## Session 5 - Solar Corona and Heliosphere

Luciano Rodriguez (ROB); Sergio Dasso (IAFE)
Monday 18/11, 14:00-15:15 & 16:00-17:15, Rogier
Tuesday 19/11, 11:15-12:30, Elisabeth

Flares, Coronal Mass Ejections (CMEs) and associated shock waves are of key interest in the field of solar-terrestrial relations. Interplanetary CMEs and their associated shock waves are the main drivers of geomagnetic storms. High speed solar wind streams emanating from coronal holes also have a big influence on geospace, in particular outside of solar maximum when CMEs are more scarce. They are also important drivers of relativistic electron enhancements in the radiation belts surrounding the Earth. Flares in turn can have an important impact (UV radiation, particles) on the Earth's atmosphere.
Recent remote observations and modelling studies have shown that CMEs can drive shock waves very low in the solar corona, which, in turn, may produce significant fluxes of solar energetic particles (SEP).
There is thus a strong need for realistic and data-driven modelling of solar wind, flares and CMEs using a variety of theoretical, physics-based and semi-empirical models, such as heliospheric models like EUHFORIA, ENLIL and SUSANOO.

In this session, we invite observational, theoretical, and modelling contributions that address the following topics:
• Flares, the coronal dynamics of CME and shock waves and their related production of SEPs
• CME propagation in the heliosphere, the interaction of ICMEs with Earth and/or with other planets
• The link between CMEs and ICMEs

Talks
Monday November 18, 14:00 - 15:15, Rogier
Monday November 18, 16:00 - 17:15, Rogier
Tuesday November 19, 11:15 - 12:30, Elisabeth

### Talks : Time schedule

Monday November 18, 14:00 - 15:15, Rogier
 16:00 Solar wind modeling by EUHFORIA Magdalenic, J et al. Invited Oral Jasmina Magdalenic [1] Royal Observatory of Belgium, Solar Physics, Brussels, Belgium Coronal mass ejections (CMEs) and associated shocks, which propagate through the highly dynamic background solar wind, play the main role in creating disturbed space weather conditions by driving geomagnetic storms. The propagation of CMEs is strongly inﬂuenced by their interaction with the ambient solar wind. Therefore, the knowledge on the background solar wind is crucial for understanding and forecasting the propagation of CMEs. Moreover, the fast solar wind itself can also impact the Earth and cause the geomagnetic disturbances. Since most of in situ measurements of both ICMEs and background solar wind are typically available at a few locations in the interplanetary space around 1 AU (e.g. STEREO, ACE, DSCOVR), we have to rely on numerical heliospheric models. EUHFORIA (EUropean Heliospheric FORecasting Information Asset), the model of the solar wind and ICME propagation, was recently developed in order to respond to a need of realistic predictions of CME, shock and fast solar wind propagation. Testing and validation of the solar wind modelling is a crucial step for improvements of EUHFORIA. In this presentation, the results on the validation of the performance of solar wind modeling with EUHFORIA in the framework of the CCSOM project (Constraining CMEs and Shocks by Observations and Modelling throughout the inner heliosphere) will be presented. 16:30 Developing fast solar wind modeling with EUHFORIA Samara, E et al. Oral Evangelia Samara [1][2], Jasmina Magdalenic [2], Luciano Rodriguez [2], Stephan G. Heinemann[3], Stefaan Poedts [1] [1] Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200b-box 2400, 3001 Leuven, Belgium [2] Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium [3] Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria The fast component of the solar wind is very important in terms of space weather. Upon arrival at Earth (or at other planets), the high speed streams (HSS) can compress the magnetosphere and generate geomagnetic storms. Moreover, the HSS and the background solar wind influence the propagation of CMEs. This work aims to enhance the fast solar wind modeling with EUHFORIA (EUropean Heliospheric FORecasting Information Asset) by focusing on three different aspects. First, by focusing on the properties of their sources, the coronal holes (CHs) observed at the Sun and by providing a statistical overview of their characteristics. To do this, we use observations and simulations between November 2017 and March 2019, during the minimum activity period of Solar Cycle. Second, by testing magnetograms from different providers. Magnetograms constitute the basic source of information for MHD simulations and modeling results can be highly variable because of them. Third, by testing different coronal models into EUHFORIA. Finally, an evaluation of the results and assessment of the goodness of the model depending on the three aforementioned aspects is made. 16:45 Statistical Analysis of SDO-era Coronal Holes using CATCH Heinemann, S et al. Oral Stephan G. Heinemann[1], Manuela Temmer[1], Niko Heinemann[1], Karin Dissauer[1], Evangelia Smara[2], Veronika Jercic[1], Stefan J. Hofmeister[1], Astrid Veronig[1], [1]University of Graz, Institute of Physics, [2]Royal Observatory of Belgium, Brussels, Belgium Coronal holes are regions of open magnetic field in the solar corona and can be observed as dark structures in the extreme ultraviolet and x-ray spectrum. Deriving reliably the coronal hole boundary is of high interest, as its area, underlying magnetic field, and other properties give important hints towards high speed solar wind acceleration processes and with that compression regions arriving at Earth. In this study we present a newly improved threshold based extraction method, that incorporates the intensity gradient along the coronal hole boundary, which is implemented as a user-friendly SSWIDL GUI. The Collection of Analysis Tools for Coronal Holes (\textsc{CATCH}) enables the user to download data, perform guided coronal hole extraction and analyze the underlying photospheric magnetic field. We use \textsc{CATCH} to analyze non-polar coronal holes of the SDO-era, based on $193$ \AA\ 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 734 coronal holes that are close to the central meridian. We find coronal holes distributed across latitudes of $\pm 63\degree$ and sizes between $0.16$ to $17.15 \cdot 10^{10}$ km$^{2}$. The absolute value of the mean signed magnetic field strength tends towards an average of $2.8\pm 1.9$ G. Also we find no distinct trend towards a preferred hemisphere in abundance or size. By investigating the parameters needed for the extraction of the coronal holes we can highlight the importance of guided individual extraction in order to achieve high quality boundaries. 17:00 From Observations Toward Prediction of the Downstream Properties of CME-Driven Shocks Kay, C et al. Oral Christina Kay [1,2] [1] Catholic University of America, [2] NASA Goddard Space Flight Center Predicting the plasma properties of coronal mass ejections, including a shock, sheath, and flux rope structure, is essential for space weather forecasting. We have shown that we reproduce a CME's flux rope structure using the ForeCAT In situ Data Observer (FIDO). We show that simple, physics-driven models can also be used to simulate the CME sheath that arrives at 1 AU. We first establish a set of well-observed CME-driven shocks using results from several online catalogs. Using the MHD Rankine-Hugoniot jump conditions with several simplifying assumptions we develop a simple model (SIT- Sheath Induced by Transient) for the downstream shock/sheath properties, which only depends on the upstream plasma properties and the downstream velocity. When given the observed downstream velocity the model reproduces the downstream density and magnetic field strength, establishing a baseline for what we can hope to achieve for actual predictions with SIT. We develop a relation between the observed downstream velocity and CME properties that can be determined before the CME reaches 1 AU. Using this predicted downstream velocity we achieve mean average errors of 3.4 cm^-3 and 3.8 nT. We also develop a model for the sheath duration or the standoff distance of the CME-driven shock. While there is certainly room for improvement, our model does perform better than those currently available, reducing the error from 7.0 hours to 4.5 hours. We present initial results from FIDO-SIT, which couples the predicted-velocity-driven sheath model to the FIDO model, allowing for comparison with in situ sheath observations.
 11:15 Understanding and forecasting of coronal mass ejections Dumbovic, M et al. Invited Oral Mateja Dumbovic[1,2], Jingnan Guo[3, 4], Manuela Temmer[2], M. Leila Mays[5], Astrid Veronig[2,6], Stephan Heinemann[2], Karin Dissauer[2], Stefan Hofmeister[2], Jasper Halekas[7], Christian Mostl[8], Tanja Amerstorfer[8], Jurgen Hinterreiter[8,2], Sasa Banjac[4], Konstantin Herbst[4], Yuming Wang[3], Lukas Holzknecht[2], Martin Leitner[2], and Robert F. Wimmer–Schweingruber[4] [1]Hvar Observatory, Faculty of Geodesy, University of Zagreb, Croatia, [2]Institute of Physics, University of Graz, Austria, [3]CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, China, [4]Department of Extraterrestrial Physics, Christian-Albrechts University in Kiel, Germany, [5]NASA Goddard Space Flight Center, USA, [6]Kanzelhohe Observatory for Solar and Environmental Research, University of Graz, Austria, [7]Department of Physics and Astronomy, University of Iowa, USA, [8]Space Research Institute, Austrian Academy of Sciences, Austria Forecasting the arrival and impact 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 understand and ultimately forecast CME arrival time and/or impact. The models differ based on the input, approach, assumptions and complexity ranging from simple empirical and analytical to complex numerical and machine learning models. However, regardless of the model, forecasting CME arrival and especially impact 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 evolution/propagation itself, either due to unrealistic solar wind background, complex interactions or additional evolutionary processes (e.g. deflections, rotations, erosion). These limits will be discussed in the scope of a recent comprehensive combined modelling-observational case study of a complex July 2017 event (Dumbovic et al., 2019, ApJ). 11:45 Tracing the Origins of Flux Ropes Observed at 1 AU in CMEs Without Obvious Low Coronal Signatures Nitta, N et al. Oral Nariaki Nitta[1], Tamtha Mulligan[2] [1] Lockheed Martin Advanced Technology Center, [2] Aerospace Corporation In order to advance our understanding of the impact of non-recurrent solar wind disturbances on the near-Earth space environment, we need to determine whether they involve an interplanetary coronal mass ejection (ICME). Then we link (1) the ICME to a coronal mass ejection (CME) observed close to the Sun, and (2) the CME to an eruption in the corona. There are many events that present difficulty in either of the two links. Especially during high solar activity, more than one CME or eruption may occur in succession, making it hard to select the correct association. In the other end of the spectrum, we may not be able to find a clear CME for the ICME or an obvious eruption in the corona for the CME. We call them stealthy events, which have been studied recently by our team hosted by the International Space Science Institute (ISSI); our focus has been on those ICMEs that produced significant geomagnetic storms measured in Dst. Here, we present our updated knowledge of the origins of the ICMEs traced back to the corona, limiting to those that show clear rotation of magnetic field, indicative of the presence of a magnetic flux rope, but releasing the restrictions on the occurrence of a significant geomagnetic storm. We evaluate the relevance of the hemispheric rule of the sign of helicity. Filament channels in weak field regions may be an important factor for the stealthy flux rope events. We discuss observational challenges in how to isolate them. 12:00 Characterising the radial evolution of the solar wind and Coronal Mass Ejections using EUHFORIA Scolini, C et al. Oral Camilla Scolini[1,2], Sergio Dasso[3,4], Luciano Rodriguez[2], Andrei N. Zhukov[2,5], Stefaan Poedts[1] [1]Centre for mathematical Plasma Astrophysics, KU Leuven, Leuven, Belgium, [2]Solar-Terrestrial Centre of Excellence - SIDC, Royal Observatory of Belgium, Uccle, Belgium, [3]CONICET, Universidad de Buenos Aires, Instituto de Astronomía y Física del Espacio, Buenos Aires, Argentina, [4]Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ciencias de la Atmósfera y los Océanos and Departamento de Física, Buenos Aires, Argentina, [5]Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, Russia Coronal Mass Ejections (CMEs) and their interplanetary counterparts (ICMEs) are considered to be the primary cause of strong geomagnetic storms. Since decades, the space weather community has devoted efforts in the development of physics-based models able to reliably reproduce and predict the ICME properties at Earth (i.e. at 1 AU) and their impact on geospace. Recent and upcoming advances in the exploration of the inner heliosphere (Parker Solar Probe, Solar Orbiter), however, advocate the need to assess model performances not only at 1 AU, but also at other heliocentric distances. Due to the spatial and temporal sparsity of solar wind monitors in the heliosphere, studies of the radial evolution of CMEs and ICMEs mostly consider statistically-relevant sets of ICME observations obtained for different events and from a variety of spacecraft. While multi-spacecraft observations of a single ICME from radially-aligned spacecraft are still very rare, 3D physics-based models represent powerful complements to observations as they allow to track a given ICME continuously during its propagation in the heliosphere. In this work we investigate the radial evolution of a case study CME in the inner heliosphere using the EUHFORIA solar wind and CME propagation model, which permits to inject CMEs as magnetic flux ropes. As test case event, we consider the Earth-directed halo CME that erupted on 12 July 2012 from the solar disk centre, previously studied in detail by Scolini et al. (2019). In order to complement observation-based results on the radial evolution of the ambient solar wind and ICMEs, in this follow-up study we use EUHFORIA (1) to characterise the radial dependence of the ambient solar wind properties, (2) to quantify the temporal/spatial extent of the solar wind perturbation induced by the ICME passage at different heliocentric distances, and (3) to investigate the radial evolution of the various CME-driven structures in the interplanetary space (shock, sheath, magnetic ejecta). Results from this study will allow not only to validate the model capabilities against observations, but also to shed light on the physical processes affecting the evolution of ICMEs in the heliosphere via their interaction with the ambient solar wind. References: Scolini, C., Rodriguez, L., Mierla, M., Pomoell, J., and Poedts, S. (2019), “Observation-based modelling of magnetised Coronal Mass Ejections with EUHFORIA”, A&A (in press) 12:15 Multi-Spacecraft Measurements of a Geo-Effective Coronal Mass Ejection: CME Radial Expansion Lugaz, N et al. Oral Noé Lugaz, Réka M. Winslow, Tarik M. Salman, Charles J. Farrugia Space Science Center, University of New Hampshire We discuss the expansion of coronal mass ejections (CMEs) through multi-spacecraft measurements between Mercury's and Earth's orbit. We first present the case study of {\it in situ} measurements of a CME that impacted both Mercury and Earth, while the two planets were in good radial conjunction ($\sim 3^\circ$). By combining information from {\it in situ} measurements and remote-sensing observations, we first determine that the CME did not decelerate much in the inner heliosphere, even though the initial speed was about 600 km\,s${-1}$. The magnetic field measurements made by MESSENGER and {\it Wind} reveal a very similar magnetic ejecta at both planets. We then turn our focus on the CME expansion through various metrics and methods. The long-duration CME is found to be associated with a relatively slowly expanding ejecta at 1~AU, revealing that the large size of the ejecta is due to the CME itself or its expansion in the corona, and not due to a rapid expansion between Mercury and Earth. Next, we discuss general results from several dozens of CMEs measured in the inner heliosphere, focusing on the radial expansion.
 1 Theory of the formation of Forbush decrease in a magnetic cloud Petukhova, A et al. p-Poster Anastasia Petukhova, Ivan Petukhov, Stanislav Petukhov Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy SB RAS A theory of the formation of Forbush decrease in a magnetic cloud is presented. It is found that the formation mechanism is the energy loss of cosmic rays in a magnetic cloud represented as a moving magnetic loop with a helical field. The Forbush decrease amplitude, the components of the vector, and tensor anisotropies are calculated along the path of magnetic cloud's passing the Earth. It is shown that the Forbush decrease characteristics depend on the following magnetic cloud parameters: magnetic field strength, the helical field structure, velocity and the velocity gradient, and geometric dimensions. It is found that the Forbush decrease characteristics mainly depend on the magnetic field strength and the state of the global helical structure of the field. 2 On density enhancement in the halo CME forecast Yordanova, E et al. p-Poster Emiliya Yordanova[1], A. L. Elisabeth Werner[2], Kellen Smith[3], Manuela Temmer[4], Andrew P. Dimmock[1] and Lisa Rosenqvist[5] [1] Swedish Institute of Space Physics, Uppsala, Sweden, [2] LATMOS/IPSL, Sorbonne Université, UVSQ, CNRS, Paris, France, [3] Uppsala University , Uppsala, Sweden, [4] Institute of Physics, University of Graz, Graz, Austria, [5] Swedish Defense Research Agency, Sweden Front-sided halo CMEs are propagating directly in the Sun-Earth line and therefore cause most of the large geomagnetic storms. However, their kinematics (angular width, radial speed and direction of propagation) are notoriously challenging to determine. This is especially true in the case of single point observations, since the coronagraph images represent 2D projections of scattered white light emission from the CMEs in the plane-of-sky. Thus the estimation of the actual kinematics is subjected to projection effects and naturally will affect the accuracy of the prediction of a halo CME arrival. On the other hand, the CMEs travel into the interplanetary space, experiencing the presence of the ambient solar wind. Therefore the state of the interplanetary medium should also be considered in the forecasting. From an assessment of the performance of WSA-ENLIL+Cone model it is known that CME propagation is mostly affected by the upper limit of the ambient solar wind speed, and the enhancement factors coming from the cone representation of the CME. In this work we focus the investigation specifically on the density enhancement factor (dcld) which refers to the density enhancement of the leading front of the CME cone relative to the density of the fast solar wind. Dcld is determined by coronagraph images, and by default is set to be equal to 4 in the model input. However, it has been shown that higher dcld factors results in higher amplitudes and earlier CME arrival times. We introduce a custom dcld factor, where the density enhancement is determined by the much fainter light feature of the shock produced by a halo CME and the background solar wind instead. The custom dcld in combination with very accurate estimation of the CME kinematics have resulted in significantly closer to the actual CME arrival times predictions – a result that has potential implications in space weather operational setting. 3 Analysis of the solar wind at 1 AU from ACE data Larrodera baca, C et al. p-Poster Carlos Larrodera, Consuelo Cid Universidad de Alcalá The study of the solar wind has improved thanks to the data taken from spacecraft which are placed in different locations out of the magnetosphere. There are many measurements close to L1 point, mainly from ACE spacecraft. We focus this work on the analysis of the level 2 data from ACE of different solar wind magnitudes such as the magnetic field, speed, density and temperature taken from 1998 to 2017. The goal of this work is to separate the behavior of the quiet solar wind, formed by the slow and fast wind, from the extreme solar wind and the structures that appears in it. Our starting point has been the fitting of the distribution functions of the magnitudes by using gaussian distributions functions. Then we have analysed the parameters coming from the fitting and the relationship among them. 4 Heavy ion SEP observations by spacecraft widely separated in longitude Zelina, P et al. p-Poster Peter Zelina[1], Silvia Dalla[2] [1] Astronomical Institute, Slovak Academy of Sciences, Stará Lesná, Slovakia, [2] Jeremiah Horrocks Institute, University of Central Lancashire, Preston, UK Solar eruptions such as flares and coronal mass ejections can release energetic particles into the heliosphere, which can be observed by spacecraft that are widely separated in longitude. The exact mechanism by which SEPs can reach these locations is presently still under discussion. In addition to protons and electrons, which are the most abundant SEPs, heavy ions can too be observed reaching regions that are magnetically not well-connected to the source. We present observations of the Fe/O ratio that were measured over a broad range of longitudes at a distance approximately 1 AU. This was possible using near-Earth spacecraft and the two STEREO spacecraft, progressively separating in longitude. The observed longitudinal distribution of the Fe/O values sometimes, but not always, follows the structure where an observer with better magnetic connection detects higher Fe/O value. In this contribution, we discuss the parameters of SEP events and the Fe/O ratio values measured by ACE, STEREO A and B. We also consider implications for our understanding of the SEP transport and the constraints for the modelling of SEP transport. 5 Clustering of fast Coronal Mass Ejections during solar cycles 23 and 24 and their implications for CME-CME interactions Rodriguez gomez, J et al. p-Poster Jenny Rodriguez Gomez[1], Tatiana Podladchikova[1], Astrid Veronig[2] [1] Skolkovo Institute of Science and Technology (Skoltech), Russia, [2] Institute of Physics & Kanzelhöhe Observatory, University of Graz, Austria. Extreme solar events are important to study in order better understand the variability of the Sun, the physics of solar eruptions as well as to better understand and predict extreme space weather events at Earth. CMEs and their interplanetary counterparts (ICMEs) are the major source for strong space weather disturbances. CMEs occurring in close succession and interacting either close to the Sun or in interplanetary space have been shown to be more geo-effective than isolated events. They can drive Forward and Fast reverse shocks, interact with planetary magnetospheres, and accelerate Solar Energetic Particles (SEPs). We present a study of statistical properties of fast CMEs and ICMEs that occurred during solar cycles 23 and 24. We apply the Max spectrum method, which provides us with two important exponents describing the temporal distribution of extreme CME and ICME events: the power tail exponent ($\alpha$) and the extremal index ($\theta$). We present our results for the full period of SOHO/LASCO observations covering almost two full solar cycles. In addition, we study the variations over different solar cycle phases, and discuss the implications of the resulting statistics of fast CMEs for the occurrence of CME-CME interactions. 7 Solar energetic particles experience EUHFORIA’s non-nominal solar winds in PARADISE Wijsen, N et al. p-Poster Nicolas Wijsen[1,2], Angels Aran[2], Jens Pomoell[3], Stefaan Poedts[1] [1]KU Leuven. [2]University of Barcelona, [3]University of Helsinki In this work, we present the Particle Radiation Asset Directed at Interplanetary Space Exploration (PARADISE) model, which describes the transport of solar energetic particles (SEPs) in the heliosphere by solving the five-dimensional focused transport equation in a stochastic manner. In our model, energetic particles are propagated in a solar wind generated by the three-dimensional magnetohydrodynamic model EUHFORIA. This approach allows us to study the effect of non-nominal solar wind conditions on the spatial, pitch-angle and energy dependencies of the energetic particle distribution function. In particular, we consider solar wind configurations containing rarefaction and/or compression regions, which can e.g., be found in transition regions between slow and fast solar wind streams. We study how such plasma structures alter the variation of the SEP peak intensities with heliocentric radial coordinate and how the energy spectrum of an impulsive SEP event changes as a function of space and time. Both the peak intensities and the energy spectrum are affected by such non-nominal solar wind conditions, since particles can e.g., be accelerated near converging plasma flows characterizing compression regions, or the particle can be efficiently decelerated in an adiabatic manner in the strongly diverging flows characterizing rarefaction regions. In addition, particle intensities will increase (decrease) near compression (rarefaction) regions, as a consequence of the underlying magnetic field topology. Finally, we study to what extent interplanetary shock waves can generate energetic particles, either through a re-acceleration process of SEPs emitted during a previous impulsive event, or by directly accelerating particles from the supra-thermal solar wind tail. 8 Investigating the evolution and interactions of the September 2017 CME events with EUHFORIA Scolini, C et al. p-Poster Camilla Scolini[1,2], Luciano Rodriguez[2], Manuela Temmer[3], Mateja Dumbovic[3,4], Jingnan Guo[5,6], Emilia Kilpua[7], Jens Pomoell[7], Stefaan Poedts[1] [1]KU Leuven, Leuven, Belgium [2]SIDC, Royal Observatory of Belgium, Uccle, Belgium [3]University of Graz, Graz, Austria [4]University of Zagreb, Zagreb, Croatia [5]University of Kiel, Kiel, Germany [6]University of Science and Technology of China, Hefei, China [7]University of Helsinki, Helsinki, Finland 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 solar wind and CME propagation 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. 9 Multiple EUV wave reflection from a coronal hole Podladchikova, T et al. p-Poster Tatiana Podladchikova[1], Astrid M. Veronig[2,3], Olena Podladchikova[4], Karin Dissauer[2], Bojan Vrsnak[5], Jonas Saqri[2], Isabell Piantschitsch[2], Manuela Temmer[2] [1] Skolkovo Institute of Science and Technology, Moscow, Russia, [2] Institute of Physics, University of Graz, Austria, [3] Kanzelhöhe Observatory of Solar and Environmental Research, University of Graz, Austria, [4] Solar-Terrestrial Centre of Excellence, Royal Observatory of Belgium, [5] Hvar Observatory, Faculty of Geodesy, University of Zagreb, Croatia 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 1300 km/s (transmitted wave), while the other one moves back toward the AR (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. 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. 10 Bayesian analysis of flaring probabilities using the effective connected magnetic field strength Paouris, E et al. p-Poster Evangelos Paouris[1], Athanasios Papaioannou[1], Anastasios Anastasiadis[1], Manolis K. Georgoulis[2,3], Ioannis Kontogiannis[4], Piers Jiggens[5] [1]Institute for Astronomy, Astrophysics, Space Applications & Remote Sensing, National Observatory of Athens, Penteli, Greece, [2]Research Center for Astronomy of the Academy of Athens, Athens, Greece, [3]Department of Physics & Astronomy, Georgia State University, USA, [4]Leibniz-Institute for Astronomy, Potsdam, Germany, [5]European Space Agency, European Research and Technology Center, Netherlands The effective connected magnetic field strength (Beff) is a useful proxy which has been successfully implemented as a predictor of the solar flare occurrence in the past (e.g. A-Effort, FORSPEF, FLARECAST). In the current work, the line-of-sight (LOS) Beff values for each active region (AR) of the period 09/2012-12/2018 were calculated using SHARP magnetograms from HMI/SDO data, obtained through the FLARECAST property-service. During this time period, 421 ARs were spotted producing 3916 C-class, 381 M-class and 20 X-class solar flares. Additionally, the Bayesian conditional flaring cumulative probabilities for warning time windows of 6, 12, 24, 48 and 72 hours ahead of the current time, with condition contingent to the Beff predictor threshold have been calculated. As a next step, a double sigmoidal fit was applied, making it possible to infer the flaring probabilities for C1.0 up to X10.0+ classes of solar flares for each given value of Beff. Furthermore, such calculations are possible in near real time when using SHARP magnetograms. This analysis was successfully incorporated as a prediction module in the Advanced Solar Particle Events Casting System (ASPECS) system. This work was supported by the project "PROTEAS II" (MIS 5002515), which is implemented under the Action "Reinforcement of the Research and Innovation Infrastructure", funded by the Operational Programme "Competitiveness, Entrepreneur- ship and Innovation" (NSRF 2014–2020) and co-financed by Greece and the European Union (European Regional Development Fund). This work partially supported through the ESA Contract No 4000120480/17/NL/LF/hh "Solar Energetic Particle (SEP) Advanced Warning System (SAWS)". 11 Long-term evolution of coronal holes and associated co-rotating interaction regions Jercic, V et al. p-Poster Veronika Jercic[1], Stephan G. Heinemann[1], Manuela Temmer[1], Mateja Dumbovic[1], Susanne Vennerstroem[2], Giuliana Verbanac[3], Stefan J. Hofmeister[1], Astrid M. Veronig[1] [1]Institute of Physics, University of Graz, Austria, [2]Institute of Astrophysics and Atmospheric Physics, Technical University of Denmark, Denmark, [3]Faculty of Science, Department of Geophysics, University of Zagreb, Croatia Between 2010 and 2015 we investigate a sample of eight well-observed persistent coronal holes with life spans of 5--12 solar rotations. We aim to increase our understanding of the formation and evolution of CHs, as well as to investigate the basic physical mechanisms that govern the CH behaviour over its lifetime. By combining EUV filtergrams from AIA/SDO and line of sight magnetograms from HMI/SDO, we derive a set of coronal hole parameters including area, intensity, and magnetic field characteristics as function of time. Using in-situ data from ACE measured near L1, we study the corresponding solar wind plasma properties. We find, based on the evolutionary pattern of the CH area, that the evolution of CHs can be divided into two types, regular ones revealing a steady area increase followed by a decrease - and irregular ones with no obvious pattern in the area evolution. For the two evolutionary phases of regular type CHs we find differences in the correlation between area and the maximum in-situ measured proton bulk velocities of the associated high-speed streams. We derive a strong correlation in the growing (Pearson cc=0.72) and a moderate one in the decaying phase (Pearson cc=0.55). The CH area is strongly related to the number of (strong) flux tubes and the magnetic field strength of the CH with their percentual coverage of the CH area. This supports the previous findings of strong flux tubes being the key elements in governing the evolution of CHs. 12 Genesis, magnetic morphology and impulsive evolution of the fast CME associated with the X8.2 flare on 2017 September 10 Veronig, A et al. p-Poster Astrid M. Veronig[1], Tatiana Podladchikova[2], Karin Dissauer[1], Manuela Temmer[1], Daniel B. Seaton[3,4], David Long[5], Jingnan Guo[6], Bojan Vrsnak[7], Louise Harra[5], Bernhard Kliem[8] [1] Institute of Physics & Kanzelhöhe Observatory, University of Graz, Austria, [2] Skolkovo Institute of Science and Technology, Moscow, Russia, [3] Cooperative Institute for Research in Environmental Science, University of Colorado at Boulder, CO, USA, [4] National Centers for Environmental Information, National Oceanic and Atmospheric Administration, Boulder, CO, USA [5] UCL-Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, UK, [6] Institut für Experimentelle und Angewandte Physik, University of Kiel, Germany, [7] Hvar Observatory, Faculty of Geodesy, University of Zagreb, Croatia, [8 ]Institute of Physics and Astronomy, University of Potsdam, Germany 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). The associated SEP event was the first GLE observed on the surface of two planets, Earth and Mars (Guo et al. 2018). Combining the high-cadence and large field-of-view imagery from GOES-16/SUVI and SDO/AIA EUV, 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. The much higher radial propagation speed of the flux rope as compared to the CME shell causes a substantial deformation of the white-light CME front and shock in the form of a faster moving bulge. Such local inhomogeneities have important implications for space weather forecasts, as they pose additional difficulties in the prediction of the CME arrival time and speed at Earth. 14 Extended white-light reconstruction and MHD modeling of the 2010 April 3 CME De koning, C et al. p-Poster Curt A de Koning[1] and Dusan Odstrcil[2] [1]University of Colorado, [2] George Mason University Typically, white-light analysis of coronagraph data is used to estimate the CME leading-edge speed, direction of propagation, and half-width. In our extended analysis of the 2010-04-03 event, we also estimate the CME mass, the duration of the CME, the trailing-edge speed, and the post-eruption speed. Furthermore, we use polarimetric reconstruction to estimate the size, location, tilt, and morphological chirality of the CME's flux rope. We use these observations to initiate a data-driven Enlil run that includes both the mass and magnetic component of this CME. We will highlight issues, especially epistemic uncertainty related to the CME magnetic-field inputs, associated with a data-driven Enlil simulation that depends on white-light observations. 15 Solar flare parameters: evidence for lognormal rather than power law distributions Verbeeck, C et al. p-Poster Cis Verbeeck[1], Emil Kraaikamp[1], Daniel F. Ryan[2], Olena Podladchikova[1] [1]Royal Observatory of Belgium, [2]NASA Goddard Space Flight Center In many statistical solar flare studies, power laws are claimed and exponents derived by fitting a line to a log-log histogram. It is well-known that this approach is statistically unstable, and very large statistics are needed to produce reliable exponent estimates. This may explain part of the observed divergence in power law exponents in various studies. Moreover, the question is seldom addressed to which extent the data really do support power law behavior. We perform a comprehensive study of 6,924 flares detected in SDO/AIA 9.4 nm images by the Solar Demon flare detection software between 2010 May 13 and 2018 March 16, and 9,601 flares detected during the same period in GOES/XRS data by the LYRAFF flare detection software. We apply robust statistics to the SDO/AIA 9.4 nm peak intensity and the GOES/XRS raw peak flux, background-subtracted peak flux, and background-subtracted fluence, and find clear indications that all background-corrected data are better described by a lognormal distribution than by a power law, while the raw GOES/XRS peak flux is best described by a power law. This may explain the success of power law fits in flare studies using uncorrected data. The behavior of flare parameter distributions has important implications for large-scale science questions such as coronal heating and the nature of solar flares. The apparent lognormal character of flare parameter distributions in our data sets suggests that the assumed power law nature of flares and its consequences need to be re-examined with great care. 16 Long-term evolution of the solar corona using PROBA2 data Mierla, M et al. p-Poster Marilena Mierla[1,2], Elke D’Huys[1], Jan Janssens[1], Laurence Wauters[1], Matthew J. West[1], Daniel B. Seaton[3], David Berghmans[1], Elena Podladchikova[1] [1]Solar-Terrestrial Centre of Excellence - SIDC, Royal Observatory of Belgium, [2]Institute of Geodynamics of the Romanian Academy, Bucharest, Romania, [3]Cooperative Institute for Research in Envionmental Sciences, University of Colorado, Boulder, Colorado, U.S.A. We are using the PROBA2/SWAP images to study the evolution of the large-scale structures of the solar corona observed in the EUV during solar cycle 24 (from 2010 to 2019). We discuss the evolution of the corona on-disk and at different heights above the solar surface. We also look at the evolution of the corona in equatorial and polar regions and compare them at different phases of the solar cycle, as well as with the sunspot number evolution and with the PROBA2/LYRA signal. 17 Numerical Simulations of Shear-Induced Consecutive Coronal Mass Ejections Talpeanu, D et al. p-Poster Dana-Camelia Talpeanu[1,2], Stefaan Poedts[1], Elke D'Huys[2], Skralan Hosteaux[1], Marilena Mierla[2,3], Ilia Roussev[4,1] [1] CmPA, KU Leuven, Belgium, [2] SIDC, Royal Observatory of Belgium, [3] Institute of Geodynamics of the Romanian Academy, Bucharest, Romania, [4] Division of Atmospheric and Geospace Sciences – Directorate of Geosciences - National Science Foundation, Arlington, Virginia, USA Coronal Mass Ejections (CMEs) are huge expulsions of magnetized plasma from the Sun into the interplanetary medium. A particular class of CMEs are the so-called stealth CMEs, i.e., solar eruptions that are clearly distinguished in coronagraph observations, but don’t have a clear source signature. Observational studies show that there is a specific subset of stealth CMEs that occur in the trail of a preceding eruption, whose solar origin could be identified. In order to determine the triggering mechanism for these stealth CMEs, we are using the MPI-AMRVAC code developed at KU Leuven. We simulate consecutive CMEs ejected from the southernmost part of an initial configuration constituted by three magnetic arcades embedded in a globally bipolar magnetic field. The first eruption is driven through shearing motions at the solar surface. The following eruption is a stealth CME resulting from the reconnection of the coronal magnetic field. Both CMEs are expelled into a bimodal solar wind. We analyse the parameters that contribute to the occurrence of the second CME. We obtain 3 different eruption scenarios and dynamics by varying the shearing speed with only 1%. The difference between the 3 cases consists in the characteristics of the second CME, which can be a failed eruption, a stealth CME, or a CME with a traceable source. Additionally, the dynamics and evolution are compared for the 3 cases, and with a similar multiple CME event that occurred between 21-22 Sept. 2009, obtaining a good height-time correlation. 18 Diagnostic of transverse temperature distribution in coronal fan, using 3-min oscillations Kaufman, A et al. p-Poster Anastasiia Kaufman, Sergey Anfinogentov, Andrei Afanasyev [1,2] Institute os Solar-Terrestrial Physics, [3] Katholieke Universiteit Leuven We investigate the possibility of applying slow MHD waves for the diagnostic of transverse temperature distribution in coronal fans associated with sunspots. We investigate multi-temperature EUV observations of slow MHD waves in coronal fans to discriminate between two possible temperature distributions in coronal fans: hot core - cold background, and cold core - hot background. Due to the complex line of sight effects, the interpretation of the EUV imaging observations of coronal structures is a challenging task. To determine the influence of the transverse temperature distribution in coronal fans to the EUV observations of propagating slow MHD waves, we use the forward modelling approach. We modeled slow MHD waves propagating upwards in a coronal fan with two different temperature distributions: hot core - cold background, and cold core - hot background. The numerical MHD simulations have been performed with the use of the Lare2D MHD code. The modelling results are then used to produce synthetic SDO/AIA images at 171 Å and 193 Å with the FoMo forward modelling code. Next, we calculate apparent delays between the oscillations seen in 171 Å and 193 Å channels. We found that this delay can be either positive (the wave firstly appears in 171 Å) or negative for both temperature distribution types, but the dependence of this delay upon the distance from the foot-point is different. The apparent delay decreases with the distance for the “cold core” distribution and increases for the “hot core” model. We perform the same measurements for real observation of 3 minutes oscillations in coronal fans in three active regions, and found that all of them support the “hot core” model. This work was supported by the Russian Foundation for Basic Research, project 18-32-00540 mol\_a. 19 Evolution of torsion in the active region NOAA12673 during the X9.3 flare Liliana, D et al. p-Poster Liliana Dumitru, Cristiana Dumitrache Astronomical Institute of Romanian Academy We study the evolution of torsion in the active region NOAA12673 during the X9.3 flare as computed by two NLFFF codes. The coronal magnetic field is extrapolated by Lee code and Valori code, computing also the alpha force-free field parameter. We compare the two results. 20 Solar north - south asymmetry and its connection with the geomagnatic activity Murakozy, J et al. p-Poster Judit Muraközy Research Centre for Astronomy and Earth Sciences Konkoly Thege Miklós Astronomical Institute One of the well-known phenomena of the solar dynamo is the hemispheric asymmetry of the solar cycles. This means that the magnetic activities of the two hemispheres are different on middle and long timescales, i.e. during four Schwabe cycles the progress of the northern hemispheric activity precedes the southern one, while in the next four cycles the southern cycle takes over the preceding role. The interplanetary magnetic field (IMF) formed by the outward solar wind. The present study intends to show how the solar-hemispheric predominance affects the interplanetary and geophysical magnetic field. The interplanetary and geophysical data sets have been chosen from various sources such as the components of the interplanetary magnetic field [B], cosmic-ray data, Ap, aa, and Dst geomagnetic indices, while the solar-hemispheric asymmetry has been examined by using sunspot data from Greenwich Photoheliographic Results (GPR) and Debrecen Photoheliographic Data (DPD). 21 2-D Monte Carlo simulations of particle transport in a structured interplanetary space Vainio, R et al. p-Poster Alexandr N. Afanasiev[1], Rami Vainio[1], Nasrin Talebpour Sheshvan[1] [1]University of Turku, Finland Relativistic particle events are observed during periods of high solar activity, when the interplanetary magnetic field often contains various magnetic structures, e.g. interplanetary coronal mass ejections. Ground level enhancements and long–duration gamma-ray events are well-known examples of such phenomena. In order to understand where and how particles are accelerated in these events, one needs a proper transport model that accounts for the presence of magnetic structures. We have developed a 2-D Monte Carlo simulation model that solves Parker’s equation for an analytically prescribed model of structured interplanetary magnetic field. We present first results of the modeling for an impulsive source of particles. 22 Towards a better understanding of the Magnetic field of Coronal Magnetic Eruptions (CMEs) Al-haddad, N et al. p-Poster Nada Al-Haddad[1], Stefaan Poedts[2], Teresa-Nieves Chinchilla[1,3], Noé Lugaz[4], Charles Farrugia[4] [1]IACS-Catholic University of America, [2]CmPA- KU Leuven, [3] NASA GSFC, [4]EOS-University of New Hampshire Understanding the magnetic field structure of Coronal Magnetic Eruptions (CMEs) has always been a challenging problem. This is due to multiple reasons: a) the limitation of measurements and observations, b) the inconsistencies in the outcome of fitting techniques, c) the idealized perception of the structure of CMEs’ magnetic field (i.e. perfectly twisted flux rope), among others. In this work we use multiple approaches to tackle the magnetic field of CMEs: 1. Using numerical simulations to understand the radial evolution of CMEs with different magnetic field structures. 2. Examining the local configurations of structurally-different CMEs using synthetic multi-spacecraft measurements. 3. Analyzing the magnetic field for a particularly defined group of CMEs “Simple CMEs”. 23 Modeling the quasi-steady background solar wind with data-driven physics-based models. Pinto, R et al. p-Poster R. F. Pinto, M. Lavarra, L. Griton, A. Rouillard, A. Kouloumvakos, N. Poirier IRAP, Université de Toulouse III, CNRS, CNES, Toulouse, France The quasi-steady solar wind flow is a key component of space weather, being the source of corotating density structures that perturb planetary atmospheres and affect the propagation of impulsive perturbations (such as CME). Fast and slow wind streams develop at different places in the solar atmosphere, reflecting the global distribution of the coronal magnetic field during solar cycle and its consequences for heat and mass transport across the corona. I will present recent advances on global solar wind simulations that provides robust and fully physics-based predictions of the structure and physical parameters of the solar wind based on a multi-1D approach (MULTI-VP, ISAM). Such advances relate to driving the models with time-dependant magnetogram data, to including of transient heating phenomena, and to switching from a fluid to a multi-species description of the solar wind. The simulations produce a large range of synthetic observables (e.g multi-spacecraft in-situ measurements, white-light and EUV imagery) meant to be compared to data from current and future missions (e.g Solar Orbiter and Parker Solar Probe), and to establish physical connections between remote observation of the solar surface and corona and the interplanetary medium. 24 Decoding the origin and the role of suprathermal populations in a non-equilibrium solar wind plasma Lazar, M et al. p-Poster Marian Lazar[1,2], Viviane Pierrard[3,4], Stefaan Poedts[1] [1]CMPA, K.U. Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium, [2]Theoretische Physik, Ruhr-University Bochum, D-44780 Bochum, Germany, [3]Royal Belgian Institute for Space Aeronomy, B-1180 Brussels, Belgium, [4]Universit\' e Catholique de Louvain (UCL), B-1348 Louvain-La-Neuve, Belgium Suprathermal particle populations (electrons, protons or heavier ions) with energy up to few keVs are ubiquitous in the solar wind and are therefore expected to have multiple implications, conditioning the non-equilibrium plasma states and triggering highly energetic events, like flares, coronal mass ejections (CMEs) or interplanetary shocks, with direct consequences on space weather, planetary environments and our terrestrial climate and technologies. The huge amount of kinetic (free) energy released by the solar outflows accumulates at micro- and macroscopic scales leading to suprathermal populations and kinetic anisotropies of plasma particles, e.g., temperature anisotropies, (counter-)beaming populations, which are at the origin of instabilities and enhanced wave fluctuations. In collision-poor plasmas from space the main mechanisms of dissipation or relaxation are mainly controlled by the wave-particle interactions, and our recent results prove a direct and significant interdependence between suprathermal populations and wave fluctuations in the solar wind. Thus, suprathermals are consequence of these interactions, by energizing and pitch-angle scattering of plasma particles, but at the same time, suprathermals trigger both spontaneous and stimulated emissions and entertain a certain level of wave fluctuations in the solar wind and planetary environments. 25 Multi-point Measurements of Solar Eruptions at Locations Throughout the Heliosphere García broock, E et al. p-Poster Elena Broock[1], Matthew J West[2], Marilena Mierla[2] , Elena Podladchikova[2] [1]Universidad de La Laguna, Spain, [2]Royal Observatory of Belgium Kinematic studies of coronal mass ejections (CMEs) are very relevant given their space weather implications. The more we know how CMEs propagate from the Sun to the Earth, the better we will be able to predict events like geomagnetic storms well in advance, and to minimize their impact. In this work, data from different instruments and satellites were used to track CMEs. A high activity period with STEREO-A and STEREO-B virtually on the plane of Sun’s limbs from the Earth perspective was selected for the study. Flares on the limb of the Sun from STEREO satellites or Earth perspective were followed, from close to the Sun to higher up in the corona. For each tracked event, velocity is derived, arrival time to the spacecraft is calculated and the corresponding in-situ data is discussed.