Session 14 - Multi-viewpoint versus single-viewpoint observations and modelling - Lessons learned from 10 years of STEREO

Barbara Thompson (NASA GSFC); Manuela Temmer (University of Graz); Jackie Davies (RAL Space); Volker Bothmer (University of Göttingen); Alexis Rouillard (IRAP); Stefaan Poedts (KU Leuven)
Friday 01/12, 9:45 - 13:00
Mercator


KEYWORDS - remote sensing, in-situ, multi-view point data, inner heliosphere, large-scale solar disturbances;

The launch of STEREO, at the end of 2006, heralded the start of a new era in the observation of the solar system. Together with SoHO, located at a fixed position at L1, STEREO has continuously provided multiple views of large-scale phenomena propagating through the inner heliosphere. With this unprecedented combination of remote-sensing and in-situ observations, in particular, we have been able to gain a much deeper understanding of the 3-dimensional nature of large-scale inner heliospheric structures such as coronal mass ejections (CMEs) and stream/corotating interaction regions (SIRs/CIRs). But what have we gleaned about the limitations of single-viewpoint observations? How can we apply that knowledge in a future with, potentially, only single-spacecraft observations? Moreover, what are the implications for the design of future multi-viewpoint missions?

In this session, we invite observational, theoretical, and modeling contributions that address these questions and cover studies on the evolution, propagation and morphology of large-scale structures (CMEs, SIRs & CIRs) from single- or multi-view point observations at any wavelength.

Poster Viewing
From Thursday morning to Friday noon

Talks
Friday December 1, 09:45 - 11:00, Mercator
Friday December 1, 11:45 - 13:00, Mercator

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Talks : Time schedule

Friday December 1, 09:45 - 11:00, Mercator

09:45	3D reconstructions of EUV wave fronts using multi-point STEREO observations	Podladchikova, T et al.	Oral
	Tatiana Podladchikova[1], Astrid M. Veronig[2], Karin Dissauer[2]
	[1]Skolkovo Institute of Science and Technology, Russia; [2]Kanzelhöhe Observatory and Institute of Physics/IGAM, University of Graz, Austria
	We present 3D reconstructions of EUV wave fronts using multi-point observations from the STEREO-A and STEREO-B spacecraft. EUV waves are large-scale disturbances in the solar corona that are initiated by coronal mass ejections, and are thought to be large-amplitude fast-mode MHD waves or shocks. The aim of our study is to investigate the heights of the EUV wave fronts, their changes during the event evolution as well as to study their influence on the derived wave kinematics. We study the events on December 7, 2007 and February 13, 2009 using data from the STEREO/EUVI-A and EUVI-B instruments in the 195 Å filter. The proposed approach is based on a complementary combination of epipolar geometry of stereo vision and perturbation profiles. We propose two different solutions to the matching problem of the wave crest on images from the two spacecraft. One solution is suitable for the early and maximum stage of event development when STEREO-A and STEREO-B see the different facets of the wave, and the wave crest is clearly outlined. The second one is applicable also at the later stage of event development when the wave front becomes diffuse and is faintly visible. This approach allows us to identify automatically the segments of the diffuse front on pairs of STEREO-A and STEREO-B images and to solve the problem of identification and matching of the objects. We find that the EUV wave observed on December 7, 2007 starts with a height of 30–50 Mm, sharply increases to a height of 100-120 Mm about 10 min later, and decreases to 10-20 Mm in the decay phase. The upward movement of the wave crest on February 9, 2009 demonstrates the increase from 20 to 100 Mm over a period of 30 min. Including the 3D evolution of the EUV wave front allowed us to correct the wave kinematics for projection effects.
10:00	Non-linear two-fluid simulation of a coronal loop	Alvarez laguna, A et al.	Oral
	Alejandro Alvarez Laguna[1,2], Nataly Ozak[1], and Stefaan Poedts[1]
	[1]Centre for mathematical Plasma Astrophysics (CmPA), KU Leuven (Belgium); [2]CFD group, von Karman Institute for Fluid Dynamics (Belgium)
	Two-fluid plasma equations are a generalization of the ideal MHD model where ions and electrons are considered as separated fluids. While MHD is suitable for scenarios where the scales are much larger than the Larmor radius and the plasma is close to thermodynamic equilibrium, the two-fluid plasma model is able to capture smaller scales, allowing ions and electrons to possess different velocities and temperatures. Multi-fluid modeling is able to explore important phenomena in the corona that are completely disregarded in ideal MHD such as charge separation, drift wave instability and Hall effect. As well, as it is a fluid model, it is able to represent full-scale non-linear processes as the kink instability or solar eruptions. In this oral contribution, we present the results of a state-of-the-art 3D non-linear multi-fluid code [1, 2, 3] simulating a flux tube in coronal conditions. For the first time, the non-linear dynamics of a coronal loop are studied using a two-fluid model. In this work, we study the evolution of the drift-wave instability in a cylindrical flux tube configuration and its contribution to the heating of the plasma. As well, we study the dynamics of a kink unstable configuration. The results of this work bring about new processes in smaller scales than MHD simulations to be compared to new high resolution observations. [1] Alvarez Laguna, A., Lani, A., Deconinck, H., Mansour, N. N., & Poedts, S. 2016, Journal of Computational Physics, 318, 252 [2] Maneva, Y. G., Alvarez Laguna, A., Lani, A., & Poedts, S. 2017, ApJ, 836, 197 [3] Alvarez Laguna, A., Lani, A., Mansour, N. N., Deconinck, H., & Poedts S. 2017 ApJ, accepted
10:15	Predicting the solar wind based on the principle of co-rotation	Vennerstrom, S et al.	Oral
	Susanne Vennerstrom[1], Astrid M. Veronig[2], Manuela Temmer[2], Stefan Hofmeister[2] and Stephan G. Heinemann[2]
	[1]Technical University of Denmark, DTU Space; [2]Institute for Physics, University of Graz, Austria
	Prediction of the solar wind parameters near Earth with a lead time larger than 1-2 hours are currently one of the major challenges in forecasting geomagnetic activity and other space weather effects associated with solar wind – magnetosphere coupling. During the late phase of the solar cycle, which we are about to enter, the solar wind speed and the associated geomagnetic activity are well-known to be highly recurrent. This mainly happens because the solar source of the wind evolves slowly and CME occurrence gets sparse, thereby allowing the solar rotation to become a dominant cause of variation in the measured speed. We use the tool AWARE, which is currently operating in L1 providing warnings of arriving ICMEs and CIRs. We apply AWARE to the many years of in situ observations in L1 to mask out ICMEs in the in-situ data in L1 and investigate how well these „cleaned“ data can predict the solar wind parameters and CIR arrival from the co-rotation principle, not only in the late declining phase but during all phases of the solar cycle. We apply AWARE to the in-situ data of STEREO A and B and examine statistically the effect of the separation angle between the predicting and „predicted“ position. We thereby assess the improvement of prediction of co-rotating structures that can be expected from multi-point in-situ observations, such as e.g. a future L5-mission.
10:30	Modeling Coronal Mass Ejections with EUHFORIA: A Parameter Study of the Gibson-Low Flux Rope Model using multi-viewpoint observations	Verbeke, C et al.	Oral
	Christine Verbeke[1], Eleanna Asvestari[2], Camilla Scolini[1,3],Jens Pomoell[2], Stefaan Poedts[1], Emilia Kilpua[2]
	[1]KU Leuven, Leuven, Belgium; [2]University of Helsinki, Helsinki, Finland; [3]SIDC, Royal Observatory of Belgium, Uccle, Belgium
	Coronal Mass Ejections (CMEs) are one of the big influencers on the coronal and interplanetary dynamics. Understanding their origin and evolution from the Sun to the Earth is crucial in order to determine the impact on our Earth and society. One of the key parameters that determine the geo-effectiveness of the coronal mass ejection is its internal magnetic configuration. We present a detailed parameter study of the Gibson-Low flux rope model. We focus on changes in the input parameters and how these changes affect the characteristics of the CME at Earth. Recently, the Gibson and Low flux rope model has been implemented into the inner heliosphere model EUHFORIA, a magnetohydrodynamics forecasting model of large-scale dynamics from 0.1 AU up to 2 AU. Coronagraph observations can be used to constrain the kinematics and morphology of the flux rope. One of the key parameters, the magnetic field, is difficult to determine directly from observations. In this work, we approach the problem by conducting a parameter study in which flux ropes with varying magnetic configurations are simulated. We then use the obtained dataset to look for signatures in imaging observations and in-situ observations in order to find an empirical way of constraining the parameters related to the magnetic field of the flux rope. In particular, we focus on events observed by at least two spacecraft (STEREO + L1) in order to discuss the merits of using observations from multiple viewpoints in constraining the parameters.
10:45	STEREO observational constraints and initialization for the coupled ENLIL+SEPMOD models	Mays, M et al.	Oral
	M. L. Mays[1], J. G. Luhmann[2], H. M. Bain[4], Y. Li[2], D. Odstrcil[3,1], C. O. Lee[2], Lan Jian[5,1], R. A. Mewaldt[6], A.B. Galvin[7]
	[1]NASA Goddard Space Flight Center; [2]Space Sciences Laboratory, University of California, Berkeley; [3]George Mason University; [4]NOAA Space Weather Prediction Center; [5]University of Maryland College Park; [6]Space Radiation Lab, California Institute of Technology; [7]University of New Hampshire
	STEREO observations have been valuable for the initialization, validation, and development of models. Heliospheric models provide contextual information of conditions in the heliosphere, including the background solar wind conditions and shock structures, and are used as input to SEP models, providing an essential tool for understanding SEP properties. The global 3D MHD WSA-ENLIL+Cone model provides a time-dependent background heliospheric description, into which a spherical shaped hydrodynamic CME can be inserted. ENLIL simulates solar wind parameters and additionally one can extract the magnetic topologies of observer-connected magnetic field lines and all plasma and shock properties along those field lines. An accurate representation of the background solar wind is necessary for simulating transients. Comparisons between STEREO in-situ solar wind observations and model outputs allow us to assess the modeled background solar wind and therefore understand and adjust model parameters to better reproduce results. STEREO remote-sensing observations increase the accuracy in 3D CME measurements used to initialize hydrodynamic CME in the WSA-ENLIL model. ENLIL simulations also drive SEP models such as the Solar Energetic Particle Model (SEPMOD) (Luhmann et al. 2007, 2010). SEPMOD injects protons onto a sequence of observer field lines at intensities dependent on the connected shock source strength which are then integrated at the observer to approximate the proton flux. The coupled ENLIL+SEPMOD models allow us to derive the longitudinal distribution of SEP profiles of different types of events throughout the heliosphere. STEREO SEP observations allow us to validate the SEPMOD results at two more locations, providing model constraints. In this presentation we demonstrate several case studies of ENLIL+SEPMOD modeling constrained and initialized by STEREO observations.

Friday December 1, 11:45 - 13:00, Mercator

11:45	Observations of the drivers of space weather with coronal and magnetic imagers	Hurlburt, N et al.	Invited Oral
	Neal Hurlburt, Alan Title, James Lemen and Cathy Chou
	Lockheed Martin Advanced Technology Center
	There is a pressing need to better understand and predict the space weather environment. This ultimately requires the deployment of new sensors at a multiple view points around the sun and earth and the development of models capable of using the resulting data to produce actionable forecasts. The underpinning of all space weather is the magnetic field emerging from the solar surface and its interaction with the solar corona.  STEREO EUVI observations have demonstrated the value of multiple views of the corona to assess trigger conditions for flares and CMEs. Accurate forecasts require a similar knowledge of the global distribution of the magnetic field. However, to date, magnetograph observations are only available from instruments located on the Sun-Earth line.  We discuss a concept for a next generation compact, space-based magnetograph that can be deployed at geocentric orbit, or at the L1 or L5 Lagrange points to enable greater observational coverage of the solar surface. A new model of the surface field evolution is also presented which can be used to better assess the impact of such constellations.  We also consider EUVI coronal observations, and in particular, we present data acquired with the SUVI instrument on the recently launched GOES-16 satellite.  Comparing the results from SUVI, SDO AIA, and STEREO EUVI informs the derivation of the coronal observational requirements for future space weather monitoring systems.
12:15	New strategies for modelling and forecasting the background solar wind combined with multi-point observations	Pinto, R et al.	Oral
	Rui F. Pinto[1], Alexis P. Rouillard[1], D. Odstrcill[2,3], L. Mays[3]
	[1]IRAP, Université de Toulouse, UPS-OMP, IRAP, Toulouse, France; [2]NASA Computational and Data Sciences, George Mason U., Fairfax,Virginia, USA; [3]Goddard Space Flight Center, Greenbelt, Maryland, USA
	I will present a new series of solar wind simulations of the background solar wind from the surface of the Sun to 1 AU. We used a new solar wind model, called MULTI-VP, which takes a coronal magnetic field map as input (past data or forecast) and calculates the dynamical and thermal properties of the solar wind from the chromosphere up to about 30 Rsun in quasi-real time (while keeping a good description the plasma heating and cooling mechanisms) and supplies the full set of physical inner boundary conditions required to initiate the model ENLIL. The two models were used to calculate the properties of the wind flow from 1 Rsun to 1AU during Carrington rotations spanning the STEREO epoch (CRs 2055 to 2149; see https://stormsweb.irap.omp.eu/doku.php?id=windmaptable, http://www.helcats-fp7.eu/). These were calibrated against in-situ measurements of different spacecraft, white-light J-Maps and coronal/heliospheric imagery in order to provide better predictions than the classical methods. These wind solutions will be available as HELCATS catalogues. I will discuss the substantial benefits of multi-point observations and in-situ measurements for the predictive capabilities of the model and present a real-time space-weather application tailored to take advantage of multiple spacecraft (e.g, both at L5 and L1). This new modeling strategy aims at estimating the state of the Earthward background solar wind up to 7-10 days in advance. The method uses early-on east-limb coronography and several intermediate control points (observations and in-situ data) to refine our physics-based solar wind forecasts.
12:30	Kinematics, shock locations and properties of a CME driven shock using LOFAR and multi-viewpoint observations.	Zucca, P et al.	Oral
	Pietro Zucca[1], Diana Morosan[2], Peter T. Gallagher[2], Richard Fallows[1], Alexis Rouillard[3], Jasmina Magdalenic[4], Christian Vocks[5], Christophe Marqué[5], Karl-Ludwig Klein[1], and Gottfried Mann[5]
	[1]Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, The Netherlands; [2]Astrophysics Research Group, School of Physics, Trinity College Dublin, 2 Dublin, Ireland; [3]Institut de Recherche en Astrophysique et Planetologie, 9 Ave. du Colonel Roche 31028, Toulouse Cedex 4, France; [4]Solar-Terrestrial Center of Excellence, SIDC, Royal Observatory of Belgium, Avenue Circulaire 3, 1180 Brussels, Belgium; [5]Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany; [6]Observatoire de Paris, LESIA, Paris, France
	Type II radio bursts are evidence of shocks in the solar atmosphere emitting radio waves ranging from metric to kilometric lengths. These shocks may be associated with coronal mass ejections (CMEs) reaching super-Alfv enic speeds. Radio imaging of the decameter wavelengths is now possible with the Low Frequency Array (LOFAR), opening a new radio window to study coronal radio shocks leaving the inner solar corona and entering the interplanetary medium and understand their association with CMEs. Here, we study a coronal shock associated with a CME and type II radio burst to determine the location where the shock is triggered in relation to the propagating CME, the ambient medium Alfvén speed and the orientation of the coronal magnetic field. The type II shock imaging and spectra were obtained using 91 simultaneous tied-array beams of LOFAR while the CME was observed and triangulated using multi-viewpoint observations including the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory (STEREO). Using the tied array beam observing mode of LOFAR we were able to locate the type II radio shock position between 45 and 75 MHz and relate it to the expanding flank of a CME leaving the inner corona. With the key help of the multi-viewpoint observations, the radio emission associated with the type II burst was found to be located at the flank of the CME in a region where the mach number is between 1.5 to 2.0 and the shock geometry is quasi-perpendicular.
12:45	Verification of real-time WSA-ENLIL+Cone simulations of CME arrival-time at the CCMC/SWRC	Wold, A et al.	Oral
	Alexandra M. Wold[1], M. Leila Mays[2], A.Taktakishvili[2,3], L. Jian[4,2], D.Odstrcil[2,5], P. MacNeice[2]
	[1]American University; [2]NASA Goddard Space Flight Center; [3]Catholic University of America; [4]University of Maryland; [5]George Mason University
	The Wang-Sheeley-Arge (WSA)-ENLIL+Cone model is used extensively in space weather operations world-wide to model CME propagation, as such it is important to assess its performance. We present validation results of the WSA-ENLIL+Cone model installed at the Community Coordinated Modeling Center (CCMC) and executed in real-time by the CMC/Space Weather Research Center (SWRC). CCMC/SWRC uses the WSA-ENLIL+Cone model to predict CME arrivals at NASA missions throughout the inner heliosphere. In this work we compare model predicted CME arrival-times to in-situ ICME shock observations near Earth (ACE, Wind), STEREO-A and B for simulations completed between March 2010 - December 2016 (over 2,000 CMEs). We report hit, miss, false alarm, and correct rejection statistics for all three spacecraft. For the 265 events where the CME was predicted to arrive at Earth, STEREO-A, or SETERO-B, and we observed an arrival (hit), the mean absolute arrival-time prediction error was 10.4 hours, with a bias to early prediction of -4 hours on average. We show the dependence of the arrival-time error on CME input parameters. We also explore the impact of the multi-spacecraft observations used to initialize the model CME inputs by comparing model verification results before and after the STEREO-B communication loss and STEREO-A side-lobe operations. We find an increase of 2 hours in the CME arrival time error during single, or limited two-viewpoint periods, compared to the full three-spacecraft viewpoint period. This trend would apply to a future space weather mission at L5 as another coronagraph viewpoint to reduce CME arrival time errors compared to a single viewpoint.

Posters

1	Deriving Kinematic Properties of Non-Radial and Asymmetric CMEs: Methods and Implications	Thompson, B et al.	e-Poster
	Barbara Thompson
	NASA Goddard Space Flight Center, USA
	There are several challenges in characterizing the kinematic properties of energetic CMEs. Most rapidly-evolving eruptions are accompanied by changes in the surrounding corona. The larger the impact on the surrounding corona, the more difficult it is to separate the “main” CME from the CME-associated brightenings. Complicating the issue is the range of observed propagation properties: super-radial expansion, asymmetric expansion, non-radial propagation, and alterations in the direction of propagation. These properties can be a function of both the internal magnetic structure of the CME and the structure of the corona through which the CME is propagating. While the relative contribution of internal/external factors can be difficult to assess, it is of fundamental importance because it not only reveals the nature of CMEs but also CME-associated phenomena.
2	Solar wind speed forecasting with a STEREO persistence model using uncertainty assessment from the evolution of coronal holes	Temmer, M et al.	e-Poster
	Manuela Temmer, Juergen Hinterreiter, Martin A. Reiss
	Institute of Physics, University of Graz, Austria
	We present the concept of a new persistence model to forecast the solar wind speed at 1 AU, using the advantage of multi-viewpoint satellite data. The model is based on STEREO in-situ measurements for satellite positions eastward of Earth, shifted forward by a variable time span according to the angle of the STEREO spacecraft with Earth (~2-10 days). The STEREO persistence model is applied on the time range 2008-2012 (STEREO-B) and 2017 (STEREO-A) and compared to a persistence model based on ACE data forward shifted by a full rotation. In addition, the STEREO persistence model is modified by assessing the speed uncertainties that are caused by the evolution of coronal holes (CH). We derive the information on CH evolution by comparing CH areas extracted in EUV data from STEREO and Earth perspective. Compared to an ACE based persistence model, the performance of the STEREO persistence model which takes into account the evolution of coronal holes, is able to reduce the number of missed high-speed streams by about 25%, the false alarms by about 20%, and to increase the hit rate by about 12%.
3	STEREO/SDO Observations of Stealthy but Earth-affecting CMEs	Nitta, N et al.	e-Poster
	Nariaki Nitta, Tamitha Mulligan
	[1]Lockheed Martin Advanced Technology Center; [2]The Aerospace Corporation
	We have long known about the existence of "problem" geomagnetic storms whose origins are elusive. In more general terms, not all the 1 AU disturbances can be clearly attributed to CMEs, HSSs or CIRs. When ICME signatures are found in in situ data, there is not always a flare or filament eruption on the Sun or even an obvious CME observed close to the Sun that correlates with the ICME within a reasonable time range. These ICMEs sometimes result in intense storms. Furthermore, there is a possibility that some of the more severe storms could be partly contributed by such ICMEs of unclear origin. Therefore space weather prediction will remain incomplete without properly understanding these ICMEs. Even if the ICME is paired with a CME, it is sometimes difficult to find where the latter comes from. This is often called the “stealth CME” that apparently lacks low coronal signatures (LCSs). STEREO's second and third view points have tremendously helped us determine its front-side origin and find when and where it forms and accelerates, which is important for isolating possible LCSs. Although SDO/AIA has been continuously taking full-disk EUV images in a wide temperature range since 2010, there are still a number of stealthy CMEs whose LCSs are unclear or ambiguous. It is assumed that they start at high altitudes, leaving weak or negligible LCSs. Some of them seem to involve multiple magnetic domains, including weak or open field regions. Using several examples including those that were observed in recent years, we emphasize the importance of monitoring the global Sun continuously, in order to detect and forecast these stealthy but Earth-affecting CMEs and to understand the eruption mechanisms behind them.
4	Continuous 360 degree observation of a large, long-living, low-latitude coronal hole during the maximum of solar cycle 24	Heinemann, S et al.	e-Poster
	Stephan G. Heinemann[1], Manuela Temmer[1], Stefan Hofmeister[1], Astrid M. Veronig[1], Susanne Vennerstrom[2]
	[1]Institute for Physics, University of Graz, Austria; [2]Technical University of Denmark, DTU
	High speed solar wind streams (HSS) emanating from coronal holes, and associated stream interaction regions, may cause geomagnetic storms and deflect coronal mass ejections propagation in interplanetary space. By understanding the evolution and the relations between coronal holes and solar wind parameters, we increase our knowledge for improving space weather forecasts. We investigate the evolution of a persistent coronal hole using EUV data from STEREO-A/B and SDO over the timerange February 2012 –October 2012. Combined STEREO-SDO data enable a continuous observation of the CH covering 360° degrees over several rotations. Together with magnetic field measurements from SDO filtergrams and in-situ solar wind observations, we analyze during different evolutionary states of the CH, the solar surface properties of the CH (intensity, area, shape, magnetic flux) and its effects at 1AU (solar wind speed). As a result we find an evolutionary pattern in most parameters, clearly showing a growing, maximum and decaying phase. At time of maximum area the open flux also reaches its maximum with about 50%, this development can also be seen in the associated HSS.
5	Can coronal dimmings serve as proxy for characteristic CME parameters?	Dissauer, K et al.	e-Poster
	Karin Dissauer[1], Astrid M. Veronig[1,2], Manuela Temmer[1], Kamalam Vanninathan[1], Tatiana Podladchikova[3], Julia M. Riedl[1]
	[1]IGAM/Institute of Physics, University of Graz, Austria; [2]Kanzelhöhe Observatory/Institute of Physics, University of Graz, Austria; [3]Skolkovo Institute of Science and Technology, Russia
	Earth-directed coronal mass ejections (CMEs) are the main driver for space weather affecting the near-Earth environment. However, they allow the least accurate measurements of their properties due to strong projection effects towards the plane of sky. The most distinct phenomena associated with Earth-directed CMEs are coronal dimmings, i.e. regions of reduced emission in the extreme-ultraviolet (EUV) and soft X-rays. They are interpreted as density depletions due to the evacuation of plasma during the CME expansion. Investigating the properties of these low coronal footprints will provide us with important additional information on the initiation and early evolution of the associated CMEs. We take advantage of the quadrature position of the SDO and STEREO spacecraft, during 2010-2012, to study CMEs and their associated dimmings precisely. We select 76 events which show on-disk dimmings with respect to SDO and have CMEs which are observed off-limb by at least one of the two STEREO spacecraft. The on-disk coronal dimming evolution is studied using the high-cadence, multi-wavelengths data of SDO/AIA and the line-of-sight (LOS) magnetograms of SDO/HMI. We use the best combination of on-disk and off-limb signatures to establish a statistical relationship between Earth-directed CMEs and their associated coronal dimmings. The basic properties of the CME, such as initial velocity, acceleration, mass and initiation height are derived and compared with characteristic coronal dimming parameters like the magnetic flux, the area, the area growth rate and the total brightness. We find moderate correlations between the derived dimming parameters, the flare strength and the timing. The dimming parameters show the strongest correlations with the CME mass. These results establish the relationship between dimmings and CMEs, and provide a means to use single-view point observations of only coronal dimmings to constrain Earth-directed CME parameters.
6	Solar signatures and eruption mechanism of the August 14, 2010 coronal mass ejection	D'huys, E et al.	e-Poster
	Elke D’Huys[1,2], Daniel B. Seaton[1,3,4], Anik De Groof[5], David Berghmans[1], Stefaan Poedts[2]
	[1]Solar-Terrestrial Center for Excellence, Royal Observatory of Belgium, Solar Influences Data Analysis Center; [2]Centre for Mathematical Plasma-Astrophysics, Katholieke Universiteit Leuven; [3]Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder; [4]NOAA National Centers for Environmental Information; [5]European Space Agency/ESAC
	On August 14, 2010 a wide-angled coronal mass ejection (CME) was observed. This solar eruption originated from a destabilized filament that connected two active regions and the unwinding of this filament gave the eruption an untwisting motion that drew the attention of many observers. In addition to the erupting filament and the associated CME, several other low-coronal signatures that typically indicate the occurrence of a solar eruption were associated with this event. However, contrary to what was expected, the fast CME was accompanied by only a weak flare. We investigate the various eruption signatures that were observed for this event and focus on the kinematic evolution of the filament in order to determine its eruption mechanism using observations from a fleet of satellites, including STEREO, PROBA2, SOHO and SDO. Had this solar eruption occurred just a few days earlier, it could have been a significant event for space weather. The risk of underestimating the strength of this eruption based solely on the weak flare illustrates the need to include all eruption signatures in event analyses in order to obtain a complete picture of a solar eruption and assess its possible space weather impact.
7	Simulation of CMEs in 2007 – 2016 Using the WSA-ENLIL+Cone Modeling System	Jian, L et al.	p-Poster
	L.K. Jian[1,2], D. Odstrcil[3,2], M.L. Mays[2], A.P. Rouillard[4,5]
	[1]University of Maryland, College Park, MD, USA; [2]NASA Goddard Space Flight Center, Greenbelt, MD, USA; [3]George Mason University, Fairfax, VA, USA; [4]Institut de Recherche en Astrophysique et Planétologie, Paul Sabatier University, Toulouse, France; [5]Centre National de la Recherche Scientifique, UMR F-5277, Toulouse, France
	The global 3D MHD WSA-ENLIL+Cone modeling system has been widely used to predict CMEs. Based on the CME parameters fitted using the remote observations by single or multiple spacecraft, we have modeled thousands of CMEs in 2007-2016. About 200-300 of them propagate toward the Earth and are found in the simulation results. In comparison with the in situ observations of about 200 CMEs in the same period, we assess the performance of the WSA-ENLIL+Cone modeling system, discuss the factors affecting the ICME arrival time, and examine the cases in which there is a large discrepancy between the simulated and observed solar wind parameters.
8	A consideration of the multi-viewpoint and single-viewpoint exploitation of heliospheric imaging in light of the ten years of the STEREO/HI instruments	Harrison, R et al.	p-Poster
	Richard Harrison, Jackie Davies
	STFC-Rutherford Appleton Laboratory, Harwell, Oxfordshire OX11 0QX, UK
	After more than a decade of successful operation of the flagship Heliospheric Imager (HI) instruments on-board NASA’s twin-spacecraft STEREO mission, we are in a unique position to assess the large volume of research that exploits the data therefrom. In particular, we review those publications that endeavour to characterise the 3D kinematic properties of coronal mass ejections (CME), as they propagate out to 1 AU and beyond; such information is vital for the provision of accurate CME arrival predictions for space weather usage. In this presentation, we consider the benefits of heliospheric imaging from two vantage points over such imaging from a single view point. Given the expectation of future operational heliospheric imaging from only a single vantage point, such an assessment is timely.
9	Automated detection of coronal mass ejections in three-dimensions using multi-viewpoint observations	Hutton, J et al.	p-Poster
	Joseph Hutton, Huw Morgan
	Aberystwyth University
	A new, automated method of detecting Coronal Mass Ejections (CMEs) in three dimensions for the LASCO C2 and STEREO COR2 coronagraphs is presented. By triangulating isolated CME signal from the three coronagraphs over a sliding window of five hours, the most likely region through which CMEs pass at 5$R_{\odot}$ is identified. The centre and size of the region gives the most likely direction of propagation and approximate angular extent. The Automated CME Triangulation (ACT) method is tested extensively using a series of synthetic CME images created using a wireframe flux rope density model, and on a sample of real coronagraph data; including halo CMEs. The accuracy of the angular difference ($\sigma$) between the detection and true input of the synthetic CMEs is $\sigma$=7.14$^{\circ}$, and remains acceptable for a broad range of CME positions relative to the observer, the relative separation of the three observers, and even through the loss of one coronagraph. For real data, the method gives results that compare well with the distribution of low coronal sources and results from another instrument and technique made further from the Sun. The true 3D-corrected kinematics and mass/density are discussed. The results of the new method will be incorporated into the CORIMP database in the near future, enabling improved space weather diagnostics and forecasting.
10	A multi-spacecraft view of a giant filament eruption during 2009 september 26/27	Schmieder, B et al.	p-Poster
	Brigitte Schmieder[1], Sanjay Gosain[2], Guy Artzner[3], Sergei Bogachev[4], Tibor Török[5]
	[1]LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris Diderot, 5 Place Jules Janssen, F-92190 Meudon, France; [2]National Solar Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719, USA; [3]CNRS UMR 8617, Institut d’astrophysique Spatiale (IAS), F-91405 Orsay Cedex, France; [4]Lebedev Physical Institute of Russian Academy of Science, Leninskij prospekt 53, Moscow 119991, Russia; [5]Predictive Science, Inc., 9990 Mesa Rim Rd., Suite 170, San Diego, CA 92121, USA
	We analyze multi-spacecraft observations of a giant filament eruption that occurred during 2009 September 26 and 27. The filament eruption was associated with a relatively slow coronal mass ejection. The filament consisted of a large and a small part, and both parts erupted nearly simultaneously. Here we focus on the eruption associated with the larger part of the filament. Detailed results can be found in Gosain et al (2012). (i) We use STEREO-A, SoHO/EIT and CORONAS/TESIS observations as a third eye (Earth view) to aid our measurements. (ii) Using trigonometry, we estimate the direction of propagation and derive the true height-time profile of the filament, (iii) further, we develop a new tomographic method that can potentially provide a more robust three-dimensional (3D) reconstruction by exploiting multiple simultaneous views. We then analyze the kinematics of the eruptive filament during its rapid acceleration phase by fitting different functional forms to the height-time data derived from the two methods.
11	Active region evolution and the formation of eruptive configurations	Green, L et al.	p-Poster
	Lucie Green, Alex James, Gherardo Valori, Stephanie Yardley
	Throughout their lifetimes, active regions can be the source of many CMEs. However, the frequency and magnitude of the region’s activity is dependent on the evolutionary stage of the active region. Combining photospheric and coronal data to capture the evolution of an active region, along with modelling of the magnetic field, has allowed a deeper understanding of the 3-dimensional magnetic field configurations that are responsible for CMEs. One particular configuration, known as a flux rope, has been identified in many CME source regions. This knowledge is feeding into our understanding of the physical processes that drive CMEs and may help in future CME predictions. This talk will look at why monitoring the time-history of active regions is important and whether knowing where the active region is in its lifetime helps understand the likelihood of CME activity. It will also address how flux ropes are identified in active regions and the timescales and mechanisms involved in their formation.
12	A regularised full-Newton VARPRO iteration for the stereoscopic reconstruction of loops in EUV images	Chifu, I et al.	p-Poster
	Bernd Inhester, Iulia Chifu
	Max Planck Institute for Solar System Research
	The reconstruction of bright coronal loops from stereo pairs of EUV images is considered an important tool to disentangle the complex 3D topology of the coronal magnetic field. Reconstructed loops have been used in different cases for the study of the magnetic field topology. Also, stereoscopically reconstructed prominences when seen as arch-like structures have been used in the determination of the CME kinematics. For the stereoscopic reconstruction one must follow two steps. First step is the tie-pointing of the same loop structure in each of the pair images. The second step uses the tie-points for a stereoscopic triangulation. While automized tools exist for the first step, we here propose an automatisation of the second step, the stereoscopic inversion. The procedure can take the placed tie-points from an image pair and calculate a spline-based approximation of the 3D loop shape from them. A preliminary version of our procedure has already been applied to observed image data in several cases. The work we present now is more robust since is using precise projective geometry for the image projection and can systematically be extended to any number of view directions.