Nonresonant Grain Acceleration in MHD Turbulence

TL;DR

This paper introduces a new nonresonant dust acceleration mechanism in MHD turbulence, showing it can produce high velocities for grains in the interstellar medium, affecting various astrophysical processes.

Contribution

It reveals that magnetic compression in MHD turbulence can accelerate grains beyond gyroresonance, especially in warm media, expanding understanding of dust dynamics.

Findings

Super-Alfvenic turbulence yields higher grain velocities.

Fast modes dominate large grain acceleration, slow modes affect sub-micron grains.

Supersonic velocities are achievable for Galactic dust grains.

Abstract

We discuss a new type of dust acceleration mechanism that acts in a turbulent magnetized medium. The magnetohydrodynamic (MHD) turbulence can accelerate grains through resonant as well as nonresonant interactions. We show that the magnetic compression provides higher velocities for super-Alfvenic turbulence and can accelerate an extended range of grains in warm media compared to gyroresonance. While fast modes dominate the acceleration for the large grains, slow modes can be important for sub-micron grains. We provide comprehensive discussion of all the possible grain acceleration mechanisms in interstellar medium. We show that supersonic velocities are attainable for Galactic dust grains. We discuss the consequence of the acceleration. The implications for extinction curve, grain alignment, chemical abundance, etc, are provided.