Damping of MHD turbulence in partially ionized plasma: implications for cosmic ray propagation

TL;DR

This paper analyzes how neutral-ion collisions damp MHD turbulence in partially ionized plasmas, affecting cosmic ray propagation, with implications for interstellar medium and solar chromosphere modeling.

Contribution

It provides a linear analysis of MHD wave damping and connects damping scales to turbulence cutoff boundaries, applying results to cosmic ray propagation in partially ionized media.

Findings

Damping rates derived from linear analysis inform turbulence damping scales.

Turbulence damping significantly impacts cosmic ray transit-time damping.

Results applicable to various interstellar medium phases and solar chromosphere.

Abstract

We study the damping from neutral-ion collisions of both incompressible and compressible magnetohydrodynamic (MHD) turbulence in partially ionized medium. We start from the linear analysis of MHD waves applying both single-fluid and two-fluid treatments. The damping rates derived from the linear analysis are then used in determining the damping scales of MHD turbulence. The physical connection between the damping scale of MHD turbulence and cutoff boundary of linear MHD waves is investigated. Our analytical results are shown to be applicable in a variety of partially ionized interstellar medium (ISM) phases and solar chromosphere. As a significant astrophysical utility, we introduce damping effects to propagation of cosmic rays in partially ionized ISM. The important role of turbulence damping in both transit-time damping and gyroresonance is identified.