Cosmic ray acceleration via magnetic reconnection of magnetic islands/flux-ropes

TL;DR

This paper provides in-situ evidence that magnetic reconnection of flux-ropes during ICMEs accelerates cosmic rays, suggesting a significant contribution of magnetic island dynamics to cosmic ray origins.

Contribution

It demonstrates that magnetic reconnection of flux-ropes in interplanetary space contributes to cosmic ray acceleration, expanding the understanding of cosmic ray sources.

Findings

In-situ evidence of flux-rope formation and reconnection during ICMEs.

Magnetic reconnection contributes to GeV cosmic ray acceleration.

Proposes magnetic island merging as a Fermi acceleration mechanism.

Abstract

The dynamic processes of magnetic reconnection and turbulence cause magnetic islands/flux-ropes generation. The in-situ observations suggest that the coalescence or/and contraction of magnetic islands are responsible to the charged particle acceleration (keV to MeV energy range). Numerical simulations also support this acceleration mechanism. However, the most fundamental question raise here is, does this mechanism contribute to the cosmic rays acceleration? To answer this, we report, in-situ evidence of flux-ropes formation, their magnetic re-connection and its manifestation as cosmic ray (GeV charged particle) acceleration in interplanetary counterpart of coronal mass ejection(ICME). Further, we propose that cosmic ray (high and/or ultra-high energy) acceleration by Fermi mechanism is valid not only through stochastic reflections of particles from the shock boundaries but also through the boundaries of contracting magnetic islands or/and their merging via magnetic re-connection. This has significant implications on cosmic ray origin and their acceleration process.