Deciphering the Dipole Anisotropy of Galactic Cosmic Rays

TL;DR

This paper explains the observed energy-dependent dipole anisotropy in Galactic cosmic rays using diffusion theory, local sources, magnetic fields, and observational limitations, highlighting Vela SNR as a key contributor.

Contribution

It provides a comprehensive diffusion-based model accounting for local sources, magnetic fields, and motion effects to explain cosmic ray anisotropy, identifying Vela SNR as a significant source.

Findings

Dipole anisotropy varies with energy in the TeV-PeV range.

Local sources and magnetic fields significantly influence anisotropy.

Vela supernova remnant is a likely source of observed anisotropy.

Abstract

Recent measurements of the dipole anisotropy in the arrival directions of Galactic cosmic rays (CRs) indicate a strong energy dependence of the dipole amplitude and phase in the TeV-PeV range. We argue here that these observations can be well understood within standard diffusion theory as a combined effect of (i) one or more local sources at Galactic longitude 120deg < l < 300deg dominating the CR gradient below 0.1-0.3 PeV, (ii) the presence of a strong ordered magnetic field in our local environment, (iii) the relative motion of the solar system, and (iv) the limited reconstruction capabilities of ground-based observatories. We show that an excellent candidate of the local CR source responsible for the dipole anisotropy at 1-100 TeV is the Vela supernova remnant.