Exclusion of cosmic rays from molecular clouds by self-generated electric fields

TL;DR

This paper proposes that self-generated electric fields in molecular clouds can significantly reduce cosmic ray electron penetration, especially in high-ionization areas like near the Galactic center, altering our understanding of cosmic ray interactions.

Contribution

It introduces a novel mechanism where electric fields generated by cosmic rays modulate their own penetration into molecular clouds, especially in electron-rich, high-ionization environments.

Findings

CR penetration can be reduced by factors of a few to hundreds.

Electric fields from cosmic rays can self-modulate their entry into molecular clouds.

High-ionization regions near the Galactic center are significantly affected.

Abstract

It was recently discovered that in some regions of the Galaxy, the cosmic ray (CR) abundance is several orders of magnitude higher than previously thought. Additionally, there is evidence that in molecular cloud envelopes, the CR ionization may be dominated by electrons. We show that for regions with high, electron-dominated ionization, the penetration of CR electrons into molecular clouds is modulated by the electric field that develops as a result of the charge they deposit. We evaluate the significance of this novel mechanism of self-modulation and show that the CR penetration can be reduced by a factor of a few to a few hundred in high-ionization environments, such as those found near the Galactic center.