Discrete stochastic charging of aggregate grains

TL;DR

This paper presents a numerical model to study discrete stochastic charge fluctuations on aggregate grains in plasma, revealing their impact on aggregate growth and morphology.

Contribution

It introduces a novel numerical approach to analyze charge fluctuations on aggregate grains and their influence on aggregation dynamics and structures.

Findings

Charge fluctuations follow trends similar to spherical grains but with larger variations.

Charge fluctuations occur on timescales relevant for aggregate growth.

Fluctuations lead to more linear or filamentary aggregate structures.

Abstract

Dust particles immersed in a plasma environment become charged through the collection of electrons and ions at random times, causing the dust charge to fluctuate about an equilibrium value. Small grains (with radii less than 1 \mum) or grains in a tenuous plasma environment are sensitive to single additions of electrons or ions. Here we present a numerical model that allows examination of discrete stochastic charge fluctuations on the surface of aggregate grains and determines the effect of these fluctuations on the dynamics of grain aggregation. We show that the mean and standard deviation of charge on aggregate grains follows the same trends as those predicted for spheres having an equivalent radius, though aggregates exhibit larger variations from the predicted values. In some plasma environments, these charge fluctuations occur on timescales which are relevant for dynamics of aggregate growth. Coupled dynamics and charging models show that charge fluctuations tend to produce aggregates which are much more linear or filamentary than aggregates formed in an environment where the charge is stationary.