Dissipation of Magnetohydrodynamic Waves on Energetic Particles: Impact on Interstellar Turbulence and Cosmic‐Ray Transport

TLDR

Diffusion of Galactic cosmic rays in the interstellar medium is governed by complex physical processes. The study investigates whether the nonlinear MHD cascade determines the turbulence spectrum that scatters charged energetic particles. The authors incorporated wave dissipation into the GALPROP propagation code to evaluate its effect on observable astrophysical data. The model shows that wave dissipation can halt the Kraichnan cascade below 10¹³ cm and that the resulting energy‑dependent diffusion coefficient explains the 1 GeV nucleon‑1 peaks in secondary‑to‑primary nuclei ratios.

Abstract

The physical processes involved in diffusion of Galactic cosmic rays in the interstellar medium are addressed. We study the possibility that the nonlinear MHD cascade sets the power-law spectrum of turbulence that scatters charged energetic particles. We find that the dissipation of waves due to the resonant interaction with cosmic-ray particles may terminate the Kraichnan-type cascade below wavelengths 1013 cm. The effect of this wave dissipation has been incorporated in the GALPROP numerical propagation code in order to asses the impact on measurable astrophysical data. The energy dependence of the cosmic-ray diffusion coefficient found in the resulting self-consistent model may explain the peaks in the secondary to primary nuclei ratios observed at about 1 GeV nucleon-1.