Charging of Fractal Dust Agglomerates in a Plasma Environment

TL;DR

This paper presents a modified orbital-motion-limited (OML) model using line-of-sight approximation to calculate charge distribution on fractal dust aggregates in plasma, revealing enhanced coagulation despite like-charged grains.

Contribution

It introduces a novel OML_LOS model for charge calculation on fractal dust aggregates, improving understanding of coagulation processes in plasma environments.

Findings

Charge distribution affects aggregate structure and growth.

Like-charged grains can coagulate more easily than previously thought.

The model predicts reduced electric potentials facilitating coagulation.

Abstract

The charge on micron-sized dust grains plays a crucial role in the structure and evolution of forming aggregates within the dust population during the coagulation process. The manner in which the charge is arranged on developing irregular structures can affect the fractal dimension of aggregates formed during collisions, which in turn influences the coagulation rate and size evolution of the dust cloud. Preliminary models for the charge evolution on fractal aggregates immersed in a plasma environment calculated using a modification to the orbital-motion-limited (OML) theory are presented in this paper. The model calculates currents to each point on the aggregate surface using a line-of-sight (LOS) approximation: only those electron or ion trajectories which are not blocked by another grain within the aggregate contribute to the charging current. Both the total charge and the dipole moment are calculated for the dust aggregate. While most coagulation theories assume that it is difficult for like-charged grains to coagulate, the OML_LOS approximation indicates that the electric potentials of aggregate structures are often reduced enough to allow significant coagulation.