Power requirements for cosmic ray propagation models involving diffusive reacceleration; estimates and implications for the damping of interstellar turbulence

TL;DR

This paper estimates the power supplied to Galactic cosmic rays by diffusive reacceleration, showing it can account for about half of the total cosmic ray power and discussing implications for interstellar turbulence damping.

Contribution

It provides quantitative estimates of the power from diffusive reacceleration in cosmic ray propagation, highlighting its significance and impact on turbulence damping.

Findings

Reacceleration contributes up to 50% of cosmic ray power.

Recent Voyager data supports the significance of reacceleration.

Implications for turbulence damping are discussed.

Abstract

We make quantitative estimates of the power supplied to the Galactic cosmic ray population by second-order Fermi acceleration in the interstellar medium, or as it is usually termed in cosmic ray propagation studies, diffusive reacceleration. Using recent results on the local interstellar spectrum from the Voyager missions we show that for parameter values, in particular the Alfv\'en speed, typically used in propagation codes such as Galprop to fit the B/C ratio, the power contributed by diffusive reacceleration is significant and can be of order 50\% of the total Galactic cosmic ray power. The implications for the damping of interstellar turbulence are briefly considered.