Observation of Cosmic Ray Anisotropy with Nine Years of IceCube Data

TL;DR

This paper reports the creation of a highly detailed map of cosmic ray arrival directions in the Southern Hemisphere using nine years of IceCube data, revealing anisotropies at high energies and small scales.

Contribution

It provides the first extensive, high-statistics anisotropy map in the TeV-PeV range with detailed temporal analysis using nearly a billion events.

Findings

Enhanced sensitivity to anisotropies at higher energies.

Detection of small-scale anisotropic features.

Observation of potential time variability over solar cycle 24.

Abstract

The IceCube Observatory has collected over 577 billion cosmic-ray induced muon events in its final configuration from May 2011 to May 2020. We used this data set to provide an unprecedented statistically accurate map of the cosmic ray arrival direction distribution in the TeV-PeV energy range scale in the Southern Hemisphere. Such an increase in event statistics makes it possible to extend the sensitivity to anisotropies at higher cosmic ray energies and smaller angular scales. It will also facilitate a more detailed assessment of the observatory stability over both short- and long-time scales. This will enable us to study the time variability of the cosmic ray anisotropy on a yearly-base and over the entire data sample period covering most of the solar cycle 24. We present the preliminary results from the study with the extended event sample.