Limits on diffusive shock acceleration in dense and incompletely ionised media

TL;DR

This paper analyzes how ion-neutral damping and particle losses limit diffusive shock acceleration in dense, partially ionized media, with implications for supernova remnant observations.

Contribution

It provides analytic and numerical solutions for shock acceleration limits considering ion-neutral damping and particle losses in partially ionized media.

Findings

Ion-neutral Alfven wave damping significantly limits acceleration.

Analytic solutions for steady upstream wave excitation are derived.

Numerical solutions illustrate the impact on shock acceleration.

Abstract

The limits imposed on diffusive shock acceleration by upstream ion-neutral Alfven wave damping, and by ionisation and Coulomb losses of low energy particles, are calculated. Analytic solutions are given for the steady upstream wave excitation problem with ion-neutral damping and the resulting escaping upstream flux calculated. The time dependent problem is discussed and numerical solutions presented. Finally the significance of these results for possible observational tests of shock acceleration in supernova remnants is discussed.