and the peak velocity at h <= 2.1 R sun (in one case, as small as 0.5 R sun). We find that the CME acceleration profile and the flare energy release as evidenced in the RHESSI HXR flux evolve in a synchronized manner. These results support the "standard" flare/CME model which is characterized by a feedback relationship between the large-scale CME acceleration process and the energy release in the associated flare. Title: STEREO quadrature observations of the large-scale EUV wave of Feb 13th, 2009 Authors: Ines Kienreich, Mag.; Veronig, Astrid; Temmer, Manuela Bibcode: 2010cosp...38.1841I Altcode: 2010cosp.meet.1841I The event on Feb 13th, 2009 was the first case of a global coronal wave observed by the STEREO twin satellites in quadrature. The wave's initiation site was at the disk center in EUVI STEREO-B and precisely at the limb in STEREO-A. Therefore it was possible to determine the wave's on-disk as well as edge-on kinematics and to study its three-dimensional structure. From the two STEREO observations we derive the height of propagation of the wave, which was found to be in the range between 80-100 Mm above the photosphere. Comparison of the early phases of the contemporaneous CME and the wave's kinematics suggest that the wave is set off by the CME lateral expansion. The wave propagates globally over the whole hemisphere with a constant velocity 263 16 km s-1, which is close to the fast magnetosonic speed in the quiet solar corona. Thus we conclude that the observed EUV wave is consistent with a MHD fast-mode wave. Title: Analysis of a Global Moreton Wave Observed on 2003 October 28 Authors: Muhr, N.; Vršnak, B.; Temmer, M.; Veronig, A. M.; Magdalenić, J. Bibcode: 2010ApJ...708.1639M Altcode: 2009arXiv0911.4405M We study the well-pronounced Moreton wave that occurred in association with the X17.2 flare/CME event of 2003 October 28. This Moreton wave is striking for its global propagation and two separate wave centers, which implies that two waves were launched simultaneously. The mean velocity of the Moreton wave, tracked within different sectors of propagation direction, lies in the range of v ≈ 900-1100 km s-1 with two sectors showing wave deceleration. The perturbation profile analysis of the wave indicates amplitude growth followed by amplitude weakening and broadening of the perturbation profile, which is consistent with a disturbance first driven and then evolving into a freely propagating wave. The Extreme-Ultraviolet Imaging Telescope wave front is found to lie on the same kinematical curve as the Moreton wave fronts indicating that both are different signatures of the same physical process. Bipolar coronal dimmings are observed on the same opposite east-west edges of the active region as the Moreton wave ignition centers. The radio type II source, which is cospatially located with the first wave front, indicates that the wave was launched from an extended source region (gsim60 Mm). These findings suggest that the Moreton wave is initiated by the coronal mass ejection expanding flanks. Title: Automated detection of coronal hole areas Authors: Rotter, Mag. Thomas; Veronig, Astrid; Temmer, Manuela Bibcode: 2010cosp...38.1890R Altcode: 2010cosp.meet.1890R Coronal holes, as regions of low-density plasma on the sun, have magnetic fields that open freely into interplanetary space and thus shape our heliosphere. Along these open magnetic fields, charged particles leave the Sun to form the high speed component of the solar wind. SOHO EIT (Extreme ultraviolet Imaging Telescope) provides for the first time continuous observations of coronal holes over a full solar cycle (no.23). These data enable us to study the solar cycle evolution of coronal holes and their relation to in-situ solar wind magnetic field and plasma parameters at 1 AU. In the poster we will present first results of an automated coronal hole detection algorithm that is currently under development. The algorithm uses a histogram-based intensity treshholding technique to determine coronal hole areas and their positions. Title: Calculation of CME kinematics and propagation directions by connecting STEREO HI-images with in situ data Authors: Rollett, Tanja; Moestl, Christian; Temmer, Manuela; Veronig, Astrid; Biernat, Helfried K. Bibcode: 2010cosp...38.1894R Altcode: 2010cosp.meet.1894R On a sample of selected events we determined the propagation directions and the kinematics of several coronal mass ejections by using data provided by the Heliospheric Imagers (HI) and the PLASTIC and IMPACT instruments onboard the two STEREO satellites and the Wind spacecraft near Earth. We tracked for each CME the leading edge and core within time-elongation plots (Jplots) and converted the measured elongation angle into distance by using different methods (Point-P, Fixed-Phi and their harmonic mean). Furthermore, we used the Sheeley-method to fit our measurements and calculate the propagation angles and arrival times at the other spacecraft assuming that the CMEs propagate with constant velocity. Finally we discuss our results by comparing the kinematics derived from the different techniques. Title: Evolution of solar wind energy densities during solar minimum 2007-2009, and features of its effects on the Earth's magnetopause and magnetosheath Authors: Farrugia, Charles; Harris, B.; Leitner, Mag. Martin; Moestl, Christian; Simunac, Kristin; Galvin, Antoinette; Veronig, Astrid; Temmer, Manuela; Luhmann, Janet G.; Szabo, Adam; Biernat, Helfried K.; Lucek, Elizabeth A. Bibcode: 2010cosp...38.1898F Altcode: 2010cosp.meet.1898F We quantify the distribution of magnetic and kinetic energies densities of the solar wind at 1 AU as the deep solar activity minimum 2007-2009 progressed. For this we use near -Earth spacecraft Wind and the STEREO-A and B probes, the latter giving us a more comprehensive description by extending the longitudinal coverage. We relate general trends in interplanetary data to observations on the Sun. We then pick out a 4-month period, characterized by minima in both the kinetic and magnetic energy densities, and examine the profiles of the plasma and magnetic field parameters. They show slow-slower solar wind interactions with pronounced compressions, and low field strengths in slow solar wind streams. These are compared with the general plasma and field properties of the slow solar wind and differences are noted. Using Cluster data, we determine the average shapes of the bow shock and magnetopause for this period. We compare these with gas dynamic and MHD predictions for the average Alfven Mach number realized. Major features of observations in the Earth's magnetosheath are discussed. This work is meant as a contribution to Sun-Earth connection studies. Title: Relation between the dynamics of coronal mass ejections and solar flare energetics derived from STEREO and RHESSI observations Authors: Bein, Bianca; Veronig, Astrid; Berkebile-Stoiser, Sigrid; Temmer, Manuela Bibcode: 2010cosp...38.3019B Altcode: 2010cosp.meet.3019B We aim to explore the relation of the energy release in solar flares to the dynamical evolution of their associated coronal mass ejections for a statistically representative sample of events. For our study, we use EUV (171˚, 195˚) and white light coronographic observations from A A the STEREO (Solar Terrestial Relations Observatory) SECCHI instrument suite. Due to the high time cadence of the STEREO EUVI and COR images, the detailed CME kinematics from the initiation through the impulsive acceleration to the propagation phase can be derived. Information on the energy release in the flares under study comes from hard X-ray observations of the RHESSI instrument (Ramaty High Energy Solar Spectroscopic Imager). RHESSI non-thermal lightcurves as well as the derivative of the GOES soft X-ray flux are compared with the acceleration curve of the associated CME. Title: Coronal mass ejections in the STEREO era Authors: Temmer, Manuela Bibcode: 2010cosp...38.2967T Altcode: 2010cosp.meet.2967T The present paper reviews recent results derived from studies of coronal mass ejections (CMEs) and associated flares. CMEs are the most violent activity signatures from our Sun. Discov-ered in the 70's, extensive studies were carried out particularly in the SOHO era, but still, our understanding of the physical characteristics of CMEs is limited. Mainly this is due to single coronagraph observations, which image CMEs in projection against the plane of sky, hence, missing their 3D structure and evolution. The Solar Terrestrial Relations Observatory -STEREO, launched on October 25th, 2006, is composed of two nearly identical spacecrafts, one ahead of Earth in its orbit (STEREO-A), the other trailing behind (STEREO-B). This unprecedented mission observes CMEs simultaneously from two different vantage points, from which new insights into the 3D aspects of CMEs are derived. In addition, with the Heliospheric Imager instruments aboard STEREO, events can be tracked seamlessly from Sun to Earth where they can be related to in-situ plasma and magnetic field measurements. High spatial and temporal resolution images of the low corona in EUV and from coronagraphs in white light give information on CME initiation and its early propagation phase. In com-bination with observations of the associated flare, those enable us to examine in detail the CME-flare relationship, from both observational and theoretical points of view. Recent studies give evidence that the energy release process in flares (HXR emission) and the acceleration of CMEs are closely related. Complementary multi-wavelength observations of eruptive events are therefore needed to understand the "big picture" including both phenomena CMEs and flares. Title: Study of the kinematics and driver of the global Moreton wave observed on 2003 October 28 Authors: Muhr, Mmag. Nicole; Vrsnak, Bojan; Temmer, Manuela; Veronig, Astrid; Magdalenic, Jasmina Bibcode: 2010cosp...38.1844M Altcode: 2010cosp.meet.1844M We analyze the evolution and kinematics of the fast, globally propagating Moreton wave of 2003 October 28 associated with the extreme X17.2 solar flare/CME event. This Moreton wave is distinct due to its strengths and azimuthal span of span 360. We study the wave kinematics in different propagation directions, and compare it with the following associated phenomena: EIT wave, coronal dimmings, fast halo CME, flare, and type II burst. The sectoral analysis yield mean velocity values in the range 900-1000 km/s; two sectors show wave deceleration. The perturbation profile evolution indicates an amplitude growth followed by amplitude weakening and broadening, which is consistent with a disturbance first driven and then evolving into a freely propagating wave. We find two `'radiant points" for the Moreton wave fronts on opposite east-west edges of the source region, roughly co-spatial with the bipolar coronal dimming. The co-spatiality of the associated radio type II burst source and the first Moreton wave fronts indicate that the wave was launched from an extended region. These findings indicate that the wave is initiated by the CME expanding flanks. Title: Direction and orientation of CME/ICME events observed by STEREO Authors: Moestl, Christian; Rollett, Tanja; Temmer, Manuela; Farrugia, Charles; Veronig, Astrid; Galvin, Antoinette; Biernat, Helfried K. Bibcode: 2010cosp...38.1881M Altcode: 2010cosp.meet.1881M The two NASA STEREO spacecraft are now approaching a quadrature configuration with respect to the Earth. In conjunction with the rising solar activity this represents a great opportunity to study coronal mass ejections (CMEs) during their journey from the Sun to 1 AU. We are in particular concerned with those events which were observed by the STEREO/SECCHI imaging instrument in the inner heliosphere and which were also detected in situ at 1 AU with STEREO (IMPACT/PLASTIC) or WIND (SWE/MFI). This allows for example to check (1) if the direction of propagation given by various direction-finding techniques is indeed correlated with the signatures which are later observed in situ and (2) if the orientation of the magnetic flux rope inside the ICME, which we model using the Grad-Shafranov technique, is reflected in properties of the CME. Also, the classic three-part structure of CMEs can be related to the in situ data. The results are discussed regarding the possibility to forecast ICME properties from observations closer to the Sun. Title: On the 3-D reconstruction of Coronal Mass Ejections using coronagraph data Authors: Mierla, M.; Inhester, B.; Antunes, A.; Boursier, Y.; Byrne, J. P.; Colaninno, R.; Davila, J.; de Koning, C. A.; Gallagher, P. T.; Gissot, S.; Howard, R. A.; Howard, T. A.; Kramar, M.; Lamy, P.; Liewer, P. C.; Maloney, S.; Marqué, C.; McAteer, R. T. J.; Moran, T.; Rodriguez, L.; Srivastava, N.; St. Cyr, O. C.; Stenborg, G.; Temmer, M.; Thernisien, A.; Vourlidas, A.; West, M. J.; Wood, B. E.; Zhukov, A. N. Bibcode: 2010AnGeo..28..203M Altcode: Coronal Mass ejections (CMEs) are enormous eruptions of magnetized plasma expelled from the Sun into the interplanetary space, over the course of hours to days. They can create major disturbances in the interplanetary medium and trigger severe magnetic storms when they collide with the Earth's magnetosphere. It is important to know their real speed, propagation direction and 3-D configuration in order to accurately predict their arrival time at the Earth. Using data from the SECCHI coronagraphs onboard the STEREO mission, which was launched in October 2006, we can infer the propagation direction and the 3-D structure of such events. In this review, we first describe different techniques that were used to model the 3-D configuration of CMEs in the coronagraph field of view (up to 15 R⊙). Then, we apply these techniques to different CMEs observed by various coronagraphs. A comparison of results obtained from the application of different reconstruction algorithms is presented and discussed. Title: Linking remote imagery of two coronal mass ejections to their in situ signatures at 1 AU Authors: Moestl, C.; Farrugia, C. J.; Temmer, M.; Miklenic, C.; Veronig, A.; Galvin, A. B.; Leitner, M.; Biernat, H. K. Bibcode: 2009AGUFMSH41A1629M Altcode: We report on how the internal structure of two coronal mass ejections at 1 AU might be deduced from white-light images of the heliosphere taken from a remote observation point. On June 6-7 2008 the STEREO-B spacecraft encountered typical signatures of a magnetic flux rope inside an interplanetary coronal mass ejection (ICME). Its axis was inclined at 45° to the solar equatorial plane, crossing it at approximately 30° east of Earth. This direction matches well with various CME direction-finding techniques to within 15°, and a possible westward deflection of 10° took place between the Sun and 1 AU. Further, we use remote images from STEREO-A to show that (1) the CME is unambiguously connected to the ICME which swept over STEREO B and can be tracked all the way to the 1 AU event, (2) the particular arc-like morphology of the CME pointing to an inclined axis, and (3) the three-part structure of the CME may be plausibly related to the in situ data with clear density variations. The CME event on Feb 13 2009 followed by a magnetic cloud on Feb 18 2009 is discussed from the same viewpoint, though the in-situ signatures are more complex than for the simple event discussed above. Title: Linking Remote Imagery of a Coronal Mass Ejection to Its In Situ Signatures at 1 AU Authors: Möstl, C.; Farrugia, C. J.; Temmer, M.; Miklenic, C.; Veronig, A. M.; Galvin, A. B.; Leitner, M.; Biernat, H. K. Bibcode: 2009ApJ...705L.180M Altcode: 2009arXiv0910.1188M In a case study (2008 June 6-7) we report on how the internal structure of a coronal mass ejection (CME) at 1 AU can be anticipated from remote observations of white-light images of the heliosphere. Favorable circumstances are the absence of fast equatorial solar wind streams and a low CME velocity which allow us to relate the imaging and in situ data in a straightforward way. The STEREO-B spacecraft encountered typical signatures of a magnetic flux rope inside an interplanetary CME (ICME) whose axis was inclined at 45° to the solar equatorial plane. Various CME direction-finding techniques yield consistent results to within 15°. Further, remote images from STEREO-A show that (1) the CME is unambiguously connected to the ICME and can be tracked all the way to 1 AU, (2) the particular arc-like morphology of the CME points to an inclined axis, and (3) the three-part structure of the CME may be plausibly related to the in situ data. This is a first step in predicting both the direction of travel and the internal structure of CMEs from complete remote observations between the Sun and 1 AU, which is one of the main requirements for forecasting the geo-effectiveness of CMEs. Title: STEREO Quadrature Observations of the Three-Dimensional Structure and Driver of a Global Coronal Wave Authors: Kienreich, I. W.; Temmer, M.; Veronig, A. M. Bibcode: 2009ApJ...703L.118K Altcode: 2009arXiv0908.3571K We present the first observations of a global coronal wave ("EIT wave") from the two STEREO satellites in quadrature. The wave's initiation site was at the disk center in STEREO-B and precisely on the limb in STEREO-A. These unprecedented observations from the STEREO Extreme Ultraviolet Imaging (EUVI) instruments enable us to gain insight into the wave's kinematics, initiation, and three-dimensional structure. The wave propagates globally over the whole solar hemisphere visible to STEREO-B with a constant velocity of ~263 ± 16 km s-1. From the two STEREO observations, we derive a height of the wave in the range of ~80-100 Mm. Comparison of the wave kinematics with the early phase of the erupting coronal mass ejection (CME) structure indicates that the wave is initiated by the CME lateral expansion, and then propagates freely with a velocity close to the fast magnetosonic speed in the quiet solar corona. Title: Analytic Modeling of the Moreton Wave Kinematics Authors: Temmer, M.; Vršnak, B.; Žic, T.; Veronig, A. M. Bibcode: 2009ApJ...702.1343T Altcode: 2009arXiv0908.3746T The issue whether Moreton waves are flare-ignited or coronal mass ejection (CME)-driven, or a combination of both, is still a matter of debate. We develop an analytical model describing the evolution of a large-amplitude coronal wave emitted by the expansion of a circular source surface in order to mimic the evolution of a Moreton wave. The model results are confronted with observations of a strong Moreton wave observed in association with the X3.8/3B flare/CME event from 2005 January 17. Using different input parameters for the expansion of the source region, either derived from the real CME observations (assuming that the upward moving CME drives the wave), or synthetically generated scenarios (expanding flare region, lateral expansion of the CME flanks), we calculate the kinematics of the associated Moreton wave signature. Those model input parameters are determined which fit the observed Moreton wave kinematics best. Using the measured kinematics of the upward moving CME as the model input, we are not able to reproduce the observed Moreton wave kinematics. The observations of the Moreton wave can be reproduced only by applying a strong and impulsive acceleration for the source region expansion acting in a piston mechanism scenario. Based on these results we propose that the expansion of the flaring region or the lateral expansion of the CME flanks is more likely the driver of the Moreton wave than the upward moving CME front. Title: CME Projection Effects Studied with STEREO/COR and SOHO/LASCO Authors: Temmer, M.; Preiss, S.; Veronig, A. M. Bibcode: 2009SoPh..256..183T Altcode: Based on a set of 11 CME events we study the impact of projection effects by tracking CME leading edge features in the plane of sky (traditional CME tracking) from combined STEREO-SECCHI and SOHO-LASCO observations up to 20R⊙. By using CME observations from two vantage points and applying triangulation techniques, the source region location of the CME on the solar surface was determined (heliospheric longitude and latitude) to correct for projection effects. With this information, the directivity and "true" speed of a CME can be estimated in a simple way. The comparison of the results obtained from the spacecraft pairs SOHO-LASCO/STEREO-A and SOHO-LASCO/STEREO-B allows us to study the reliability of the method. The determined CME source region is generally coincident within ≲10°. Title: Multispacecraft recovery of a magnetic cloud and its origin from magnetic reconnection on the Sun Authors: Möstl, C.; Farrugia, C. J.; Miklenic, C.; Temmer, M.; Galvin, A. B.; Luhmann, J. G.; Kilpua, E. K. J.; Leitner, M.; Nieves-Chinchilla, T.; Veronig, A.; Biernat, H. K. Bibcode: 2009JGRA..114.4102M Altcode: 2009JGRA..11404102M Multipoint spacecraft observations of a magnetic cloud on 22 May 2007 have given us the opportunity to apply a multispacecraft technique to infer the structure of this large-scale magnetic flux rope in the solar wind. Combining WIND and STEREO-B magnetic field and plasma measurements, we construct a combined magnetic field map by integrating the Grad-Shafranov equation, this being one of the very first applications of this technique in the interplanetary context. From this we obtain robust results on the shape of the cross section, the orientation and magnetic fluxes of the cloud. The only slightly “flattened” shape is discussed with respect to its heliospheric environment and theoretical expectations. We also relate these results to observations of the solar source region and its associated two-ribbon flare on 19 May 2007, using Hα images from the Kanzelhöhe observatory, SOHO/MDI magnetograms and SECCHI/EUVI 171 Å images. We find a close correspondence between the magnetic flux reconnected in the flare and the poloidal flux of the magnetic cloud. The axial flux of the cloud agrees with the prediction of a recent 3-D finite sheared arcade model to within a factor of 2, which is evidence for formation of at least half of the magnetic flux of the ejected flux rope during the eruption. We outline the relevance of this result to models of coronal mass ejection initiation, and find that to explain the solar and interplanetary observations elements from sheared arcade as well as erupting-flux-rope models are needed. Title: Multi-spacecraft STEREO observations of magnetic clouds Authors: Möstl, C.; Farrugia, C. J.; Miklenic, C.; Temmer, M.; Veronig, A.; Biernat, H. K.; Kilpua, E. K. J.; Galvin, A. B.; Luhmann, J. G.; Ogilvie, K. W. Bibcode: 2009EGUGA..11.4987M Altcode: In addition to 3D imaging capabilities, the two STEREO spacecraft also provide unprecedented in-situ observations of the local solar wind plasma and magnetic field at 1 AU at increasing longitudinal separation from Earth. This presents a very good opportunity to model interplanetary coronal mass ejections with a clearly rotating magnetic field (magnetic clouds) using more than one spacecraft to probe their full spatial extent and flux content. This is important not only for space weather prediction purposes but also for understanding CME initiation processes. To this end, we employ the Grad-Shafranov reconstruction technique suitably extended for the use of multi-spacecraft data. We present a summary of results on some magnetic clouds seen by STEREO and WIND where this approach was feasible. Furthermore, we search for the solar sources of these events and, wherever possible, also discuss comparisons with CME triangulation techniques. Title: Cosmic ray modulation by corotating interaction regions Authors: Čalogović, Jaša; Vršnak, Bojan; Temmer, Manuela; Veronig, Astrid M. Bibcode: 2009IAUS..257..425C Altcode: We analyzed the relationship between the ground-based modulation of cosmic rays (CR) and corotating interaction regions (CIRs). Daily averaged data from 8 different neutron monitor (NM) stations were used, covering rigidities from Rc = 0 - 12.91 GeV. The in situ solar wind data were taken from the Advanced Composition Explorer (ACE) database, whereas the coronal hole (CH) areas were derived from the Solar X-Ray Imager onboard GOES-12. For the analysis we have chosen a period in the declining phase of solar cycle 23, covering the period 25 January-5 May 2005. During the CIR periods CR decreased typically from 0.5% to 2%. A cross-correlation analysis showed a distinct anti-correlation between the magnetic field and CR, with the correlation coefficient (r) ranging from -0.31 to -0.38 (mean: -0.36) and with the CR time delay of 2 to 3 days. Similar anti-correlations were found for the solar wind density and velocity characterized by the CR time lag of 4 and 1 day, respectively. The relationship was also established between the CR modulation and the area of the CIR-related CH with the CR time lag of 5 days after the central-meridian passage of CH. Title: EUV Wave Reflection from a Coronal Hole Authors: Gopalswamy, N.; Yashiro, S.; Temmer, M.; Davila, J.; Thompson, W. T.; Jones, S.; McAteer, R. T. J.; Wuelser, J. -P.; Freeland, S.; Howard, R. A. Bibcode: 2009ApJ...691L.123G Altcode: We report on the detection of EUV wave reflection from a coronal hole, as observed by the Solar Terrestrial Relations Observatory mission. The EUV wave was associated with a coronal mass ejection (CME) erupting near the disk center. It was possible to measure the kinematics of the reflected waves for the first time. The reflected waves were generally slower than the direct wave. One of the important implications of the wave reflection is that the EUV transients are truly a wave phenomenon. The EUV wave reflection has implications for CME propagation, especially during the declining phase of the solar cycle when there are many low-latitude coronal holes. Title: Solar Differential Rotation Determined by Tracing Low and High Brightness Temperature Regions at 8 mm Authors: Romštajn, I.; Brajša, R.; Wöhl, H.; Benz, A. O.; Temmer, M.; Roša, D.; Ruždjak, V. Bibcode: 2009CEAB...33...79R Altcode: At the wavelength of 8 mm absorption features (Low brightness Temperature Regions, LTRs) and emission features (High brightness Temperature Regions, HTRs) can be traced for determination of solar rotation. From earlier studies it is known that about two thirds of LTRs are associated with Hα filaments. The goal of the present analysis is to determine the heights of these solar structures and their rotational velocities. We used the method for the simultaneous determination of the solar synodic rotation velocity and the height of tracers. The rotation velocities were determined by the linear least-square fit of their central meridian distances as a function of time. The mean value of the low brightness temperature regions' heights is about 45 600 km. The results of solar rotation determined by tracing LTRs and HTRs are mutually compared and also compared with the results using other tracers and methods. The method for the simultaneous determination of the solar synodic rotation velocity and the height of the tracers could be applied properly only on LTRs, since a wide distribution over latitudes and central meridian distances of a large data set is necessary, which was not available for HTRs. Observational findings that HTRs rotate systematically faster than LTRs and the possibility that they can be observed at and outside the solar limb are consistent with relatively high altitudes of HTRs. It was concluded that the radiation mechanism of HTRs is thermal bremsstrahlung, probably associated with flaring active regions. Title: Triangulation of CME Source Region Locations on the Sun and Dependence on Spacecraft Observation Angles Authors: Preiss, S.; Temmer, M.; Hanslmeier, A. Bibcode: 2009CEAB...33..125P Altcode: STEREO-A, STEREO-B, and LASCO/SOHO observe coronal mass ejections (CMEs) from three different vantage points. On the basis of the radial plane-of-sky (POS) measurements of a CME in these three projection planes, the CME source region (SR) location was determined using the triangulation method of Temmeretal2009. As this triangulation method needs distance-time measurements in one POS as reference input, the determined SR varies with the change of the reference system. In the present study we vary the reference system, which shows the dependence of the resulting SR location of a CME on the spacecraft observation angles, and also reveals the limitation of the radial POS measurements. Title: Heights of solar tracers observed at 8 mm and an interpretation of their radiation Authors: Brajša, R.; Romštajn, I.; Wöhl, H.; Benz, A. O.; Temmer, M.; Roša, D. Bibcode: 2009A&A...493..613B Altcode: Context: At the wavelength of 8 mm, emissive features (high brightness-temperatrue regions, HTRs) and absorptive features (low brightness-temperature regions, LTRs) can be traced for the determining the solar rotation. From earlier studies it is known that about two thirds of LTRs are associated with Hα filaments.
Aims: Thermal bremsstrahlung and gyromagnetic (cyclotron) radiation mechanism can be important for explaining the observed phenomena, so we determine the heights of solar structures and interpret their radiation mechanism(s).
Methods: We use the method of simultaneous determination of the solar synodic rotation velocity and the height of tracers. The rotation velocities were determined by the linear least-square fit of their central meridian distance as a function of time. We used a procedure for calculating the brightness temperature for a given wavelength and model atmosphere, which integrates the radiative transfer equation for the thermal bremsstrahlung.
Results: The mean value of the low brightness-temperature regions' heights is about 45 600 km. This height was used as input for constructing prominence and coronal condensation models, which, when assuming thermal bremsstrahlung as the radiation mechanism, yield a decrease in the brightness temperature of 2-14%, in agreement with observations. If the same radiation mechanism is considered, the models of the solar corona above active regions give an increase in the brightness temperature of 5-19%, also in agreement with observations. In this case an indirect indication (from the rotational analysis) that the HTRs are located higher in the solar atmosphere than the LTRs was taken into account.
Conclusions: The method for simultaneously determining the solar synodic rotation velocity and the height of tracers could have only been properly applied on LTRs, since a homogeneous distribution over latitudes and central meridian distances of a large enough data set is necessary. Thermal bremsstrahlung can explain both the LTR (prominences and coronal condensations) and HTR (ordinary active regions) phenomena observed at 8 mm. At this wavelength, thermal gyromagnetic emission is almost surely excluded as a possible radiation mechanism. Title: Cylindrical and Spherical Pistons as Drivers of MHD Shocks Authors: Žic, Tomislav; Vršnak, Bojan; Temmer, Manuela; Jacobs, Carla Bibcode: 2008SoPh..253..237Z Altcode: 2008SoPh..tmp..153Z We consider an expanding three-dimensional (3-D) piston as a driver of an MHD shock wave. It is assumed that the source-region surface accelerates over a certain time interval to achieve a particular maximum velocity. Such an expansion creates a large-amplitude wave in the ambient plasma. Owing to the nonlinear evolution of the wavefront, its profile steepens and after a certain time and distance a discontinuity forms, marking the onset of the shock formation. We investigate how the formation time and distance depend on the acceleration phase duration, the maximum expansion velocity (defining also acceleration), the Alfvén velocity (defining also Mach number), and the initial size of the piston. The model differs from the 1-D case, since in the 3-D evolution, a decrease of the wave amplitude with distance must be taken into account. We present basic results, focusing on the timing of the shock formation in the low- and high-plasma-beta environment. We find that the shock-formation time and the shock-formation distance are (1) approximately proportional to the acceleration phase duration; (2) shorter for a higher expansion velocity; (3) larger in a higher Alfvén speed environment; (4) only weakly dependent on the initial source size; (5) shorter for a stronger acceleration; and (6) shorter for a larger Alfvén Mach number of the source surface expansion. To create a shock causing a high-frequency type II burst and the Moreton wave, the source region expansion should, according to our results, achieve a velocity on the order of 1000 km s−1 within a few minutes, in a low Alfvén velocity environment. Title: Multi-spacecraft Recovery of a Magnetic Cloud and its Origin From Magnetic Reconnection on the Sun Authors: Möstl, C.; Farrugia, C. J.; Miklenic, C.; Temmer, M.; Galvin, A. B.; Luhmann, J. G.; Biernat, H. K.; Huttunen, K. E.; Leitner, M.; Nieves-Chinchilla, T.; Veronig, A. Bibcode: 2008AGUFMSH23B1634M Altcode: Multi-point spacecraft observations of a magnetic cloud on May 22, 2007 has given us the opportunity to apply a multi-spacecraft technique to infer the structure of this large-scale magnetic flux rope in the solar wind. Combining WIND and STEREO-B magnetic field and plasma measurements, since these spacecraft entered the ejecta, we construct a combined magnetic field map by integrating the Grad-Shafranov equation, this being one of the very first applications of this technique in the interplanetary context. From this we obtain robust results on the shape of the cross-section, the orientation and magnetic fluxes of the cloud. The only slightly "flattened" shape is discussed with respect to its heliospheric environment and theoretical expectations. We also relate these results to observations of the Solar source region and its associated two- ribbon flare on May 19, 2007 using Hα images from the Kanzelhöhe observatory, SOHO/MDI magnetograms and SECCHI/EUVI 171~Å~images. We find a close correspondence between the magnetic flux reconnected in the flare and the poloidal flux of the magnetic cloud. The axial flux of the cloud agrees with the prediction of a recent 3D finite sheared arcade model to within a factor of 2, which is evidence for formation of at least half of the magnetic flux of the ejected flux rope during the eruption. We outline the relevance of this result to models of coronal mass ejection initiation, and find that to explain the solar and interplanetary observations elements from sheared-arcade as well as erupting-flux-rope models are needed. Title: A Flare-Generated Shock during a Coronal Mass Ejection on 24 December 1996 Authors: Magdalenić, J.; Vršnak, B.; Pohjolainen, S.; Temmer, M.; Aurass, H.; Lehtinen, N. J. Bibcode: 2008SoPh..253..305M Altcode: 2008SoPh..tmp..120M We present a multiwavelength study of the large-scale coronal disturbances associated with the CME - flare event recorded on 24 December 1996. The kinematics of the shock wave signature, the type II radio burst, is analyzed and compared with the flare evolution and the CME kinematics. We employ radio dynamic spectra, position of the Nançay Radioheliograph sources, and LASCO-C1 observations, providing detailed study of this limb event. The obtained velocity of the shock wave is significantly higher than the contemporaneous CME velocity (1000 and 235 km s−1, respectively). Moreover, since the main acceleration phase of the CME took place 10 - 20 min after the shock wave was launched, we conclude that the shock wave on 24 December 1996 was probably not driven by the CME. However, the shock wave was closely associated with the flare impulsive phase, indicating that it was ignited by the energy release in the flare. Title: Investigation of geomagnetic and solar activity over time span 1960-2001 Authors: Verbanac, G.; Vrsnak, B.; Korte, M.; Mandea, M.; Temmer, M. Bibcode: 2008AGUFMSH13A1502V Altcode: The solar-terrestrial relationship has been widely studied by means of space weather indices and various solar wind parameters. In this study we perform such an investigation over four decades (1960--2001) on the global scale, and for the first time on the regional scale as well. The variations regarded as the remaining external field signal (thereafter RES) and present in the European observatory annual means of the Northward, X, magnetic component is used as an indicator of the regional geomagnetic activity and are investigated regarding different processes occurring on the Sun. In order to understand how various geomagnetic activity indices respond to the interplanetary disturbances during different periods of the solar cycle, the annual means of the solar activity index, F10.7, and geomagnetic Ap and Dst indices, are studied. The indices are inherently complex since they include contributions from different solar phenomena. By studying the cross-correlations we aim to distinguish between different generation mechanisms. The relationships between the solar parameter F10.7 and RES, Dst, Ap, characterized by high cross-correlation coefficients, suggest the possibility to evaluate the behaviour of these geomagnetic parameters on short timescale. We found finite time lags among the investigated parameters. Our study suggests a one year delay of both RES and Dst after F10.7. The Ap is clearly delayed for about two years with respect to F10.7 and about one year with respect to Dst and RES. This indicate that the Ap responds to the solar activity in a different manner than Dst and RES, which are dominated by the coronal mass ejections activity. On the other hand, it seems that Ap is more sensitive to the high--speed streams (HSS) and Alfvenic waves present in HSS. The existence of time lags gives us the possibility to forecast different parameters. Importantly, the proposed forecasting procedure offers the possibility to reconstruct the F10.7 from the inferred geomagnetic activity for the epochs prior to solar activity monitoring. This study contributes to understanding some physical processes on the Sun that cause the perturbations in the near-Earth interplanetary space and consequently in the Earth's magnetic field. Moreover such investigations may provide a better insight into the time evolution of the open and closed solar magnetic field, and into long term changes in the solar activity with related physical processes. Title: Global thermospheric density variations caused by high-speed solar wind streams during the declining phase of solar cycle 23 Authors: Lei, Jiuhou; Thayer, Jeffrey P.; Forbes, Jeffrey M.; Sutton, Eric K.; Nerem, R. Steven; Temmer, Manuela; Veronig, Astrid M. Bibcode: 2008JGRA..11311303L Altcode: Thermosphere densities at 400 km altitude from accelerometer measurements on the CHAMP satellite are used to investigate oscillations at periods of less than 13 days during the declining phase of solar cycle 23 (2002-2007). The periodic oscillations around 7 and 9 days in neutral density tend to occur during the latter part of the declining solar cycle when periodically recurrent fast streams in the solar wind modulate the level of geomagnetic activity in the geospace environment. It is interesting that the periodic oscillations in neutral density are felt globally and are proportional to the periodic Kp perturbations at the same frequency. Moreover, the periods of 7 and 9 days apparently reflect subharmonics of the 27-day rotation and may be related to the longitudinal distribution of coronal holes; however the comparison of the temporal evolution of the periodicities between the coronal holes area and solar wind in 2005 indicates that their relationships are rather complex. Title: Two-spacecraft reconstruction of a magnetic cloud and comparison to its solar source Authors: Möstl, C.; Miklenic, C.; Farrugia, C. J.; Temmer, M.; Veronig, A.; Galvin, A. B.; Vršnak, B.; Biernat, H. K. Bibcode: 2008AnGeo..26.3139M Altcode: This paper compares properties of the source region with those inferred from satellite observations near Earth of the magnetic cloud which reached 1 AU on 20 November 2003. We use observations from space missions SOHO and TRACE together with ground-based data to study the magnetic structure of the active region NOAA 10501 containing a highly curved filament, and determine the reconnection rates and fluxes in an M4 flare on 18 November 2003 which is associated with a fast halo CME. This event has been linked before to the magnetic cloud on 20 November 2003. We model the near-Earth observations with the Grad-Shafranov reconstruction technique using a novel approach in which we optimize the results with two-spacecraft measurements of the solar wind plasma and magnetic field made by ACE and WIND. The two probes were separated by hundreds of Earth radii. They pass through the axis of the cloud which is inclined -50 degree to the ecliptic. The magnetic cloud orientation at 1 AU is consistent with an encounter with the heliospheric current sheet. We estimate that 50% of its poloidal flux has been lost through reconnection in interplanetary space. By comparing the flare ribbon flux with the original cloud fluxes we infer a flux rope formation during the eruption, though uncertainties are still significant. The multi-spacecraft Grad-Shafranov method opens new vistas in probing of the spatial structure of magnetic clouds in STEREO-WIND/ACE coordinated studies. Title: Large-scale Coronal Waves Observed with EUVI/STEREO Authors: Veronig, A.; Temmer, M.; Vrsnak, B. Bibcode: 2008ESPM...12.2.97V Altcode: We report first observations and analysis of flare/CME associated large-scale coronal waves (so-called "EIT waves") observed with high time cadence by the EUVI instruments onboard the recent STEREO mission. The EIT instrument onboard SOHO for the first time directly imaged global disturbances in the solar corona, but the observations are severely hampered by the low cadence of EIT (12-15 min). Thus, the nature and origin of these large-scale disturbances are still not sufficiently constraint by observations, and it is an intense matter of debate whether EIT waves: a) are the coronal counterparts of Moreton waves observed in the chromosphere; b) are caused by the flare explosive energy release or by the erupting CME; c) are waves at all or rather propagating disturbances related to magnetic field line opening and restructuring associated with the CME lift-off. The high cadence full-disk coronal imaging by the EUVI instruments on the twin STEREO spacecraft provide us with the unprecedented opportunity to study the dynamics and origin of flare/CME associated coronal waves. We present first studies of global coronal waves observed with EUVI finding wave deceleration, indicative of an MHD blast wave (Veronig et al. 2008, ApJ Lett., in press). Title: Relation between CME SchmiederAcceleration Profile and Flare Energy Release derived from Combined STEREO and RHESSI Observations Authors: Temmer, M.; Veronig, A. M.; Vrsnak, B. Bibcode: 2008ESPM...12.2.96T Altcode: In the standard flare/CME picture magnetic reconnection occurs in a current sheet formed behind the CME, which may provide a feedback relationship between both phenomena. To study the relationship of the large-scale CME acceleration and the energy release in the associated flare we analyze three well observed events. The observations cover the early (low corona) evolution of the CMEs with the EUVI instruments aboard the twin STEREO spacecraft and the RHESSI hard X-ray emission of the associated flare. Since the flare hard X-rays are due to fast electrons, they provide the most direct indicator of the evolution of the flare energy release in the flare. The results are compared to case studies for halo-CMEs where a close synchronization between the CME acceleration and the flare energy release was found (Temmer et al., ApJ, 2008, 673, L95). Title: High-Cadence Observations of a Global Coronal Wave by STEREO EUVI Authors: Veronig, Astrid M.; Temmer, Manuela; Vršnak, Bojan Bibcode: 2008ApJ...681L.113V Altcode: 2008arXiv0806.0710V We report a large-scale coronal wave (so-called EIT wave) observed with high cadence by EUVI on board STEREO in association with the GOES B9.5 flare and double CME event on 2007 May 19. The EUVI instruments provide us with the unprecedented opportunity to study the dynamics of flare/CME associated coronal waves. The coronal wave under study reveals deceleration, indicative of a freely propagating MHD wave. Complementary analysis of the associated flare and erupting filament/CME hint at wave initiation by the CME expanding flanks, which drive the wave only over a limited distance. The associated flare is very weak and occurs too late to account for the wave initiation. Title: Analysis of a Moreton Wave Associated with the X17.2/4B Flare/CME of 28-10-2003 Authors: Muhr, M.; Temmer, M.; Veronig, A.; Vršnak, B.; Hanslmeier, A. Bibcode: 2008CEAB...32...79M Altcode: The fast Moreton wave of 28-Oct-2003 associated with the extreme X17.2 solar flare/CME event is studied. It can be followed in four sectors, spanning almost over 360° on the visible solar disc. The mean wave velocity lies in the range of v∼900-1000 km s^{-1}. We find two wave ignition centres on opposite edges of the source region, which may indicate that the wave is driven by the CME expanding flanks. Title: Acceleration in Fast Halo CMEs and Synchronized Flare HXR Bursts Authors: Temmer, M.; Veronig, A. M.; Vršnak, B.; Rybák, J.; Gömöry, P.; Stoiser, S.; Maričić, D. Bibcode: 2008ApJ...673L..95T Altcode: We study two well-observed, fast halo CMEs, covering the full CME kinematics including the initiation and impulsive acceleration phase, and their associated flares. We find a close synchronization between the CME acceleration profile and the flare energy release as indicated by the RHESSI hard X-ray flux onsets, as well as peaks occur simultaneously within 5 minutes. These findings indicate a close physical connection between both phenomena and are interpreted in terms of a feedback relationship between the CME dynamics and the reconnection process in the current sheet beneath the CME. Title: Large-scale coronal waves observed with STEREO/EUVI Authors: Veronig, Astrid; Temmer, Manuela; Vrsnak, Bojan Bibcode: 2008cosp...37.3328V Altcode: 2008cosp.meet.3328V The EUVI instruments onboard the twin STEREO spacecraft provide high-cadence full-disk imaging of the solar atmosphere with four different filters at EUV wavelengths. These observations are highly suitable to study the kinematics and dynamics of flare/CME associated coronal waves, so-called "EIT waves". We present a detailed analysis of one coronal wave captured by the EUVI instruments, with particular emphasis on the wave dynamics and its connection to the associated flare (RHESSI hard X-rays) and CME (STEREO COR1) in terms of blast wave versus driven wave scenario. Title: Synchronization between the CME acceleration and the energy release in the associated flare Authors: Temmer, Manuela; Veronig, Astrid; Vrsnak, Bojan Bibcode: 2008cosp...37.3167T Altcode: 2008cosp.meet.3167T In the standard flare/CME picture magnetic reconnection occurs in a current sheet formed behind the CME, which is indicative of a feedback relationship between both phenomena. We analyze two X-class flare/CME events which were well covered by RHESSI hard X-ray observations, and the early evolution of the CMEs could be observed in TRACE and GOES/SXI images. Since the flare hard X-rays are due to fast electrons, they provide the most direct indicator of the evolution of the energy release in the flare. This data set enables us to study in detail the relationship of the large-scale CME acceleration and the energy release in the associated flare. Title: On the relation between in situ observations of a magnetic cloud and its solar source Authors: Christiane, Miklenic; Möstl, Christian; Temmer, Manuela; Veronig, Astrid; Farrugia, Charles; Biernat, Helfried K. Bibcode: 2008cosp...37..543C Altcode: 2008cosp.meet..543C During flare/CME events, fast plasma clouds and shocks may be generated, which propagate through interplanetary space. Interplanetary coronal mass ejections, which contain a magnetic cloud, can induce, if Earth-directed, geomagnetic storms, which can cause deleterious effects on space-borne and ground-based installations. Since our dependency on space-borne technical equipment is increasing, the importance of reliable space weather forecasts is indisputable. To achieve better space weather forecasts, it is essential to understand the relation between solar source observations and in situ observations of the magnetic cloud. For the CME/flare event on July 6, 2006, we present a detailed analysis of the magnetic field configuration of the solar source and the reconnection flux of the flare, which is related to the associated magnetic cloud properties observed at the Earth. The event is well covered by multi-wavelength observations from SoHO, TRACE, RHESSI, as well as ground-based Hα observations. The magnetic field geometry of the magnetic cloud at 1 AU is modeled with the Grad-Shafranov reconstruction technique, applying observations from two satellites, namely WIND and ACE. Title: Projection effects in coronal mass ejections studied with STEREO and SoHO Authors: Temmer, Manuela; Preiss, Stefanie; Veronig, Astrid; Vrsnak, Bojan Bibcode: 2008cosp...37.3168T Altcode: 2008cosp.meet.3168T The STEREO mission consists of two identical satellites, positioned ahead (A) and behind (B) the Earth, which observe the Sun from viewing angles different from that of LASCO aboard SoHO (positioned at L1). The kinematics (speed) and width of a coronal mass ejection (CME) is derived by measuring distinct CME features observed in projection against the plane of sky. As STEREO-A, STEREO-B, and LASCO/SoHO, observe a CME from three different viewing angles, the resulting CME kinematics and widths differ. By combining the observations from the three satellites we study for several well observed CMEs the importance of projection effects for the CME kinematics and expansion. Title: Two-spacecraft Reconstruction of a Magnetic Cloud and Comparison to its Solar Source Authors: Moestl, C.; Miklenic, C.; Farrugia, C.; Temmer, M.; Veronig, A.; Galvin, A.; Biernat, H. Bibcode: 2007AGUFMSH32A0781M Altcode: Relating observations of coronal mass ejections (CMEs) and their interplanetary counterpart (ICMEs) is a centerpoint of Sun-Earth connection studies and our ability to forecast space weather. Here we focus on the ICME containing a magnetic cloud which reached Earth on November 20, 2003 and gave rise to the strongest storm of solar cycle 23, with a minimum Dst of -472 nT. Its strong geoeffective impact came about two weeks after the massive eruptions known as "Halloween" events resulted in comparable geo-effects. The aims of this study are threefold. We first apply an advanced methodology to analyze with diverse observations the event on the solar disk, which occurred on Nov 18, 2003, and was associated with an M4 flare and a halo CME. We then employ a Grad-Shafranov reconstruction technique to model the magnetic field geometry at 1 AU. To this end, we use measurements acquired by spacecraft WIND and ACE, ~400 RE apart. We show how these twin-spacecraft observations allow us to optimize the reconstructed map. Finally, we relate the solar to the interplanetary observations, paying special attention to the orientations and the magnetic fluxes involved at the two locales. By comparing the flare with the original cloud fluxes we infer a possible in-situ flux rope formation during the eruption, though uncertainties are still significant. The error margins in the comparisons are also carefully assessed. Title: An Interpretation of the Coronal Holes' Visibility in the Millimeter Wavelength Range Authors: Brajša, R.; Benz, A. O.; Temmer, M.; Jurdana-Šepić, R.; Šaina, B.; Wöhl, H. Bibcode: 2007SoPh..245..167B Altcode: Various observations indicate that coronal holes generally appear as low brightness temperature regions (LTRs) in the centimeter and millimeter wavelength ranges. However, within their borders local enhancements of radiation, that is, high brightness temperature regions (HTRs), often occur. The theory behind the described behavior is not fully understood and therefore we analyze full-disk solar images obtained at a wavelength of 8 mm at Metsähovi Radio Observatory and compare them with data simultaneously taken in other wavelength ranges. The observational finding that the average brightness temperature of coronal holes is not much different from the quiet-Sun level (with localized deviations toward higher and lower intensities on the order of a few percent) is compared with theoretical models of the thermal bremsstrahlung radiation originating in the solar chromosphere, transition region, and corona. Special attention is devoted to the interpretation of the localized enhancements of radiation observed inside coronal holes at millimeter wavelengths. The main conclusion is that the most important contribution to the brightness temperature comes from an increased density in the transition region and low corona (i.e., at the heights where the temperature is below 106 K). This can explain both the LTRs and HTRs associated with coronal holes. Title: Periodic Appearance of Coronal Holes and the Related Variation of Solar Wind Parameters Authors: Temmer, Manuela; Vršnak, Bojan; Veronig, Astrid M. Bibcode: 2007SoPh..241..371T Altcode: We compared the variability of coronal hole (CH) areas (determined from daily GOES/SXI images) with solar wind (daily ACE data) and geomagnetic parameters for the time span 25 January 2005 until 11 September 2005 (late declining phase of solar cycle 23). Applying wavelet spectral analysis, a clear 9-day period is found in the CH time series. The GOES/SXI image sequence suggests that this periodic variation is caused by a mutual triangular distribution of CHs ∼120° apart in longitude. From solar wind parameters a 9-day periodicity was obtained as well, simultaneously with the 9-day period in the CH area time series. These findings provide strong evidence that the 9-day period in solar wind parameters, showing up as higher harmonic of the solar rotation frequency, is caused by the "periodic" longitudinal distribution of CHs on the Sun recurring for several solar rotations. The shape of the wavelet spectrum from the Dst index matches only weakly with that from the CH areas and is more similar to the wavelet spectrum of the solar wind magnetic field magnitude. The distinct 9-day period does not show up in sunspot group areas which gives further evidence that the solar wind modulation is strongly related to CH areas but not to active region complexes. The wavelet power spectra for the whole ACE data range (∼1998 - 2006) suggest that the 9-day period is not a singular phenomenon occurring only during a specific time range close to solar minimum but is occasionally also present during the maximum and decay phase of solar cycle 23. The main periods correspond to the solar rotation (27d) as well as to the second (13.5d) and third (9d) harmonic. Title: Acceleration Phase of Coronal Mass Ejections: I. Temporal and Spatial Scales Authors: Vršnak, Bojan; Maričić, Darije; Stanger, Andrew L.; Veronig, Astrid M.; Temmer, Manuela; Roša, Dragan Bibcode: 2007SoPh..241...85V Altcode: We study kinematics of 22 coronal mass ejections (CMEs) whose motion was traced from the gradual pre-acceleration phase up to the post-acceleration stage. The peak accelerations in the studied sample range from 40, up to 7000 m s−2, and are inversely proportional to the acceleration phase duration and the height range involved. Accelerations and velocities are, on average, larger in CMEs launched from a compact source region. The acceleration phase duration is proportional to the source region dimensions; i.e., compact CMEs are accelerated more impulsively. Such behavior is interpreted as a consequence of stronger Lorentz force and shorter Alfvén time scales involved in compact CMEs (with stronger magnetic field and larger Alfvén speed being involved at lower heights). CMEs with larger accelerations and velocities are on average wider, whereas the widths are not related to the source region dimensions. Such behavior is explained in terms of the field pile-up ahead of the erupting structure, which is more effective in the case of a strongly accelerated structure. Title: Acceleration Phase of Coronal Mass Ejections: II. Synchronization of the Energy Release in the Associated Flare Authors: Maričić, Darije; Vršnak, Bojan; Stanger, Andrew L.; Veronig, Astrid M.; Temmer, Manuela; Roša, Dragan Bibcode: 2007SoPh..241...99M Altcode: We analyze the relationship between the acceleration of coronal mass ejections (CMEs) and the energy release in associated flares, employing a sample of 22 events in which the CME kinematics were measured from the pre-eruption stage up to the post-acceleration phase. The data show a distinct correlation between the duration of the acceleration phase and the duration of the associated soft X-ray (SXR) burst rise, whereas the CME peak acceleration and velocity are related to the SXR peak flux. In the majority of events the acceleration started earlier than the SXR burst, and it is usually prolonged after the SXR burst maximum. In about one half of the events the acceleration phase is very closely synchronized with the fastest growth of the SXR burst. An additional one quarter of the events may be still considered as relatively well-synchronized, whereas in the remaining quarter of the events there is a considerable mismatch. The results are interpreted in terms of the feedback relationship between the CME dynamics and the reconnection process in the wake of the CME. Title: Coronal Holes and Solar Wind High-Speed Streams: II. Forecasting the Geomagnetic Effects Authors: Vršnak, Bojan; Temmer, Manuela; Veronig, Astrid M. Bibcode: 2007SoPh..240..331V Altcode: We present a simple method of forecasting the geomagnetic storms caused by high-speed streams (HSSs) in the solar wind. The method is based on the empirical correlation between the coronal hole area/position and the value of the Dst index, which is established in a period of low interplanetary coronal mass ejection (ICME) activity. On average, the highest geomagnetic activity, i.e., the minimum in Dst, occurs four days after a low-latitude coronal hole (CH) crosses the central meridian. The amplitude of the Dst dip is correlated with the CH area and depends on the magnetic polarity of the CH due to the Russell - McPherron effect. The Dst variation may be predicted by employing the expression Dst(t)=(−65±25×cos λ)[A(t*)]0.5, where A(t*) is the fractional CH area measured in the central-meridian slice [−10°,10°] of the solar disc, λ is the ecliptic longitude of the Earth, ± stands for positive/negative CH polarity, and t−t*=4 days. In periods of low ICME activity, the proposed expression provides forecasting of the amplitude of the HSS-associated Dst dip to an accuracy of ≈30%. However, the time of occurrence of the Dst minimum cannot be predicted to better than ±2 days, and consequently, the overall mean relative difference between the observed and calculated daily values of Dst ranges around 50%. Title: Coronal Holes and Solar Wind High-Speed Streams: I. Forecasting the Solar Wind Parameters Authors: Vršnak, Bojan; Temmer, Manuela; Veronig, Astrid M. Bibcode: 2007SoPh..240..315V Altcode: We analyze the relationship between the coronal hole (CH) area/position and physical characteristics of the associated corotating high-speed stream (HSS) in the solar wind at 1 AU. For the analysis we utilize the data in the period DOY 25 - 125 of 2005, characterized by a very low coronal mass ejection (CME) activity. Distinct correlations between the daily averaged CH parameters and the solar wind characteristics are found, which allows us to forecast the solar wind velocity v, proton temperature T, proton density n, and magnetic field strength B, several days in advance in periods of low CME activity. The forecast is based on monitoring fractional areas A, covered by CHs in the meridional slices embracing the central meridian distance ranges [−40°,−20°], [−10°,10°], and [20°,40°]. On average, the peaks in the daily values of n, B, T, and v appear delayed by 1, 2, 3, and 4 days, respectively, after the area A attains its maximum in the central-meridian slice. The peak values of the solar wind parameters are correlated to the peak values of A, which provides also forecasting of the peak values of n, B, T, and v. The most accurate prediction can be obtained for the solar wind velocity, for which the average relative difference between the calculated and the observed peak values amounts to \overline{\vertδ\vert}≈10 %. The forecast reliability is somewhat lower in the case of T, B, and n ( \overline{\vertδ\vert}≈20 , 30, and 40%, respectively). The space weather implications are discussed, including the perspectives for advancing the real-time calculation of the Sun - Earth transit times of coronal mass ejections and interplanetary shocks, by including more realistic real-time estimates of the solar wind characteristics. Title: Analysis of the Flare Wave Associated with the 3B/X3.8 Flare of January 17, 2005 Authors: Thalmann, J. K.; Veronig, A. M.; Temmer, M.; Vršnak, B.; Hanslmeier, A. Bibcode: 2007CEAB...31..187T Altcode: The flare wave associated with the 3B/X3.8 flare and coronal mass ejection (CME) of January 17, 2005 are studied using imaging data in the Hα and EUV spectral channels. Due to the high-cadence Hα observations from Kanzelhöhe Solar Observatory (KSO), a distinct Moreton wave can be identified in ∼40 Hα frames over a period of ∼7 minutes. The associated coronal EIT wave is identifiable in only one EUV frame and appears close to the simultaneously observed Moreton wave front, indicating that they are closely associated phenomena. Beside the morphology of the wave across the solar disc (covering an angular extend of ∼130°), the evolution in different directions is studied to analyse the influence of a coronal hole (CH) on the wave propagation. The Moreton wave shows a decelerating character which can be interpreted in terms of a freely propagating fast-mode MHD shock. The parts of the wave front moving towards the CH show a lower initial and mean speed, and a greater amount of deceleration than the segments moving into the undisturbed direction. This is interpreted as the tendency of high Alfvén velocity regions to influence the propagation of wave packets. Title: On the Visibility of Coronal Holes in Microwaves Authors: Brajša, R.; Benz, A. O.; Temmer, M.; Jurdana-Šepić, R.; Šaina, B.; Wöhl, H.; Ruždjak, V. Bibcode: 2007CEAB...31..219B Altcode: Previous observations indicate that coronal holes generally appear as low brightness temperature regions in microwaves. However, within their borders local enhancements of radiation often occur. This is confirmed by comparing a full-disc solar image obtained at 37 GHz on 27 May 1993 with full-disc solar images obtained at various wavelengths. Microwave brightness temperatures of three coronal holes are determined and interpreted. Title: Spatial Restriction to HXR Footpoint Locations by Reconnection Site Geometries Authors: Temmer, M.; Vršnak, B.; Veronig, A.; Miklenic, M. Bibcode: 2007CEAB...31...49T Altcode: 2007astro.ph..1203T It is assumed that HXR sources map to the primary energy release site in flares where particle acceleration occurs. Strong HXR sources are mostly observed at confined regions along the reconnecting magnetic arcade. We make a general approach on how the geometry of the reconnecting current sheet (CS) may influence the strength and localization of observed HXR sources. For this we use results from an analysis on the 3B/X3.8 flare on January 17, 2005 (Temmer et al., 2007), as well as measurements from the associated CME. Due to the close match of the CME acceleration profile and the flare HXR flux, we suppose that the CME might play a certain role in modifying the geometry of the CS (``symmetric'' versus ``asymmetric'' vertically stretched CS). This could be the driver for ``guiding'' the accelerated particles to confined areas along the flaring arcade and might explain the spatially limited occurrence of strong HXR sources in comparison to elongated ribbons as seen in Hα and UV. Title: Energy Release Rates along Hα Flare Ribbons and the Location of Hard X-Ray Sources Authors: Temmer, M.; Veronig, A. M.; Vršnak, B.; Miklenic, C. Bibcode: 2007ApJ...654..665T Altcode: Local reconnection and energy release rates for an X3.8 flare that occurred on 2005 January 17 are derived. In particular, we distinguish between Hα flare ribbon segments that were accompanied by RHESSI hard X-ray (HXR) footpoints and those without HXRs. We find that the reconnection and energy release rates are not uniform along the flare ribbons but much larger at the locations where the HXR footpoints are observed. The difference is about 2 orders of magnitude in the case of the energy release rates and 1 order of magnitude for the reconnection rates (with peak values up to 8 kV m-1). These differences are enough to explain the different flare morphologies typically observed in HXRs (compact footpoints) and Hα/UV (extended ribbons) by the limited dynamic range of present HXR instruments. Our results are consistent with a scenario in which the electrons are accelerated primarily along a certain subsystem of magnetic loops as outlined by the HXR footpoints, and only a minor fraction (for the 2005 January 17 flare estimated to be about 1/15) go into the large flare arcade outlined by the Hα ribbons and EUV postflare loops. Title: Interaction of a Moreton/EIT Wave and a Coronal Hole Authors: Veronig, Astrid M.; Temmer, Manuela; Vršnak, Bojan; Thalmann, Julia K. Bibcode: 2006ApJ...647.1466V Altcode: 2006astro.ph..4613V We report high-cadence Hα observations of a distinct Moreton wave observed at Kanzelhöhe Solar Observatory associated with the 3B/X3.8 flare and coronal mass ejection (CME) event of 2005 January 17. The Moreton wave can be identified in about 40 Hα frames over a period of 7 minutes. The EIT wave is observed in only one frame, but the derived propagation distance is close to that of the simultaneously measured Moreton wave fronts, indicating that they are closely associated phenomena. The large angular extent of the Moreton wave allows us to study the wave kinematics in different propagation directions with respect to the location of a polar coronal hole (CH). In particular, we find that the wave segment whose propagation direction is perpendicular to the CH boundary (``frontal encounter'') is stopped by the CH, which is in accordance with observations reported from EIT waves. However, we also find that at a tongue-shaped edge of the coronal hole, where the front orientation is perpendicular to the CH boundary (the wave ``slides along'' the boundary), the wave signatures can be found up to 100 Mm inside the CH. These findings are briefly discussed in the frame of recent modeling results. Title: Shrinking and Cooling of Flare Loops in a Two-Ribbon Flare Authors: Vršnak, Bojan; Temmer, Manuela; Veronig, Astrid; Karlický, Marian; Lin, Jun Bibcode: 2006SoPh..234..273V Altcode: We analyze the evolution of the flare/postflare-loop system in the two-ribbon flare of November 3, 2003, utilizing multi-wavelength observations that cover the temperature range from several tens of MK down to 104 K. A non-uniform growth of the loop system enables us to identify analogous patterns in the height-time, h(t), curves measured at different temperatures. The "knees," "plateaus," and "bends" in a higher-temperature curve appear after a certain time delay at lower heights in a lower-temperature curve. We interpret such a shifted replication as a track of a given set of loops (reconnected field lines) while shrinking and cooling after being released from the reconnection site. Measurements of the height/time shifts between h(t) curves of different temperatures provide a simultaneous estimate of the shrinkage speed and cooling rate in a given temperature domain, for a period of almost ten hours after the flare impulsive phase. From the analysis we find the following: (a) Loop shrinkage is faster at higher temperatures - in the first hour of the loop-system growth, the shrinkage velocity at 5 MK is 20 - 30 km s−1, whereas at 1 MK it amounts to 5 km s−1; (b) Shrinking becomes slower as the flare decays - ten hours after the impulsive phase, the shrinkage velocity at 5 MK becomes 5 km s−1; (c) The cooling rate decreases as the flare decays - in the 5 MK range it is 1 MK min−1 in the first hour of the loop-system growth, whereas ten hours later it decreases to 0.2 MK min−1; (d) During the initial phase of the loop-system growth, the cooling rate is larger at higher temperatures, whereas in the late phases the cooling rate apparently does not depend on the temperature; (e) A more detailed analysis of shrinking/cooling around one hour after the impulsive phase reveals a deceleration of the loop shrinkage, amounting to ā ≈ 10 m s−2 in the T < 5 MK range; (f) In the same interval, conductive cooling dominates down to T ≈ 3 MK, whereas radiation becomes dominant below T ≈ 2 MK; (g) A few hours after the impulsive phase, radiation becomes dominant across the whole T < 5 MK range. These findings are compared with results of previous studies and discussed in the framework of relevant models. Title: Multi-wavelength study of coronal waves associated with the CME-flare event of 3 November 2003 Authors: Vršnak, B.; Warmuth, A.; Temmer, M.; Veronig, A.; Magdalenić, J.; Hillaris, A.; Karlický, M. Bibcode: 2006A&A...448..739V Altcode: The large flare/CME event that occurred close to the west solar limb on 3 November 2003 launched a large-amplitude large-scale coronal wave that was observed in Hα and Fe xii 195 Å spectral lines, as well as in the soft X-ray and radio wavelength ranges. The wave also excited a complex decimeter-to-hectometer type II radio burst, revealing the formation of coronal shock(s). The back-extrapolation of the motion of coronal wave signatures and the type II burst sources distinctly marks the impulsive phase of the flare (the hard X-ray peak, drifting microwave burst, and the highest type III burst activity), favoring a flare-ignited wave scenario. On the other hand, comparison of the kinematics of the CME expansion with the propagation of the optical wave signatures and type II burst sources shows a severe discrepancy in the CME-driven scenario. However, the CME is quite likely associated with the formation of an upper-coronal shock revealed by the decameter-hectometer type II burst. Finally, some six minutes after the launch of the first coronal wave, another coronal disturbance was launched, exciting an independent (weak) decimeter-meter range type II burst. The back-extrapolation of this radio emission marks the revival of the hard X-ray burst, and since there was no CME counterpart, it was clearly ignited by the new energy release in the flare. Title: Hemispheric sunspot numbers {Rn} and {Rs} from 1945-2004: catalogue and N-S asymmetry analysis for solar cycles 18-23 Authors: Temmer, M.; Rybák, J.; Bendík, P.; Veronig, A.; Vogler, F.; Otruba, W.; Pötzi, W.; Hanslmeier, A. Bibcode: 2006A&A...447..735T Altcode: From sunspot drawings provided by the Kanzelhöhe Solar Observatory, Austria, and the Skalnaté Pleso Observatory, Slovak Republic, we extracted a data catalogue of hemispheric Sunspot Numbers covering the time span 1945-2004. The validated catalogue includes daily, monthly-mean, and smoothed-monthly relative sunspot numbers for the northern and southern hemispheres separately and is available for scientific use. These data we then investigated with respect to north-south asymmetries for almost 6 entire solar cycles (Nos. 18-23). For all the cycles studied, we found that the asymmetry based on the absolute asymmetry index is enhanced near the cycle maximum, which contradicts to previous results that are based on the normalized asymmetry index. Moreover, the weak magnetic interdependence between the two solar hemispheres is confirmed by their self-contained evolution during a cycle. For the time span 1945-2004, we found that the cycle maxima and also the declining and increasing phases are clearly shifted, whereas the minima seem to be in phase for both hemispheres. The asymmetric behavior reveals no obvious connection to either the sunspot cycle period of ~11- or the magnetic cycle of ~22-years. The most striking excess of activity is observed for the northern hemisphere in cycles 19 and 20. Title: X-ray sources and magnetic reconnection in the X3.9 flare of 2003 November 3 Authors: Veronig, A. M.; Karlický, M.; Vršnak, B.; Temmer, M.; Magdalenić, J.; Dennis, B. R.; Otruba, W.; Pötzi, W. Bibcode: 2006A&A...446..675V Altcode: Context: .Recent RHESSI observations indicate an apparent altitude decrease of flare X-ray loop-top (LT) sources before changing to the commonly observed upward growth of the flare loop system.
Aims: .We performed a detailed study of the LT altitude decrease for one well observed flare in order to find further hints on the physics of this phenomenon and how it is related to the magnetic reconnection process in solar flares.
Methods: .RHESSI X-ray source motions in the 2003 November 3, X3.9 flare are studied together with complementary data from SXI, EIT, and Kanzelhöhe Hα. We particularly concentrate on the apparent altitude decrease of the RHESSI X-ray LT source early in the flare and combine kinematical and X-ray spectral analysis. Furthermore, we present simulations from a magnetic collapsing trap model embedded in a standard 2-D magnetic reconnection model of solar flares.
Results: .We find that at higher photon energies the LT source is located at higher altitudes and shows higher downward velocities than at lower energies. The mean downward velocities range from 14 km s-1 in the RHESSI 10-15 keV energy band to 45 km s-1 in the 25-30 keV band. For this flare, the LT altitude decrease was also observed by the SXI instrument with a mean speed of 12 km s-1. RHESSI spectra indicate that during the time of LT altitude decrease the emission of the LT source is thermal bremsstrahlung from a "superhot" plasma with temperatures increasing from 35 MK to 45 MK and densities of the order of 1010 cm-3. The temperature does not significantly increase after this early (pre-impulsive superhot LT) phase, whereas the LT densities increase to a peak value of (3-4) × 1011 cm-3.
Conclusions: .Modeling of a collapsing magnetic trap embedded in a standard 2D magnetic reconnection model can reproduce the key observational findings in case that the observed emission is thermal bremsstrahlung from the hot LT plasma. This agrees with the evaluated RHESSI spectra for this flare. Title: Hemispheric Sunspot Numbers 1945--2004: data merging from two observatories Authors: Temmer, M.; Rybák, J.; Bendík, P.; Veronig, A.; Vogler, F.; Pötzi, W.; Otruba, W.; Hanslmeier, A. Bibcode: 2006CEAB...30...65T Altcode: For the time span 1945--2004 from daily sunspot drawings northern and southern relative sunspot numbers are extracted using drawings provided by Kanzelhöhe Solar Observatory, Austria, and Skalnaté Pleso Observatory, Slovak Republic. The derived data will be used to improve and extend an already existing catalogue of hemispheric sunspot numbers (Temmer et al., 2002). Since northern and southern solar hemispheres do not evolve in phase during the cycle, hemispheric data are very important for activity studies. In the present paper the compilation of the data for the period 1945--2004 is described. Furthermore as a quality check of the derived hemispheric data a regression analysis and the comparison to the international hemispheric sunspot numbers from the Sunspot Index Data Center for the time span 1992--2004 is presented. Title: Periodical patterns in major flare occurrence and their relation to magnetically complex active regions Authors: Temmer, M.; Veronig, A.; Rybák, J.; Brajša, R.; Hanslmeier, A. Bibcode: 2006AdSpR..38..886T Altcode: A periodical occurrence rate of major solar flares (observed in hard X-rays) of ∼24 days (synodic) was first reported by Bai (1987) [Bai, T. Distribution of flares on the sun superactive regions and active zones of 1980 1985. ApJ 314, 795 807, 1987] for the years 1980 1985. Here, we report a significant relation between the appearance of the 24-day period in major Hα flares and magnetically complex sunspot groups (i.e., including a γ and/or δ configuration). From synoptic maps of magnetograms (NSO/KP) patterns in the magnetic flux evolution are traced which might be the cause of the 24-day period observed in flare activity. Title: X-Ray Sources and Magnetic Reconnection in AN X-Class Flare Authors: Veronig, A. M.; Vršnak, B.; Karlický, M.; Temmer, M.; Magdalenić, J.; Dennis, B. R.; Otruba, W.; Pötzi, W. Bibcode: 2005ESASP.600E..32V Altcode: 2005ESPM...11...32V; 2005dysu.confE..32V No abstract at ADS Title: Hemispheric Sunspot Numbers RN and RS from 1945-2004: Extended and Improved Catalogue Authors: Temmer, M.; Rybák, J.; Veronig, A.; Bendík, P.; Vogler, F.; Pötzi, W.; Otruba, W.; Hanslmeier, A. Bibcode: 2005ESASP.600E..52T Altcode: 2005ESPM...11...52T; 2005dysu.confE..52T No abstract at ADS Title: Wave Phenomena Associated with the X3.8 Flare/cme of 17-JAN-2005 Authors: Temmer, M.; Veronig, A.; Vršnak, B.; Thalmann, J.; Hanslmeier, A. Bibcode: 2005ESASP.600E.144T Altcode: 2005ESPM...11..144T; 2005dysu.confE.144T No abstract at ADS Title: VizieR Online Data Catalog: Hemispheric Sunspot Numbers 1945-2004 (Temmer+, 2006) Authors: Temmer, M.; Rybak, J.; Bendik, P.; Veronig, A.; Vogler, F.; Otruba, W.; Poetzi, W.; Hanslmeier, A. Bibcode: 2005yCat..34470735T Altcode: From sunspot drawings provided by the Kanzelhoehe Solar Observatory, Austria, and the Skalnate Pleso Observatory, Slovak Republic, a data catalogue of hemispheric Sunspot Numbers covering the time span 1945-2004 is extracted. The validated catalogue includes daily, monthly-mean and smoothed-monthly relative sunspot numbers for the northern and southern hemispheres separately and is available for scientific use. Based on this data set an analysis concerning the North-South asymmetry is made within this paper.

(2 data files). Title: Spatial Distribution and North-South Asymmetry of Coronal Bright Points from Mid-1998 to Mid-1999 Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Rušdjak, V.; Clette, F.; Hochedez, J. -F.; Verbanac, G.; Temmer, M. Bibcode: 2005SoPh..231...29B Altcode: Full-disc full-resolution (FDFR) solar images obtained with the Extreme Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse the centre-to-limb function and latitudinal distribution of coronal bright points. The results obtained with the interactive and the automatic method, as well as for three subtypes of coronal bright points for the time period 4 June 1998 to 22 May 1999 are presented and compared. An indication of a two-component latitudinal distribution of coronal bright points was found. The central latitude of coronal bright points traced with the interactive method lies between 10∘ and 20∘. This is closer to the equator than the average latitude of sunspots in the same period. Possible implications for the interpretation of the solar differential rotation are discussed. In the appendix, possible differences between the two solar hemispheres are analysed. More coronal bright points were present in the southern solar hemisphere than in the northern one. This asymmetry is statistically significant for the interactive method and not for the automatic method. The visibility function is symmetrical around the central meridian. Title: Broadband Metric-Range Radio Emission Associated with a Moreton/EIT Wave Authors: Vršnak, B.; Magdalenić, J.; Temmer, M.; Veronig, A.; Warmuth, A.; Mann, G.; Aurass, H.; Otruba, W. Bibcode: 2005ApJ...625L..67V Altcode: We present the evolution and kinematics of a broadband radio source that propagated collaterally with an Hα/EIT wave, linking it with the type II burst that was excited higher up in the corona. The NRH wave emission extended from the frequency f~327 to f<151 MHz and was considerably weaker than the flare-related type IV burst. The emission centroid propagated at a height of 0-200 Mm above the solar limb and was intensified when the disturbance passed over enhanced coronal structures. We put forward the ad hoc hypothesis that the NRH wave signature is optically thin gyrosynchrotron emission excited by the passage of the coronal MHD fast-mode shock. The identification of radio emission associated with the coronal wave front is important since it offers us new diagnostic information that could provide us with better insight into the physical conditions in the disturbance itself. Title: What causes the 24-day period observed in solar flares? Authors: Temmer, M.; Rybák, J.; Veronig, A.; Hanslmeier, A. Bibcode: 2005A&A...433..707T Altcode: Previous studies report a 24-day (synodic) period in the occurrence rate of solar flares for each of the solar cycles studied, Nos. 19-22 (Bai 1987, ApJ, 314, 795; Temmer et al. 2004, Sol. Phys. 221, 325). Here we study the 24-day period in the solar flare occurrence for solar cycles 21 and 22 by means of wavelet power spectra together with the solar flare locations in synoptic magnetic maps. We find that the 24-day peak revealed in the power spectra is just the result of a particular statistical clumping of data points, most probably caused by a characteristic longitudinal separation of about +40circ to +50circ of activity complexes in successive Carrington rotations. These complexes appear as parallel, diverging or converging branches in the synoptic magnetic maps and are particularly flare-productive. Title: The Two Complexes of Activity Observed in the Northern Hemisphere during 1982 and the 24-Day Periodicity of Flare Occurrence Authors: Ruždjak, V.; Ruždjak, D.; Brajša, R.; Temmer, M.; Hanslmeier, A. Bibcode: 2005HvaOB..29..117R Altcode: Daily numbers of solar Hα flares of importance classes ≥ 1 for the northern solar hemisphere in 1982 are studied applying wavelet power spectra (WPS). Special attention is paid to the occurrence of a 24-day period in the WPS. The wavelet power spectra method is combined with synoptic maps of the magnetic fields. Separately, flare indices of two activity complexes mainly contributing to flare occrrence in this period are examined. It is found that the detected 24-day signal in the WPS is mainly a consequence of the presence of the two flare activity complexes separated by about 45° in longitude during several succesive Carrington rotations. Title: Properties of Type IV Radio Bursts with Periodical Fine Structures Authors: Magdalenić, J.; Vršnak, B.; Zlobec, P.; Messerotti, M.; Temmer, M. Bibcode: 2005ASSL..320..259M Altcode: 2005smp..conf..259M No abstract at ADS Title: On the Relation Between the Coronal Free Energy and Solar Flare Occurrence Authors: Temmer, M.; Veronig, A.; Hanslmeier, A. Bibcode: 2005HvaOB..29..109T Altcode: A significant delay with a 22-year modulation in solar flare occurrence was found by te{temmer03solph} with respect to the solar cycle defined on the basis of the relative sunspot number. These observational results were modelled by te{litvi03} through a time-dependent balance of the magnetic free energy in the solar corona. The free magnetic energy is assumed to be depleted mainly by flares and lags behind the variation of the energy supply (emerging magnetic flux - proxy: relative sunspot numbers) to this system. For solar cycles 21 and 23, in accordance with the delay obtained for flare rates, the rate of sunspot group numbers lags behind the solar cycle maximum. Theses findings suggest that the energy supply itself is delayed, most prominent in odd numbered solar cycles which subsequently causes the delay observed for flare and sunspot group occurrences. Title: Loop-Top Altitude Decrease in an X-Class Flare Authors: Veronig, A.; Vršnak, B.; Karlický, M.; Temmer, M.; Magdalenić, J.; Dennis, B. R.; Otruba, W.; Pötzi, W. Bibcode: 2005HvaOB..29..127V Altcode: We study RHESSI X-ray source motions in the X3.9 flare of 2003 November 3. Particular attention is drawn to the apparent altitude decrease of a distinct loop-top (LT) source at the early flare phase before then changing to the commonly observed upward expansion of the flare loop system. We obtain that the downward motion is more pronounced at higher X-ray energies (peak values up to 50 km s^{-1}) consistent with recent findings by Sui et al. (2004). RHESSI spectra indicate that the emission process in the LT source is thermal bremsstrahlung from a super hot plasma (∼40 MK) with high densities increasing from ∼10^{10} cm^{-3} early in the flare to several times 10^{11} cm^{-3} at the end of RHESSI observations. Title: On the 24- and 155-Day Periodicity Observed in Solar Hα Flares Authors: Temmer, M.; Veronig, A.; Hanslmeier, A. Bibcode: 2005ASSL..320..211T Altcode: 2005smp..conf..211T No abstract at ADS Title: On the 24-day period observed in solar flare occurrence Authors: Temmer, M.; Veronig, A.; Rybák, J.; Brajša, R.; Hanslmeier, A. Bibcode: 2004SoPh..221..325T Altcode: Time series of daily numbers of solar Hα flares from 1955 to 1997 are studied by means of wavelet power spectra with regard to predominant periods in the range of ∼ 24 days (synodic). A 24-day period was first reported by Bai (1987) for the occurrence rate of hard X-ray flares during 1980-1985. Considering the northern and southern hemisphere separately, we find that the 24-day period is not an isolated phenomenon but occurs in each of the four solar cycles investigated (No. 19-22). The 24-day period can be established also in the occurrence rate of subflares but occurs more prominently in major flares (importance classes ≥ 1). A comparative analysis of magnetically classified active regions subdivided into magnetically complex (i.e., including a γ and/or δ configuration) and non-complex (α, β) reveals a significant relation between the appearance of the 24-day period in Hα flares and magnetically complex sunspot groups, whereas it cannot be established for non-complex groups. It is suggested that the 24-day period in solar flare occurrence is related to a periodic emergence of new magnetic flux rather than to the surface rotation of sunspots. Title: Merging two data sets of hemispheric Sunspot Numbers Authors: Rybák, J.; Bendík, P.; Temmer, M.; Veronig, A.; Hanslmeier, A. Bibcode: 2004HvaOB..28...63R Altcode: First results on merging two data sets of hemispheric sunspot numbers -- from the Kanzelhöhe Solar Observatory and the Skalnaté Pleso Observatory -- for the time span 1977 -- 1978 are presented. A total coverage of 86% was reached for the merged data set. In order to have a homogeneous time series, the daily sunspot numbers for the full disk from both observing stations were normalized to the international relative sunspot number of the day. The derived hemispheric sunspot numbers from Kanzelhöhe and Skalnaté Pleso Observatory %compared for 290 common observing show very high correlations (r ≳ 0.95), and the estimated data noise yields significant differences only for small values of sunspot numbers. These outcomes demonstrate the high potential of the applied merging procedure, and are the basis for an ongoing project to derive hemispheric sunspot numbers back to the year 1945 using sunspot drawings from Kanzelhöhe and Skalnaté Pleso Observatory. Title: Importance of magnetically complex active regions on solar flare occurrence Authors: Temmer, M.; Veronig, A.; Rybák, J.; Brajša, R.; Hanslmeier, A. Bibcode: 2004HvaOB..28...95T Altcode: Daily numbers of solar Hα flares from 1955 to 1997 and daily numbers of magnetically classified active regions for the time span 1964--1997 are studied applying wavelet power spectra. The occurrence of dominant periods in the range of ∼24 days (synodic) is investigated considering the northern and southern hemisphere separately. From the flare events it is revealed that the 24-day period occurs in each of the four solar cycles investigated (no. 19--22). The 24-day period can be established also in the occurrence rate of subflares but occurs more prominently in major flares (importance classes ≥1). Magnetically complex active regions, i.e. including a γ and/or δ configuration, show the 24-day period closely related to those found for major Hα flares, whereas it cannot be established for non-complex α, β groups. Title: Periodical patterns in major flare occurrence and their relation to magnetically complex active regions Authors: Temmer, M.; Veronig, A.; Rybak, J.; Brajsa, R.; Hanslmeier, A. Bibcode: 2004cosp...35.1395T Altcode: 2004cosp.meet.1395T A periodical occurrence rate of solar major flares (observed in hard X-rays) of about 24 days (synodic) was first reported by Bai (1987) for the years 1980--1985. Its origin is still far from being understood. Applying wavelet analyses for daily numbers of Hα flare events covering almost four entire solar cycles (no. 19--22) reveals a 24-day period in each of the cycles studied. This can be established primarily in the occurrence rate of major flares but is also seen in subflares. Since large flares occur preferentially in association with active regions of complex magnetic configuration a comparative study of magnetically classified active regions, subdivided into magnetically complex (i.e. including a γ and/or δ configuration) and non-complex (α, β) was performed. A significant relation between the appearance of the 24-day period in major Hα flares and magnetically complex sunspot groups is found, whereas it cannot be established for non-complex groups. From solar rotation studies based on tracing sunspots practically no siderial rotation velocities as high as 16 deg/day (which corresponds to a synodic period of ∼24 days) are reported. Thus the cause of the 24-day period is very likely not related to solar surface rotation. Alternatively it might be due to periodical patterns in magnetic flux emergence which is an important driver of flare eruptions. We test this hypothesis by investigating synoptic maps of magnetograms (National Solar Observatory/Kitt Peak) for selected time ranges in which the 24-day period is revealed for both flares and magnetically complex active regions. Title: The solar soft X-ray background flux and its relation to flare occurrence Authors: Veronig, Astrid M.; Temmer, Manuela; Hanslmeier, Arnold Bibcode: 2004SoPh..219..125V Altcode: The soft X-ray background flux (XBF) based on GOES 1-8 Å measurements for the period 1975-2003 is studied. There is strong evidence that in the XBF the flare contribution is not eliminated but the XBF is dominated by flare and post-flare emission of intense events. The significant delay (∼ 2 years) of the peak of the X-ray background flux with regard to sunspot numbers reported for cycle 21 recurs in the present cycle 23. The relation between monthly XBF and sunspot numbers can be well represented by a power law. For cycles 21 and 23 the derived fit values are the same within the uncertainties, whereas the values for cycle 22 are significantly different. It is suggested that the lag of the XBF in cycles 21 and 23 is a secondary effect related to the substantial contribution of energetic flares which is not fully subtracted out by the actual XBF definition. Title: On rotational patterns of the solar magnetic field Authors: Temmer, M.; Veronig, A.; Rybák, J.; Hanslmeier, A. Bibcode: 2003ESASP.535..157T Altcode: 2003iscs.symp..157T Solar magnetic field variations (NSO/Kitt Peak data) through solar cycle 23 with respect to rotational modulations are analyzed. A comparative study to solar cycles 21 and 22 is performed. The results are compared to the rotational behavior of activity tracers like sunspots and solar Hα flares. Periodical occurrences of flares often match the 27-day solar rotation due to recurrent stable sunspot groups and complexes of activity which likely produce more flare events than short-living small sunspots. However, periods with strong deviations from the 27-day period are obtained for higher energetic flares. The solar magnetic field is found to vary on similar time scales, which suggests a close relation to the occurrence of strong flare events. Title: Solar cycle variations of the soft X-ray background flux and its relation to flare occurrence Authors: Veronig, A.; Temmer, M.; Hanslmeier, A. Bibcode: 2003ESASP.535..259V Altcode: 2003iscs.symp..259V The X-ray background flux (XBF) based on GOES 1-8 Å measurements for the period 1975-2000 is studied. We come to the conclusion that in the XBF the flare contribution is not eliminated but the XBF is dominated by flare and post-flare emission of intense events. Furthermore, we suggest that the characteristic lag of the X-ray background flux with regard to Sunspot Numbers reported for cycle 21 is a secondary effect related to the substantial contribution of large flares to the XBF. Title: Radio signatures of fast oscillatory phenomena in the solar corona Authors: Magdalenic, Jasmina; Zlobec, P.; Vršnak, B.; Messerotti, M.; Aurass, H.; Temmer, M. Bibcode: 2003ESASP.535..619M Altcode: 2003iscs.symp..619M During type IV solar radio bursts different types of periodic fine structures (PFSs) are frequently observed, which can be interpreted as radio signatures of fast oscillatory phenomena in the coronal plasma. We analyze a large set of type IV bursts containing PFSs, recorded with high time resolution at single frequencies in the metric and decimetric bands. Focusing on the association with flares and flare-like phenomena we found: PFSs can be found in about 50% of type IV bursts characterized by fine structures; 10% of PFS-containing events are weak/short type IV-like radio bursts that occur in absence of any flare-like activity. In the weakest events the whole radio burst was in fact just one short PFS-episode recorded at only one observing frequency; In flare associated events we found two distinct classes of PFSs - impulsive phase and decay phase related PFSs; yet, no statistically significant difference in the characteristic periods and amplitudes is found between the two classes; PFS-rich radio events are characterized by large SXR and radio peak fluxes - neither one of the weak type IV bursts was PFS-rich. The opposite is not true: mainly powerful bursts are PFS-poor. Title: Does solar flare activity lag behind sunspot activity? Authors: Temmer, M.; Veronig, A.; Hanslmeier, A. Bibcode: 2003SoPh..215..111T Altcode: Recently, Wheatland and Litvinenko (2001) have suggested that over the solar cycle both the flaring rate and the magnetic free energy in the corona lag behind the energy supply to the system. To test this model result, we analyzed the evolution of solar flare occurrence with regard to sunspot numbers (as well as sunspot areas), using Hα flare data available for the period 1955-2002, and soft X-ray flare data (GOES 1-8 Å) for the period 1976-2002. For solar cycles 19, 21, and 23, we find a characteristic time lag between flare activity and sunspot activity in the range 10≲τ≲15 months, consistent with the model predictions by Wheatland and Litvinenko (2001). The phenomenon turns out to be more prominent for highly energetic flares. The investigation of solar activity separately for the northern and southern hemisphere allows us to exclude any bias due to overlapping effects from the activity of both hemispheres and confirms the dynamic relevance of the delay phenomenon. Yet, no characteristic time lag τ>0 is found for solar cycles 20 and 22. The finding that in odd-numbered cycles flare activity is statistically delayed with respect to sunspot activity, while in even-numbered cycles it is not, suggests a connection to the 22-year magnetic cycle of the Sun. Further insight into the connection to the 22-year magnetic cycle could possibly be gained when a 22-year variation in the energy supply rate is taken into account in the Wheatland and Litvinenko (2001) model. The existence of a 22-year modulation in the energy supply rate is suggested by the empirical Gnevyshev - Ohl rule, and might be caused by a relic solar field. Title: Rotational modulation of northern and southern activity tracers Authors: Temmer, M.; Veronig, A.; Rybák, J.; Hanslmeier, A. Bibcode: 2003HvaOB..27...59T Altcode: We study solar activity phenomena, Hα flares and sunspots, with respect to their periodical occurrence related to the solar rotation. The analysis is carried out separately for the northern and the southern hemisphere. Furthermore, flare occurrences are studied with respect to different importance classes, and the results are compared to the predominant periods derived from Sunspot Numbers. Significant asymmetries are obtained between the northern and southern activity for both Sunspot Numbers and flare occurrences. Differences between Sunspot Numbers and flares result particularly when only higher energetic flares are considered. A 24-day period is found for large flare events in both hemispheres which is not detected in Sunspot Numbers. Title: Catalogue of hemispheric sunspot numbers RN and RS: 1975 - 2000 Authors: Temmer, M.; Veronig, A.; Hanslmeier, A. Bibcode: 2002ESASP.506..855T Altcode: 2002svco.conf..855T; 2002ESPM...10..855T Sunspot drawings are provided on a regular basis at the Kanzelhöhe Solar Obseratory, Austria, and the derived relative sunspot numbers are reported to the Sunspot Index Data Center in Brussels. From the daily sunspot drawings, we derived the northern, Rn, and southern, Rs, relative sunspot numbers for the time span 1975-2000. In order to accord with the International Sunspot Numbers Ri, the Rn and Rs have been normalized to the Ri, which ensures that the relation Rn+Rs = Ri is complied. For validation, the derived Rn and Rs are compared to the international northern and southern relative sunspot numbers, which are available since 1992. The regression analysis performed for the period 1992-2000 reveals good agreement with the International hemispheric Sunspot Numbers. The monthly mean and the smoothed monthly mean hemispheric Sunspot Numbers are compiled to a catalogue. In addition, the daily hemispheric Sunspot Numbers are made available via Internet. Title: Cycle dependence of hemispheric activity Authors: Temmer, M.; Veronig, A.; Rybák, J.; Hanslmeier, A. Bibcode: 2002ESASP.506..859T Altcode: 2002ESPM...10..859T; 2002svco.conf..859T Data of daily hemispheric Sunspot Numbers are analyzed including the time span 1975-2001. The study of north-south asymmetries concerning solar activity and rotational behaviors is in particular relevant, as it is related to the solar dynamo and the generation of magnetic fields. As diagnostic tools we use wavelets and autocorrelation functions in combination with statistical significance tests that are applied separately to the northern and southern hemisphere. Pronounced differences between the northern and southern rotational periods are obtained. The northern hemisphere shows a rigid rotation of ~27 days which can be followed up to ~15 periods in the autocorrelation function. The signal of the southern hemisphere is strongly attenuated after 3 recurrences showing variable periods in the range ~26-28.5 days. The presence of these periods is not permanent during a cycle suggesting activity pulses in each hemisphere. For the northern hemisphere strong relations to the motions of deeper lying convective structures building up long-living 'active zones' are suggested. Title: The Neupert effect and the electron-beam-driven evaporation model Authors: Veronig, A.; Vršnak, B.; Dennis, B. R.; Temmer, M.; Hanslmeier, A.; Magdalenić, J. Bibcode: 2002ESASP.506..367V Altcode: 2002svco.conf..367V; 2002ESPM...10..367V Based on a sample of ~1100 solar flares observed simultaneously in hard and soft X-rays, we performed a statistical analysis of the Neupert effect. For a subset of ~500 events, supplementary Hα flare data were considered. The timing behavior of >50% of the events is consistent with the Neupert effect. A high correlation between the soft X-ray peak flux and the hard X-ray fluence is obtained, being indicative of electron-beam-driven evaporation. However, about one fourth of the events (predominantly weak flares) reveal strong deviations from the predicted timing, with a prolonged increase of the thermal emission beyond the end of the hard X-rays. These findings suggest that electron-beam-driven evaporation plays an important role in solar flares. Yet, in a significant fraction of events there is also evidence for an additional energy transport mechanism from the energy release site other than electron beams, presumably thermal conduction. Title: The Neupert effect in solar flares and implications for coronal heating Authors: Veronig, A.; Vrsnak, B.; Dennis, B. R.; Temmer, M.; Hanslmeier, A.; Magdalenić, J. Bibcode: 2002ESASP.505..599V Altcode: 2002solm.conf..599V; 2002IAUCo.188..599V; 2002astro.ph..8089V Based on simultaneous observations of solar flares in hard and soft X-rays we studied several aspects of the Neupert effect. About half of 1114 analyzed events show a timing behavior consistent with the Neupert effect. For these events, a high correlation between the soft X-ray peak flux and the hard X-ray fluence is obtained, being indicative of electron-beam-driven evaporation. However, for about one fourth of the events there is strong evidence for an additional heating agent other than electron beams. We discuss the relevance of these findings with respect to Parker's idea of coronal heating by nanoflares. Title: Hemispheric asymmetry of solar activity phenomena: north-south excesses rotational periods and their links to the magnetic field Authors: Temmer, M.; Veronig, A.; Hanslmeier, A. Bibcode: 2002ESASP.505..587T Altcode: 2002solm.conf..587T; 2002IAUCo.188..587T We present a cycle dependent analysis of various solar activity phenomena, namely Sunspot Numbers and Hα flares, including the time range 1975-2000. The data are studied on a statistical basis with relation to their spatial distribution, significance of the north-south asymmetry and rotational periods. For the considered time span we obtain significant values of north-south asymmetries. For the northern hemisphere the significant excesses are revealed during the increasing and maximum phase of a solar cycle whereas a southern excess dominates near the end of a cycle. Furthermore, we obtain differences in rotational periods and activity gaps between both hemispheres that suggest an independent evolution in hemispheric activity for these indices. Hence, a weak interdependence of the magnetic field system originating in the two hemispheres is suggested. Additionally we find differences in the dominant rotational periods of photospheric and chromospheric tracers. Title: Investigation of the Neupert effect in solar flares. I. Statistical properties and the evaporation model Authors: Veronig, A.; Vršnak, B.; Dennis, B. R.; Temmer, M.; Hanslmeier, A.; Magdalenić, J. Bibcode: 2002A&A...392..699V Altcode: 2002astro.ph..7217V Based on a sample of 1114 flares observed simultaneously in hard X-rays (HXR) by the BATSE instrument and in soft X-rays (SXR) by GOES, we studied several aspects of the Neupert effect and its interpretation in the frame of the electron-beam-driven evaporation model. In particular, we investigated the time differences (Delta t) between the maximum of the SXR emission and the end of the HXR emission, which are expected to occur at almost the same time. Furthermore, we performed a detailed analysis of the SXR peak flux - HXR fluence relationship for the complete set of events, as well as separately for subsets of events which are likely compatible/incompatible with the timing expectations of the Neupert effect. The distribution of the time differences reveals a pronounced peak at Delta t = 0. About half of the events show a timing behavior which can be considered to be consistent with the expectations from the Neupert effect. For these events, a high correlation between the SXR peak flux and the HXR fluence is obtained, indicative of electron-beam-driven evaporation. However, there is also a significant fraction of flares (about one fourth), which show strong deviations from Delta t = 0, with a prolonged increase of the SXR emission distinctly beyond the end of the HXR emission. These results suggest that electron-beam-driven evaporation plays an important role in solar flares. Yet, in a significant fraction of events, there is also clear evidence for the presence of an additional energy transport mechanism other than nonthermal electron beams, where the relative contribution is found to vary with the flare importance. Title: Hemispheric Sunspot Numbers Rn and Rs: Catalogue and N-S asymmetry analysis Authors: Temmer, M.; Veronig, A.; Hanslmeier, A. Bibcode: 2002A&A...390..707T Altcode: 2002astro.ph..8436T Sunspot drawings are provided on a regular basis at the Kanzelhöhe Solar Observatory, Austria, and the derived relative sunspot numbers are reported to the Sunspot Index Data Center in Brussels. From the daily sunspot drawings, we derived the northern, Rn, and southern, Rs, relative sunspot numbers for the time span 1975-2000. In order to accord with the International Sunspot Numbers Ri, the Rn and Rs have been normalized to the Ri, which ensures that the relation Rn+Rs=Ri is fulfilled. For validation, the derived Rn and Rs are compared to the international northern and southern relative sunspot numbers, which are available from 1992. The regression analysis performed for the period 1992-2000 reveals good agreement with the International hemispheric Sunspot Numbers. The monthly mean and the smoothed monthly mean hemispheric Sunspot Numbers are compiled into a catalogue. Based on the derived hemispheric Sunspot Numbers, we study the significance of N-S asymmetries and the rotational behavior separately for both hemispheres. We obtain that ~ 60% of the monthly N-S asymmetries are significant at a 95% level, whereas the relative contributions of the northern and southern hemisphere are different for different cycles. From the analysis of power spectra and autocorrelation functions, we derive a rigid rotation with ~ 27 days for the northern hemisphere, which can be followed for up to 15 periods. Contrary to that, the southern hemisphere reveals a dominant period of ~ 28 days, whereas the autocorrelation is strongly attenuated after 3 periods. These findings suggest that the activity of the northern hemisphere is dominated by an active zone, whereas the southern activity is mainly dominated by individual long-lived sunspot groups. The catalogue is available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/390/707 Title: Relative timing of solar flares observed at different wavelengths Authors: Veronig, A.; Vršnak, B.; Temmer, M.; Hanslmeier, A. Bibcode: 2002SoPh..208..297V Altcode: 2002astro.ph..8088V The timing of 503 solar flares observed simultaneously in hard X-rays, soft X-rays and Hα is analyzed. We investigated the start and the peak time differences in different wavelengths, as well as the differences between the end of the hard X-ray emission and the maximum of the soft X-ray and Hα emission. In more than 90% of the analyzed events, a thermal pre-heating seen in soft X-rays is present prior to the impulsive flare phase. On average, the soft X-ray emission starts 3 min before the hard X-ray and the Hα emission. No correlation between the duration of the pre-heating phase and the importance of the subsequent flare is found. Furthermore, the duration of the pre-heating phase does not differ for impulsive and gradual flares. For at least half of the events, the end of the non-thermal emission coincides well with the maximum of the thermal emission, consistent with the beam-driven evaporation model. On the other hand, for ∼ 25% of the events there is strong evidence for prolonged evaporation beyond the end of the hard X-rays. For these events, the presence of an additional energy transport mechanism, most probably thermal conduction, seems to play an important role. Title: VizieR Online Data Catalog: Hemispheric Sunspot Numbers 1975-2000 (Temmer+, 2002) Authors: Temmer, M.; Veronig, A.; Hanslmeier, A. Bibcode: 2002yCat..33900707T Altcode: Hemispheric sunspot numbers including the time span from 1975-2000 are presented. The Sunspot Numbers are calculated from sunspot drawings made at the Kanzelhoehe Solar Observatory (KSO), Austria. The counted northern and southern Sunspot Numbers are normalized and multiplied with the International Sunspot Numbers taken from SIDC for matching days in order to provide the data within an international usage. Days without observation by KSO (about 27 percent) were reconstructed applying a linear interpolation method. As validation of the data, regression methods and a cross-correlation analysis are made with hemispheric Sunspot Numbers from SIDC for the available time span 1992-2000 obtaining very good agreements. The results are given in monthly mean and smoothed monthly mean Sunspot Numbers. Based on this data set an analysis concerning the North-South asymmetry is made in the paper. (1 data file). Title: Soft X-ray flares for the period 1975-2000 Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.; Otruba, W.; Messerotti, M. Bibcode: 2002ESASP.477..175T Altcode: 2002scsw.conf..175T Statistical aspects of solar soft X-ray (SXR) flares for the period September 1975 to December 2000 are investigated. In particular, we analyzed the spatial distribution of SXR flares with regard to the solar hemispheres, i.e. N-S and E-W asymmetries, as well as the occurrence of SXR flares in the course of the solar cycle. We obtain that the occurrence rate of SXR flares is delayed in relation to the Sunspot Numbers which can be interpreted as an interaction between the northern and southern hemisphere activity. Title: Temporal characteristics of solar soft X-ray and Hα flares Authors: Veronig, A.; Temmer, M.; Hanslmeier, A.; Messerotti, M.; Otruba, W.; Moretti, P. F. Bibcode: 2002ESASP.477..187V Altcode: 2002scsw.conf..187V Temporal aspects of solar soft X-ray and Hα flares for the period 1997-2000 are investigated. For the considered time span about 8400 SXR and 11400 Hα flares are reported in the SGD. Related flares observed in Hα as well as in SXR are identified amounting to about 2100 events. Correlations among corresponding SXR and Hα events are analyzed and their relative timing is investigated. From the timing analysis we infer that for most of the events (84%) the start of the Hα emission is delayed with respect to the SXR emission. On average, the Hα flare starts 3 minutes after the SXR flare. The peaks occur preferentially simultaneously with a slight tendency that the Hα peak precedes the SXR peak. Title: Temporal aspects and frequency distributions of solar soft X-ray flares Authors: Veronig, A.; Temmer, M.; Hanslmeier, A.; Otruba, W.; Messerotti, M. Bibcode: 2002A&A...382.1070V Altcode: 2002astro.ph..7234V A statistical analysis of almost 50 000 soft X-ray (SXR) flares observed by GOES during the period 1976-2000 is presented. On the basis of this extensive data set, statistics on temporal properties of soft X-ray flares, such as duration, rise and decay times with regard to the SXR flare classes is presented. Correlations among distinct flare parameters, i.e. SXR peak flux, fluence and characteristic times, and frequency distributions of flare occurrence as function of the peak flux, the fluence and the duration are derived. We discuss the results of the analysis with respect to statistical flare models, the idea of coronal heating by nanoflares, and elaborate on implications of the obtained results on the Neupert effect in solar flares. Title: Frequency Distributions of solar Flares Authors: Veronig, A.; Temmer, M.; Hanslmeier, A. Bibcode: 2002HvaOB..26....7V Altcode: Flare frequency distributions as function of the soft X-ray peak flux and fluence are investigated. We analyse GOES 1--8 Å data for the period 1986--2000. The results are discussed with respect to avalanche flare models and the hypothesis of coronal heating by nanoflares. Title: Statistical analysis of solar Hα flares Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.; Otruba, W.; Messerotti, M. Bibcode: 2001A&A...375.1049T Altcode: 2002astro.ph..7239T A statistical analysis of a large data set of Hα flares comprising almost 100 000 single events that occurred during the period January 1975 to December 1999 is presented. We analyzed the flares evolution steps, i.e. duration, rise times, decay times and event asymmetries. Moreover, these parameters characterizing the temporal behavior of flares, as well as the spatial distribution on the solar disk, i.e. N-S and E-W asymmetries, are analyzed in terms of their dependency on the solar cycle. The main results are: 1) The duration, rise and decay times increase with increasing importance class. The increase is more pronounced for the decay times than for the rise times. The same relation is valid with regard to the brightness classes but in a weaker manner. 2) The event asymmetry indices, which characterize the proportion of the decay to the rise time of an event, are predominantly positive (~90%). For about 50% of the events the decay time is even more than 4 times as long as the rise time. 3) The event asymmetries increase with the importance class. 4) The flare duration and decay times vary in phase with the solar cycle; the rise times do not. 5) The event asymmetries do not reveal a distinct correlation with the solar cycle. However, they drop during times of solar minima, which can be explained by the shorter decay times found during minimum activity. 6) There exists a significant N-S asymmetry over longer periods, and the dominance of one hemisphere over the other can persist for more than one cycle. 7) For certain cycles there may be evidence that the N-S asymmetry evolves with the solar cycle, but in general this is not the case. 8) There exists a slight but significant E-W asymmetry with a prolonged eastern excess. Title: Statistical Study of Solar Flares Observed in Soft X-Ray, Hard X-Ray and Hα Emission Authors: Veronig, A.; Vršnak, B.; Temmer, M.; Magdalenić, J.; Hanslmeier, A. Bibcode: 2001HvaOB..25...39V Altcode: Correlations among statistical properties of solar flares observed in soft X-rays, hard X-rays and Hα are studied. We investigate corresponding HXR flares measured by BATSE, SXR flares observed by GOES and Hα flares reported in the SGD for the period 1997--2000. Distinct correlations are found among the SXR peak flux and Hα area, as well as between the SXR peak flux and HXR fluence. This can be comprehended in the frame of the chromospheric evaporation model of flares. Title: Automatic Image Processing in the Frame of a Solar Flare Alerting System Authors: Veronig, A.; Steinegger, M.; Otruba, W.; Hanslmeier, A.; Messerotti, M.; Temmer, M.; Gonzi, S.; Brunner, G. Bibcode: 2000HvaOB..24..195V Altcode: In the present paper we describe image processing techniques applied to solar H-alpha full-disk images, with the objective of automatic and quasi real-time detection of the onset of H-alpha flares and describing their evolution. For this purpose we utilize a combination of region-based and edge-based image segmentation methods. Title: Automatic Image Segmentation and Feature Detection in Solar Full-Disk Images Authors: Veronig, A.; Steinegger, M.; Otruba, W.; Hanslmeier, A.; Messerotti, M.; Temmer, M.; Brunner, G.; Gonzi, S. Bibcode: 2000ESASP.463..455V Altcode: 2000sctc.proc..455V At Kanzelhoehe Solar Observatory, Austria, a solar activity monitoring and flare alerting system is under development, which will be based on the parametrization of solar flare activity using photometric and magnetic full-disk images of the Sun obtained simultaneously with high time cadence. An important step in this project is the automatic image segmentation and feature detection of solar activity phenomena related to the occurrence of solar flares. In a first step we have developed a procedure for automatically detecting the onset and describing the evolution of flares in H-alpha full-disk images. Title: Statistical Properties Relevant to Solar Flare Prediction Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.; Steinegger, M.; Brunner, G.; Gonzi, S.; Otruba, W.; Messerotti, M. Bibcode: 2000HvaOB..24..185T Altcode: We statistically analyzed the characteristic temporal properties of H-alpha flares, such as duration, rising and setting times, with the aim to determine a proper acquisition rate for H-alpha patrol observations, which will be the basis for the automatic flare alerting and prediction system at the Kanzelhoehe Solar Observatory, Austria. Furthermore, the comparison of absolute and normalized values reveals interesting aspects on how flares of different importance classes behave with respect to the rising and decay phase. Title: Solar Activity Monitoring - a New Approach Using Combined Datasets, Pattern Recognition and Neural Networks Authors: Hanslmeier, A.; Veronig, M.; Steinegger, M.; Brunner, G.; Gonzi, S.; Temmer, M.; Otruba, W.; Messerotti, M. Bibcode: 1999HvaOB..23...31H Altcode: In this paper we give an overview of the activities of the recently established solar activity monitoring and flare alerting working group at the University of Graz and its planned activities. Solar flares can trigger events at the earth environment that can be dangerous to technological systems as well as to human life. Therefore, it is an important target in solar physics to predict such events, providing an essential contribution to space weather forecasts.