Session 10 - ICME and SEPs throughout the Heliosphere: multi-spacecraft observations and data-driven modeling

Jingnan Guo (Univ of Kiel); Christian Moestl (Space Research Centre Graz); Mateja Dumbovic (Univ of Zagreb); Nina Dresing (Univ of Kiel); Markus Battarbee (Univ of Central Lancashire)
Thursday 30/11, 9:45 - 13:00
Mercator


KEYWORDS - ICMEs, SEPs, multi-point observations, data-driven modeling

Simultaneous measurement of ICMEs and SEPs at multiple locations (e.g., the Earth, STEREOs, Moon, Mercury, Mars, Rosetta, Voyager, and so on) has ushered in an era where it is possible to study space weather events as they propagate and evolve through the heliosphere. Their propagation properties, spatial and temporal evolution and their arrival times at different locations can be derived from these multi-point measurements. Such studies can benefit from various data-based MHD models and transport tools, and in turn increase their value through validation. This session aims to bring together the observation and modelling communities and focus on employing multi-point measurements to study interplanetary solar events and their evolution in the heliosphere.

Poster Viewing
From Thursday morning to Friday noon

Talks
Thursday November 30, 09:45 - 11:00, Mercator
Thursday November 30, 11:45 - 13:00, Mercator

Click here to toggle abstract display in the schedule

Talks : Time schedule

Thursday November 30, 09:45 - 11:00, Mercator

09:45	Statistical methods for the optimal planning of multi spacecraft missions to monitor space weather.	Lapenta, G et al.	Invited Oral
	G. Lapenta[1], M. E. Innocenti[1], C. Skandrani[2], F. Crespon[2], J. Lamouroux[2]
	[1]Center for Mathematical Plasma Astrophysics, Department of Mathematics, KULeuven – University of Leuven, Celestijnenlaan 200B, bus2400, 3001 Leuven, Belgium; [2]NOVELTIS, Space and Remote Sensing Department, Space Weather Unit, rue du Lac 153, 31670 Labège, France
	Space weather is a strongly driven system where the Sun is the primary driver of most of what happens in the solar system (with some notable exception as for example the moons of gas giant planets having a strong impact on their magnetospheres). The typical model of heliospheric space weather evolution in the heliosphere requires to follow the evolution of a number of state variables (e.g. density, temperature, magnetic field) in a very large grid of points covering the portion of interest of the solar system. These models are driven by the information we have on the solar sources which includes visual information on the state of the photosphere and corona as well as the measured magnetic field. Empirical models and field lines extrapolations also supplement this information with our best guess of the sources of the solar wind. The model predictions can then be tested for a handful of locations with specifically dedicated missions: primarily ACE and DISCOVR as well as other solar-dedicated missions like Stereo, Soho, but also magnetospheric missions who spend part of their time in the solar wind: CLUSTER, THEMIS, MMS and others. For Earth mangetopheric modelling, the main driver is the data from ACE (or DISCOVER but on specific events it can also be Cluster, MMS or THEMIS when they are in the solar wind) to be tested against other missions that are inside the magnetosphere and can observe consequences that have been modelled such as depolarisation fronts or electron jets. For all these models there is a mind blowing disparity between the internal degrees of freedom of the model with the input data. For example, in our coupled MHD-PIC model of the Earth magnetosphere [1-3], we use hundred of billions of particles and millions of grid points. What data drives the system? Three quantities: the solar wind density, temperature, velocity and magnetic field, all together 8 real numbers known with a significant error bar. The question is how reliable is a model with trillions of internal degrees of freedom constrained by only 8 real numbers? And given the limited foreseeable funding for future missions, where can we position new missions to give us other sets of 8 numbers taken from measurements elsewhere to maximise the accuracy and reliability of our models? Data assimilation into forecasting models has the ability to control model state errors. We report a sensitivity study performed through the analysis of the ensemble variances and the representers technique [4] is used here to assess how process and model state errors propagate in a nonlinear MagnetoHydro Dynamic (MHD) system. The aim is to understand the impact of the input parameters on the evolution of MHD heliospheric models and the potentialities of data assimilation techniques in solar wind forecasting. The representer technique in fact allows one to understand how far from the observation point the improvement granted from the assimilation of a measure propagates. The outcome of the study is an indication of where it is most fruitful to locate additional measurement points to maximise the impact on the accuracy of the models. This can in turn provide planning information for future missions. [1] Ashour‐Abdalla, M., Lapenta, G., Walker, R. J., El‐Alaoui, M., & Liang, H. (2015). Multiscale study of electron energization during unsteady reconnection events. Journal of Geophysical Research: Space Physics, 120(6), 4784-4799. [2] Lapenta, G., Ashour‐Abdalla, M., Walker, R. J., & El Alaoui, M. (2016). A multiscale study of ion heating in Earth's magnetotail. Geophysical Research Letters. [3] Lapenta, G., Berchem, J., Zhou, M., Walker, R. J., El‐Alaoui, M., Goldstein, M. L., ... & Strangeway, R. J. (2017). On the origin of the crescent‐shaped distributions observed by MMS at the magnetopause. Journal of Geophysical Research: Space Physics, 122(2), 2024-2039. [4] Skandrani, C., Innocenti, M. E., Bettarini, L., Crespon, F., Lamouroux, J., & Lapenta, G. (2014). FLIP-MHD-based model sensitivity analysis. Nonlinear Processes in Geophysics, 21(2), 539-553.
10:09	Statistical Properties of the 20 Largest SEP Events	Zheng, Y et al.	Oral
	Yihua Zheng[1], Mary Aronne[2]
	[1]NASA Goddard Space Flight Center, Space Weather Laboratory, Greenbelt, MD 20771, USA; [2]University of Maryland Baltimore County, USA
	In this paper, we will provide statistical results of the 20 largest SEP events from radiation impact perspective. The 20 SEP events occurred from 1981 to 2006 where a 20-day interval of very high SEP fluences were detected. Flares, CMEs and associated active regions for each of the 20 event intervals will be analyzed, along with energy spectra properties by taking advantage of multi-spacecraft and ground observations. We aim to locate any feature(s) that could lead to improved forecasting capabilities of such SEP events.
10:26	Long-lasting solar energetic electron injection during the 26 Dec 2013 widespread SEP event	Heber, B et al.	Oral
	N.Dresing[1], A. Klassen[1], B. Heber[2], R. Gómez-Herrero[2], M. Temmer[3] and A. Veronig[3]
	[1]Institut für Experimentelle und Angewandte Physik, University of Kiel, D-24118, Kiel, Germany; [2]Dpto. de Física y Matemáticas, Universidad de Alcalá, E-28871 Alcalá de Henares, Madrid, Spain; [3]Institute of Physics/Kanzelhöhe Observatory, University of Graz, A-8010 Graz, Austria
	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, requiring an extended electron injection. The remote-sensing observations reveal a CME-CME interaction during the early phase of the SEP event which might play an important role for providing the extended SEP injection. Four hours after the onset of the event a second component is measrued at all three viewpoints on top of the first SEP increase, mainly consisting of high energy particles. We discuss 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.
10:43	Why is solar cycle 24 an inefficient producer of high-energy particle events?	Vainio, R et al.	Oral
	Rami Vainio[1], Osku Raukunen[1], Allan J. Tylka[2], William F. Dietrich[3], Alexandr Afanasiev[1]
	[1]Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland; [2]Emeritus, NASA Goddard Spaceflight Center, Greenbelt, MD 20771, USA; [3]Consultant, Prospect Heights, IL 60070, USA
	We investigate the reason for the low productivity of high-energy SEPs in the present solar cycle. We employ scaling laws derived from diffusive shock acceleration theory and simulation studies including proton-generated upstream Alfvén waves to find out how the changes observed in the long-term average properties of the erupting and ambient coronal and/or solar wind plasma would affect the ability of shocks to accelerate particles to the highest energies. Provided that self-generated turbulence dominates particle transport around coronal shocks, it is found that the most crucial factors controlling the diffusive shock acceleration process are the number density of seed particles and the plasma density of the ambient medium. Assuming that suprathermal populations provide a fraction of the particles injected to shock acceleration in the corona, we show that the lack of most energetic particle events as well as the lack of low charge-to-mass ratio ion species in the present cycle can be understood as a result of the reduction of average coronal plasma and suprathermal densities in the present cycle over the previous one.

Thursday November 30, 11:45 - 13:00, Mercator

11:45	Creating an index for Solar Energetic Particle (SEP) events using multivariate analysis	Papaioannou, A et al.	Oral
	A. Papaioannou[1], A. Anastasiadis[1], M. Paassilta[2], R. Vainio[2], E. Valtonen[2], A. Kouloumvakos[1], A. Belov[3], E. Eroshenko[3], V. Yanke[3], M. Abunina[3], A. Abunin[3]
	[1]Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS), National Observatory of Athens, I. Metaxa & Vas. Pavlou St., GR-15236, Penteli, Greece; [2]Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland; [3]Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation by N.V. Pushkov RAS (IZMIRAN), Moscow Troitsk, Russia
	Solar Energetic Particle (SEP) events and their parent solar events (e.g. solar flares - SFs and coronal mass ejections - CMEs) are closely related. A wealth of statistical studies has indicated the dependence of the probability of occurrence of SEP events on the magnitude and the longitude of the SF, as well as the velocity and the width of the CME. However, most studies are limited to two dimensional correlations. In addition, similar coefficients are identified for the pair-wise correlation of the SEP peak intensity (at E>10 MeV) to both the SF magnitude and the CME speed. The situation is further complicated by the fact that the solar parameters are not independent. In this work, we perform a principal component analysis (PCA) on a set of six (6) solar variables (i.e. CME width and velocity, logarithm of the SF magnitude, SF longitude, duration and rise time), in order to create an index for the possible prediction of SEP events. In our analysis, we utilize 126 SEP events with complete solar information. Each SEP event is a vector in six dimensions (corresponding to the six solar variables used in this work). PCA transforms the input vectors into a set of orthogonal components. The PCA of the variables yielded a first principal component (PC1) that accounted for the 33% of the variance in the data, and a second component (PC2) accounted for another 26% leading to a cumulative 59%. The variables that significantly load (e.g. with a weight of ≥ 0.3) on PC1 are the SF duration and rise time, and on PC2 the velocity and width of the CME, as well as, the logarithm of the SF magnitude. We present and interpret the resulted score and loading plots that characterize the observations in our data set. The resulting index from the six variable PCA is further tested against its relation to the occurrence of the SEP events. Acknowledgement: This work was funded from the State Scholarships Foundation of Greece (I.K.Y.) under the contract No 2016-050-0503-7338, in the framework of: "Funding Post-doctoral Researchers" (MIS:5001552) of the b.p.: "Human Resources Development, Education and Lifelong Learning" from ESPA (2014-2020). AA would further like to acknowledge the "SPECS: Solar Particle Events and foreCasting Studies” research grant of the National Observatory of Athens
12:02	Interplanetary coronal mass ejection observed at STEREO-A, Mars, comet 67P/Churyumov-Gerasimenko, Saturn, and New Horizons en-route to Pluto. Comparison of its Forbush decreases at 1.4, 3.1 and 9.9 AU	Mays, M et al.	Invited Oral
	Olivier Witasse[1], Beatriz Sanchez-Cano[2], M.Leila Mays[3], Primoz Kajdic[4], Hermann Opgenoorth[5], Heather Elliott[6], Ian Richardson[3]
	[1]ESA-ESTEC Netherlands; [2]University of Leicester UK; [3]NASA-Goddard US; [4]Universidad Nacional Autonoma de Mexico; [5]Swedish Institute of Space Physics; [6]Southwest Research Institute, TX, US
	We discuss observations of the journey throughout the Solar System of a large interplanetary coronal mass ejection (ICME) that was ejected at the Sun on 14 October 2014. The ICME hit Mars on 17 October, as observed by the Mars Express, MAVEN, Mars Odyssey and MSL missions, 44 hours before the encounter of the planet with the Siding-Spring comet, for which the space weather context is provided. It reached comet 67P/Churyumov-Gerasimenko, which was perfectly aligned with the Sun and Mars at 3.1 AU, as observed by Rosetta on 22 October. The ICME was also detected by STEREO-A on 16 October at 1 AU, and by Cassini in the solar wind around Saturn on the 12 November at 9.9 AU. Fortuitously, the New Horizons spacecraft was also aligned with the direction of the ICME at 31.6 AU. We investigate whether this ICME has a non-ambiguous signature at New Horizons. A potential detection of this ICME by Voyager-2 at 110-111 AU is also discussed. The multi-spacecraft observations allow the derivation of certain properties of the ICME, such as its large angular extension of at least 116°, its speed as a function of distance, and its magnetic field structure at four locations from 1 to 10 AU. Observations of the speed data allow two different solar wind propagation models to be validated. Finally, we compare the Forbush decreases (transient decreases followed by gradual recoveries in the galactic cosmic ray intensity) due to the passage of this ICME at Mars, comet 67P and Saturn.
12:26	Forbush Decreases and Interplanetary Coronal Mass Ejections at Earth and Mars	Lester, M et al.	Oral
	Mark Lester[1], Beatriz Sanchez-Cano[1], Emma Thomas[1], Adam Langeveld[1], Jingnan Guo[2], Hermann Opgenoorth[3]
	[1]University of Leicester; [2]University of Kiel; [3]Instutute for Space Physics, Uppsala
	It is well established that Interplanetary Coronal Mass Ejections (ICMEs) cause rapid decreases in the galactic cosmic ray flux at the surface of Earth. These are known as Forbush decreases. In this paper we present a study of Forbush decreases both in orbit about, and at the surface of Earth and Mars using data from the Bartol neutron monitor, the ACE spacecraft, Mars Science Laboratory (MSL) and Mars Odyssey. The objective of this study is to demonstrate that the signatures of Forbush decreases at Mars in the MSL and Mars Odyssey data sets are the same as at Earth. This will enable these data sets to be used both as past as well as future indicators of ICMEs at Mars. We focus on a 2 year period, 2012 – 2014, during which the two planets moved from being in alignment with the Sun, to being on opposite sides of the Sun, and then back to an aligned position. We also discuss the in situ observations at Mars during a sub set of events to investigate the impact of ICMEs at Mars during this increasing phase of the solar cycle.
12:43	CME dynamics using STEREO and LASCO observations: relative importance of Lorentz forces and solar wind drag	Sachdeva, N et al.	Oral
	Nishtha Sachdeva[1], Prasad Subramanian[1], Angelos Vourlidas[2], Volker Bothmer[3]
	[1]Indian Institute of Science Education and Research, Pune, India; [2]Applied Physics Laboratory, United States; [3]University of Göttingen, Institute of Astrophysics, Germany
	Hot, massive blobs of plasma and magnetic fields, called Coronal Mass Ejections (CMEs) are major contributers of disturbances in the near- Earth environment, sometimes causing disruptions to space-bound tech- nologies as well. Space weather predictions are therefore, crucially de- pendent on accurate understanding and modeling of the CME structure and propagation dynamics. Forces that affect CME propagation include, aerodynamic drag and driving Lorentz forces. The heliocentric distances at which these dominate is still unclear. Depending on how slow or fast a CME is travelling (with respect to the ambient solar wind), the CME is “picked up” or “dragged down” by the solar wind. The Lorentz forces are thought to be effective very early on. In our work, we attempt to quantify the relative contributions of the driving Lorentz forces and aero- dynamic drag acting on CMEs. In doing so we appeal to Torus Instabil- ity model and drag based model. With the availability of extensive data from STEREO & LASCO observations we reconstruct the 3D geometrical flux-rope structure of a set of 38 CMEs using the Graduated Cylindrical Shell Model (GCS; Thernisien et al., 2009; Thernisien, 2011). We use a microphsyical model for computing the solar wind aerodynamic drag and find that the Drag-based models typically succeed only if they are initiated at heliocentric distances as large as 12–50 $R_{\odot}$ (in case of slow CMEs) (Sachdeva et al., 2015). We find that the Lorentz forces generally peak between 1.65 and 2.35 $R_{\odot}$ for all CMEs. For fast CMEs, Lorentz forces become negligible in comparison to aerodynamic drag as early as 3–4 $R_{\odot}$. For slow CMEs, however, they become negligible only by 12–50 $R_{\odot}$. For these slow events, our results suggest that some of the magnetic flux might be expended in CME expansion or heating. In other words, not all of it contributes to directed propagation. Combining the effects of these two forces, our results are expected to be important in building a comprehensive physical model for understanding the Sun-Earth dynamics of CMEs.

Posters

1	Solar energetic electron events during solar cycles 23 and 24	Samwel, S et al.	p-Poster
	Susan Samwel[1], Rositsa Miteva[2], Marcus Costa-Duarte[3]
	[1]National Research Institute of Astronomy and Geophysics (NRIAG), 11421 Cairo, Egypt; [2]Space Research and Technology Institute – Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria; [3]Institute of Astronomy, Geophysics and Atmospheric Sciences - University of São Paulo, 05508-090 SP, Brazil
	In the present study, a new catalog of solar electron events along the solar cycle 23 and the rising half of the solar cycle 24, detected by ACE/DE instrument is given. We collected and analyzed the observed in situ electron data for two energy channels; 103-175 KeV and 175-315 KeV. The onset time, peak time and intensity are evaluated. The characteristic quantities of the associated solar events, namely, solar flares and coronal mass ejection, are identified using timing arguments. A statistical analysis is performed using both Pearson and partial correlation methods in order to identify the relationships between the properties of the electron events and the associated solar events. This catalog is considered as a first comprehensive electron catalog during the interval 1997-2016. It can be used by both solar and space weather communities and is considered essential for models that are used to predict the particle events.
2	Multi-spacecraft observations and transport simulations of solar energetic particles for the May 17th 2012 ground level event	Battarbee, M et al.	p-Poster
	Markus Battarbee[1,4], Jingnan Guo[2], Silvia Dalla[1], Robert Wimmer-Schweingruber[2], Bill Swalwell[1], David J. Lawrence[3]
	[1]Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE, Preston, UK; [2]Institut fuer Experimentelle und Angewandte Physik, University of Kiel, Germany; [3]Johns Hopkins University Applied Physics Laboratory, MD, USA; [4]Currently at department of Physics, University of Helsinki, Finland
	The injection, propagation and arrival of solar energetic particles (SEPs) is an important and current research topic of heliospheric physics. During the largest solar events, particles may have energies up to a few GeVs and trigger ground-level enhancements (GLEs) at Earth. These large SEP events are best investigated through multi-spacecraft observations. We present our study of the May 17th 2012 solar eruption, using data from multiple spacecraft (SOHO, GOES, MSL, STEREO-A, STEREO-B and MESSENGER). We investigate proton time profiles at several energy channels between 12 and 200 MeV, obtained via instruments aboard the above spacecraft. We present results of three-dimensional SEP propagation simulations, gathering virtual time profiles and performing qualitative and quantitative comparisons with observations. We investigate issues due to magnetic connectivity, and distinguish different time profile shapes for well-connected and weakly connected observers. At select observers, we identify additional low-energy components of Energetic Storm Particles (ESPs). Using well-connected observers for normalisation, we show that our simulations are able to accurately recreate both time profile shapes and peak intensities at multiple observer locations. Our novel analysis provides valuable proof of the ability to simulate SEP propagation throughout the inner heliosphere, at a wide range of longitudes. This synergetic approach combining numerical modeling with multi-spacecraft observations is crucial for understanding the propagation of SEPs within the inner heliosphere.
3	Cosmic ray modulation by ICME-driven shocks	Vrsnak, B et al.	p-Poster
	Anamarija Kirin[1], Bojan Vršnak[2], Mateja Dumbović[3], Bernd Heber[4], Slaven Lulić[1]
	[1]Karlovac University of Applied Sciences; [2]Hvar Observatory Faculty of Geodesy Zagreb; [3]Institute of Physics University of Graz; [4]Institut für Experimentelle und Angewandte Physik Christian-Albrechts-Universität zu Kiel
	Forbush decreases are decreases in the cosmic ray count rate which last typically for about a week, and were first reported by Scott E. Forbush in 1937. They can be caused by corotating interaction regions (CIRs) or interplanetary coronal mass ejections (ICMEs). We study modulation of cosmic ray flux in the downstream region (so called “sheath region”) of ICME-driven oblique fast-mode magnetohydrodynamical shocks, where magnetic field contains components both parallel and normal to the shock front. In particular, we consider two effects: magnetic mirror at the shock and the convective compression of the downstream region. Magnetic mirror effect decreases the particle flux, while compression increases it. Since the magnetic mirror effect is stronger, the flux in the downstream region is smaller than in the upstream region. The results can be applied to CIRs too. The calculated flux decreases have somewhat larger amplitudes than observed, indicating that other mechanisms, like, e.g., diffusion, play a significant role too.
4	Using Forbush decreases to derive the transit time of ICMEs propagating from 1 AU to Mars	Freiherr von forstner, J et al.	p-Poster
	Johan L. Freiherr von Forstner[1],Jingnan Guo[1],Robert F. Wimmer-Schweingruber[1],Donald M. Hassler[2, 3],Manuela Temmer[4],Mateja Dumbović[4],Lan K. Jian[5, 6],Jan K. Appel[1],Jaša Čalogović[7],Bent Ehresmann[2],Bernd Heber[1],Henning Lohf[1],Arik Posner[8],Christian T. Steigies[1],Bojan Vršnak[7],Cary J. Zeitlin[9]
	[1]Institute of Experimental and Applied Physics, University of Kiel, Germany; [2]Southwest Research Institute, Boulder, Colorado, USA; [3]Institut d'Astrophysique Spatiale, University Paris Sud, Orsay, France; [4]Institute of Physics, University of Graz, Austria; [5]University of Maryland, College Park, Maryland, USA; [6]NASA Goddard Space Flight Center, Greenbelt, MD, USA; [7]Hvar Observatory, Faculty of Geodesy, University of Zagreb, Croatia; [8]NASA Headquarters, Washington, DC, USA; [9]Leidos, Houston, Texas, USA
	The propagation of 15 interplanetary coronal mass ejections (ICMEs) from Earth's orbit (1 AU) to Mars ($\sim$ 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 rays measured on-ground. We have used galactic cosmic ray (GCR) data from in-situ measurements at Earth, from both STEREO A and B as well as GCR measurements by the Radiation Assessment Detector (RAD) instrument onboard Mars Science Laboratory (MSL) on the surface of Mars. 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 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.
5	The analytical diffusion-expansion model for Forbush decreases caused by flux ropes	Dumbovic, M et al.	p-Poster
	Mateja Dumbovic, Manuela Temmer
	Institute of Physics, University of Graz
	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.
6	Unusual cosmic ray intensity variations during the last solar cycles	Lingri, D et al.	p-Poster
	Athanasios Smponias, Ioannis Lytrosyngounis, Evangelia Samara, Dimitra Lingri, Helen Mavromichalaki
	Faculty of Physics, National and Kapodistrian University of Athens, 15784 Athens, Greece
	During the maximum and the declining phase of the last two solar cycles, a number of extreme events characterized by rather peculiar properties takes place. Dynamic phenomena related to solar flares and coronal mass ejections (CMEs) dominate the heliosphere in the most profound way resulting to large variations in cosmic ray intensity up to energies of at least 10 GeV. Specifically, during the maximum and declining phase of solar cycles 23 and 24 a new type of cosmic ray variations has been observed. It is characterized by a deep decrease of the cosmic ray intensity with a complicated shape and an intermediate large increase recorded by neutron monitors during a non significant disturbance of the solar wind. Right after the main phase of the Forbush decrease, an enhancement of cosmic ray intensity is registered only to be followed by a second decrease within less than one day. Such events occurred for example on 9 November 2004, on 16 July 2005, on 21 December 2014 and on 22 June 2015. Especially, on the complex event of December 2014 three different Forbush decreases have been observed. These events encountered with another type of inconsistency related to a western source and they differ from the events of eastern origin by greater anisotropy. They occur significantly rarer, characterized as a definite sub-class of Forbush decreases. Analysis of such events testifies that the cosmic ray variations are able to give us the information on sufficiently complicated heliospheric phenomena. Such events are worthy of special attention and individual studying.
7	Precursor signals on Forbush decreases of cosmic ray intensity without shock	Lingri, D et al.	p-Poster
	Dimitra Lingri[1], Helen Mavromichalaki[1], Anatoly Belov[2], Eugenia Eroshenko[2], Maria Abunina[2]
	[1]Faculty of Physics, National and Kapodistrian University of Athens, 15784 Athens, Greece; [2]Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAS (IZMIRAN), Moscow, Russia
	Forbush decreases of the cosmic ray intensity are produced either from a sudden solar eruption, as a CME or from a high speed solar wind stream that comes from the Sun as a result for example of a coronal hole. The first events, in the most cases, are connected with a sudden storm commencement (SSC) that reaches the Earth and creates a Forbush decrease at the cosmic ray intensity. The second ones can also create Forbush decreases of smaller amplitude but without the appearance of a SSC. In this study the Forbush decreases that do not orientate by a SSC are studied for the last five solar cycles where cosmic ray intensity data recorded at the neutron monitors are available (1964-2016). These data have been taken from the IZMIRAN database for Forbush effects. An analysis of Forbush decreases that follow this criterion with solar and interplanetary associated parameters will be performed, as it is crucial to know the conditions of the interplanetary environment before the appearance of each cosmic ray decrease. Finally, from the 33 events that follow the above criteria, the possibility of observing precursory signals before the beginning of these Forbush decreases without a shock wave will be examined.
8	Tracking the evolution of solar storms in interplanetary space through the identification of Forbush decreases at Earth and at Mars	Papaioannou, A et al.	p-Poster
	A. Papaioannou[1,2], A. Anastasiadis[1], J. Guo[3], A. Belov[4], E. Eroshenko[4], A. Abunin[4], M. Abunina[4]
	[1]Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS), National Observatory of Athens, I. Metaxa and Vas. Pavlou St., GR-15236, Penteli, Greece; [2]Nuclear and Particle Physics Department, Faculty of Physics, National and Kapodistrian University of Athens, 15784 Athens, Greece; [3]Christian-Albrechts-Universitaet zu Kiel, Leibnizstrasse 11, 24118 Kiel, Germany; [4]Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), 42092 Troitsk, Moscow Region, Russia
	During their travel from the Sun to Earth, coronal mass ejections (CMEs) and their interplanetary (IP) counterparts (interplanetary coronal mass ejections, ICMEs) interact with Galactic cosmic rays (GCRs) that fill the IP space. The leading shock wave of the ICME (if any) and the following ejecta modulate GCRs, which results in a reduction in the cosmic ray (CR) intensity, known as the Forbush decrease (FD). On the other hand, high-speed streams (HSS) from coronal holes (CHs) rotate with the Sun, forming Corotating Interaction Regions (CIRs). These can also modulate GCRs and result to FDs. Although, there are observational differences between the FD events of each category - based on the different underlying physical mechanisms, one should keep into account that quite often this distinct categorization is not valid and probably not appropriate. In this work we present FD events that have been recorded at Earth by neutron monitors and at Mars by the Radiation Assessment Detector (RAD) instrument on the Mars Science Laboratory (MSL). We discuss the observational evidence at hand using in-situ plasma measurements from Wind, ACE and MAVEN trying to shed light to the physical mechanisms involved at each case.
9	Modeling observations of solar coronal mass ejections with heliospheric imagers verified with the Heliophysics System Observatory	Moestl, C et al.	p-Poster
	C. Möstl[1,2], A. Isavnin[3], P. D. Boakes[1,2], E. K. J. Kilpua[3], J. A. Davies[4], R. A. Harrison[4], D. Barnes[4,5], V. Krupar[6], J. P. Eastwood[7], S. W. Good[7], R. J. Forsyth[7], V. Bothmer[8], M. A. Reiss[2], T. Amerstorfer[1], R. M. Winslow[9], B. J. Anderson[10], L. C. Philpott[11], L. Rodriguez[12], A. P. Rouillard[13,14], P. Gallagher[15], T. Nieves-Chinchilla[16] and T. L. Zhang[1]
	[1]Space Research Institute, Austrian Academy of Sciences, Graz, Austria; [2]IGAM-Kanzelhöhe Observatory, Institute of Physics, University of Graz, Austria; [3]Department of Physics, University of Helsinki, Helsinki, Finland; [4]RAL Space, Rutherford Appleton Laboratory, Harwell, Oxford, UK; [5]University College London, UK; [6]Institute of Atmospheric Physics CAS, Prague, Czech Republic; [7]The Blackett Laboratory, Imperial College London, London, UK; [8]Institute for Astrophysics, University of Göttingen, Göttingen, Germany; [9]Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, USA; [10]The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA; [11]Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada; [12]Solar–Terrestrial Center of Excellence – SIDC, Royal Observatory of Belgium, Brussels, Belgium; [13]Institut de Recherche en Astrophysique et Planétologie
	We present results from the HELCATS project concerning the arrival of CMEs, with modeling based on a single-spacecraft heliospheric imager validated with multipoint in situ observatories. The databases we have created, available via http://helcats-fp7.eu should be of great value for studying the propagation of SEPs and for other projects such as FLARECAST. Here, we validate modeling results of 1337 CMEs observed with the Solar Terrestrial Relations Observatory (STEREO) heliospheric imagers (HI) (science data) from 8 years of observations by 5 in situ observing spacecraft. We use the self-similar expansion model for CME fronts assuming 60 degree longitudinal width, constant speed and constant propagation direction. With these assumptions we find that 23%-35% of all CMEs that were predicted to hit a certain spacecraft lead to clear in situ signatures, so that for 1 correct prediction, 2 to 3 false alarms would have been issued. In addition, we find that the prediction accuracy does not degrade with the HI longitudinal separation from Earth. Predicted arrival times are on average within 2.6 ± 16.6 hours difference of the in situ arrival time, similar to analytical and numerical modeling, and a true skill statistic of 0.21. We also discuss various factors that may improve the accuracy of space weather forecasting using wide-angle heliospheric imager observations. These results form a first order approximated baseline of the prediction accuracy that is possible with HI and other methods used for data by an operational space weather mission at the Sun-Earth L5 point.
10	Modelling Solar Energetic Particle Propagation in 3D Heliospheric Solar Wind Conditions	Wijsen, N et al.	p-Poster
	Nicolas Wijsen[1], Angels Aran[2], Stefaan Poedts[1], Jens Pomoell[3]
	[1]Centre for mathematical Plasma Astrophysics, Department of Mathematics, K.U.Leuven; [2]Dep. Física Quàntica i Astrofísica, Institut de Ciències del Cosmos, Universitat de Barcelona; [3]Department of Physics, University of Helsinki
	Solar energetic particles (SEPs) are electrons, protons and heavy ions originating from solar eruptive events. These particles can be energised at solar flare sites during magnetic reconnection events, or in shock waves propagating in front of coronal mass ejections (CMEs). These CME-driven shocks may be powerful accelerators of charged particles throughout their propagation in the solar corona and interplanetary medium. After escaping from their acceleration site, SEPs propagate through the heliosphere following the interplanetary magnetic field and may eventually reach our planet where they can disrupt the microelectronics on satellites in orbit and endanger astronauts among other effects. Therefore it is of vital importance to understand and thereby build models capable of predicting the characteristics of SEP events. The propagation of SEPs in the heliosphere can be described by the time-dependent focused transport equation. This five-dimensional parabolic partial differential equation can be solved using e.g., a finite difference method or by integrating a set of corresponding first order stochastic differential equations. In this work we take the latter approach to model SEP events under different solar wind and scattering conditions. First we present the results of the model when using a nominal interplanetary magnetic field for fast and slow solar wind configurations. We discuss the differences when modelling the transport of particles assuming pitch angle scattering and perpendicular diffusion conditions. We also show the resulting intensity-time profiles when including the adiabatic deceleration and solar wind convection effects on the transport of particles. Next we use a realistic solar wind from a 3D MHD simulation using the EUHFORIA model to focus on exploring the influence of high speed solar wind streams originating from coronal holes that are located close to the eruption source region on the resulting particle characteristics at Earth. Finally, we discuss our upcoming efforts towards integrating our particle propagation model with time-dependent heliospheric MHD space weather modelling.