Large-scale sidereal anisotropy of multi-TeV galactic cosmic rays and the heliosphere

TL;DR

This paper presents a model that successfully explains the large-scale anisotropy of multi-TeV galactic cosmic rays, revealing significant modulation in the heliotail and asymmetry in the heliosphere based on Tibet AS array observations.

Contribution

The study introduces a novel anisotropy model incorporating excesses in the hydrogen deflection plane, explaining observed sky-map features including heliotail effects.

Findings

Discovered significant GCR intensity modulation in the heliotail.

Identified asymmetry in the heliosphere with a stronger southern excess.

Successfully reproduced observed sky-map features with the new model.

Abstract

We develop a model anisotropy best-fitting to the two-dimensional sky-map of multi-TeV galactic cosmic ray (GCR) intensity observed with the Tibet III air shower (AS) array. By incorporating a pair of intensity excesses in the hydrogen deflection plane (HDP) suggested by Gurnett et al., together with the uni-directional and bi-directional flows for reproducing the observed global feature, this model successfully reproduces the observed sky-map including the "skewed" feature of the excess intensity from the heliotail direction, whose physical origin has long remained unknown. These additional excesses are modeled by a pair of the northern and southern Gaussian distributions, each placed ~50 degree away from the heliotail direction. The amplitude of the southern excess is as large as ~0.2 %, more than twice the amplitude of the northern excess. This implies that the Tibet AS experiment discovered for the first time a clear evidence of the significant modulation of GCR intensity in the heliotail and the asymmetric heliosphere.