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

Luciano Rodriguez, Sergio Dasso

The study of Interplanetary Coronal Mass Ejections (ICMEs) has advanced greatly in the last few years thanks to multispacecraft observations and high performance numerical MHD simulations. The comparisons between models and observations are clarifying several problems, such as the effects of the ambient solar wind on their propagation and internal configuration, the link between ICMEs and non-thermal energetic particles in the heliosphere (solar, interplanetary, and galactic origin), etc. In this session we invite contributions based on models and/or observations of ICMEs, which can cover the ICME propagation in the heliosphere, the interaction of ICMEs with Earth and/or with other planets, the effects of ICMEs on energetic particles, as well as on other general topics linked with ICMEs in the heliosphere.

Talks
Tuesday November 24, 11:00 - 13:00, Permeke

Poster Viewing
Tuesday November 24, 10:00 - 11:00, Poster area

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Talks : Time schedule

Tuesday November 24, 11:00 - 13:00, Permeke

11:00	Interplanetary shocks and space weather	Dal lago, A et al.	Invited Oral
	Alisson Dal Lago[1], Aline de Lucas[2], Carlos Roberto Braga[1]
	[1] National Institute for Space Research - INPE, Brazil; [2] IFSP - Jacareí, Brazil
	Interplanetary coronal mass ejections (ICMEs) play a central role among the origins of geomagnetic storms. Of special importance are their driven shocks, which often are associated to strong southward pointing (Bs) sheath fields. Several statistical studies have found that such sheath Bs can be as effective as ICME Bs fields for energizing the magnetospheric ring current, as measured by the Dst index. Multipoint observations of shocks have revealed that their extensions are much larger than their driving ICMEs. An extensive study was possible during the Helios mission, from 1974 to 1986, which covered an entire solar cycle. Among the most important findings was the fact that shocks driven by CMEs near the solar limb have 50% chance of hitting the earth. It is also important to note that the importance of interplanetary shocks for space weather varies in distinctive solar cycle phases. It has been found that shocks were the dominant interplanetary structure causing intense magnetic storms during the maximum phase of solar cycle 23. Attempts to model ICMEs and their related shocks using ground cosmic ray observations were carried out recently with good results. As an earth perspective, recent studies have highlighted the connection between interplanetary shocks and the dynamics of the earth’s outer radiation belt electrons.
11:30	Solar radio observations as a tool to forecast the arrival of coronal mass ejections near Earth ?	Klein, K et al.	Oral
	C. Salas Matamoros, G. Trottet, K.-L. Klein
	Observatoire de Paris, LESIA, 92190 Meudon, France
	The propagation of a coronal mass ejection (CME) to the Earth takes between about 13 hours and several days. Observations of early radiative signatures of CMEs therefore provide a possible means to predict the arrival time of the CME near Earth. The fundamental tool to measure CME speeds in the corona is coronography, but the Earth-directed speed of a CME cannot be measured by a coronagraph located on the Sun-Earth line. Various proxies have been devised to circumvent this problem, based on the coronographic measurement. As an alternative, we explore radiative proxies. We have recently shown that when a soft X-ray burst accompanies a CME, one can use its peak flux or its fluence as a proxy of the CME speed, by means of a relationship established for CMEs at the limb (Salas Matamoros & Klein, Solar Phys., 2015). In the present contribution we investigate if microwave observations can be employed instead of soft X-rays. Caroubalos (1964) had shown that the higher the fluence of a solar radio burst near 3 GHz, the shorter is the time lapse between the solar event and the sudden commencement of a geomagnetic storm. We reconsider the relationship between CME speed and microwave fluence for limb CMEs in cycle 23 and early cycle 24. Then we use the microwave fluence as a proxy of CME speed of Earth-directed CMEs, together with the empirical interplanetary acceleration model devised by Gopalswamy et al. (2001), to predict the CME arrival time at Earth. These predictions are compared with observed arrival times of CMEs near Earth and with the predictions based on other proxies, including soft X-rays and coronographic measurements.
11:45	Propagation of the 7 January 2014 CME and Resulting Geomagnetic Non-Event	Mays, M et al.	Oral
	M. L. Mays[1,2], B. J. Thompson[2], L. K. Jian[2,3], R. C. Colaninno[4], D. Odstrcil[6], C. Möstl[7,8], M. Temmer[8], N. P. Savani[5,2], A. Taktakishvili[1,2], P. J. MacNeice[2], Y. Zheng[2]
	[1] Catholic University of America; [2] NASA Goddard Space Flight Center; [3] University of Maryland, College Park; [4] Naval Research Laboratory; [5] Johns Hopkins Applied Physics Laboratory; [6] George Mason University, Fairfax; [7] Space Research Institute, Austrian Academy of Sciences; [8] IGAM-Kanzelhöhe Observatory, Institute of Physics, University of Graz
	We present a case study of the 7 January 2014 CME event in order to highlight current challenges in space weather forecasting of CME arrival time and geomagnetic storm strength. On 7 January 2014 an X1.2 flare and CME with a radial speed ~2500 km/s was observed from active region 11943. The flaring region was only ten degrees southwest of disk center with extensive dimming south of the active region and preliminary analysis estimated a fairly rapid arrival at Earth (~36 hours). Of the forecasting groups world-wide who participated in CCMC CME Scoreboard (http://kauai.ccmc.gsfc.nasa.gov/CMEscoreboard/), nearly all predicted earlier arrival times and many predicted strong geomagnetic storm impacts. However, the CME only had a flank arrival at Earth with a transit time of ~49 hours and the Kp geomagnetic index only reached 3-. Möstl et al. (2015) present a study of this event illustrating that the CME undergoes coronal channeling due to a strong nearby active region by ~ 37 degrees away from the source longitude below 2.1 Rs, rather than deflection by coronal holes. In order to further understand the interplanetary propagation of the 7 January 2014 CME we use the ensemble implementation of the WSA-ENLIL+Cone model from the CCMC. We explore a series of WSA-ENLIL+Cone simulations, to isolate the effects of the background solar wind solution and CME input parameters, and compare these results with the observed CME arrival at Venus, Earth, and Mars. We show that using elliptical major and minor axis widths and tilt measurements obtained by GCS fitting for the initial CME parameters in ENLIL would have improved the forecast to better reflect the observed in-situ signatures at Venus, Earth, and Mars. The modeling results show that the CME orientation and geometry with respect to observatories at Venus, Earth, and Mars may play an important role in understanding the propagation of this CME.
12:00	Analysis of CMEs-ICMEs on the ascending phase of SC24	Mierla, M et al.	Oral
	Marilena Mierla[1,2], Emilia Kilpua[3], Luciano Rodriguez[1], Andrei Zhukov[1]
	[1] Royal Observatory of Belgium; [2] Institute of Geodynamics of the Romanian Academy; [3] University of Helsinki
	We analyse the coronal mass ejections which arrived to STEREO or SOHO spacecraft in 2010. We focus on their 3D reconstruction and propagation into the interplanetary space in an effort to improve the arrival time forecast.
12:15	Analysis of CME arrival times at 1 AU with neural network	Sudar, D et al.	Oral
	Davor Sudar[1], Mateja Dumbović[1], Bojan Vršnak[1], Darije Maričić[2]
	[1] Hvar Observatory, Faculty of Geodesy, Kačićeva 26, University of Zagreb, 10000 Zagreb, Croatia; [2] Astronomical Observatory Zagreb, Opatička 22, 10000 Zagreb, Croatia
	Predicting CME arrival times to Earth from CME initial parameters is one of the most important topics in space weather research. We used initial CME velocity and central meridian distance, CMD, of CME's associated flare source position as input parameters to train the neural network, while CME transit time was used as the output parameter. The network was trained on the sample of 120 CME-ICME events, while the remaining 20 events were used as a test sample. Once trained, the network can be used to plot empirical curves of transit time as a function of the full range of input parameters. Resulting curve as a function of initial CME speed reveals a drag-like behavior, while its CMD shape indicates that CMEs are subjected to deflection in the east-west direction. Average error of the trained neural network is about 12 hours which is comparable to other works.
12:30	Lagrangian MHD Particle-in-Cell simulations of coronal interplanetary shocks driven by observations	Bacchini, F et al.	Oral
	Fabio Bacchini[1], Roberto Susino[2], Alessandro Bemporad[2], Giovanni Lapenta[1]
	[1] KU Leuven; [2] Turin Astronomical Observatory
	In this work, we compare the spatial distribution of the plasma parameters along the June 11, 1999 CME-driven shock front with the results obtained from a CME-like event simulated with the FLIPMHD3D code, based on the FLIP-MHD Particle-in-Cell (PiC) method. The observational data are retrieved from the combination of white-light (WL) coronagraphic data (for the upstream values) and the application of the Rankine-Hugoniot (RH) equations (for the downstream values). The comparison shows a higher compression ratio X and Alfvénic Mach number $ M_A $ at the shock nose, and a stronger magnetic field deflection d towards the flanks, in agreement with observations. Then, we compare the spatial distribution of $ M_A $ with the profiles obtained from the solutions of the shock adiabatic equation relating $ M_A $, X, and $ \theta_{Bn} $ (the angle between the upstream magnetic field and the shock front normal) for the special cases of parallel and perpendicular shock, and with a semi-empirical expression for a generically oblique shock. The semi-empirical curve approximates the actual values of $ M_A $ very well, if the effects of a non-negligible shock thickness $ \delta_{sh} $ and plasma-to magnetic pressure ratio $ \beta_u $ are taken into account throughout the computation. Moreover, the simulated shock turns out to be supercritical at the nose and sub-critical at the flanks. Finally, we develop a new 1D Lagrangian ideal MHD method based on the GrAALE code, to simulate the ion-electron temperature decoupling due to the shock transit. Two models are used, a simple solar wind model and a variable-$ \gamma $ model. Both produce results in agreement with observations, the second one being capable of introducing the physics responsible for the additional electron heating due to secondary effects (collisions, Alfvén waves, etc.).
12:45	Automatic detection of CMEs in STEREO-HI data	Rodriguez, L et al.	Oral
	Luciano Rodriguez[1], Sarah Willems[1], Vaibhav Pant[2], Marilena Mierla[1] and the HELCATS team
	[1] Royal Observatory of Belgium [2] Indian Institute of Astrophysics
	In the framework of the FP7 project HELCATS (http://www.helcats-fp7.eu/), a catalog of CMEs detected by the Heliospheric Imagers (HI) onboard the STEREO spacecraft has been created. This catalog was created by applying an automatic detection technique in order to identify and characterize the CMEs. The method will be explained and results will be shown and discussed.

Posters

Tuesday November 24, 10:00 - 11:00, Poster area

1	Study of energy input into the magnetosphere during SC23 intense geomagnetic storms	Besliu-ionescu, D et al.	e-Poster
	Diana Besliu-Ionescu[1], Marilena Mierla[2,1], Georgeta Maris Muntean[1]
	[1] Institute of Geodynamics of the Romanian Academy; [2] Royal Observatory of Belgium
	Geomagnetic storms are intensively studied because of their direct impact to space and ground based technology. Solar cycle 23 had 28 strong geomagnetic storms (Dst < -150 nT) that were correlated to solar eruptive phenomena. We present here a comparative study of the energy transferred from the solar wind into the magnetosphere during these storms. In order to compute this energy transfer we use two different formulas introduced by Akasofu (1981) and by Wang et al. (2014). The aim of this study is to see which formula better correlated the quantity of the transferred energy to the intensity of the geomagnetic storm.
2	IMF disturbances and ICMEs over 5 solar cycles	Vennerstrom, S et al.	e-Poster
	Susanne Vennerstrom, Kristoffer Leer
	DTU Space
	A major reason for the efficiency of ICMEs in creating geomagnetic storms are their association with IMF disturbances, in particular intervals of southward IMF. Using as a starting point newly developed tools for automated detection of IMF disturbances and subsequent classification as ICMEs and/or stream interaction regions (SIRs)/high speed streams, we examine statistically the occurrence of IMF disturbances and their association with ICMEs over the past 5 solar cycles. We show the solar cycle variation of characteristics of these disturbances, in particular their pattern of magnetic field variation, source association and geo-impact. The geo-impact is assessed in more detail by using multiple parameters such AE, Kp and Dst, but also measures such as the auroral boundary and Joule heating indices.
3	Geoeffective ICMEs Propagation Properties	Ontiveros, V et al.	p-Poster
	V. Ontiveros[1,2], J.A. Gonzalez-Esparza[2], P. Corona-Romero[2], M. Rodríguez-Martínez[1]
	[1] ENES Morelia, UNAM; [2]SCIESMEX, Instituto de Geofisica, UNAM
	We present a study of the characteristics and propagation properties of the ICMEs associated with the largest Geomagnetic Storms (GSs) for the ongoing Solar Cycle 24. Despite it is well known that the strength and orientation of the magnetic field carried by the ICMEs are the most relevant quantities for the occurrence of GSs; the interaction between ICMEs and other large scale structures in the solar wind, as well as the ICME front-section impacting the Earth, may play an important role modulating the intensity and duration of the registered geomagnetic disturbances.
4	Predicting in-situ transits of plasma sheaths and shock arrivals associated to fast halo CMEs	Corona-romero, P et al.	p-Poster
	P. Corona-Romero, J.A. Gonzalez-Esparza, V. de-la-Luz, J.C. Mejia-Ambriz, L.X. Gonzaelz
	Space Weather Service Mexico (SCiESMEX), Instituto de Geofisica Unidad Michoacan, Universidad Nacional Autonoma de Mexico
	Interplanetary coronal mass ejections (ICMEs) faster than solar wind are commonly accompanied by shock waves. Together, Earth-directed fast ICMEs, associated shocks, and perturbed solar wind in between them, i.e. plasma sheath, are one of the most important precursors of major perturbations in Earth's space climate. The hazard that fast ICME-plasma sheath-shock combination represents to geomagnetic stability has motivated interest in estimating the characteristics with which they arrive to Earth environment. There are multiple (empiric, analytic and numeric) efforts to forecast transit times and arrival speeds of ICMEs and shoscks, as well to approximate their trajectories. However, descriptions of in-situ properties or ''synthetic-transits'' of ICME-plasma sheath-shock are generally reserved for numerical modeling. In this work we present an analytic method to estimate in-situ synthetic-transits of plasma sheaths and shocks associated with fast ICMEs. This method combines an analytic model to describe fast ICME-shock trajectories, and the MHD polytropic jump relations. In order to calculate the synthetic-transits, our method requires in-situ conditions of solar wind, data from coronograph images, and values of X-ray fluxes. We validated our method by analysing twelve fast ICMEs, including the ''Bastille'' and ''Halloween'' events. Under optimum conditions, our calculated predictions (synthetic-transits) showed quantitative and qualitative agreements with in-situ profiles.
5	Geoeffectiveness of Disk Centre Full Halo Coronal Mass Ejections During 1996-2014	Ameri, D et al.	p-Poster
	Dheyaa Ameri, Eino Valtonen
	Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland
	We investigate geoeffectiveness and characteristics of full halo coronal mass ejections (FHCMEs)from source locations close to the central meridian of the Sun. We study FHCMEs detected between 1996 and end of 2014 which originated from source locations between solar longitudes E10 and W10 and latitudes N20 and S20 directed toward the Earth. We found that: First, the number of disk centre FHCME events (D.C.FHCMEs) was 64 of which 49 led to geomagnetic storms (GMs), i.e., about 76.5% of the D.C.FHCMEs were geoeffective. Second, the number of D.C.FHCME events which caused weak GMs was 7 (11% of the total number of geoeffective D.C.FHCMEs), moderate GMs were caused by 21 events (33%), strong GMs by 12 events (19%), severe GMs. by 6 events (9.3%), and great GMs by 3 events (4.6%). Third, the observed 49 D.C.FHCMEs caused 43 GMs. Five GMs originated from multiple D.C.FHCMEs. In four cases GMs originated from a single D.C.FHCME associated with another CME from the same active region. The rest 34 GMs originated from single D.C.FHCMEs. There were 21 MGs with Dst ≤ -100 nT (strong, severe, and great storms), which represent 20% of the total MGs with Dst ≤ -100 nT during the period 1996-2014 . In this research, we study the correlation between the intensity of the magnetic storms (Dst) and the characteristics of the D.C.FHCMEs, IP shock and ICMEs associated with them and solar activity.
6	Geo-efficiency of solar wind flows during 24th solar cycle	Shugay, Y et al.	p-Poster
	Yu. Shugay[1], F. Goryaev[2], D. Rodkin[2], V. Slemzin[2], I. Veselovsky[1]
	[1] M.V.Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics (SINP MSU); [2] P.N. Lebedev Physical Institute of the Russian Academy of Sciences
	Transient flows of solar wind (SW) associated with interplanetary coronal mass ejections (ICMEs) sometimes propagate in the heliosphere on the background of recurrent high-speed solar wind (HSSW) flow from coronal holes (CHs). This combination affects the time of arrival and geo-effectiveness of the flow. In some cases interaction of the ICME and HSSW flows enhances geo-effectiveness of the event, in other it weakens, which depends on the physical parameters of the CHs, sources of CMEs, as well as their relative position and interactions. Conditions in the Earth's magnetosphere can also influence the final geo-effectiveness. In this report, we consider ICME events observed during the 24th solar cycle and included in “ISEST/ICME event list” (http://solar.gmu.edu/heliophysics/index.php/The_ISEST_Event_List). We selected the cases when ICMEs overlapped on the HSSW flows from CHs. We divided all selected events into groups according to the resulting geo-effectiveness, and for each group described parameters of the coronal SW sources. The relative positions of CHs and active regions (ARs), sources of CMEs, their magnetic configuration, as well as parameters of SW flows at 1 a.e. were analyzed. As a result, the relationship was found between parameters of the CME and HSSW sources and the final geo-effectiveness caused by their interactions.
9	False alarms of geomagnetic storms triggered by halo coronal mass ejections.	Leer, K et al.	p-Poster
	K. Leer[1], S. Vennerstrom[1], N. Crosby[2], M. Dumbović[3], D. Sudar[3] and B. Vršnak[3]
	[1] DTU Space, Technical University of Denmark, Elektrovej, 2800 Lyngby, Denmark; [2] Belgian Institute for Space Aeronomy, Ringlaan-3-Avenue Circulaire, B-1180 Brussels, Belgium; [3] Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kaciceva 26, 10 000 Zagreb, Croatia
	Coronal Mass Ejections (CMEs) are one of the drivers of geomagnetic storms. When forecasting space weather it is therefore of great interest to be able to predict whether a CME will be geo-effective or a false alarm. This study is dedicated to analyze the causes of false alarms of geomagnetic storms triggered by halo CMEs and study the variation in false alarms. The SOHO/LASCO Halo-CME catalogue is combined with the Dst-index to define a list of fast Earth-directed CMEs which did not generate a geomagnetic storm within 4 days of the eruption (false alarms). In situ solar wind measurements have been inspected to identify the causes of the false alarms, and it is found that 53% of the false alarms arrived at Earth either as shock or ICME ejecta (half of these had a very small southward component of B-field), 25 % did not show any disturbance in the solar wind data (miss events). The last 22% showed a disturbance in the solar wind data and it was found that the source could be something else than the CME. It is demonstrated that the main parameter associated with false alarms is the time of year, since the false alarms show a semi-annual variation anti-correlated with the well-known pattern from the semi-annual variation of geomagnetic activity. The flare associated with the CME is also a signature of the probability of the CME being a false alarm. The two factors are combined to one probability of false alarm.