Stochastic Theory of Dust-Grain Charging in Low-Pressure Plasmas

TL;DR

This paper reviews dust grain charging in low-pressure plasmas, proposing a Fokker-Planck based theory that explains positive charging and charge variations, aligning with experimental data.

Contribution

It introduces a novel theoretical model combining Fokker-Planck and orbital motion limited approaches for dust charging in low-pressure plasmas.

Findings

Dust grains can become positively charged in certain plasma conditions.

Variations in plasma potential can cause spatial charge differences on grains.

The theory aligns with experimental observations of dust charging behavior.

Abstract

Charging of dust grains in low-pressure plasmas is reviewed critically. A theory based on the Fokker-Planck equation and orbital motion limited approximation is proposed. The theory predicts that dust grains can acquire a positive charge in low-pressure electropositive plasmas having a sufficiently high plasma potential, in agreement with experimental observations. It is also shown that variations in the plasma potential (electron temperature) can lead to spatial regions in which grains have opposite charges.