Heliospheric Imaging of 3D Density Structures During the Multiple Coronal Mass Ejections of Late July to Early August 2010
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It is usually difficult to gain a consistent global understanding of a coronal mass ejection (CME) eruption and its propagation when only near-Sun imagery and the local measurements derived from single-spacecraft observations are available. Three-dimensional (3D) density reconstructions based on heliospheric imaging allow us to “fill in” the temporal and spatial gaps between the near-Sun and in situ data to provide a truly global picture of the propagation and interactions of the CME as it moves through the inner heliosphere. In recent years the heliospheric propagation of dense structures has been observed and measured by the heliospheric imagers of the Solar Mass Ejection Imager (SMEI) and on the twin Solar TErrestrial RElations Observatory (STEREO) spacecraft. We describe the use of several 3D reconstruction techniques based on these heliospheric imaging data sets to distinguish and track the propagation of multiple CMEs in the inner heliosphere during the very active period of solar activity in late July – early August 2010. We employ 3D reconstruction techniques used at the University of California, San Diego (UCSD) based on a kinematic solar wind model, and also the empirical Tappin–Howard model. We compare our results with those from other studies of this active period, in particular the heliospheric simulations made with the ENLIL model by Odstrcil et al. (J. Geophys. Res., 2013) and the in situ results from multiple spacecraft provided by Möstl et al. (Astrophys. J. 758, 10 – 28, 2012). We find that the SMEI results in particular provide an overall context for the multiple-density flows associated with these CMEs. For the first time we are able to intercompare the 3D reconstructed densities with the timing and magnitude of in situ density structures at five spacecraft spread over 150° in ecliptic longitude and from 0.4 to 1 AU in radial distance. We also model the magnetic flux-rope structures at three spacecraft using both force-free and non-force-free modelling, and compare their timing and spatial structure with the reconstructed density flows.
KeywordsSolar Wind Coronal Mass Ejection Flux Rope Ecliptic Plane Stereo Spacecraft
We acknowledge the organisers of and the beneficial discussions at the three August 2010 events workshops, held in January 2011 in Abingdon, England, March 2011 in Graz, Austria, and June 2011 in Aberystwyth, Wales, which were vital in producing this paper. The Solar Mass Ejection Imager (SMEI) instrument is a collaborative project of the U.S. Air Force Research Laboratory, NASA, the University of California at San Diego, the University of Birmingham, UK, Boston College, and Boston University. The STEREO SECCHI Heliospheric Imager (HI) instrument was developed by a collaboration that included the Rutherford Appleton Laboratory and the University of Birmingham, both in the United Kingdom, the Centre Spatial de Liège (CSL), Belgium, and the US Naval Research Laboratory (NRL), Washington DC, USA. The SECCHI project is an international consortium of the Naval Research Laboratory, Lockheed Martin Solar and Astrophysics Lab, NASA Goddard Space Flight Center, Rutherford Appleton Laboratory, University of Birmingham, Max-Planck-Institut für Sonnensystemforschung, Centre Spatial de Liège, Institut d’Optique Théorique et Appliquée, and Institut d’Astrophysique Spatiale. We also benefited from data from the SOHO mission, which is an international collaboration between NASA and ESA, and also from the SOHO/LASCO CME catalog, generated and maintained by the Center for Solar Physics and Space Weather, The Catholic University of America in cooperation with NRL and NASA. The work of DFW was supported at Boston College by Air Force contracts AF19628-00-K-0073 and FA8718-04-C-0006 and Navy contracts N00173-07-1-G016 and N00173-10-1-G001. The work of CM was supported by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 263252 (COMESEP), and by a Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme. MT acknowledges the Austrian Science Fund (FWF): FWF V195-N16. BVJ, JMC, and H-SY were supported by UCSD NSF grants ATM-0852246 and AGS-1053766, NASA grant NNX11AB50G, and AFOSR grant 11NE043. MMB acknowledges support on these analyses from UCSD NSF grant ATM-0925023, and also from a UK STFC Standard Grant to Aberystwyth University for continued CME and heliospheric interplanetary scintillation (IPS) and white-light analyses. TAH was partially supported by the NSF/SHINE Competition (Award 0849916) and the NASA Heliophysics program (grant NNX10AC05G). CJF was supported by NASA grant NX10AQ29G and NSF grant AGS-1140211.
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