Session 4 - The role of Interplanetary Coronal Mass Ejections in Space Weather

Luciano Rodriguez (ROB); Sergio Dasso (IAFE/UBA)
Tuesday 28/11, 9:45 - 13:00
Delvaux


KEYWORDS - ICME, Interplanetary Coronal Mass Ejections, space weather, in situ data

Interplanetary Coronal Mass Ejections (ICMEs) are the main drivers of large geomagnetic storms. Their influence on space weather is a topic of intense research. In recent years, multispacecraft observations and high performance numerical MHD simulations have contributed largely to this field. The comparisons between models and observations are clarifying several problems, such as the effects of the ambient solar wind on their propagation and internal configuration, the link between ICMEs and non-thermal energetic particles in the heliosphere (solar, interplanetary, and galactic origin), etc. In this session we invite contributions focused on ICME studies, including ICME propagation in the heliosphere, the interaction of ICMEs with Earth and/or with other planets, the link between CMEs and ICMEs, their relation with energetic particles, as well as on other general topics linked with ICMEs.

Poster Viewing
From Monday noon to Wednesday morning

Talks
Tuesday November 28, 09:45 - 11:00, Delvaux
Tuesday November 28, 11:45 - 13:00, Delvaux

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Talks : Time schedule

Tuesday November 28, 09:45 - 11:00, Delvaux

09:45	EUHFORIA: Current Status and Path Towards Modeling the Evolution of the Magnetic Structure of Coronal Mass Ejections	Pomoell, J et al.	Invited Oral
	Jens Pomoell[1], Christine Verbeke[2], Eleanna Asvestari[1], Camilla Scolini[2,3], Stefaan Poedts[2], Emilia Kilpua[1], Manuela Temmer[4], Nicolas Wijsen[2], Erkka Lumme[1], Alexey Isavnin[1], Erika Palmerio[1], Jasmina Magdalenic[3]
	[1]University of Helsinki, Finland; [2]KU Leuven, Leuven, Belgium; [3]Royal Observatory of Belgium, Belgium; [4]University of Graz, Austria
	Unraveling the formation and evolution of coronal mass ejections (CMEs) from the Sun to Earth remains one of the outstanding goals in current solar-terrestrial physics and space weather research. In particular, capturing the dynamical evolution of the magnetic field configuration of CMEs from initiation to in-situ detection is of key importance in order to advance the accuracy of predictions of geo-effectiveness. Providing accurate and routine modeling of the Sun-to-Earth evolution of flux rope CMEs using EUHFORIA is the main focus of the current development effort of the model. EUHFORIA is a magnetohydrodynamics model that computes the dynamics in the inner heliosphere from 0.1 AU up to the orbit of Mars. The model uses data-driven methodologies relying mainly on photospheric magnetograms and coronagraph observations to capture the dynamic solar wind including coronal mass ejections. In this work, the current status of EUHFORIA is presented. In addition, we highlight on-going work to advance beyond the baseline in the modeling pipeline. In particular, the path towards using magnetized CMEs in the model is discussed.
10:15	Probabilistic model for heliospheric propagation of Interplanetary Coronal Mass Ejections: Drag-based ensemble model (DBEM)	Dumbovic, M et al.	Oral
	Mateja Dumbovic[1], Jasa Calogovic[2], Bojan Vrsnak[2], Manuela Temmer[1], Astrid Veronig[1], Leila M. Mays[3]
	[1]Kanzelhöhe Observatory-IGAM, Institute of Physics, University of Graz; [2]Hvar Observatory, Faculty of Geodesy, University of Zagreb; [3]NASA Goddard Space Flight Center
	The drag-based model (DBM) for heliospheric propagation of ICMEs is a widely used simple analytical model which can predict ICME arrival time and speed at a given heliospheric distance (Vršnak et al., 2013, SolPhys). It is based on the assumption that the heliospheric propagation of ICMEs, is solely under the influence of MHD drag, where ICME propagation is determined based on CME properties as well as the properties of the ambient solar wind. The current version of the DBM is operational as part of ESA’s SSA programme (http://swe.ssa.esa.int/web/guest/graz-dbm-federated). The DBM takes into account the ICME geometry to track the whole leading edge of an ICME, and can estimate whether or not an ICME will reach the observer, and if, when and at what impact speed. However, there is a lack of uncertainty estimation for a single event, which can be established using an ensemble modeling approach. We present a newly developed Drag-Based Ensemble Model (DBEM) which takes into account the uncertainties of observation-based model input by making an ensemble, i.e. sets of n CME observations and m synthetic measurements of ambient solar wind speed and drag parameter. Using multiple model runs with different input parameters, DBEM calculates a distribution of predicted arrival times and speeds allowing to forecast the confidence in the likelihood of the ICME arrival.
10:30	Forecasting the arrival time of the CME’s shock at the Earth	Paouris, E et al.	Oral
	Evangelos Paouris, Helen Mavromichalaki
	Faculty of Physics, National and Kapodistrian University of Athens
	A new model obtained from an extended study of the ICME’s properties and applied for the estimation of the arrival time of the CME’s associated shock at the Earth, is presented. This model is based on the Effective Acceleration Model-EAM (Paouris and Mavromichalaki, Solar Physics, 2017) where the acceleration of the CME is calculated by its initial speed, as it is observed by LASCO/SOHO coronagraphs and then taking into account the distance of the Earth from the Sun, the arrival time of the shock as well as the velocity of the CME at L1 (v), are calculated. This technique has been applied to selected events of the last time period and the results are discussed. It is already used by the Athens Space Weather Forecasting Center of the University of Athens for the forecasting of the geomagnetic conditions useful for the issued daily space weather report. This model is also available to the CME scoreboard at the Community Coordinated Modeling Center – CCMC for comparison with other related models.
10:45	Observations and Simulations of the Sun to Earth Evolution of a STEREO-Era Set of Earth-Impacting CMEs and their In Situ Magnetic Field	Kay, C et al.	Oral
	Christina Kay, Nat Gopalswamy
	NASA Goddard Space Flight Center Code 671
	Coronal mass ejections (CMEs) drive extreme space weather events throughout the solar system. Predicting the effects of a CME impact requires knowing not only if a CME will impact a given point, but also which part of the CME impacts, and what its magnetic properties are upon impact. We explore the relation between CME deflections and rotations, which change the position and orientation of a CME, and the resulting magnetic profiles at 1 AU. For 45 STEREO-era, Earth-impacting CMEs, we determine the region from which each CME erupts, reconstruct its coronal position and orientation, and perform a ForeCAT (Kay et al. 2015) simulation of the coronal deflection and rotation. From this large set of reconstructed and modeled CME deflections and rotations, we determine variations in the behavior over the solar cycle as well as correlations with CME properties. We then couple the ForeCAT results with the FIDO in situ magnetic field model (Kay et al. 2017), allowing for comparisons with ACE and Wind observations. FIDO successfully reproduces the in situ magnetic field for all but three of the CMEs. From random walk best fits, we distinguish between ForeCAT's ability to determine FIDO's input parameters, and the limitations of using a simple flux rope model to reproduce complicated in situ structures. We find that the FIDO results are quite sensitive to changes of order a degree in the CME latitude, longitude, and tilt, suggesting that accurate space weather predictions require accurate measurements of a CME's position and orientation.

Tuesday November 28, 11:45 - 13:00, Delvaux

11:45	LOFAR Observations of the Full Passage of a CME	Fallows, R et al.	Oral
	Richard Fallows[1], Mario Bisi[2], Golam Shaifullah[1], Caterina Tiburzi[3] and Gemma Janssen[1]
	[1]ASTRON - the Netherlands Institute for Radio Astronomy; [2]Rutherford Appleton Laboratory; [3]MPIfR/Bielefeld University
	Interplanetary scintillation (IPS – the scintillation of compact radio sources due to density variations in the solar wind) enables the determination of solar wind speed and estimates of solar wind density throughout the inner heliosphere. Several observations using the Low Frequency Array (LOFAR - a radio telescope centred on the Netherlands with stations across Europe) have been undertaken using this technique to observe the passage of CMEs across various points in interplanetary space. In particular, a set of long-duration observations taken over two days sought to observe the full passage, from nose to prominence material, of a CME which launched from the Sun on 28th April 2015: Current analyses suggest that the full passage was indeed observed, with the CME taking approximately 12 hours to fully pass over the line of sight in an observation lasting 15 hours, representing one of very few occasions in which this has been achieved in observations of IPS. Measurement of the strength and direction of the magnetic field within CMEs as they pass through interplanetary space remains something of a “holy grail” for space weather forecasting. One of the only methods by which this could be achieved is via the observation of heliospheric Faraday rotation in the polarised signal from either a polarised radio source or a Galactic polarised background. This is a challenging measurement which is only remotely possible using a LOFAR-type instrument. An observation of a pulsar was also taken in association with this CME to attempt measurement of the Faraday rotation due to it’s passage. Here, we will present the latest results from these observations.
12:00	The properties of CMEs embedded in extreme solar wind	Cid, C et al.	Oral
	Consuelo Cid, Judith Palacios, Antonio Guerrero, Elena Saiz, Yolanda Cerrato
	Universidad de Alcala
	The role of CMEs in space weather is undeniable, specifically for intense geomagnetic activity. But for triggering a geomagnetic storm, first the CME has to reach the terrestrial environment being observed as an ICME. In this case the bulk speed and southward magnetic field component play a key role in the severity of the geomagnetic storm. Other solar wind parameters, as the dynamic pressure, are also relevant in the geomagnetic disturbance. While intense geomagnetic activity is considered in terms of index scales like Dst or Kp, and intense solar activity is considered in terms of flaring activity (being the largest X-class flares), ‘extreme solar wind’ has never been defined. This communication analyzes solar wind measurements from ACE spacecraft to set the thresholds that, when overpassed during events, they can be classified as ‘extreme solar wind event’. We also analyze the role and properties of the ICMEs involved in some relevant events selected with these criteria, and their CME sources.
12:15	Quantification of disturbance periods of solar wind speed in interplanetary space due to coronal mass ejections	Temmer, M et al.	Oral
	Manuela Temmer[1], Reiss Martin A.[1], Nikolic Ljubomir[2], Hofmeister Stefan J.[1], Veronig Astrid[1]
	[1]Institute of Physics, University of Graz, Austria; [2]Canadian Hazards Information Service, Natural Resources Canada, Ottawa, Canada
	Interplanetary space is characteristically structured mainly by high-speed solar wind streams emanating from coronal holes and transient disturbances such as coronal mass ejections (CMEs). While high-speed solar wind streams pose a continuous outflow, CMEs abruptly disrupt the rather steady structure causing large deviations from the quiet solar wind conditions. We present a quantification of the duration of disturbed conditions (preconditioning) for interplanetary space caused by CMEs by investigating the plasma speed component of the solar wind and the impact of in situ detected CMEs (ICMEs), compared to different background solar wind models (ESWF, WSA, persistence model) for the time range 2011–2015. We obtain for periods within an ICME interval an increase of 18-32% above the expected quiet Sun background and for the period of 2 days after the ICME an increase of 9-24%. The total duration of enhanced deviations is about 3 and up to 6 days after the ICME start, which is much longer than the average duration of an ICME disturbance itself (about 1.3 days), concluding that interplanetary space needs about 2-5 days to recover from the impact of ICMEs. The obtained results have strong implications for studying CME propagation behavior and also for space weather forecasting.
12:30	Plasma diagnostics of CMEs via coronal dimming regions	Veronig, A et al.	Oral
	Astrid M. Veronig, Kamalam Vanninathan, Karin Dissauer, Manuela Temmer
	Kanzelhöhe Observatory & Institute of Physics, University of Graz, Austria
	Coronal Mass Ejections (CMEs) are often associated with coronal dimmings, i.e. transient dark regions in the solar corona that are most prominently observed at Extreme Ultra-violet (EUV) wavelengths. Coronal dimmings are thought to be formed by the evacuation and expansion of mass related to the erupting CME structure. Using data from the six EUV channels of the Atmospheric Imaging Assembly (AIA) onboard SDO, we apply Differential Emission Measure (DEM) diagnostics, to study the plasma characteristics of coronal dimming regions. We analysed in detail seven on-disk coronal dimming events associated with Earth-directed CMEs, distributed over a speed range from 300 to 1250 km/s. We derived the weighted emission measure, density and temperature as a function of time for both the core and the secondary dimming regions. Using co-registered magnetic field maps from the Helioseismic Magnetic Imager (HMI) onboard SDO, we also calculated the magnetic flux in the dimming regions, which is an important means to estimate the magnetic flux contained in the interplanetary CME (ICME). In the core dimming regions, the plasma parameters reached a minimum within about 30 min after the CME onset, whereas the secondary dimming regions tend to show a more gradual evolution. For most of the events, the values of these parameters remained low within the core dimming region for the entire duration of this study (~10 hrs after the flare) while the secondary dimming region showed a gradual increase after 1-2 hrs indicating refilling of these regions with plasma. The emission measure decrease in the core dimming region was found to lie in the range from 60-90%, the density decrease from 35-70% and the temperature decrease from 5-30%. In the secondary dimming region, the decreases of the plasma parameters derived are smaller. The findings of our study are discussed with respect to the different coronal structures involved in the dimming regions and how they relate to decisive parameters of the ICME.
12:45	Inferring ICME Magnetic Fields at 1 AU and Elsewhere: the H-CME Method	Georgoulis, M et al.	Oral
	Manolis K. Georgoulis[1], Spiros Patsourakos[2]
	[1]RCAAM of the Academy of Athens, Athens, Greece; [2]Physics Department, University of Ioannina, Ioannina, Greece
	We outline a statistical method to infer the near-Sun and heliospheric (axial) magnetic field of coronal mass ejections (CMEs). In spite of its statistical nature, the method applies also to specific solar eruptions provided that photospheric solar-source (active-region) information and CME geometrical properties are available. In particular, the method requires the helicity content of the CME source and the length / radius of the CME at a few solar radii. The fundamental helicity conservation principle and various CME flux-rope models then work to constrain the near-Sun CME magnetic field that is extrapolated outward in the heliosphere. A magnetic-pressure-based magnetopause compression is then estimated based on the equatorial terrestrial magnetic field. Avoiding potentially unnecessary complexity, the method (i) provides a worst-case scenario for CME geoeffectiveness and (ii) explains why Earth, otherwise subject to extreme space weather, seems not susceptible to extinction-level atmospheric erosion by extreme solar eruptions, even larger than the Carrington event. In addition, it can be generalized to stellar and exoplanet cases, affording a further - sometimes stringent - exoplanet habitability criterion.

Posters

1	Magnetic clouds and their driven shocks/sheaths near Earth: geoeffective properties studied with a superposed epoch technique	Dasso, S et al.	e-Poster
	Sergio Dasso[1,2], Jimmy Joel Masías-Meza[1], Pascal Demoulín[3], Luciano Rodríguez[4], and Miho Janvier[5]
	[1]Universidad de Buenos Aires, Buenos Aires, Argentina; [2]CONICET – Universidad de Buenos Aires. Instituto de Astronomía y Física del Espacio (IAFE), Buenos Aires, Argentina; [3]Observatoire de Paris, Meudon Principal Cedex, France; [4]Royal Observatory of Belgium, Brussels, Belgium; [5]Institut d’Astrophysique Spatiale, Orsay Cedex, France
	Magnetic Clouds (MCs) are huge interplanetary manifestations of solar eruptions. When MCs travel faster than the surrounding solar wind, the overtaken interplanetary plasma forms a sheath of heated and compressed plasma at their front. The main aim of this work is to find which are the common plasma and magnetic properties present in (and around) MCs observed near Earth. We apply a superposed epoch method to a large set of MCs observed in situ by the spacecraft ACE. We find that slow MCs at 1 AU have on average sheaths that are more massive, and we conclude that the low bulk speed of these events is mainly due to the drag (then MCs slow down during their travel from the Sun) and not due to their initial conditions near the corona. Furthermore, we find that slow MCs also have a more symmetric magnetic field profile and that their sheaths are in a self-similar expansion as the associated MC. In contrast, fast MCs have an asymmetric magnetic profile and a sheath in compression. In all the types of MCs, we find that the proton density, the temperature, and the magnetic fluctuations present in the sheath can diffuse within the front of the MC; we propose that this is a consequence of magnetic reconnection. The obtained typical profiles of sheath and MC properties corresponding to slow, middle, and fast structures, can be used for forecasting or modelling these events. They are also useful for improving future operative space weather activities.
2	Quantification of solar wind parameters from measurments by SOHO and DSCOVR spacecrafts during series of Interplanetary Coronal Mass Ejections in the helioactive period September 2-15, 2017	Mishev, A et al.	e-Poster
	Yordan Tassev[1], Peter I.Y. Velinov[1], Dimitrinka Tomova[2], Alexander Mishev[3,4]
	[1]Institute for Space Research and Technology Bulgarian Academy of Sciences Sofia, Bulgaria; [2]Sofia University “St. Kliment Ohridski” Faculty of Mathematics and Informatics Sofia, Bulgaria; [3]Space Climate Research Unit, University of Oulu, Finland; [4]Sodankyla Geophysical Observatory (Oulu unit), University of Oulu, Finland
	Serie of Interplanetary Coronal Mass Ejections (ICMEs) during extreme solar activity in early September 2017 at minimum of solar cycle 24 is analized. The origin of the intensive solar-terrestrial disturbances was the Active Region AR2673, which produced four powerful eruptions, including the strongest flare X9.3 of Solar Cycle 24 on September 6, 2017, after which began G4 - Severe geomagnetic storm on 07-08.09.2017 with Ap = 106, and also - the second strongest flare X8.2 of Solar Cycle 24 on September 10, 2017, which produced ground level enhancement of cosmic rays (GLE72). Calculations of the solar wind parameters from measurments by SOHO and DSCOVR spacecrafts in the point of Lagrange L1 between Sun and Earth (0.99 AU) are made: the kinetic (dynamic) energy density Ek, thermal energy density Et and magnetic energy density Em during the investigated period September 2-15, 2017. We found a specific distribution of the solar wind energies during and after the ICMEs. It is likely that both kinetic and magnetic energies can be used as predictors of strong geomagnetic storms.
3	Multipoint, galactic cosmic ray observations associated with a series of interplanetary coronal mass ejections: the case study of June 2015	Papaioannou, A et al.	e-Poster
	A. Papaioannou[1], B. Heber[2], A. Anastasidis[1], A. Belov[3], K. Herbst[2], E. Eroshenko[3], A. Abunin[3], M. Abunina[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]Christian-Albrechts-Universitaet zu Kiel, Leibnizstrasse 11, 24118 Kiel, Germany; [3]Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), 42092 Troitsk, Moscow Region, Russia
	Galactic cosmic rays (GCRs) fill the interplanetary (IP) space and have an important role in our understanding of the heliospheric environment. In this work, we compare, multipoint space-based and ground based GCR data to explore structures in the IP space. In particular, we look for correlations between the GCR time series observed from the Electron Proton Helium INstrument (EPHIN) aboard the SOHO and neutron monitors (NMs) on the ground. We analyze the period of June 2015 during which a sequence of coronal mass ejections (CMEs) and their corresponding interplanetary counterparts (ICMEs) fill the IP space. Those drive shocks that clearly affect the distributions of GCRs resulting to a large Forbush decrease (FD). We employ in-situ plasma and particle data as well as ground based NM measurements and we discuss the efficiency of the series of the ICMEs in modulating the GCRs.
4	Galactic cosmic rays and Forbush decreases at Mars: comparison of measurement by MAVEN in orbit and by MSL on ground	Guo, J et al.	e-Poster
	Jingnan Guo[1], Niklas Lundt[1], Rob Lillis[2], Robert F. Wimmer-Schweingruber[1], Donald M. Hassler[3], Christina Lee[2], Henning Lohf[1], Arik Posner[4], Cary Zeitlin[5]
	[1]University of Kiel; [2]Space Science Laboratory, University of California, Berkeley, USA; [3]Southwest Research Institute, Boulder, CO, USA; [4]NASA Headquarters, Science Mission Directorate, Washington DC, USA; [5]Leidos, Houston, Texas, USA
	The Radiation Assessment Detector (RAD), on board Mars Science Laboratory’s (MSL) rover Curiosity, has been measuring the ground level particle fluxes along with the radiation dose rate at the surface of Mars since August 2012. Similar to neutron monitors at Earth, RAD sees many Forbush decreases (FDs) in the galactic cosmic ray (GCR) induced surface fluxes and dose rates. These FDs are associated with coronal mass ejections (CMEs) and/or streaming/corotating interaction regions (SIRs/CIRs). On top of the Martian atmosphere, the solar energetic particle (SEP) instrument aboard of the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft orbiting Mars has also been detecting particle fluxes including both SEPs and GCRs and the high energy flux channel can also be employed to detect FDs. For the first time, we study the statistics and properties of a list of FDs observed in-situ at Mars, both on the surface seen by MSL/RAD and at the orbit detected by MAVEN/SEP. These measurements of the FD magnitudes both at ground and in orbit agree with simulation results. The consistent difference between the magnitudes of the FDs within and outside the Martian atmosphere can be attributed to energy-dependent modulation of GCR particles by both the Martian atmosphere and the varying levels of solar activity.
5	Sun-to-Earth simulations of geo-effective coronal mass ejections with EUHFORIA: A heliospheric-magnetospheric model chain approach	Scolini, C et al.	p-Poster
	Camilla Scolini[1,2], Christine Verbeke[1], Stefaan Poedts[1], Luciano Rodriguez[2], Jens Pomoell[3], William D. Cramer[4], Joachim Raeder[4], Nat Gopalswamy[5]
	[1]KU Leuven, Leuven, Belgium; [2]SIDC, Royal Observatory of Belgium, Uccle, Belgium; [3]University of Helsinki, Helsinki, Finland; [4]Space Science Center, University of New Hampshire, NH, USA; [5]NASA GSFC, Greenbelt, MD, USA
	Coronal Mass Ejections (CMEs) and their interplanetary counterparts are considered to be the major space weather drivers. An accurate modelling of their onset and propagation up to 1 AU represents a key issue for more reliable space weather forecasts, and predictions about their actual geo-effectiveness can be performed by coupling global heliospheric models to 3D models describing the terrestrial environment. In this work we perform a Sun-to-Earth comprehensive analysis of the July 12, 2012 CME with the aim of testing the space weather predictive capabilities of the newly developed EUHFORIA heliospheric model integrated with a flux-rope CME model. In order to achieve this goal, we make use of a model chain approach by using EUHFORIA outputs at Earth as input parameters for the OpenGGCM magnetospheric model. We first reconstruct the CME kinematic parameters by means of single- and multi- spacecraft reconstruction methods based on coronagraphic and heliospheric CME observations. The magnetic field-related parameters of the flux rope are estimated based on imaging observations of the photospheric and low coronal source regions of the eruption. We then simulate the event with EUHFORIA, testing the effect of the flux-rope CME model compared to the cone CME model, on simulation results at L1. We compare simulation outputs with in-situ measurements of the Interplanetary CME and we use them as input for the OpenGGCM model, so to investigate the magnetospheric response to solar perturbations. From simulation outputs we extract some global geomagnetic activity indexes and compare them with actual data records and with results obtained by the use of empirical relations. Finally, we discuss the forecasting capabilities of such kind of approach and its future improvements.
6	Modelling coronal mass ejections with EUHFORIA: Testing the effect of different shapes on predictions at 1 AU	Scolini, C et al.	p-Poster
	Camilla Scolini[1,2], Christine Verbeke[1], Stefaan Poedts[1], Jens Pomoell[3]
	[1]KU Leuven, Leuven, Belgium; [2]SIDC, Royal Observatory of Belgium, Uccle, Belgium; [3]University of Helsinki, Helsinki, Finland
	Coronal Mass Ejections (CMEs) and their interplanetary counterparts are considered to be the major space weather drivers, and an accurate modelling of their onset and propagation up to 1 AU represents a key issue for more reliable space weather forecasts. In this work we use the newly developed EUHFORIA 3D MHD heliospheric code to test the effect of different CME shapes, all based on a spherical or quasi-spherical geometry, on simulation results at different spacecraft locations at 1 AU. We take as case study an artificial CME launched on June 6, 2008, corresponding to a period of quiet solar wind conditions near Earth. We run several simulations testing different implementations of the cone model, all assuming a spherical or quasi-spherical CME shape but using different relations to define the inner boundary shape as well as the CME radius and insertion profile in the heliospheric domain. Our analysis indicates that all these parameters significantly affect simulation results, both in terms of the resulting global CME shape once inserted in the heliosphere, as well as in terms of the predicted in-situ plasma properties at 1 AU. We discuss the implication of such effects on space weather predictions, with the aim of bringing to the attention of the community the role such details may play on space weather forecasting operations.
7	Determination of diffusion coefficients of cosmic rays in the inner heliosphere	Masías meza, J et al.	p-Poster
	Jimmy Masías-Meza[1],Sergio Dasso[2]
	[1]Instituto de Astronomía y Física del Espacio (UBA-CONICET), Buenos Aires, Argentina; [2]Departamento de Ciencias de la Atmósfera y los Océanos (FCEN-UBA), Buenos Aires, Argentina
	One of the most important processes in the transport of Galactic Cosmic Rays (GCRs) is the spatial diffusion due to the presence of magnetic irregularities in the medium. In order to characterize quantitatively these processes, we perform test-particle simulations with an in-house C++ code, to calculate the mean free paths associated to spatial diffusion in the turbulent interplanetary medium. We present some verifications of our code, and present results on the determination of the GCR mean free paths as a function of the radial distance to the Sun inside the heliosphere.
8	LISA-like missions for possible space weather applications	Benella, S et al.	p-Poster
	Simone Benella
	University of Urbino "Carlo Bo" and National Institute for Nuclear Physics, Florence
	LISA Pathfinder was the mission of the European Space Agency devoted to the testing of the technology that will be placed aboard the first interferometer for gravitational wave detection in space: LISA. Second and third generation interferometers may consist of constellations of several LISA-like instruments. Diagnostics detectors devoted to the control of the environment on these satellites include particle detectors and magnetometers. The integral galactic cosmic-ray flux measured aboard LISA Pathfinder in L1 from February 18th 2016 to July 18th 2017 indicates that decreases of the cosmic-ray flux may be correlated to the transit of interplanetary magnetic structures resulting at the origin of geomagnetic storms of different intensity. The occurrence of these depressions, in case of near-real time downlink, may be used to generate alerts for geomagnetic activity. In particular, the effects of a non-recurrent Forbush decrease associated with an ICME transit on August 2nd 2016 is discussed in detail. Periodicities of recurrent galactic cosmic-ray depressions observed aboard LISA Pathfinder are also investigated with the Empirical Mode Decomposition (EMD) method.
9	Accurate estimation of the near-Sun magnetic field of coronal mass ejections	Moraitis, K et al.	p-Poster
	Kostas Moraitis[1], Etienne Pariat[1], Antonia Savcheva[2]
	[1]LESIA, Observatoire de Paris; [2]Harvard-Smithsonian Center for Astrophysics
	The geoeffectiveness of a Coronal Mass Ejection (CME) is related to the properties of its magnetic field. The proper estimation of the CME magnetic field intensity is thus crucial to space weather. One of the methods to estimate the CME magnetic field is based on magnetic helicity and its conservation property. The accuracy of the determined CME magnetic field depends then on the accurate knowledge of the value of helicity in the CME source region. The estimation of relative magnetic helicity in an active region is optimally computed in the spherical geometry, the natural coordinate system for the Sun. We present here the first method that properly computes relative magnetic helicity in spherical coordinates. The volumes considered (in the low corona) are wedge-shaped and the three-dimensional magnetic field is considered known there. The method is first tested with well-known semi-analytic force-free solutions for the magnetic field. Then, it is applied to nonlinear force-free reconstructions of the magnetic field of a solar active region, where a flux-rope is first inserted and then it is relaxed magnetofrictionally to force-free state. From the change in helicity during the evolution of the eruption, the CME magnetic field is deduced and then it is compared with the known characteristics of the inserted flux rope. We find that the improved helicity calculation method has the potential to lead to proper estimations of the near-Sun CME magnetic field.
10	First-principles simulations of magnetic reconnection within the solar environment	Boella, E et al.	p-Poster
	E. Boella, D. Gonzalez-Herrero, M. E. Innocenti and G. Lapenta
	Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
	Fully understanding magnetic reconnection in the solar corona constitutes a fundamental step towards the correct modeling and subsequent forecasting of space weather events relevant for Earth. Kinetic simulations are essential in advancing our comprehension of a phenomenon whose macroevolution is determined by tiny microscopic scales \cite{Bemporad}. Their importance is even more significant considering the fact that no direct observations are possible since the intrinsic scales of reconnection are smaller than the resolution of the current instruments. The Particle-In-Cell (PIC) method \cite{PIC}, due to the reduced number of physical approximation, is the perfect tool to perform first-principles simulations of magnetic reconnection in the solar corona. However, as it models physics at a microscopic level, it is computationally demanding, especially when the aim is to study a process like reconnection, which spans over a multitude of time and spatial scales. Very recently, we have developed an efficient new PIC algorithm, which has been proven to be tremendously stable and accurate over a wide range of temporal and spatial resolutions \cite{Lapenta}, thus enabling the first (to the authors' knowledge) realistic three-dimensional kinetic simulations of magnetic reconnection in the solar corona. In this talk, we are going to describe the main steps that led to this great breakthrough and report the implementation of the method on a new massively parallel three-dimensional PIC code, called ECsim \cite{Lapenta2}. The new approach is then used to model realistic reconnection events in the solar environment, considering a large domain sufficient to describe the interaction of large scale dynamics with microscopic processes. In particular, the evolution of a macroscopic current sheet, with width much larger than the ion skin depth, is investigated, proving the occurrence of fractal reconnection \cite{Taijima}. Results show the formation of magnetic islands of smaller sizes at different spatial scales inside the macroscopic current sheet leading to turbulent reconnection and thus providing a possible explanation about the difference between the much bigger observed and theoretically estimated thickness of current sheets in the solar corona. \begin{thebibliography}{99} \bibitem{Bemporad} A. Bemporad, Astrophys. J. \textbf{689}, 572 (2008). \bibitem{PIC} \vspace{-8pt} J. M. Dawson, Rev. Mod. Phys. \textbf{55}, 403, (1983); C. K. Birsdall and A. B. Langdon, \textit{Plasma physics via computer simulation}, McGraw-Hill Book Company, 1985; R. Hockney and J. Eastwood, \textit{Computer simulation using particles}, Taylor and Francis, 1988. \bibitem{Lapenta}\vspace{-8pt} G. Lapenta, J. Comput. Phys. \textbf{334}, 349 (2017). \bibitem{Lapenta2}\vspace{-8pt} G. Lapenta, D. Gonzalez-Herrero and E. Boella, J. Plasma Phys. \textbf{83} (2017). \bibitem{Taijima}\vspace{-8pt} T. Taijima and K. Shibata, \textit{Plasma Astrophysics}, Reading: Addison-Wesley (1997). \end{thebibliography}
11	Comparison between EUHFORIA and ENLIL: CME on September 4, 2010	Mierla, M et al.	p-Poster
	Marilena Mierla[1,2], Camilla Scolini[3], Leila Mays[4], Jens Pomoell[5], Luciano Rodriguez[1]
	[1]Royal Observatory of Belgium, Brussels, Belgium; [2]Institute of Geodynamics of the Romanian Academy, Bucharest, Romania; [3]Center for mathematical Plasma Astrophysics, KU Leuven, Belgium; [4]NASA/GSFC, USA; [5]University of Helsinki, Department of Physics, Finland
	In this study we aim to compare two CME propagation MHD codes (ENLIL, Odstrcil et al. 1999 and EUHFORIA, Pomoell et al. 2017) by applying them to the same coronal mass ejection (CME) of September 4, 2010. The CME could be followed all the way from the Sun to the STEREO-A spacecraft, where it arrived on September 7, 2010. Comparison of the results obtained with the two models is presented.
12	Analysis of the magnetic field fluctuations during a substorm	Kozak, L et al.	p-Poster
	Liudmyla Kozak[1,2], Bogdan Petrenko[1], Elena Kronberg[3], Elena Grigorenko[4], Antony Lui[5], Andrew Prokhorenkov[1]
	[1]Kyiv Taras Shevchenko University, Kyiv, Ukraine; [2]Space Research Institute National Academy of Sciences of Ukraine and State Space Agency of Ukraine, Kyiv, Ukraine; [3]Max Planck Institute for Solar System Research, Göttingen, Germany; [4]Space Research Institute, Russian Academy of Sciences, Moscow, Russia; [5]Applied Physics Laboratory, Laurel, Maryland, United States
	The Earth’s magnetosphere is the nonlinear dynamical system, which shows a complex behavior in response to the changes of the solar wind conditions. One of the major displays of the magnetospheric dynamics is a substorm. Turbulence is the natural state of the hydrodynamic flows and cosmic plasma; therefore, studying its characteristics is essential for the understanding of the fundamental properties of nature. In magnetohydrodynamics, the properties of turbulence can be dramatically affected both by flow boundaries and the scales of the structures (waves, vortices, etc.) formed by magnetic and electric fields. The turbulence of plasma flows can be generated by many classes of instabilities: drift dissipative, kinetic, magnetohydrodynamic, etc. In addition, the turbulence is characterized by a large number of degrees of freedom and nonlinearly interacting modes. Scientists typically use statistical physics and the theory of probability to describe such a medium. This way they can obtain information about average variations in the macroscopic parameters of the plasma medium in time (or space) without scrutinizing the conditions of excitation of specific nonlinear processes. In this work, we address the features of turbulent processes in the magnetospheric tail. We analyzed the properties of the small-scale turbulence in the near Earth environment. We use measurements of the space mission Cluster, spacecraft 2 with time resolution 22,5 Hz during magnetic field dipolarization for the analysis of turbulent processes in the tail of the Earth's magnetosphere. We consider four events (17.10.2005, 20.07.2013, 12.08.2014, 12.09.2015). In the frame of the investigation fractal and multifractal research methods were supplemented with spectral and wavelet analysis. In particular, we have carried out the following: analysis of tails and evolution on different scale of the probability density function of magnetic field fluctuations (fractal analysis); Determination of excess and analysis of expanded self-similarity ESS-analysis (multifractal analysis); Spectral power density analysis (spectral studies); Amplitude analysis and wavelet power spectra of the signal (wavelet analysis). The work is done in the frame of the grant Az. 90 312 from the Volkswagen Foundation («VW-Stiftung»).
13	Validation of Drag-Based Ensemble Model (DBEM): probabilistic model for heliospheric propagation of CMEs	Calogovic, J et al.	p-Poster
	Jaša Čalogović[1], Mateja Dumbović[2], Bojan Vršnak[1], Manuela Temmer[2], Leila M. Mays[3], Astrid Veronig[2]
	[1]Hvar Observatory, Faculty of Geodesy, Kačićeva 26, HR-10000 Zagreb, Croatia; [2]Institute of Physics, University of Graz, Universitätsplatz 5, A-8010 Graz, Austria; [3]Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
	The Drag-based Model (DBM) is a simple empirical model for heliospheric propagation of Coronal Mass Ejections (CMEs). It is based on the equation of motion that depends on the CME launch speed, background solar wind speed and CME mass and density (gamma parameter). The model predicts the CME arrival time and speed at Earth or any other targets in the solar system. However, the main problem of empirical and numerical models (e.g. ENLIL) is the lack of reliable observations that are needed for the model input. This can induce a large error in the CME arrival time (−1.7 $\pm$ 18.3 h; Vršnak et al., 2014) when observations and DBM forecasts are compared. The main advantage of DBM is its very fast computational time (<< 1s). This allows an ensemble modeling approach to provide a probabilistic forecasting of CME arrival time and speed within several minutes compared to numerical models that would need several hours (e.g., ENLIL). The Drag-Based Ensemble Model (DBEM) takes into account the variability of model input parameters by making an ensemble of n different input parameters to calculate a distribution and significance of DBM results. Using such approach DBEM can determine most likely CME arrival times and speeds, quantify the prediction uncertainties and calculate the forecast confidence intervals. We present the DBEM output and compare it to the observed ICME arrival times at Earth as well as to the numerical ENLIL model output using the list of ICME events.