Energy-Dependent Shifts of Medium-Scale Anisotropies in Very-High-Energy Cosmic Rays Observed by LHAASO-KM2A

TL;DR

This paper reports the detection of medium-scale anisotropies in very-high-energy cosmic rays with energy-dependent shifts in their positions, providing insights into local magnetic turbulence affecting cosmic ray propagation.

Contribution

It presents the first observation of energy-dependent shifts in medium-scale anisotropies at energies above 10 TeV using LHAASO-KM2A, constraining local magnetic turbulence models.

Findings

Identification of four excess and four deficit regions of cosmic rays.

Detection of significant energy-dependent shifts in two excess regions.

Characterization of the energy evolution of fractional intensity in anisotropies.

Abstract

Small deviations from isotropy in the arrival directions of Galactic cosmic rays serve as a unique probe of the local magnetic environment. In this Letter, we report observations of medium-scale anisotropies (MSA) at energies above 10 TeV using the LHAASO-KM2A array. Our analysis identifies four regions of excess and four regions of deficit, each spanning angular scales of approximately ten degrees. Crucially, we detect significant energy-dependent shifts in the centroids of two excess regions: Region B and the newly identified Region $\mathrm{\widetilde{D}}$. We also characterize the energy evolution of the fractional relative intensity across both excess and deficit regions. These findings imply that the observed anisotropies are shaped by the specific realization of the local turbulent magnetic field within the cosmic ray scattering length. Such energy-dependent behaviors impose strict constraints on local turbulence models and cosmic ray propagation theories.