On Temporal Variations of the Multi-TeV Cosmic Ray Anisotropy using the Tibet III Air Shower Array

TL;DR

This study examines the stability of multi-TeV cosmic ray anisotropy over nine years, finding it remains consistent despite solar activity variations, suggesting a stable galactic cosmic ray distribution.

Contribution

It provides the first long-term analysis of multi-TeV cosmic ray anisotropy stability over a nine-year period using Tibet Air Shower Array data.

Findings

Anisotropy magnitude about 0.1% remains stable over nine years.

No significant correlation between anisotropy and solar activity.

Anisotropy is insensitive to solar cycle variations.

Abstract

We analyze the large-scale two-dimensional sidereal anisotropy of multi-TeV cosmic rays by Tibet Air Shower Array, with the data taken from 1999 November to 2008 December. To explore temporal variations of the anisotropy, the data set is divided into nine intervals, each in a time span of about one year. The sidereal anisotropy of magnitude about 0.1% appears fairly stable from year to year over the entire observation period of nine years. This indicates that the anisotropy of TeV Galactic cosmic rays remains insensitive to solar activities since the observation period covers more than a half of the 23rd solar cycle.