New estimation of the spectral index of high-energy cosmic rays as determined by the Compton-Getting anisotropy

TL;DR

This paper measures the spectral index of high-energy cosmic rays using the Compton-Getting anisotropy with Tibet air-shower data, providing an independent estimate consistent with direct measurements and offering insights into cosmic-ray origins.

Contribution

It introduces a novel method to estimate the cosmic-ray spectral index via anisotropy analysis, complementing traditional spectral measurements.

Findings

Spectral index estimated as -3.03 ± 0.55 (stat) ± 0.62 (syst).

Result consistent with -2.7 from direct measurements.

Potential to confirm the cosmic-ray 'knee' origin.

Abstract

The amplitude of the Compton-Getting (CG) anisotropy contains the power-law index of the cosmic-ray energy spectrum. Based on this relation and using the Tibet air-shower array data, we measure the cosmic-ray spectral index to be $-3.03 \pm 0.55_{stat} \pm < 0.62_{syst}$ between 6 TeV and 40 TeV, consistent with $-$2.7 from direct energy spectrum measurements. Potentially, this CG anisotropy analysis can be utilized to confirm the astrophysical origin of the ``knee'' against models for non-standard hadronic interactions in the atmosphere.