Coalescence of Macroscopic Magnetic Islands and Electron Acceleration from STEREO Observation

Hong-Qiang Song,Gang Li,Xiang-Liang Kong,Shi-Wei Feng,Yao Chen

doi:10.1103/physrevx.2.021015

Hong-Qiang Song, Gang Li + Show 3 more

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https://doi.org/10.1103/physrevx.2.021015

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Abstract

Spacecraft data on immense solar coronal mass ejection (CME) combined with numerical magnetohydrodynamic simulations reveals for the first time both the merging of magnetic islands in a CME's trailing current sheet and associated electron acceleration.

Highlights

Magnetic reconnection is a fundamental plasma process
Using data from the STEREO spacecraft, we report in this article the first observation of macroscopic magnetic-island coalescence and a possible splitting, and the associated electron acceleration
We have examined the period from 1 January 2007 to 31 August 2011 and found 45 multiple-blob events. The properties of these blobs are listed online [32]. According to their physical origins, we classify these 45 events into three types: type I denotes events in which blobs are observed along a CMEtrailing ray structure; type II denotes events in which blobs are observed along a preexisting streamer plasma sheet that is strongly disturbed by a nearby coronal mass ejection (CME) eruption; and type III denotes events in which blobs are caused by a streamer disconnection without CME involved

Summary

INTRODUCTION

Magnetic reconnection is a fundamental plasma process. It is believed to occur at solar flares [1], substorms in the Earth’s magnetosphere [2], and other astrophysical sites such as magnetized neutron stars [3]. In situ observation of electron energization at magnetic islands has been reported by Chen et al [16], who used the Cluster observations to show that energetic electrons are correlated with low-density regions within magnetic islands during reconnections in the Earth’s magnetosphere These authors noted that the presence of energetic electrons in the energy range of 35–94 keV coincides nicely with magnetic islands encountered by Cluster, providing the first in situ evidence of electron acceleration at reconnecting magnetic islands. Unlike in situ observations in the Earth’s magnetosphere, remote observations of magnetic-island-like structures at solar flare sites are rare This is partly because, at a distance of 1 A.U., the angular resolution of a flare is too small. Recent simulations [18] based on a 2.5-D (two dimensions in configuration space and three dimensions in velocity space) PIC model have been

Published by the American Physical Society

CME principal angle c

This yields the ratio of

Findings

SUMMARY