An Interpretation of a Possible Mechanism for the

Authors: K A Firoz W Q Gan Y P Li J RodríguezPacheco

Publish Date: 2014/11/18

Volume: 290, Issue: 2, Pages: 613-626

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Abstract

It is well known that solar flares and shocks driven by coronal mass ejections CMEs are highenergy particle acceleration processes that might cause a highenergy particle event known as a groundlevel enhancement GLE In this context we have attempted to understand the processes responsible for the first GLE event GLE71 17 May 2012 0150 UT of Solar Cycle 24 We studied the spatial and spectral data from the Solar Dynamics Observatory SDO the Culgoora radioheliograph and Wind/WAVES instrument and analyzed the temporal data of the solarflare components the solar radioflux density and the electron fluxes from the Reuven Ramaty High Energy Solar Spectroscopic Imager RHESSI the Geostationary Operational Environmental Satellite GOES the Radio Solar Telescope Network RSTN and Wind spacecraft The flare had two ribbons separated by the neutral line between negative and positive magnetic polarity Their structure was also almost consistent with the contours of some flare components which were almost saturated during the flarepeak time As indicated by the metric–kilometric TypeII burst and because it extended over a wide heliolongitude  ≈ 41∘ range the CMEdriven shock was fast enough to cause highenergy particle acceleration at a high altitude in the solar corona Moreover the CME and flareflash phases were aligned along the same direction which implies that if the CMEdriven shock played the leading role in causing the GLE preceding flare components may have contributed to the shockWe are grateful to the anonymous referee for the constructive comments and valuable suggestions that greatly helped us to improve the manuscript We used NM data from NMDB funded by European Union’s FP7 program contract No 213007 To study possible causes of GLEs data provided by NOAA’s National Geophysical Data Center NGDC NASA’s Wind/WAVES and RHESSI have been used We acknowledge discussions with David J Thompson NASA YJ Moon KHU Z Ning PMO/CAS QM Zhang PMO/CAS and R GómezHerrero EPD/ESA WQG acknowledges the projects of MSTC 2011CB811402 and NNSFC 11233008 and 11427803 JRP acknowledges the projects of Solar OrbiterEnergetic Particle Detector EPD Ciencia y Gestión de Sistemas AYA201239810C0201 funded by the Ministerio de Economia y Competitividad the Solar Orbiter Energetic Particle Detector System Management AYA201129727C0201 and DETECTOR DE PARTÍCULAS ENERGÉTICAS PARA SOLAR ORBITER II ESP201348346C21R We have used data provided by NOAA’s National Geophysical Data Center NGDC NASA’s Wind/WAVES SDO RHESSI missions and the ESA/NASA SOHO mission SOHO is a mission of international cooperation between ESA and NASA The SDO/HMI and EVE data are available by courtesy of NASA/SDO and the AIA and EVE science teamsIf reconnection of magnetic fields takes place more than once at different heights of the corona and the shock wave is produced low in the corona there might be a possibility that the shock would be turned into a blast wave see cartoons in eg Aschwanden 2006 Chen 2008 Kumar et al 2010 Liu Chen and Petrosian 2013 If the shock were a freely propagating blast wave it would decay before reaching the interplanetary medium because it does not have any driver to back it up In contrast the CMEdriven shocks continuously receive energy from the driver so the CMEdriven shock is more energetic and longlived eg Liu et al 2009 Although there is a possibility of blast waves during CMEless shock events eg Shanmugaraju et al 2006 we did not find any evidence of a blast wave for the GLE71 event which is associated with a very fast CME ≈ 1582 km s−1 In practice the low frequency of TypeII bursts corresponds to densities typical of the upper corona Since the possible time line exists within the TypeII burst Figure 2 we can therefore assume for the GLE71 event that the CMEdriven shock naturally has a leading role in accelerating the particles Figure 3

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