Localised acceleration of energetic particles by a weak shock in the solar corona

Abstract

Globally-propagating shocks in the solar corona have long been studied to quantify their involvement in the acceleration of energetic particles. However, this work has tended to focus on large events associated with strong solar flares and fast coronal mass ejections (CMEs), where the waves are sufficiently fast to easily accelerate particles to high energies. Here we present observations of particle acceleration associated with a global wave event which occurred on 1 October 2011. Using differential emission measure analysis, the global shock wave was found to be incredibly weak, with an Alfvén Mach number of ~1.008-1.013. Despite this, spatially-resolved type III radio emission was observed by the Nançay RadioHeliograph at distinct locations near the shock front, suggesting localised acceleration of energetic electrons. Further investigation using a magnetic field extrapolation identified a fan structure beneath a magnetic null located above the source active region, with the erupting CME contained within this topological feature. We propose that a reconfiguration of the coronal magnetic field driven by the erupting CME enabled the weak shock to accelerate particles along field lines initially contained within the fan and subsequently opened into the heliosphere, producing the observed type III emission. These results suggest that even weak global shocks in the solar corona can accelerate energetic particles via reconfiguration of the surrounding magnetic field.

13 pages, 5 figures, accepted for publication in The Astrophysical Journal

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Cited by in corpus (8)

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• Recurrent narrow quasi-periodic fast-propagating wave trains excited by the intermittent energy release in the accompanying solar flare
• Simulation of the Solar Energetic Particle Event on 2020 May 29 Observed by Parker Solar Probe
• Tracking the motion of a shock along a channel in the low solar corona
• Investigation of the Two-Dimensional Velocity Field of the Large-Scale Coronal Wave from September 6, 2011 using the SOLERwave Tool
• Signatures of localised particle acceleration at a global coronal shock wave
• Predicting Solar Flares with Remote Sensing and Machine Learning