Shielding of absorbing objects in collisionless flowing plasma

TL;DR

This paper investigates how ion absorption affects the electrostatic shielding of charged dust grains in collisionless plasmas, revealing that absorption significantly impacts potential in subthermal flows but is negligible in superthermal flows.

Contribution

It provides a detailed analysis of absorption effects on grain potential in different flow regimes using a kinetic model with ion absorption.

Findings

Absorption reduces the attractive potential in subthermal flows.

In superthermal flows, absorption has negligible effect on shielding.

Absorption effects can be ignored for typical grain sizes in superthermal regimes.

Abstract

The electrostatic shielding of a charged absorbing object (dust grain) in a flowing collisionless plasma is investigated by using the linearized kinetic equation for plasma ions with a point-sink term accounting for ion absorption on the object. The effect of absorption on the attractive part of the grain potential is investigated. For subthermal ion flows, the attractive part of the grain potential in the direction perpendicular to the ion flow can be significantly reduced or completely destroyed, depending on the absorption rate. For superthermal ion flows, however, the effect of absorption on the grain attraction in the direction perpendicular to the ion flow is shown to be exponentially weak. It is thus argued that, in the limit of superthermal ion flow, the effect of absorption on the grain shielding potential can be safely ignored for typical grain sizes relevant to complex plasmas.