Method for testing diffusive shock acceleration and diffusion propagation of 1-100 TeV cosmic electrons with multiwavelength observations of the Geminga halo and pulsar wind nebula

TL;DR

This paper develops a method to test diffusive shock acceleration and diffusion propagation theories of cosmic rays using multiwavelength data from the Geminga pulsar wind nebula and halo, spanning 1 TeV to several hundred TeV.

Contribution

The work introduces a new approach to validate cosmic ray acceleration and diffusion models at very high energies with recent observational data.

Findings

The theories are consistent with current observations.

Current data's wide energy bins limit high-precision testing.

Future observations could confirm energy-dependent diffusion coefficients.

Abstract

Diffusive shock acceleration and diffusion propagation are essential components of the standard cosmic ray model. These theories are based on extensive observations of high-energy solar processes, providing substantial direct evidence in the MeV energy range. Although the model is widely and successfully used to explain high-energy cosmic phenomena, direct validation has been elusive. The multi-wavelength spectra and angular profile measurements of the Geminga pulsar wind nebula and its pulsar halo, particularly the precise spectral observations by HAWC and LHAASO-KM2A in recent years, offer a rare opportunity to test these theories with cosmic rays energies between 1 TeV and several hundred TeV. These observations are expected to elevate the direct testing of theoretical models from multi-MeV to sub-PeV energies. In this work, a method is developed to test the diffusive shock acceleration and diffusion propagation model between one and several hundred TeV energies through the latest spectral and morphological data of the Geminga region from HAWC and Fermi-LAT. Our results show that the theories of diffusive shock acceleration and diffusion propagation are consistent with experimental observations. However, the published morphological data adopted rather wide energy bins and currently do not allow a high precision test of the inferred energy dependent diffusion coefficient by observed energy spectra with DSA theory. It is anticipated that future HAWC and LHAASO-KM2A observations will yield higher-precision results, and the confirmation of a rapidly increasing diffusion coefficient above 100 TeV would serve as important evidence supporting the diffusive shock acceleration and diffusion propagation theory. Similar tests would be both important and valuable for other models.