Acceleration of Small Dust Grains due to Charge Fluctuations

TL;DR

This paper demonstrates that charge fluctuations significantly accelerate very small dust grains, like PAHs, in the diffuse interstellar medium, impacting grain coagulation and shattering processes.

Contribution

It introduces a Monte Carlo simulation of charge fluctuations and identifies this as the dominant acceleration mechanism for tiny dust grains in low-ionization environments.

Findings

Charge fluctuations lead to efficient grain acceleration in low-ionization ISM.

The mechanism affects grain coagulation and shattering in various astrophysical environments.

Charge fluctuation-induced acceleration surpasses other known mechanisms for small grains.

Abstract

We consider the acceleration of very small dust grains including Polycyclic Aromatic Hydrocarbons (PAHs) arising from the electrostatic interactions of dust grains that have charge fluctuations in time due to charging events. We simulate the charge fluctuations of very small grains due to their sticking collisions with electrons and ions in plasma, and the emission of photoelectrons by UV photons using Monte Carlo method. We identify the acceleration induced by the charge fluctuations as the dominant acceleration mechanism of very small grains in the diffuse interstellar medium (ISM). We show that this acceleration mechanism is efficient for environments with low degree of ionization (i.e., large Debye length), where the charge fluctuations are slow but have a large amplitude. We also discuss the implications of the present mechanism for grain coagulation and shattering in the diffuse ISM, molecular clouds, and protoplanetary disks.