Magnetic reconnection as the cause of cosmic ray excess from the heliospheric tail

TL;DR

This paper proposes that magnetic reconnection in the heliospheric tail's magnetotail could be responsible for the observed excess and anisotropy of cosmic rays from that region.

Contribution

It introduces the idea that magnetic reconnection in the heliospheric tail can accelerate cosmic rays, explaining observed excesses and anisotropies.

Findings

Cosmic ray excess aligns with the heliospheric tail direction.

Localized anisotropy has a small angular scale (~10 degrees).

Magnetic reconnection is a plausible acceleration mechanism.

Abstract

The observation of a broad excess of sub-TeV cosmic rays compatible with the direction of the heliospheric tail (Nagashima et al. 1998) and the discovery of two significant localized excess regions of multi-TeV cosmic rays by the MILAGRO collaboration (Abdo et al. 2008), also from the same region of the sky, have raised questions on their origin. In particular, the coincidence of the most significant localized region with the direction of the heliospheric tail and the small angular scale of the observed anisotropy (~ 10deg) is suggestive a local origin and of a possible connection to the low energy broad excess. Cosmic ray acceleration from magnetic reconnection in the magnetotail is proposed as a possible source of the energetic particles.