Interplay between Escaping Cosmic Rays and Interstellar Medium: Driving of Galactic Winds and Shaping the Local Proton Spectrum

TL;DR

This study uses simulations to explore how escaping cosmic rays influence the interstellar medium, driving galactic winds and affecting local proton spectra, with implications for observations and cosmic ray behavior.

Contribution

It introduces detailed CR-hydrodynamical simulations that incorporate spectral evolution, radiative cooling, and thermal conduction to analyze CR-ISM interactions and their astrophysical consequences.

Findings

CRs heat and accelerate the ISM depending on diffusion coefficients.

CR heating may explain unexpected emission lines in supernova remnants.

CR-driven outflows could match the Galactic star formation rate and influence halo metal enrichment.

Abstract

We study the effects of escaping cosmic rays (CRs) on the interstellar medium (ISM) around their source with spherically symmetric CR-hydrodynamical simulations taking into account the evolution of the CR energy spectrum, radiative cooling, and thermal conduction. We show how the escaping CRs accelerate and heat the ISM depending on the CR diffusion coefficient. The CR heating effects are potentially responsible for the recent observations of the unexpected H$\alpha$ and [OIII]$\lambda5007$ lines in old supernova remnants. The implied gas outflow rate by CRs can be comparable to the Galactic star formation rate, compatible with the Galactic wind required for polluting the halo gas with metals. Assuming a locally suppressed CR diffusion and a few nearby CR sources in the Local Bubble, we also propose alternative interpretations for the Galactic CR proton spectrum around the Earth measured with CALET, AMS02, and Voyager 1.