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Deriving the properties of coronal pressure fronts in 3D: application to the 2012 May 17 ground level enhancement

Rouillard, A. P. and Plotnikov, I. and Pinto, R. F. and Tirole, M. and Lavarra, M. and Zucca, P. and Vainio, R. and Tylka, A. J. and Vourlidas, A. and de Rosa, M. L. and Linker, J. and Warmuth, A. and Manney, G. and Cohen, C. M. S. and Mewaldt, R. A. (2016) Deriving the properties of coronal pressure fronts in 3D: application to the 2012 May 17 ground level enhancement. Astrophysical Journal, 833 (1). Art. No. 45. ISSN 0004-637X. doi:10.3847/1538-4357/833/1/45.

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We study the link between an expanding coronal shock and the energetic particles measured near Earth during the ground level enhancement of 2012 May 17. We developed a new technique based on multipoint imaging to triangulate the three-dimensional (3D) expansion of the shock forming in the corona. It uses images from three vantage points by mapping the outermost extent of the coronal region perturbed by the pressure front. We derive for the first time the 3D velocity vector and the distribution of Mach numbers, M FM, of the entire front as a function of time. Our approach uses magnetic field reconstructions of the coronal field, full magnetohydrodynamic simulations and imaging inversion techniques. We find that the highest M FM values appear near the coronal neutral line within a few minutes of the coronal mass ejection onset; this neutral line is usually associated with the source of the heliospheric current and plasma sheet. We illustrate the variability of the shock speed, shock geometry, and Mach number along different modeled magnetic field lines. Despite the level of uncertainty in deriving the shock Mach numbers, all employed reconstruction techniques show that the release time of GeV particles occurs when the coronal shock becomes super-critical (M FM > 3). Combining in situ measurements with heliospheric imagery, we also demonstrate that magnetic connectivity between the accelerator (the coronal shock of 2012 May 17) and the near-Earth environment is established via a magnetic cloud that erupted from the same active region roughly five days earlier.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Vourlidas, A.0000-0002-8164-5948
Cohen, C. M. S.0000-0002-0978-8127
Mewaldt, R. A.0000-0003-2178-9111
Additional Information:© 2016. The American Astronomical Society. Received 2016 May 13; revised 2016 July 28; accepted 2016 August 23; published 2016 December 6. We acknowledge usage of the tools made available by the plasma physics data center (Centre de Donnes de la Physique des Plasmas; CDPP;, the Virtual Solar Observatory (VSO;, the Multi Experiment Data & Operation Center (MEDOC;, the French space agency (Centre National des Etudes Spatiales; CNES;, and the space weather team in Toulouse (Solar-Terrestrial Observations and Modeling Service; STORMS; This includes the data mining tools AMDA ( and CLWEB ( and the propagation tool ( RFP and IP acknowledge financial support from the HELCATS project under the FP7 EU contract number 606692. RV acknowledges financial support from the HESPERIA project under the EU/H2020 contract number 637324. AW acknowledges the support by DLR under grant No. 50 QL 0001. APR acknowledges funding from CNES and the Leibniz Institute für Astrophysik Potsdam (AIP) to visit AIP and to collaborate with AW and GM on the present project. The STEREO SECCHI data are produced by a consortium of RAL (UK), NRL (USA), LMSAL (USA), GSFC (USA), MPS (Germany), CSL (Belgium), IOTA (France), and IAS (France). The ACE data were obtained from the ACE science center. The Wind data were obtained from the Space Physics Data Facility.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
European Research Council (ERC)606692
European Research Council (ERC)637324
Deutsches Zentrum für Luft- und Raumfahrt (DLR)50 QL 0001
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Leibniz Institute für Astrophysik PotsdamUNSPECIFIED
Subject Keywords:shock waves; Sun: coronal mass ejections (CMEs) ; Sun: particle emission
Issue or Number:1
Record Number:CaltechAUTHORS:20170119-112814729
Persistent URL:
Official Citation:A. P. Rouillard et al 2016 ApJ 833 45
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73549
Deposited By: Ruth Sustaita
Deposited On:19 Jan 2017 21:04
Last Modified:11 Nov 2021 05:18

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