Session 4 - Flares, coronal mass ejections and solar energetic particles: Space Weather Impact
Kamen Kozarev (Smithsonian Astrophysical Observatory), Luciano Rodriguez (ROB), Nicole Vilmer (LESIA), Neus Agueda (Universitat de Barcelona), Sergio Dasso (IAFE/UBA), Manolis Georgoulis (Academy of Athens), Olga Malandraki (National Observatory of Athens)
Monday 14/11, 17:00-18:30
Mercator
Tuesday 15/11, 10:00-13:00
Delvaux
Flares, Coronal Mass Ejections (CMEs) and their interplanetary counterparts (ICMEs) remain topics of important research in the field of solar-terrestrial relations. Flares can have an important impact (UV radiation, particles) on the Earth's atmosphere. Recent remote observations and modeling studies have shown that coronal mass ejections (CMEs) can drive shock waves very low in the solar corona, which, in turn, may produce significant fluxes of solar energetic particles (SEP). Interplanetary Coronal Mass Ejections (ICMEs) are the main drivers of large geomagnetic storms.
In this session, we invite observational, theoretical, and modeling contributions that address the following topics: Particle acceleration at flares as well as the response of the lower ionosphere to a variety of external forcing during flares, such as energetic particles and solar UV and X-ray variability. The coronal dynamics of CME and shocks, the related early production of SEPs, as well as their magnetic connectivity and early-stage transport in the heliosphere. 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. Other general topics linked with flares, CMEs and ICMEs.
Poster ViewingTuesday November 15, 10:00 - 11:00, Poster Area Talks Monday November 14, 17:00 - 18:30, Mercator Tuesday November 15, 11:00 - 13:00, Delvaux Click here to toggle abstract display in the schedule
Talks : Time scheduleMonday November 14, 17:00 - 18:30, Mercator| 17:00 | Formation of Geoeffective Structures in Interplanetary Coronal Mass Ejections | Kilpua, E et al. | Invited Oral | | | Emilia Kilpua | | | Department of Physics, University of Helsinki | | | Formation of Geoeffective Structures in Interplanetary Coronal Mass Ejections and Their Sheath Regions
Transformation of coronal mass ejections (CME) to their interplanetary counterparts is one of the outstanding questions in solar-terrestrial studies.
In this talk I will discuss the multipart ICME structure, including different layers in their sheath regions, based on a comprehensive set of in-situ measurements. The focus will be on how different ICME and sheath sub-structures form and evolve, either already during the launch of the CME or during the processes related to the interplanetary propagation and interactions. In addition, I will discuss how various in-situ ICME structures correspond different white-light CME features in remote-sensing observations and their potential in driving space weather disturbances.
| | 17:22 | The physical mechanisms that trigger coronal mass ejections | Zuccarello, F et al. | Invited Oral | | | Francesco P. Zuccarello[1,2], Guillaume Aulanier[2] | | | [1]Centre for mathematical Plasma-Astrophyisc, KULeuven; [2]LESIA, Observatoire de Paris | | | Solar filaments are magnetic structures often observed in the solar atmosphere and consisting of plasma that is cooler and denser than their surroundings. They are visible for days – and even weeks – which suggests that they are often in equilibrium with their environment before erupting, resulting in flares and associated coronal mass ejections (CMEs).
When a CME lifts-off a huge amount of magnetized plasma it is ejected from the Sun into the interplanetary medium, eventually resulting in hazardous space weather conditions.
After introducing the theoretical background of the different CME’s initiation models I will review the results of recent numerical magnetohydrodynamic simulations aimed to determine the physical mechanism that trigger solar eruptions and the key parameters for the occurrence of CMEs. I will conclude by discussing how these criteria derived from the models relates —and apply— to actual observations of eruptive flares.
| | 17:44 | Analysis of coronal mass ejections propagating in different solar wind conditions | Mierla, M et al. | Oral | | | Marilena Mierla[1,2], Andrea Verdini[3],Emilia Kilpua[4], Luciano Rodriguez[1], Matt West[1] | | | [1]Royal Observatory of Belgium; [2]Institute of Geodynamics of the Romanian Academy; [3]LESIA, Observatoire de Paris; [4]Department of Physics, University of Helsinki | | | The aim of this work is to improve the forecast of CME arrivals at different spacecraft.
We analyzed all the coronal mass ejections (CMEs) which arrived at the STEREO and L1 positioned spacecraft throughout 2010. All the CMEs had speeds varying between 300 and 1400 km/s and they propagated in different solar wind backgrounds (slow wind, fast wind, disturbed wind etc.) By using a drag-based model incorporating different wind conditions (variable and non-variable) we compared the expected CME arrival conditions with the observed ones. A discussion on the limitations of the data and the methods is also given. | | 17:56 | Combining Observations of Interplanetary Scintillation and Heliospheric Visible-Light Imaging for Space-Weather Purposes as part of the EU FP7 HELCATS Project: CMEs and SIRs | Bisi, M et al. | Oral | | | Mario M. Bisi[1], David Barnes[1], Jonathan Eastwood[2], Vratislav Krupar[2], Jasmina Magdalenic[3], Richard A. Harrison[1], Jackie A. Davies[1], and Richard A. Fallows[4]. | | | [1]STFC-RAL Space, UK; [2]Imperial College London, UK; [3]ROB, Belgium; [4]ASTRON, NL. | | | The Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project is one of the European Union's Seventh Framework Programme (EU FP7) projects. The project is primarily targeted to the cataloguing of transient and background structures observed in the heliosphere by the visible-light Heliospheric Imagers (HIs) on board the twin spacecraft STEREO mission, including identification of their source regions and in-situ signatures. The current version of the HELCATS manually-generated Coronal Mass Ejection (CME) Catalogue contains more than 1,000 CMEs observed between 2007 and 2014, and the current HELCATS Stream Interaction Region (SIR) Catalogue contains signatures of nearly 200 co-rotating density structures in the ecliptic plane. HELCATS also includes an assessment of the complementarity of ground-based radio observations of interplanetary scintillation (IPS), which is yielding catalogues of IPS features (from EISCAT/MERLIN/ESR and/or LOFAR where available) that is being compared to the STEREO HI catalogues. Here we discuss the current status of this work and insights that have been gleaned from preliminary analyses of this joint cataloguing exercise, those insights that relate, in particular, to the space weather exploitation of these two complementary observational techniques. For example, there are cases where a CME is imaged by the STEREO HI instruments but then not detected using IPS, and vice versa, and preliminary investigations of these will be discussed. | | 18:08 | Typical profiles and distributions of plasma and magnetic field parameters in magnetic clouds at 1 AU | Rodriguez, L et al. | Oral | | | Luciano Rodriguez[1], Jimmy J. Masias-Meza[2], Sergio Dasso[2], Pascal Demoulin[3], Andrei Zhukov[1,4], Adriana Gulisano[2,5], Marilena Mierla[1,6],Emilia Kilpua[7], Matthew West[1], Dana Lacatus[6], Alin Razvan Paraschiv[6], Miho Janvier[8] | | | [1]Royal Observatory of Belgium; [2]Universidad de Buenos Aires; [3]Observatoire de Paris; [4]Skobeltsyn Institute of Nuclear Physics, Moscow State University; [5]Instituto Antártico Argentino; [6]Institute of Geodynamics of the Romanian Academy; [7]University of Helsinki; [8]Institut d'Astrophysique Spatiale | | | Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs). They are important due to their simple internal magnetic field confi guration, which resembles a magnetic flux rope, and because they represent one of the most geoeff ective types of solar transients. In this study, we analyze their internal structure using a superposed epoch method on 63 events observed at L1 by ACE, between 1998 and 2006. In this way, we obtain an average pro file for each plasma and magnetic field parameter at each point of the cloud. Furthermore, we take a fi xed time window upstream and downstream from the MC, in order to sample also the regions preceding the cloud and the wake trailing it. We then perform a detailed analysis of the internal characteristics of the clouds, and their surrounding solar wind environments. We find that the parameters studied are compatible with log-normal distribution functions. The plasma beta and the level of fluctuations in the magnetic fi eld vector are the best parameters to de fine the boundaries of clouds. We find that in one third of the events, there is a peak in plasma density close to the trailing edge of the
flux ropes. We provide several possible explanations for this result and investigate if the density peak is of a solar origin (e.g. erupting prominence material) or formed during the magnetic cloud travel from the Sun to 1 AU. The most plausible explanation is the compression due to a fast overtaking flow, coming from a coronal hole located to the east of the solar source region of the magnetic cloud. | | 18:20 | Relating CME characteristics from remote-sensing image data to in-situ measurements for Earth-affecting events | Temmer, M et al. | Oral | | | Manuela Temmer[1], Karin Dissauer[1], Julia K. Thalmann[1], Astrid M. Veronig[1], Luciano Rodriguez[2], Johannes Tschernitz[1], Jürgen Hinterreiter[1] | | | [1]Institute of Physics, University of Graz, Austria; [2]Royal Observatory of Belgium, Brussels, Belgium | | | We analyze two well observed flare-CME events and cover the complete chain of action – from the Sun to Earth. We study in detail the solar surface and atmosphere (SDO and ground-based instruments) associated to the flare/CME and also track the off-limb CME signatures (STEREO), in order to cover the temporal evolution of associated flare ribbons in the low solar atmosphere and coronal dimmings. This is complemented by surface magnetic field information and 3D coronal magnetic field modeling. By applying 3D reconstruction techniques (GCS, total mass) to combined STEREO-SoHO coronagraph data, we track the temporal and spatial evolution of the CMEs in interplanetary space and derive its geometry and mass. From in-situ measurements (Wind), we extract the corresponding ICME characteristics. We discuss in detail the results derived from remote-sensing imagery and in- situ measurements as well as the relationship of the different derived parameters.
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Tuesday November 15, 11:00 - 13:00, Delvaux| 11:00 | Observational Evidence for High-Mach Number Regime of Coronal Shock Waves During Powerful Solar Particle Events | Rouillard, A et al. | Invited Oral | | | Rouillard, A.P.[1], Plotnikov, I.[1], Pinto, R.[1], Zucca, P.[2], Vainio, R.[3], Tylka, A.[4], Vourlidas, A.[5], Warmuth, A.[6], Mann, G.[6] | | | [1]Institut de Recherche en Astrophysique et Planétologie, Universitée de Toulouse III; [2]LESIA-UMR 8109 - Observatoire de Paris, CNRS, Univ. Paris; [3]University of Turku, Turku, Finland; [4]Emeritus, NASA Goddard Space Flight Center, Greenbelt; [5]Johns Hopkins Applied Physics Laboratory, Laurel, Maryland; [6]Leibniz-Institut fur Astrophysik Potsdam, Potsdam | | | Identifying the physical mechanisms that produce the most energetic particles is a
long-standing observational and theoretical challenge in astrophysics. Strong shock waves
have been proposed as efficient accelerators both in the solar physics and astrophysical
contexts via various acceleration mechanisms. The proposed processes rely on shock waves
being super-critical or moving several times faster than the characteristic speed of the medium
they propagate through. Using recent imaging of the NASA STEREO, SOHO and
SDO spacecraft, we provide the first observations of the time-dependent 3-dimensional
distribution of the expansion speed and MA of several coronal shock waves. These observations show
that the high-energy particles measured near Earth are produced at the time of the sharp rise in
the shock Mach number (>3) magnetically connected to Earth. These findings provide direct
evidence to energetic particles being accelerated during the formation of a strong coronal
shock. Using our new technique, we study the longitudinal spread and timing of a number of
other energetic particle events during cycle 24 and the detailed relation between the formation of shock waves and type II bursts. | | 11:22 | Peak intensities of solar energetic particle events at heliocentric distances < 1 AU | Aran, A et al. | Invited Oral | | | Angels Aran[1], Monica Laurenza[2], Giuseppe Consolini[2], David Lario[3], Raúl Gómez-Herrero[4], Javier Rodríguez-Pacheco[4], Juan José Blanco[4] | | | [1]Dep. de Físcia Quàntica i Astrofísica i Institut de Ciències del Cosmos, Universitat de Barcelona, Spain; [2]Istituto di Astrofisica e Planetologia Spaziali, National Institute for Astrophysics, Italy; [3]Applied Physics Laboratory, The Johns Hopkins University, USA; [4]Space Research Group, University of Alcalá, Spain | | | Most of our knowledge of solar energetic particle (SEP) events in the inner heliosphere comes from Helios observations at heliocentric distances between 0.29 AU and 0.98 AU. We study and/or revisit gradual SEP events observed simultaneously by one of the Helios spacecraft and by IMP-8. We pay special attention to the local intensity peaks, observed in association with the passage of interplanetary shocks by the spacecraft, as well as to the peak at the prompt phase. For observations within 0.8 AU, we use 1.3 – 50.7 MeV proton measurements from the HELIOS/E6 experiment. We use equivalent energies from IMP-8/CPME that we obtain by fitting the observed intensity spectra with a Weibull functional form. We select SEP events where the spacecraft configuration allows us to determine the efficiency of interplanetary shocks in particle acceleration as a function of heliocentric distance. In particular, we analyze events for which: (i) the spacecraft nominal magnetic footpoints were close; (ii) the two spacecraft were close to radial alignment. In the first case, the events recorded by the two spacecraft shared a common history of shock acceleration processes since they were both connected, in a good approximation, to the same region of the shock front. In the second scenario, the two spacecraft were crossed by the same part of the shock front; thus, allowing us to study how the same region of shock weakened as intercepted each spacecraft at different helioradii. We attempt to provide predictions of the peak intensity that would have been observed during these events down to approximately the perihelion of both Solar Orbiter (SO, ~0.28 AU) and Solar Probe Plus (SPP, ~0.05 AU). | | 11:44 | Solar Flares, Coronal Mass Ejections and Solar Energetic Particle Event Characteristics | Anastasiadis, A et al. | Invited Oral | | | A. Anastasiadis[1], A. Papaioannou[1], I. Sandberg[1], A. Kouloumvakos[2], M. K. Georgoulis[3], K. Tziotziou[1], G. Tsiropoula[1], P. Jiggens[4], A. Hilgers[4] | | | [1]IAASARS, National Observatory of Athens, Greece; [2]Depatment of Physics, University of Ioannina, Greece; [3]RCAAM, Academy of Athens, Greece; [4]ESA/ESTEC, The Netherlands | | | Solar Energetic Particle (SEP) events are typically divided into two basic classes, the so-called “gradual” and the “impulsive” ones. Impulsive SEP events are associated with short timescales and are attributed to solar flares (SFs). Gradual events are associated with longer timescales, coronal and interplanetary shocks and are associated to coronal mass ejections (CMEs). We examined the properties and associations of 314 SEP events occurred in the years 1984 to 2013. The properties of the SEP events include the peak proton flux and the fluence at several integral energies (E>10;30;60 and 100 MeV). The associated solar events were parameterized by solar flare (SF) and coronal mass ejection (CME) characteristics, as well as related radio emissions. In particular, for SFs: the maximum flare flux, the flare fluence, the heliographic location, the rise time and the duration were exploited; for CMEs the plane-of-sky velocity as well as the size (as expressed by the width) were utilized. For radio emissions, type III, II and IV radio bursts were identified. Furthermore, we utilized element abundances of Fe and O. We found evidence that most of the SEP events in our catalogue do not conform to a simple two-class paradigm, exhibiting both impulsive phase (type III radio bursts) and shock (type II radio bursts) emissions, and that a continuum of event properties is present. Although, the so-called hybrid or mixed SEP events seem to be present in our catalogue, suggesting that both SFs and CMEs have a prevalent role in the generation, acceleration and propagation of SEP events, it was not possible to strictly affirm each SEP event to a mixed/hybrid sub-category. Our findings further suggest that gradual SEP events that stem from the central part of the visible solar disk are increasingly important and constitute a significant radiation risk. Finally, the velocity of the associated CMEs, as well as the peak flare flux and fluence, are all fairly significantly correlated to both the peak proton flux and the fluence of the SEP events in our catalogue. The strongest correlation to SEP characteristics is manifested by the CME velocity.
This work has been funded through the “FORSPEF: FORecasting Solar Particle Events and Flares”, ESA Contract No. 4000109641/13/NL/AK and the “SPECS: Solar Particle Events and foreCasting Studies” program of the National Observatory of Athens.
| | 12:06 | Are protons accelerated by CME-driven shocks responsible for high-energy solar gamma-ray events? | Afanasiev, A et al. | Oral | | | A. Afanasiev[1], R. Vainio[1], A. Aran[2], G. Share[3,4], A. Rouillard[5], R. Siipola[1], M. Battarbee[6], J. Pomoell[7], and B. Sanahuja[2] | | | [1]Department of Physics and Astronomy, University of Turku, Turku, Finland; [2]Departament de Física Quàntica i Astrofísica, Institut de Ciències del Cosmos, Universitat de Barcelona, Barcelona, Spain; [3]Department of Astronomy, University of Maryland, College Park, Maryland, USA; [4]National Observatory of Athens, Athens, Greece; [5]Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, Toulouse, France; [6]Jeremiah Horrocks Institute, University of Central Lancashire, Preston, UK; [7]Department of Physics, University of Helsinki, Helsinki, Finland | | | During recent years, observations with the Fermi/LAT instrument have revealed over twenty-five >100 MeV
gamma-ray events on the Sun lasting from tens of minutes to several hours. All are associated with solar flares
and all but one are associated with fast CMEs. The observations indicate that the gamma-ray emission is most
probably from decay of pions produced by >300 MeV proton and >200 MeV alpha particle interactions deep in the
chromosphere. Whether those particles are produced in the associated flare or in the CME-driven shock has been
under active debate. In this work, we present modeling aimed at testing the shock hypothesis. The modeling was
performed for two gamma-ray events: 17 May 2012 and 23 January 2012, and consists of two steps: 1) determination
of the energy spectrum of protons injected from the shock into the downstream and 2) simulation of the transport
of injected particles back to the Sun. For the first event, the shock-injected proton spectrum was simulated using the Coronal Shock Acceleration (CSA) model with input from semi-empirical modeling of shock kinematics and
upstream medium. For the second event, the shock-injected spectrum was constrained by using the Shock-and-
Particle (SaP) model utilizing solar energetic particle observations at 1 AU. The downstream transport simulations were performed in the diffusive approximation. We present the modeled spectra of interacting protons at the Sun, compare them with the proton spectral parameters derived from the gamma-ray observations, and discuss the implications for the shock-acceleration hypothesis.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme
under grant agreement No 637324 (HESPERIA). Academy of Finland is thanked for financial support (project
267186). | | 12:18 | Interplanetary transport of near-relativistic solar electron events under different solar wind conditions. | Pacheco, D et al. | Oral | | | D. Pacheco[1], R. Gómez-Herrero[2], N. Agueda[1], A. Aran[1] | | | [1]Dep. de Física Quàntica i Astrofísica i Institut de Ciències del Cosmos, Universitat de Barcelona, Spain; [2]SRG, Dpto. de Física y Matemáticas, Universidad de Alcalá, E-28871 Alcalá de Henares, Spain | | | The interplanetary transport conditions of solar energetic particles (SEPs) depend on the amount of fluctuations in the interplanetary magnetic field. This has a direct influence on the characteristics of the observed temporal profiles and particle anisotropies at the spacecraft location.
We aim to explore for possible correlations between SEP interplanetary transport conditions and local solar wind properties. For that purpose, we use a Monte Carlo interplanetary transport model combined with an inversion procedure to fit in-situ observations of near-relativistic electron events detected by STEREO during different solar wind conditions. We select a sample of well-connected impulsive SEP events with an unambiguous solar source location and not accompanied by type II radio bursts. Finally, we compare the inferred radial mean free path values with different plasma parameters. We present and discuss the results for the studied sample of events. | | 12:30 | Plasma Diagnostics of a Moreton Wave | Veronig, A et al. | Oral | | | A.M. Veronig[1], K. Vaninnathan[1], K. Dissauer[1], M. Temmer[1], N. Nitta[2], B. Vrsnak[3], P. Mesa Ortega[1] | | | [1]Institute of Physics / Kanzelhöhe Observatory, University of Graz, Austria; [2]Lockheed Martin Advanced Technology Center, CA, USA; [3]Hvar Observatory, Faculty of Geodesy, University of Zagreb, Croatia | | | Moreton waves are the chromospheric signature of large-scale MHD shock waves propagating in the solar corona that occur in association with coronal mass ejections. Whereas large-amplitude coronal waves, observed as so-called "EIT waves", are frequently observed in association with CMEs, Moreton waves are very rare phenomena. In the present solar cycle no. 24, no more than five events have been reported so far. Moreton waves are highly space weather relevant as they are signatures of shock waves formed low in the corona, and are associated with type II bursts and solar energetic particle events (SEPs). We present a detailed case study of a Moreton wave observed by the GONG Halpha network that occurred in association with the X1 flare/CME/SEP event on 29th March 2014. We perform a kinematical analysis of the wave and the associated CME, as well as Differential Emission Measure analysis based on the six AIA/SDO EUV filters, in order to study the plasma changes associated with the passing Moreton wave front. We find that the Moreton wave front is co-spatial with a propagating pulse of enhanced density, up to about 15% compared to the pre-event state, and also associated with an increase in temperature. These changes are higher than the increase derived for other strong cases of EIT waves that were not associated with a Moreton wave (Kozarev et al. 2011, Vaninnathan et al. 2015), providing further evidence for the shock nature of the phenomenon. | | 12:42 | Radio Diagnostics of Electron Acceleration Sites During the Eruption of a Flux Rope in the Solar Corona | Carley, E et al. | Oral | | | Eoin Carley[1,2], Nicole Vilmer[2], Peter Gallagher[1] | | | [1]School of Physics, Trinity College Dublin; [2]LESIA, Paris Observatory. | | | Electron acceleration in the solar corona is often associated with flares and the eruption of twisted magnetic structures known as flux ropes. However, the locations and mechanisms of such particle acceleration during the flare and eruption are still subject to much investigation. Observing the exact sites of particle acceleration can help confirm how the flare and eruption evolve and also help in identifying the origin of solar energetic particles amongst the erupting structure. Here we use the Atmospheric Imaging Assembly to analyse a flare and erupting flux rope on 2014-April-18, while observations from the Nan cay Radio Astronomy Facility allows us to diagnose the sites of electron acceleration during the eruption. At event initiation, 110 keV energetic electrons are accelerated in a tether-cutting reconnection process to produce type III radio bursts. We show these electrons may be those eventually detected in-situ by ACE EPAM. During eruption acceleration, up to 5 keV energetic electrons are produced in a site of magnetic reconnection above the flux rope for a period of up to 5 minutes. We then show that electrons are injected into the erupting structure, eventually allowing the CME legs to be imaged. In total, our radio observations allow us to better understand the sites of electron acceleration during the eruptive event, and also to understand the evolution of the eruptive event itself. |
PostersTuesday November 15, 10:00 - 11:00, Poster Area| 1 | Solar Energetic Particle Event Forecasting | Quinn, R et al. | e-Poster | | | Lisa Winter, Valerie Bernstein, Rick Quinn | | | AER, Villanova University, AER | | | Solar energetic particle events (SEPs) are enhancements in the particle flux received at Earth as a result of solar activity. These events can be disruptive to ionospheric communications, destructive to satellites, and pose a health risk to astronauts. To develop a useful forecast predicting when SEP events will occur, how long, and the resultant energy and flux profiles, it is important to understand the relationship between SEPs and their drivers. Therefore, we present results from analyses of the high energy flares and coronal mass ejections in relation to the SEP properties from the current solar cycle. In particular, we investigated the connection with gamma-ray flares detected by the Fermi Gamma-ray Space Telescope at >100 MeV. At this intensity, the flares are likely produced in proton acceleration processes. When long duration flares occur, they are further connected to fast, halo CMEs. We also compare the flare and CME properties to the occurrence of DH type II radio bursts observed from Wind/WAVES as an indicator of shocks that are magnetically well-connected to Earth. Finally, we present the statistics of which properties lead to SEPs, the resulting durations of the events, and energy and intensity properties. These results will be used to develop a new empirical SEP forecast model. | | 2 | Searching for relationships between the solar regular daily magnetic variation at mid latitude and the solar irradiance at different ionizing wavelengths | Saiz, E et al. | e-Poster | | | Elena Saiz, Judith Palacios, Antonio Guerrero, Consuelo Cid, Yolanda Cerrato | | | Space Research Group-Space Weather, University of Alcala (SPAIN) | | | In the development of a geomagnetic storm major changes in the geomagnetic field measured on the ground are observed because of the involved ionospheric and magnetospheric current enhancements. In a general approximation, magnetic field disturbance is added to that of quiet time. To separate accurately the magnetic field disturbances from the total magnetic field is necessary, among others, to determine the solar regular daily magnetic variation, SR, associated to the Sq current system. Although this is a fundamental issue to elaborate high-resolution local geomagnetic indices, at mid-latitude locations a precise solar regular daily variation is not easy to be determined due to its dynamics and day-to-day variability.
Therefore, local empirical relationships between the quiet-time geomagnetic response on the ground through SR and the solar irradiance, co-responsible for the Sq current system, are useful (even necessary) especially during disturbed magnetic conditions. The study is focused on relationships between solar irradiance at different ionizing wavelengths with the magnetic variation amplitude of SRs obtained for the SPT station (Spain), which can be seen as a typical mid-latitude observatory. The International Quiet Days SR curves throughout at least one solar cycle are analyzed. These local results could be extrapolated to any other mid-latitude location. Data from GOES, PROBA2 and SPT observatory are handled.
| | 3 | A New Methodology to Predict the Axial ICME Magnetic Field at 1 AU | Georgoulis, M et al. | e-Poster | | | Manolis K. Georgoulis[1], Spiros Patsourakos[2] | | | [1]RCAAM of the Academy of Athens, Athens, Greece; [2]Department of Physics, University of Ioannina, Ioannina, Greece | | | A newly developed methodology to predict an active-region CME’s near-Sun magnetic field and its evolution during the ICME transit to 1 AU is presented. The analysis can be undertaken on a case-by-case basis and relies on a number of distinct steps. In particular, (a) the magnetic helicity conservation principle is used to constrain the CME helicity budget from the respective budget of its parent active region, (b) a forward-fitting geometrical CME modeling is used to infer the near-Sun length and radius of the CME under the cylindrical flux-rope assumption, (c) semi-analytical CME modeling is then applied to infer the CME’s axial magnetic field strength, and (d) a self-similar radial fall-off of the near-Sun CME magnetic field is projected from Sun to 1 AU to provide the final outcome, namely the magnetic cloud’s axial magnetic field at the edge of geospace. A parametric study over a wide range of radial-expansion indices allows us to constrain a statistically meaningful power-law index and reach results that stand in ballpark agreement with in-situ measurements of 162 magnetic clouds at L1. The main pros and cons of the overall methodology are also discussed and follow-up developments that could offer insight to the magnetic clouds’ geoeffectiveness are pointed out, with the main caveat being our present inability to routinely perform the methodology in a fully automated fashion. | | 4 | The relationship between the intensity of X-ray flares and their effects in the horizontal component of the geomagnetic magnetic field | Cid, C et al. | e-Poster | | | María Jesús Rivas[1,2] and Consuelo Cid[1] | | | [1]Universidad de Alcalá; [2]Instituto Nacional de Técnica Aeroespacial | | | Intense solar flares produce sometimes a disturbance on the ground magnetic field labelled as magnetic-crochet or solar flare effect (SFE). The intensity of the flare has been suggested to be related to the size of the SFE, but no relationship between both magnitudes has been established up to date. In this communication we present the results from a statistical analysis along one solar cycle involving some parameters related to the intensity of the X-flares (integral flux and peak flux) and the size of the SFE at different magnetic observatories from the INTERMAGNET data network. The position of the magnetic observatory relative to the Subsolar point has also been considered in this study. | | 5 | Examining the relationship between flare occurrence and the Hale sector boundary | Loumou, K et al. | e-Poster | | | Konstantina Loumou[1], Iain. G. Hannah[1], Hugh S. Hudson[1,2] | | | [1]University of Glasgow; [2]University of California, Berkeley | | | We present our work on the occurrence of solar flares with respect to the presence of the Hale sector boundary based on heliospheric measurements. The heliospheric magnetic field typically is organized into two or four different sectors of alternating polarity. The Hale sector boundary is the segment for which the change in magnetic sector polarity agrees with that of the leading and following sunspots in each hemisphere. For the times that we determine that the sector boundary is at central meridian, the RHESSI flare positions concentrate in the hemisphere of the Hale boundary. This suggests a connection between flux emergence and release of free magnetic energy with the deep interior. Sunspots also follow the Hale boundary (Svalgaard and Wilcox, 1976) but flares sharpen this relationship. The behaviour of flare occurrence was previously presented for Cycle 23 (Svalgaard, Hannah and Hudson 2011) and we present the evolution of the sector boundary through declining phase of Cycle 23 as well as the rising phase of Cycle 24. We find that it follows the expected change between northern and southern hemispheres although the association is not as distinct for Cycle 24. So we also investigate the Hale sector structure via photospheric magnetic field extrapolations in comparison to our heliospheric proxy, which additionally allows us to increase the flare sample in our work.
| | 6 | The Coronal Automated Analysis of SHocks and Waves (CASHeW) Framework | Kozarev, K et al. | e-Poster | | | Kamen Kozarev, Alisdair Davey, Alexander Kendrick, Michael Hammer, Celeste Keith | | | [1]Smithsonian Astrophysical Observatory; [2]Smithsonian Astrophysical Observatory; [3]Stanford University; [4]University of Arizona; [5]University of Wisconsin-Madison | | | Recent studies of individual solar eruptive events have used extreme UV (EUV) observations of coronal bright fronts (CBF) and metric radio type II observations to show the intimate connection between waves in the low corona and CME-driven shocks. EUV imaging with the Atmospheric Imaging Assembly(AIA) instrument on SDO has proven particularly useful for detecting large-scale short-lived coronal bright fronts, which, combined with radio and in situ observations, holds great promise for early CME-driven shock characterization capability. This characterization can further be automated, and related to models of particle acceleration to produce estimates of particle fluxes early in events. We are building a framework for the Coronal automated Analysis of SHocks and Waves (CASHeW). It combines analysis of NASA Heliophysics System Observatory data products and relevant data-driven models, into an automated system for the characterization of coronal waves and shocks and the evaluation of their capability to accelerate SEPs. The system utilizes EUV observations and analysis tools written in IDL. In addition, it leverages the analysis tools in the SolarSoft package of libraries. The CASHeW framework is being tested and extensively validated on a representative list of coronal bright front events. Here we present its features, as well as some initial results. With this framework, we hope to contribute to the overall understanding of coronal shock waves, their importance for energetic particle acceleration, as well as to the better ability to forecast SEP events fluxes. | | 7 | The influence of environmental parameters on the 3D Kelvin-Helmholtz instability at the magnetopause | Leroy, M et al. | e-Poster | | | M. Leroy, R. Keppens | | | Centre for mathematical Plasma-Astrophysics KU Leuven, Leuven, Belgium | | | The transfer of matter from the solar-wind to the Earth's magnetosphere during southward solar wind is mostly well understood but the same phenomenon during northward solar wind remains to be fully apprehended. Given the typical parameters at the magnetosphere-solar wind interface, the situation must be considered in the frame of Hall-MHD, due to the fact that the current layers widths and the gradient lengths can be in the order of the ion inertial length. Because magnetic perturbations can affect the field configuration at a distance in all directions and not only locally, three-dimensional treatment is necessary. In this spirit three-dimensional simulations of a configuration approaching the conditions leading to the development of Kelvin-Helmholtz instabilities at the flank of the magnetosphere during northward oriented solar-wind are performed as means to study the entry of solar-wind matter into Earth's magnetic field. In the scope of assessing the effect of the Hall-term in the physical processes, the simulations are also performed in the MHD frame. Furthermore the influence of the density and velocity jump through the shear layer on the rate of mass entering the magnetosphere is explored. Indeed, depending on the exact values of the physical quantities, the Kelvin-Helmholtz instability may have to compete with secondary instabilities and the non-linear phase may exhibit vortex merging and large-scale structures reorganisation, creating very different mixing layers, or generate different reconnection sites, locally and at a distance. These different configurations may have discernible signatures that can be identified by spacecraft diagnostics. | | 8 | Joint Ne/O and Fe/O analysis as a new diagnostic tool of flare suprathermal fraction in large solar energetic particle events | Malandraki, O et al. | p-Poster | | | Olga E. Malandraki, Lun C. Tan | | | IAASARS, National Observatory of Athens, Athens, Greece | | | Since the Fe/O ratio observed in the solar energetic particle (SEP) event would experience
the interplanetary transport effect, the Ne/O ratio should be more useful in the examination
of shock acceleration origin of large SEP events. Thus the Ne/O ratio is newly deduced by
re-binning ion intensity data into the form of equal bin widths in the logarithmic energy scale.
A joint examination of Ne/O and Fe/O ratios in 29 large SEP events during the solar cycle
23 is in progress. The emphasis of our examination is put on the analysis of ion ratio data in
the joint energy range (3-40 MeVnucleon-1) of Wind/LEMT and ACE/SIS sensors. Through
the analysis we will deduce the ion energy dependence of Ne/O and Fe/O ratios, which would
be important in the diagnosis of the flare suprathermal fraction in large SEP events, and
hence in the discrimination between the quasi-parallel and quasi-perpendicular shock origins of
these events. Acknowledgement: This project has received funding from the European Union’s
Horizon 2020 research and innovation programme under grant agreement No 637324. | | 9 | Release History and Transport Parameters of Relativistic Solar Electrons Inferred from Near-the-Sun In-situ Observations | Agueda, N et al. | p-Poster | | | Neus Agueda[1], David Lario[2] | | | [1]Institut de Ciències del Cosmos, University of Barcelona, Spain; [2]The Johns Hopkins University, Applied Physics Laboratory, USA | | | We study four consecutive 300-800 keV electron events observed on 1980 May 28 by Helios-1, when the spacecraft was located at a heliocentric distance of 0.31 AU. We use two different techniques to extract the release time history of electrons from the Sun: (1) a data-driven method based on the assumption that particle propagation between the Sun and the spacecraft is scatter free and (2) an inversion method that makes use of particle transport simulation results. Both methods make use of the particle angular distributions measured relative to the local direction of the magnetic field. The general characteristics of the release time profiles obtained by these two techniques are remarkably similar, especially when the inferred value of the electron mean free path is large. We find indications that the strength of the interplanetary scattering varies systematically with the size of the solar parent event, which suggests that the magnetic field fluctuations leading to the scattering are not necessarily an inherent property of the medium, but they are related to the amount of released particles at the Sun. We use the inferred release profiles to compute the expected intensities at 1 AU. In contrast to simultaneous IMP-8 observations, our simulations predict the observation of four separate events at 1 AU. Processes that could contribute to the observation of one single time-extended event at 1 AU include (1) distinct magnetic connections of the spacecraft to the particle sources, (2) the spatio-temporal evolution of the particle sources, and (3) different particle transport conditions beyond 0.31 AU. | | 10 | Modeling of proton acceleration in application to the 17 May 2012 GLE event | Afanasiev, A et al. | p-Poster | | | A. Afanasiev[1], R. Vainio[1], A. Rouillard[2], and M. Battarbee[3] | | | [1]Department of Physics and Astronomy, University of Turku, Turku, Finland; [2]Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, Toulouse, France; [3]Jeremiah Horrocks Institute, University of Central Lancashire, Preston, UK | | | One of the unsolved problems in solar physics is the source (flare or coronal shock) of high-energy protons (above ~500 MeV) responsible for the so-called ground level enhancements (GLEs). Detailed numerical simulations of the involved particle acceleration processes should help in solving the puzzle. In this work, we present a simulation study of proton acceleration in the 17 May 2012 GLE event. The modeling of the event was performed assuming that particles are accelerated by the shock driven by the coronal mass ejection. The shock evolution and the ambient plasma parameters were determined based on a combination of recently developed techniques utilizing imaging observations from SDO, SOHO and STEREO spacecraft and magnetohydrodynamic modeling of the ambient corona. The parameters were determined for a large set of individual magnetic field lines. Using the derived information on shock and medium, we then employed the Coronal Shock Acceleration (CSA) simulation model to study the acceleration of protons on selected field lines. The CSA models proton acceleration self-consistently with evolution of the Alfvénic foreshock. We have found that the acceleration efficiency differs significantly for different field lines: there are field lines (magnetic flux tubes) where particles experience very minor acceleration and field lines where particles reach GLE energies in less than ten minutes after the shock formation.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme
under grant agreement No 637324 (HESPERIA). Academy of Finland is thanked for financial support (project
267186). | | 11 | A new way to estimate the solar wind geoefficiency and its impact on the radiation belts | Rochel, S et al. | p-Poster | | | S. Rochel Grimald, D. Boscher, R. Benacquista | | | Onera | | | A magnetosphere is an isolated volume dropped inside the solar wind. It is in equilibrium in the solar wind. If the solar wind parameters change, then, the magnetospheric balance is upset. Moreover, the magnetosphere is not a solar-wind-proof bulkhead. Using several processes, particles and energy from the solar wind can go inside, disturbing the magnetosphere and being responsible of variation of currents and generation of waves. Those phenomena allow absorbing the energy overflow and the come back to the equilibrium. Nevertheless, if the phenomenon is geoefficient, it also impacts the inner magnetosphere populations, and in particular the radiation belts particle flux. The purpose of this work is to understand the solar wind main structures (CMEs and CIRs) impact in the terrestrial magnetosphere. The existing magnetic indices allow estimating how much the system is disturbed at a given time, but they do not allow estimating how long the disturbance modify the magnetosphere. In this paper, we use the Am index to define a new parameter allowing estimating the energy level in the magnetosphere. Using this parameter, we will first present a comparative study of the impact of the CIRs and of the CMEs on the magnetosphere. This study will highlight the role of the multiple CMEs events to fill the magnetosphere energy level. Then, the radiation belts will be analysed from this new point of view in order to understand their role as energy tanks. | | 13 | Comparison of 3-D CME Parameters Derived from Single and Multi-view Observations | Lee, H et al. | p-Poster | | | Harim Lee[1,2], Y.-J. Moon[1], Hyeonock Na[1], Soojeong Jang[1,3] and Jae-Ok Lee[1] | | | [1]School of Space Research, Kyung Hee University, Yongin, South Korea; [2]RRA Korean Space Weather Center, Jeju, South Korea; [3]Korea Astronomy and Space Science Institute, Yuseong, South Korea | | | To prepare for when only single-view observations are available, we have made a test whether the 3-D parameters (radial velocity, angular width, and source location) of halo coronal mass ejections (HCMEs) from single-view observations are consistent with those from multiview observations. For this test, we select 44 HCMEs from December 2010 to June 2011 with the following conditions: partial and full HCMEs by SOHO and limb CMEs by twin STEREO spacecraft when they were approximately in quadrature. In this study, we compare the 3-D parameters of the HCMEs from three different methods: (1) a geometrical triangulation method, the STEREO CAT tool developed by NASA/CCMC, for multiview observations using STEREO/SECCHI and SOHO/LASCO data, (2) the graduated cylindrical shell (GCS) flux rope model for multiview observations using STEREO/SECCHI data, and (3) an ice cream cone model for single-view observations using SOHO/LASCO data. We find that the radial velocities and the source locations of the HCMEs from three methods are well consistent with one another with high correlation coefficients (≥0.9). However, the angular widths by the ice cream cone model are noticeably underestimated for broad CMEs larger than 100∘ and several partial HCMEs. A comparison between the 3-D CME parameters directly measured from twin STEREO spacecraft and the above 3-D parameters shows that the parameters from multiview are more consistent with the STEREO measurements than those from single view. | | 14 | An Aerodynamic Drag Analysis of CMEs from In Situ Measurements and Multipoint Space Observations | Mrotzek, N et al. | p-Poster | | | Niclas Mrotzek, Malte Venzmer, Volker Bothmer, Adam Pluta | | | Institute for Astrophysics at the University of Goettingen | | | Understanding the kinematics of Coronal Mass Ejections (CME) is the first step in forecasting their trajectories and so their possible arrival times at greater heliospheric distances. After an early Lorenz acceleration phase in the first solar radii near the sun, the aerodynamic drag force takes over and becomes the dominating driver affecting the CME propagation dramatically. To gain a better understanding of the influence of certain CME parameters like initial velocity, mass and geometry on the interaction between CME and the ambient solar wind, we analysed a set of CMEs using both coronagraphic multipoint observations and in situ measurements by the STEREO A/B or ACE satellites. The analysis is based on GCS-modelling and includes observations from the STEREO heliospheric imagers, to extend the height-time-profiles further away from the sun, as well as observations from the SDO satellite of the associated Solar Source Regions (SSR). The kinematics of the CMEs results from the solution of the drag-based model that best fits the height-time-profile and are compared for further analysis with the SSR parameters.
We discuss the implications of our results in the context of state-of-the-art space weather predictions. The studies are carried out in the EU FP7 project HELCATS (Heliospheric Cataloguing, Analysis and Techniques Service). | | 15 | Comparative analysis of the CME- and CIR/HSS-related storm effects on ionosphere | Buresova, D et al. | p-Poster | | | Dalia Buresova[1], Jaroslav Urbar[1], John Bosco Habarulema[2], Jaroslav Chum[1], Daniel Kouba[1], Zama Thobeka Katamzi[2] | | | [1]Institute of Atmospheric Physics, CAS, Prague, Czech Republic; [2]SANSA Space Sciences, Hermanus, South Africa | | | Nowadays studies related to the effects of space weather phenomena on the Earth’s ionosphere are of great interest because of their importance to sophisticated space- and ground-based infrastructure. In order to give users advanced and reliable information/warning of changing space weather conditions that may affect a diverse range of technological systems, thoroughgoing knowledge of the state of ionosphere and its disturbance sources and dependence of the effects are needed. In the presented analysis we focused on ionospheric effects related to different solar activity phenomena such as CMEs and CIR/HSSs. The analysis is based on digisonde and GPS TEC data and deals primarily with the ionospheric storm-time variability above middle latitudes. The variability of main ionospheric parameters obtained for magnetic storms of different intensity, which occurred during the last two solar cycles (23 and 24), is analysed. Ionospheric response to weak geomagnetic storms during the deep 23/24 solar minimum is found to be comparable or even slightly stronger than that of strong storms under higher solar activity conditions, which might be partly related to specific features of the different sources of geomagnetic activity and ionospheric conditions during the last solar minimum. Weak seasonal dependence of the CIR/HSS-related magnetic storm effects was also observed. | | 16 | HELCATS: Catalogue of slow drifting radio emissons observed by STEREO/Waves | Krupar, V et al. | p-Poster | | | V. Krupar[1,2], J. P. Eastwood[1], J. Magdalenic[3], M. M. Bisi[4], J. A. Davies[4], R. A. Harrison[4], D. Barnes[4] | | | [1]Imperial College London, UK; [2]Institute of Atmospheric Physics CAS, Czech Republic; [3]Royal Observatory of Belgium, Belgium; [4]Rutherford Appleton Laboratory, UK | | | Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) is a project of the European Union's Seventh Framework Programme. Its main aim is to produce catalogues of solar transient and background structures observed by the heliospheric imagers on board the two STEREO spacecraft. The current version of the HELCATS manually-generated Coronal Mass Ejection (CME) catalogue contains more than 1,000 CMEs observed between 2007 and 2014. We present the results of our endeavours to identify slow drifting radio emissions observed by STEREO/Waves between 125 kHz and 2 MHz that are associated with these CMEs. We find that only about 10% of all of the manually-identified CMEs are associated with such radio emissions. Our results indicate that faster CMEs are more likely to produce radio emissions arising from CME flanks. | | 17 | A Raspberry Pi magnetometer for measuring the effects of space weather | Bingham, S et al. | p-Poster | | | Lucia Calverley[1], Jennifer Haskell[1], Jacqueline Pitts[1], John Puddy[1], Callum Roberts[1], Sharon Strawbridge[1], Suzy Bingham[2], Ciaran Beggan[3], Steve Marple[4], Iain Grant[5] | | | [1]University of Exeter; [2]Met Office; [3]British Geological Survey; [4]University of Lancaster; [5]Norman Lockyer Observatory. | | | A Raspberry Pi, fluxgate magnetometer has been installed at the Norman Lockyer Observatory, south-west UK, as part of a student project to measure the impacts of geomagnetic storms. The installation and operation of the magnetometer system will be described and comparison of data with other instruments will be discussed. | | 18 | The mid-latitude geomagnetic field and ionospheric response to solar and interplanetary triggers of St. Patrick's 2013 and 2015 events as seen from Spanish records | Guerrero, A et al. | p-Poster | | | A.Guerrero[1], J.Palacios[1], M.Rodríguez-Bouza[2], I. Rodríguez-Bilbao[2], A. Aran[5], C. Cid[1], G. Rodríguez-Caderot[2,4], E. Saiz[1], M.Herraiz[2,3], Y.Cerrato[1] | | | [1]Universidad de Alcalá (UAH), Physics and Mathematics Department, Alcalá de Henares, Spain; [2]Departamento de Física de la Tierra, Astronomía y Astrofísica I (Geofísica y Meteorología), Facultad de Ciencias Físicas, Universidad Complutense de Madrid (UCM), Madrid, Spain; [3]Instituto de Geociencias (UCM,CSIC), Madrid, Spain; [4]Instituto de Matemáticas Interdisciplinar (UCM), Madrid, Spain; [5]Department de Física Quàntica i Astrofísica i Institut de Ciències del Cosmos, Universitat de Barcelona, Barcelona, Spain | | | The coincidental occurrence on the 17th of March (St.Patrick’s day) of two geomagnetic storms, separated by exactly two years (2013-2015), provides the opportunity to test much of our current understanding of the Sun-Earth interaction. Not only the day and the season were the same for both events, but also the UT time of commencement of the event. Hence, in this naturally replicated experiment some constraints, which are difficult to identify and remove, may be excluded from the analysis as they can be assumed because of their common role in both events. In this work, we study the response of the geospace at mid latitude through ground magnetometer data from SPT observatory and ionospheric parameters in Madrid, from GNSS receivers. Similarities and differences appear when comparing both events. The whole Sun-to-Earth chain (remote and in-situ, including SEPs among others) has been analyzed in order to provide explanations for similarities and differences found in the geospace response. | | 19 | | , | | | | | | 20 | Redefining the boundaries of interplanetary coronal mass ejections from observations at the ecliptic plane | Cid, C et al. | p-Poster | | | Consuelo Cid, Judith Palacios, Elena Saiz, and A. Guerrero | | | Universidad de Alcala | | | On 2015 January 6-7, an interplanetary coronal mass ejection (ICME) was observed at L1. This event, which can be associated with a weak and slow coronal mass ejection (CME), allows us to discuss on the differences between the boundaries of the magnetic cloud and the compositional boundaries. A fast stream from a solar coronal hole surrounding this ICME offers a unique opportunity to check the boundaries process definition and to explain differences between them. Using Wind and ACE data, we perform a complementary analysis involving compositional, magnetic, and kinematic observations providing relevant information regarding the evolution of the ICME as travelling away from the Sun. We propose erosion at least at the front boundary of the ICME as the main reason for the difference of the boundaries, and compositional signatures as the most precise diagnostic tool for the boundaries of ICMEs. | | 21 | Eruptive and confined flare topological conditions | Schmieder, B et al. | p-Poster | | | Brigitte Schmieder[1], Francesco Zucarello[2], Guillaume Aulanier[1], Ramesh Chandra[3] | | | [1]LESIA, Observatoire de Paris; [2]CPA, Leuven; [3]Kumaun University, Nainital, India | | | Explaining the trigger and energy release processes of flares is a fundamental problem of solar physics. It is commonly held that magnetic reconnection plays a key role in converting magnetic energy into other forms of energy. In 2D magnetic field configurations, when oppositely directed magnetic fields are brought together they may reconnect thereby releasing stored magnetic energy eventually resulting in a flare.
In 3D configurations, the magnetic topology should be considered and the reconnection is favored at the null point. We present a case-study showing the evolution of key topological structures, such as spines and fans which may determine the eruptive versus non-eruptive behavior. The series of eruptive flares, followed by confined flares, are all originating from the same site. This change of behavior can be attributed to the change of orientation of the magnetic field below the fan with respect to the orientation of the overlaying spine. Flares tend be more-and-more confined when those two fields gradually become less-and-less antiparallel, as a direct result of changes in the photosopheric flux distribution, being themselves driven by some continuous flux emergence.
| | 22 | Linking stellar dynamo action to flux emergence and flares | Brun, A et al. | p-Poster | | | A.S. Brun[1], A. Strugarek[2] | | | [1]AIM, CEA-Saclay, France; [2]University of Montreal, Canada | | | Stars are active magnetic objects. We will discuss how the surface activity is linked to its deep
internal origin via dynamo action and flux emergence. Based on 3-D MHD simulations performed with both ASH and
PLUTO codes we will show how turbulence and shear (either in convection or radiation zones) can help building
intense coherent magnetic structures amidst disorganized magnetic fields that can subsequently rise and emerge at
the stellar surface. Those intense twisted magnetic features, the amount of magnetic flux they possess and the shape
of the emerged structures are likely the source/ingredients of the intense magnetic flaring activity seen in most solarlike
stars and in particular of the associated X-ray emission. | | 23 | Investigating the reliability of photospheric eruptivity proxies | Guennou, C et al. | p-Poster | | | C. Guennou[1], E. Pariat[1], N. Vilmer[1] and the flarecast team[2] | | | [1]LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universites, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cite; [2]AA (GR), TCD (IE), UNIGE (IT), CNR (IT), CNRS (FR), UPSud (FR), FHNW (CH), Met Office (UK) | | | Flares and CMEs are among the most energetic events in the solar system, impacting the near-Earth environment and thus our technologies. The European H2020 research project Flarecast (Flare Likelihood and Region Eruption Forecasting) aims to develop a fully automated solar flare forecasting system with previous unmatched accuracy. Flarecast will automatically extract various active regions magnetic parameters from solar magnetogram and white-light images to produce accurate predictions using the current state-of-art forecasting techniques based on data-mining and machine learning.
Flare productivity is empirically known to be correlated with the size and the complexity of active regions. Several other parameters, based on magnetic field data from active regions have been tested in the recent years. Solely, none of these parameters have provided a clear eruptivity criterion yet. However, the predictability of these parameters has so far only been tested from observational data and never from controlled-cases, e.g. originating from numerical datasets..
In this context, we used the MHD numerical simulations of the formation of stable and unstable magnetic flux ropes of Leake et al. (2013) and Leake et al. (2014) to evaluate the predictive potential of the magnetic parameters. These eruptive / non-eruptive simulations only differs by the orientation of the dipole magnetic field, favoring or not the reconnection between the emerging and dipole fields. We used time series of magnetograms from the parametric simulations of stable and unstable flux emergence, in order to compute about 60 different parameters. This parameters list includes both new parameters, such as helicity, and parameters usually used as proxies in actual forecasting methods. We show that only the quantities $L_{ssm}$ and $L_{sgm}$ and $WL_{sg}$ measuring the total non-potentiality of a whole active region (Falconer et al. 2008), as well as the total length of the inversion line present significant preflare signatures, most likely making them successful flare predictors. | | 24 | Exploring the solar-flare predictive potential of non-neutralized currents and Ising energy in solar active regions | Kontogiannis, I et al. | p-Poster | | | Ioannis Kontogiannis[1], Manolis Georgoulis[1], Kostas Florios[1], Sung-Hong Park[2] | | | [1]Research Center for Astornomy and Applied Mathematics, Academy of Athens; [2]Trinity College Dublin | | | The immediate effect of solar flares on the geospace environment imposes strict conditions on the efficiency of prediction and requires the development of new methods with increasing sophistication and accuracy. In this context, we investigate the predictive potential of certain solar active-region properties reported in the literature as flare-associated but never widely used in an operational framework. We use Spaceweather Helioseismic Magnetic Imager Active Region Patch (SHARP) data to calculate the non-neutralized currents and Ising energy of a sizable sample of active regions. These quantities were chosen because a) electric currents supply the free magnetic energy necessary for flaring activity, b) the magnetic complexity, as modeled by the Ising energy, is an indication of potentially intense flaring activity, and c) promising results have been reported in the literature about their potential as flare predictors but no study has been performed on more extended samples. We describe the extraction process of these properties from SHARP data. Preliminary results show that both non-neutralized currents and Ising energy facilitate some distinction between flaring and non-flaring active regions and that there is a tendency for larger flares to occur for larger values of these properties. We finally discuss their efficiency and integrability of these predictors in the operational framework of the FLARECAST project of the European Commission.
Presentation supported by the EC/H2020 FLARECAST project, grant no. 640216.
| | 25 | Comparative Analysis of Flaring and Non-Flaring Active Regions | Guerra, J et al. | p-Poster | | | Jordan A. Guerra[1], D. Shaun Bloomfield[1,2], Sung-Hong Park[1], Peter T. Gallagher[1], Antti Pulkkinen[3], Vadim Uritsky[4] | | | [1]Trinity College Dublin, College Green, Dublin 2, Ireland; [2]Northumbria University, Newcastle Upon Tyne, NE1 8ST, UK; [3]Space Weather Lab. NASA GSFC, Greenbelt MD, USA; [4]The Catholic University of America, Washington DC, USA | | | Using a small sample of solar active regions we investigated if flaring regions can be effectively distinguished from non-flaring regions. Photospheric magnetic and coronal intensity measures were used to characterize time evolution of the active regions and their lifetime averages. Photospheric parameters were calculated using SDO/HMI SHARP data corresponding to the radial component of the photospheric field, B_r, remapped to the Cylindrical Equal Area coordinate system. Coronal intensities were extracted from SDO/AIA images in different wavelengths. We analyzed approx. 17K magnetogram/coronal maps, corresponding to the full lifetimes of 12 active regions. We find that some parameters are more effective in showing differences between flaring and non-flaring regions – i.e., flaring and non-flaring distributions overlap to a reasonable degree but flaring regions are offset towards higher values. In addition the temporal evolution of these parameters prior to flaring will be presented. Finally, we explore possibility of providing flaring probabilities from those parameters that showed clear separation between flaring and non-flaring regions. | | 26 | Parameterization of Solar Active Region Magnetic Fields and Flows for Flare Forecasting | Park, S et al. | p-Poster | | | Sung-Hong Park[1], Jordan A. Guerra[1], Peter T. Gallagher[1], D. Shaun Bloomfield[1,2] and the FLARECAST team | | | [1]Trinity College Dublin, College Green, Dublin 2, Ireland; [2]Northumbria University, Newcastle Upon Tyne, NE1 8ST, UK | | | Solar active regions that produce major flares and coronal mass ejections exhibit complicated magnetic structures and dynamic evolution. We have developed several novel algorithms to quantify magnetic fields and photospheric flows in active regions using vector-magnetic data from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We present how well flaring and non-flaring active regions are distinguished based on the examination of a statistical data set covering 4 days evolution for several active regions in 2012 to 2014. The correlation between these parameters and the peak GOES soft X-ray intensity of flares will be shown, along with the probabilities of flaring in the next 24 hours. The most promising algorithms will be applied to the full SDO/HMI catalogue within the pipeline of the Flare Likelihood And Region Eruption foreCASTing (FLARECAST) project, providing both a better understanding of solar flare physics and a near-realtime forecasting service.
This research was supported by the European Union's Horizon 2020 research and innovation programme under grant agreement No. 640216 (FLARECAST project). | | 27 | CME kinematics and solar source region characteristics – HELCATS results | Bothmer, V et al. | p-Poster | | | V. Bothmer[1], N. Mrotzek[1], S. Murray[2], P. Gallagher[2], A. Pluta[1], D. Barnes[3], J. Davies[3], R.A. Harrison[3] | | | [1]Institute for Astrophysics, University of Göttingen, Göttingen, Germany; [2]Astrophysics Research Group, Trinity College Dublin, Dublin, Ireland; [3]STFC, Rutherford Appleton Laboratory, Didcot, Chilton, UK | | | One objective of the EU FP7 project HELCATS is to derive and catalogue the kinematic properties of CMEs observed with the STEREO/COR2/HI imagers based on geometrical and forward modelling. Here we present the results of the analysis of a subset of the 122 CME events that have been dynamically modelled with the GCS-method in the COR2 field of view and which are compiled in the KINCAT database at http://www.affects-fp7.eu/helcats-database/database.php. The CME kinematic properties, such as speeds, masses, angular widths, as derived from modelling, are compared with magnetic field properties of the corresponding solar source active region, such as magnetic flux, area, and polarity line characteristics. | | 28 | EUV and X-ray emission in simulations of flaring coronal loops | Pinto, R et al. | p-Poster | | | R. F. Pinto[1,2], N. Vilmer[3], K. Kentheswaran[1,2] | | | [1]Université de Toulouse; UPS-OMP; IRAP; Toulouse, France; [2]CNRS; IRAP; 9 Av. colonel Roche, BP 44346, F-31028 Toulouse cedex 4, France; [3]LESIA, Observatoire Paris, CNRS, UPMC, Université Paris-Diderot, 5 place Jules Janssen, 92195 Meudon, France | | | Solar flares are associated with intense EUV and X-ray emission generated by hot flaring plasma and by energetic particles in coronal magnetic loops. We investigate the temporal, spatial and spectral evolution of the properties of the emission produced in simulated kink-unstable magnetic flux-ropes (using MHD and test-particle methods). The numerical setup used consists of highly twisted coronal loops embedded in regions of untwisted background coronal magnetic field. The magnetic flux-rope reconnects with the background flux after the triggering of the kink instability and is then allowed to relax to a lower energy state. Strong ohmic heating leads to strong and quick heating (up to more than 15 MK), to a strong peak of soft X-ray (thermal) emission and to the hardening of the X-ray spectrum. Particles are accelerated in all the flaring loop volume, but the associated synthetic hard X-ray emission is nevertheless concentrated near the footpoints. The amount of twist deduced from the thermal X-ray emission alone is considerably lower than the maximum twist in the simulated flux-ropes. The flux-rope plasma becomes strongly multi-thermal during the flaring episode, and the emission measure evolves into a bi-modal distribution as a function of temperature during the saturation phase, and later converges to the power-law distribution during the relaxation/cooling phase. | | 29 | The discovery of an electron current at Earth's McIlwain L=6 | Katsiyannis, T et al. | p-Poster | | | Thanassis Katsiyannis[1], Marie Dominique[1], Viviane Pierrard[2], Kris Borremans[2], Johan De Keyser[2], David Berghmans[1], Michel Kruglanski[2], Ingolf Dammasch[1], Erwin De Donder[2] | | | [1]Royal Observatory of Belgium, SIDC [2]Royal Belgian Institute for Space Aeronomy, SIDC | | | The Large Yield RAdiometer (LYRA) is an ultraviolet solar radiometer on-board ESA's PROBA2 micro-satellite. Since its launch in 2009 to an altitude of 735km, one of the most peculiar and intriguing results of LYRA is the detection of short, strong, bursts that do not directly correlate with solar coronal events, nor with pointing of the instrument to Earth's upper atmosphere, but correlate well with high a$_{p}$ index on Earth's surface and the crossing by the satellite of the L=6 shell.
Very similar detections were more recently made by the Energetic Particles Telescope (EPT) on board the PROBA-V micro-satellite, establishing the identification of the detections as relativistic electrons of the 2.4-8 MeV energy range.
Several attributes of those detections, including their dependency to various space weather indexes (ap, $D_st$, etc), their geographical distribution, a dawn/dusk asymmetry and others will be presented. Open questions related to the discovery of this phenomenon will also be discussed.
| | 30 | The presence of Active Longitude form photosphere to interplanetary space | Gyenge, N et al. | p-Poster | | | N. Gyenge[1,2], M. Dósa[3], G. Erdős[3], R. Erdélyi[1,2] | | | [1]Solar Physics and Space Plasmas Research Centre (SP2RC), School of Mathematics and Statistics, University of Sheffield Hounsfield Road, Hicks Building, Sheffield S3 7RH, UK; [2]Debrecen Heliophysical Observatory (DHO), Konkoly Observatory, Research Centre for Astronomy and Earth Sciences Hungarian Academy of Sciences, Debrecen, P.O.Box 30, H-4010, Hungary; [3]MTA Wigner FK RMI, Department of Space Physics, Budapest, Hungary | | | The aim of the present work is to investigate the signatures of the spatio-temporal characteristics of the non-axisymmetric magnetic field of the Sun. The presence of active longitude (AL) is argueed for to exist in various solar phenomena, such as the spatial distribution of sunspot groups, solar flares and CMEs. By using our method, developed for this purpose, we identified the AL in every Carrington Rotation. The data is provided by the Sheffield Solar Catalog (SSC). The migration paths outline a set of patterns with high confidence in which an activity zone has alternating prograde / retrograde angular velocities with respect to the Carrington Rotation rate. The temporal profiles of these variations can be described by a set of successive parabolae. The widths of the longitudinal active domains are rather narrow, their half-widths are in the range of 20 - 30 degrees.
In our study, the so-called complexity parameter was used to reveal the morphological properties of sunspot groups near and far from the AL. This parameter is able to characterise the mixing of subgroups of sunspots with an opposite polarity. We found that, within the AL significantly higher number of morphologically complex sunspot groups emerge. These active regions also produce more energetic solar flares and CMEs as compared to regions outside of the active zone around the AL. Next, the relationship between the longitudinal position of solar flares and CME occurrences is also investigated. Statistics show that a significant fraction of these eruptive phenomena are also located near to the AL. Finally, the influence of AL is remarkably detectable in solar wind velocity measurements. We conclude that the manifestation of the non-axisymmetric magnetic field is observable in a wide range of solar phenomena from the photosphere to interplanetary space. | | 31 | Dimmings as a magnetic footprint of coronal mass ejections | Thompson, B et al. | p-Poster | | | Barbara Thompson[1], Joel C. Allred[1], Christina D. Kay[1], Emil Kraaikamp[2], Larisza D. Krista[3], James P. Mason[3], M. Leila Mays[1,4], Teresa Nieves-Chinchilla[1,4], Alysha A. Reinard[3], Cis Verbeeck[2], David F. Webb[5] | | | [1]NASA GSFC; [2]Observatoire royal de Belgique; [3]University of Colorado; [4]Catholic University of America; [5]Boston College | | | Large regions of coronal dimming often accompany coronal mass ejections (CMEs). Of all of the EUV signatures of CMEs, dimmings (when present) are the best match to the location and extent of the coronagraph CME observations. They last on timescales from minutes to hours, are sometimes patchy in appearance, and can extend far (>1 RSun) from the flaring region. They are known to be good indicators of the site of evacuated material, and have been extensively studied as a CME mass source.
We investigate the idea that dimmings also serve as a magnetic footprint of CMEs. Dimmings develop during or soon after the eruption, and may trace field lines locally opened during the CME. These dimming regions can be extensive, representing at least part of the “base” of a CME and the mass and magnetic flux transported outward by it. We report on three-dimensional observations of the co-development of dimmings in EUV and coronagraph images, magnetic field topologies represented by the dimmings, and (when available) in situ observations that can be used as a diagnostic of the erupting field topology. Finally, we discuss the use of dimmings as a means of constraining the 3D extent and kinematics of an eruption.
| | 32 | Forecasting of Corotating Interaction Regions geoeffectiveness | Calogovic, J et al. | p-Poster | | | Jaša Čalogović[1], Mateja Dumbović[1], Bojan Vršnak[1], Bernd Heber[2], P. Kühl[2], Manuela Temmer[3], Astrid Veronig[3] | | | [1]Hvar Observatory, Faculty of Geodesy, Kačićeva 26, HR-10000 Zagreb, Croatia; [2]Institute for Experimental and Applied Physics, Christian-Albrechts-University Kiel, Germany; [3]Institute of Physics, University of Graz, Universitätsplatz 5, A-8010 Graz, Austria | | | In the declining phase and minimum of the solar cycle, when the occurrence of
interplanetary coronal ejections (ICME) becomes very low, the major driver of the solarwind
disturbances and geomagnetic storms are corotating interaction regions (CIR). CIRs
are produced as fast solar wind streams, originating from coronal holes (CH), interact
with the preceding slow solar wind. To improve space weather predictions, we
investigated the relationship between the area of CHs and Dst index during the
minimum phase of the solar cycle 23-24 (2007-2010). CHs are visible as dark regions in
the solar corona due to their low temperature and electron density, and thus can be
extracted with an intensity-based thresholding technique from the SOHO EIT 195 Å
images. Since interplanetary near-Earth disturbances are delayed about 4 days after
changes in CH area, this gives a good opportunity to forecast a geoeffectiveness of CIRs
as well as their effect on the cosmic-ray flux during the solar minimum in the absence of
ICMEs. This work has been fully supported by Croatian Science Foundation under the
project 6212 „Solar and Stellar Variability“. | | 33 | A new ICMEs catalogue: Tracking a CME from Sun to the Earth | Paouris, E et al. | p-Poster | | | Evangelos Paouris, Helen Mavromichalaki | | | Faculty of Physics, National and Kapodistrian University of Athens, Athens, Greece | | | It is well known that the interplanetary coronal mass ejections (ICMEs) play the most important role on the interactions with the magnetosphere as they are the dominant drivers of intense geomagnetic storms. A number of 180 ICMEs associated with CMEs were spotted from SOHO-LASCO coronagraph and their characteristics were calculated by in situ observations from ACE data covering the years 1996–2009 are presented. The result of this study is a new ICME catalogue which contains all the available information. Especially, characteristics of a) the CME obtained from LASCO list which is responsible for the upcoming ICME, like the linear speed, the angular width and the coordinates on the Sun, the peak time and the active region of the associated solar flare, b) the initial/background solar wind plasma and magnetic field conditions before the arrival of the CME, such as the solar wind speed, the magnetic field B, the southward component Bz, the proton temperature and density, the ratio of alpha particles to protons and the plasma β, c) the sheath of the ICME, such as the presence or not of a shock wave, the arrival time of the ICME-driven shock and the solar wind plasma and magnetic field conditions of the sheath, d) the main part of the ICME, like the solar wind plasma and magnetic field conditions, the duration of the ICME with start/end time and the transit velocity from Sun to Earth, e) the geomagnetic conditions of the ICME’s impact at Earth, such as Ap and Dst indices and the exact time of their maximum and minimum values, respectively and finally f) remarks on every event, are determined. Interesting results revealed from this study as the high correlation coefficient values of the magnetic field Bz component and the Ap index (r = 0.86), as well as the Dst index (r = 0.82), of the effective acceleration against the CME linear speed (r = 0.92) and of the transit velocity against the linear speed of the CME (r = 0.70). The amount of information makes this new catalogue the most comprehensive ICMEs catalogue for the solar cycle 23. | | 34 | On the evolution of pre-flare patterns in a 3-dimensional solar Active Region | Korsos, M et al. | p-Poster | | | Korsos, Marianna[1,2], Gyenge, Norbert[1], Ruderman, M.S.[1], Fedun, V. and Erdelyi, R.[1,2] | | | [1]University of Sheffield; [2]Debrecen Heliophysical Observatory,Hungarian Academy of Sciences Research Centre for Astronomy and Earth Sciences Konkoly Thege Miklós Astronomical Institute | | |
Solar flares can have a major impact on life and modern technological infrastructure present in Space or on Earth. In this presentation, we address newly discovered pre-flare behavioural patterns in typical sunspot groups by focusing on their evolution as a function of height above the solar surface in a 3-dimensional solar Active Region.
Here, we introduce and discuss the relevant properties and their capability to improve Space Weather forecasting of pre-flare behavioural patterns in typical solar ARs by focusing on their evolution from the photosphere towards the chromosphere, Transition Region and low corona. The basis of proxy measure of our approach is the so-called weighted horizontal gradient of magnetic field (W_GM) defined between spots of opposite polarities closer to polarity inversion line(s) of an AR. The value and the temporal variation of W_GM is found to possess novel and potentially important diagnostic information about (i) the intensity of expected flares, (ii) the accuracy of onset time prediction, and (iii) whether a flare, with same energetic class in terms of the GOES classification, is followed by another one within an 18-hour window on the photosphere.
Next, we will demonstrate how by tracking the temporal evolution of W_GM, distance between opposite polarity spots and the associated net flux at various heights in the lower solar atmosphere then evolves as function of height. We show that this latter temporal behaviour across the chromosphere-low corona has fundamentally new forecast capabilities. We found, that at a certain height the converging of opposite polarities begin much earlier than at the photosphere or at other heights. The gained forecast capability time could be as high as 24 hrs. Therefore we present a tool to identify the optimum height in the solar atmosphere for flare forecasting that may considerably increase the forecast time. This would be a significant progress in the field. | | 35 | Helical Kink Instability: From a Confined Solar Eruption to a CME | Hassanin, A et al. | p-Poster | | | Alshaimaa Hassanin[1], Bernhard Kliem[2] | | | University of Potsdam, Institute of Physics and Astronomy | | | On 2002 May 27 a confined filament eruption event accompanied by a solar flare but no coronal mass ejection (CME) took place. A model to explain this eruption based on the kink instability was proposed by Török and Kliem (2005). This could explain the rise of the flux rope up to the terminal height. Here, we seek not only to extend this previous study to model the whole event, but also to offer some insights on homologous flares and CMEs. Firstly, we perform more detailed investigations on the kinked magnetic flux tube model by setting the parameters such that the flux rope twist is close to the threshold for the onset of the helical kink instability. The flux rope represents the filament and the overlying flux represents the main magnetic flux of the modeled active region, rooted in the main polarities (sunspots). This confined eruption involves two phases of reconnections. One is between the flux rope and the ambient magnetic field and the other is between the two legs of the flux rope forming a new, less twisted and stable rope. Secondly, we apply rotating and converging motions (which are often observed) near the neutral line in our simulation to build up new magnetic energy and helicity in the reformed flux rope, which could lead to a further eruption which can become a CME. | | 36 | Hall-MHD simulations of the Kelvin-Helmholtz instability at the magnetopause: reconnection and transport of the northward solar-wind | Leroy, M et al. | p-Poster | | | M. Leroy, R. Keppens | | | Centre for mathematical Plasma-Astrophysics KU Leuven, Leuven, Belgium | | | While the transfer of matter from the solar-wind to the Earth's magnetosphere during southward solar wind is widely attributed to reconnection, the processes governing the same phenomenon during northward solar wind remains to be fully apprehended.
Given the typical parameters at the magnetosphere-solar wind interface, the situation must be considered in the frame of Hall-MHD, due to the fact that the current layers widths and the gradient lengths can be in the order of the ion inertial length and lead to a different reconnection regime. Local flow perturbations can also affect the magnetic field configuration at a distance, making three-dimensional treatment necessary to render phenomenon like the double mid-latitude reconnection.
In this spirit three-dimensional simulations of Kelvin-Helmholtz instabilities at the flank of the magnetosphere during northward oriented solar-wind are performed as means to study the entry of solar-wind matter into Earth's magnetic field, both in the MHD and Hall frame. Furthermore the influence of the density and velocity jump through the shear layer on the rate of mass entering the magnetosphere is explored. Indeed, depending on the exact values of the physical quantities, the Kelvin-Helmholtz instability may have to compete with secondary instabilities and the non-linear phase may exhibit vortex merging and large-scale structures reorganisation, creating very different mixing layers, or generate different reconnection sites. These different configurations may have discernible signatures that can be identified by spacecraft diagnostics. At last, particle populations are evolved inside fixed snapshots of the different resulting configurations to complete the set of diagnostics.
| | 37 | Halo CMEs During Solar Cycle 24: Reconstruction of the Global Scenario and Study of Their Geoeffectiveness | Scolini, C et al. | p-Poster | | | Camilla Scolini[1], Mauro Messerotti[1,2] | | | [1]Department of Physics, University of Trieste, Italy; [2]INAF-Astronomical Observatory of Trieste, Italy | | | Coronal Mass Ejections (CMEs), in particular Earth-directed ones, are regarded as the main drivers of geomagnetic activity. In this work we address the problem of reconstructing the global evolution of geoeffective CMEs from the Sun to the Earth, with the final aim of identifying peculiar features that can be used as precursors of CME-driven geomagnetic storms. In particular, we present an analysis of a set of 53 CMEs observed by the SOHO/LASCO instrument in the period Jan. 2010 - Jul. 2015. Because of their higher probability of triggering strong geomagnetic storms, we selected all fast (V 1, 000 km s−1) Earth-directed halo CMEs during the time period considered.
We first investigate the association of selected CMEs with other solar activity features such as solar flares, active regions, filaments/prominences and other ones, by means of multi-instrument observations of magnetic and plasma properties obtained by the Solar Dynamics Observatory (SDO). We then make use of the CCMC ENLIL with cone model to reconstruct the propagation and global evolution of each event up to its arrival at Sun-Earth lagrangian point L1, where we compare model results with Interplanetary CMEs (ICMEs) signatures observed in-situ by Wind spacecraft. By using some coupling functions linking upstream solar wind properties to most widely used geomagnetic activity indices (namely Kp and Dst indices), we estimate the geomagnetic activity level expected and compare it with global data records.
This statistical analysis of recent CME/ICME events is aimed at providing new insights on the solar conditions from which CMEs triggering strong geomagnetic storms are most likely to erupt. The analysis indicates that only 60% of the fast Earth-directed halo CMEs resulted in a strong geomagnetic storm. Among them, complex sunspot-rich active regions associated with X- and M-class flares are the most favourable configurations from which geoeffective CMEs originate. Moreover, the internal magnetic structure of ICMEs represents one critical issue in determining their impact on geospace and future models will have to take this point into account to provide reliable space weather predictions. | | 38 | Effect of a magnetic field on Rayleigh-Benard convection in a Solar Tachocline: quasi-geostrophic approximation | Pirguliyev, M et al. | p-Poster | | | M.Sh.Pirguliyev[1], N.S. Dzhalilov[1], E.S. Babayev[1], B.M. Shergelashvili[2] and S. Poedts[3] | | | [1]Shamakhy Astrophysical Observatory of the Azerbaijan Academy of Sciences, Baku, Azerbaijan; [2]Space Research Institute, Austrian Academy of Sciences, Graz, Austria; [3]Centre for Mathematical Plasma Astrophysics, KU Leuven, Leuven, Belgium | | | The linear dynamics of rotating Solar Tachocline Rayleigh-Benard magnetoconvection with free-free boundary conditions investigated at the quasi-geostrophic approximation on the beta-plane using thermal time-scale normalisation. We determined the marginal stability boundary and critical wavenumbers and corresponding critical Rayleigh number for the onset of convection in the given system. A simple formula is derived for the Rayleigh number and the results were tabulated numerically in either as stationary and in an oscillatory fashion.
We used the full set of MHD equations with the Boussinesq approximation in the rotating frame with angular velocity $\Omega$ and for normalisation of the perturbation equations we base on the thermal diffusion time scale ($\tau_{\chi}=d_{0}^2 / \chi$). For this reason our system characterized with dimensionless parameters, such as the thermal Prandtl number $Pr$, the magnetic Prandtl number $Pm$, the Ekman number $E$, the Rayleigh number $Ra$ and the Elsasser number $\Lambda$. As basic state geometry we get the magnetic field is a $\vec{B}_{0}=B_{0} \vec{\hat{y}}$, temperature gradient is a $\hat{\nabla T_{0}}=\hat{\vec{x}}$ and rotation axis is a $\vec{\hat{\Omega}}=\vec{\hat{z}}$. $\vec{u}_{0}=0$ is a solution to the steady state balance.
In generally, since we consider tachocline layer, with free top and bottom surfaces $z=1$ and $z=0$, respectively, characteristic flow velocity $U\sim10^{-7}$ $m \cdot s^{-1}$ and the lengthscale $\delta_{\chi}=\chi / U$ has magnitude $\sim 0.014$ $Mm$, which is very smaller than the local pressure scale height, $H_{p} \approx 60$ $Mm$. It is a reason that why we employ the Boussinesq approximation in modelling the confinement layer. Properly the Rossby number $Ro=U / \Omega\delta_{\chi}$ is far smaller than 1, $Ro\sim 1.19 \cdot 10^{-6} \ll 1$, whereby we can neglect ageostrophic flow effects, i.e. $\vec{u}_{H} \approx \vec{u}_{G}$.
We reviewed the linear stability of the system to normal mode disturbances for the $z-$component of vorticity $\omega_{z}=\hat{\vec{z}} \cdot (\vec{\nabla} \times \vec{u})$, the electric current density $j_{z}=\hat{\vec{z}} \cdot (\vec{\nabla} \times \vec{B})$ , the temperature $\theta(x,y,t)$, the components $u_{x,y}(x,y,t)$ and the streamfunction $\psi(x,y,t)$ as $P(x,y,t)=\Re[P(y) \exp(iax+\sigma t)]$. We calculate the critical value of the Rayleigh number, for a particular wave number, at which convection could occur. This was done for the case of no rotation, as well as the rotating system. Furthermore, we distinguished between the type of instability at the onset of convection-stationary or oscillatory. We computed stability conditions to determine the type of instability at the onset of convection that were dependent on the value of the Ekman number and the Prandtl numbers.
For the case with rotation $E^{-1}\neq0$ and with magnetic field with $Pm^{-1}\neq0$ and $\Lambda\neq0$, we obtained cubic formula for dispersion relation in terms of the growth-rate $\sigma$. Guided by Chandrasekhar \cite{chandrasekhar} considered a stationary and oscillatory instabilities. Stabilities considered for given values of dimensionless parameter $\Lambda$, which are corresponding to any values of the magnetic field strength.
The solutions of cubic dispersion relation $\sigma$ depend on the non-dimensional parameters h, which is a function of coefficients of cubic equation. Instability conditions is a h > 1. In particulary, discussed strongly unstable case, when h >> 1.
| | 39 | Kelvin-Helmholtz instability features in the solar winds | Ismayilli, R et al. | p-Poster | | | Rajab Ismayilli[1], Namig Dzhalilov[1], Bidzina Shergelashvili[2,3], Stefaan Poedts[4] | | | [1]Shamakhy Astrophysical Observatory of the Academy of Sciences (ShAO), Azerbaijan; [2]Abastumani Astrophysical Observatory, Ilia State University, Tbilisi, Georgia; [3]Space Research Institute Austrian Academy of Sciences, Graz, Austria; [4]Dept. of Mathematics, Centre for mathematical Plasma Astrophysics, KU Leuven, Leuven, Belgium | | | We study wave properties and instabilities in a magnetized, anisotropic, collisionless plasma in the fluid approximation using the 16-momentum formalism. In particular, we investigated equations different from the ideal MHD equations by including evolution equations for the heat fluxes with different components along the magnetic field $S_{\parallel}$ and in the transverse direction $S_{\perp}$. In this work, we studied the Kelvin-Helmholtz instability that occurs in the contact discontinuity interactions of the slow (350-400 km/s), fast (600-850 km/s) and CME (900-1200 km/s) components of solar wind, taking into account the pressure anisotropic properties ($p_{\perp}, p_{\parallel}$) of the wind plasma. This instability is investigated by solving the 16-momentum set of equations based on an assumed geometry.
We solved these equations in Cartesian coordinates and considered an equilibrium state with velocity $\vec{v}_0=(0,0,{v}_{0z}(x))$ and magnetic field $\vec{B}_0=(0,0,{B}_{0})$. We also assume that the intial equilibrium state with non-zero thermal fluxes is homogeneous, i.e. gravitional acceleration is ignored, $g=0$, and the quantities $ \rho_0, p_{\perp0}, p_{\parallel0}, B_0, S_{\perp0}, S_{\parallel0} $ are all assumed to be constant. We considered the stability of the system to linear perturbations of all the physical variables, according to the form $f=f_0+f'(x,y,z,t)$, where $f'(x,y,z,t) \sim F'(x) \ exp [i(k_y y + k_z z - \omega t)]$. Here, $\omega$ is the wave frequency and $k_y, k_z$ are the wave numbers. We reduced the number of linearized equations governing the perturbations and obtained a second order differential equation for the $x$-component of the magnetic field. Applying boundary conditions, when the mass flux ($\rho_0 {v}_x$) and the total pressure ($p'_\perp + B_0 B_z / 4 \pi$) are equals to zero at the point $x=0$, and by using a step discontinuous velocity profile, we obtained the dispersion relation.
A preliminary study of this equation for solar wind plasma parameters showed that in places of contacts of different streams having the Kelvin-Helmholtz instability properties are highly dependent on the plasma anisotropy and heat flow along magnetic field. The results should be used for the interpretation of the observed facts of wave turbulence in CIR.
| | 40 | The D-region Ionospheric Perturbations Caused by Solar Flares: Inferred from Very Low Frequency (VLF) Waves observations in Mid-latitude region | Mustafa, F et al. | p-Poster | | | Famil Mustafa[1], Elchin S. Babayev[1],Namig Dzhalilov[1], Stefaan Poedts[2], Rajesh Singh[3], Ajeet K. Maurya[4], Ilgar Alakbarov[1] | | | [1]Shamakhy Astrophyiscal Observatory, Azerbaijan National Academy of Sciences, Baku, Azerbaijan; [2]Department of Mathematics, Centre for Mathematical Plasma-Astrophysics, KU Leuven, Leuven, Belgium; [3]K.S. Krishnan Geomagnetic Research Laboratory (KSK GRL), Indian Institute of Geomagnetism, Allahabad, India; [4]School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA | | | The measurement of Very Low Frequency (VLF) signals, generated by navigational
transmitters, is one of the reliable and cost-effective tools for remote sensing of the D-region electron density perturbations associated with solar flares as well as for understanding the dynamical processes in the D-region ionosphere.
The Automatic Weather Electromagnetic System for Observation Modelling and Education (AWESOME, Stanford University, USA) VLF receiver located in the middle latitude geographical station at the Shamakhy Astrophysical Observatory, Pirgulu, Azerbaijan (latitude 40°46’204 N, longitude 48°35’04E) was used to record the amplitude and phase perturbations of three VLF signals transmitted by the GBZ transmitter (frequency f = 19,6 kHz) at Anthorn, Great Britain, JJI transmitter (f = 22.2 kHz) at Ebino, Miyazaki, Japan and DHO transmitter (f = 23,4 kHz) at Rhauderfehn, Germany and propagating along the Earth-ionosphere waveguide (EIWG).
Data on VLF waves, transmitted by navigational transmitters for the years 2010-2011 were used to study changes in the VLF signal amplitude and phase in the D-region with respect to solar flares. The C, M and X class solar flares that occurred during 2010-2011 (in total 133 flares – 110 C class, 21 M class, 2 X-class; low solar activity period of the solar cycle 24) are selected for a comparative analysis of VLF data. Geostationary Operational Environmental Satellite (GOES) data were also involved in this study. The local time dependence of solar flare effects on the change in the VLF amplitude, the time delay between VLF peak amplitude and X-ray flux peak have been studied during the morning, noon and evening periods of local daytime. Using the Long Wave Propagation Capability code V2.1, the D-region reflection height (H/) in km and the D-region electron density gradient or sharpness factor (β) in km-1 have been estimated for each class of solar flare (C, M and X).
The results show that solar flare effects on the sub-ionospheric VLF signals are identified by the sudden increase in their amplitudes. These sudden changes are manifestations of rapid enhancements in the D-region ionospheric plasma density associated with flares. It was revealed that solar flares of C, M and X classes affect VLF signal amplitude and lead to its consequent increase from ~1dB to ~10 dB. All selected examples (JJİ, DHO and GBZ) showed that the amplitude of VLF signals were perturbed by solar X-ray flares occurrence. D region ionospheric parameters (H/, β) show significant dependence on the local time of flare’s occurrence and their classes. | | 41 | Estimating the CMEs speed from ground detected type II solar radio bursts | Uwamahoro, J et al. | p-Poster | | | Jean Uwamahoro[1], Sarathiel Tuyizere[2], Christian Monstein[3] | | | [1]University of Rwanda, College of Education, Kigali, Rwanda; [2]University of Rwanda, College of Science and Technology, Kigali, Rwanda; [3]Institute for Astronomy- ETH Zurich- Switzerland | | | Type II solar radio bursts (SRBs) are often considered being associated with CME-driven shocks in the solar corona. Their detection either from space or at ground level can serve as advance warning of incoming extreme space weather events. By using a database of ground-based network of CALLISTO solar spectrometers, we have analyzed a sample of 32 type II SRBs observed in the metric wavelengths from 2012 until 2015. SRBs drift rate is calculated from CALLISTO dynamic spectra data and used in a model to compute the speed of associated CMEs. In this paper, we will present preliminary results from our investigation that gives a very good estimate of CMEs speed. Further, the results are compared with previous similar investigations using WIND /waves data. | | 42 | Radio signatures of the shock waves and their association with coronal structures seen by the SWAP and coronagraph observations | Krupar, V et al. | e-Poster | | | V. Krupar[1], J. Magdalenic[2], M. West[2], E. D'Huys[2], L. Prech[3], O. Kruparova[4] | | | [1]Imperial College London; [2]Royal Observatory of Belgium; [3]Charles University, Faculty of Mathematics and Physics, Czech Republic; [4]Institute of Atmospheric Physics CAS, Prague, Czech Republic
| | | placeholder | | 44 | MHD simulation of ICMEs | Hosteaux, S et al. | p-Poster | | | Skralan Hosteaux, Stefaan Poedts, Emmanuel Chané | | | KULeuven | | | We study the propagation of ICMEs via MHD numerical simulations. We want to understand how the polarity of the ICMEs, their initial speeds and the properties of the solar wind affect the propagation in the interplanetary medium. Characteristics such as the arrival time at 1 AU, the velocity profile of the magnetic cloud and of the shock, as well as the standoff distance are studied in detail. In our simulations, an adaptive mesh refinement algorithm is used to obtain a very high accuracy in the regions of interest and to limit the computation time. The simulations are then used as a tool to help us to understand multi-spacecraft in situ measurements of ICMEs.
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