# Plasma-grains interaction mediated by streaming non-Maxwellian ions

## TL;DR

This paper investigates how streaming non-Maxwellian ions influence plasma-grain interactions using advanced particle-in-cell simulations, revealing nonlinear effects and limitations of linear models in complex plasma environments.

## Contribution

It introduces a nonlinear approach to plasma-grain interaction modeling considering streaming non-Maxwellian ions, extending beyond linear response theories.

## Key findings

- Nonlinear plasma response significantly alters grain interactions.
- Electrostatic force between grains can be attractive or repulsive depending on conditions.
- Shadow effects and ion trapping influence inter-grain forces and separation limits.

## Abstract

A comprehensive parametric study of plasma-grain interaction for non-Maxwellian streaming ions in steady-state employing particle-in-cell simulations is delineated. Instead of considering the inter-grain interaction potential to be the linear sum of isolated grain potentials, we incorporate the numerical advancement developed fully for grain shielding by including nonlinear contributions from the plasma and shadowing effect. The forces acting on grains versus inter-grain distance, streaming velocity of the ions, and impact of trapped ions density (number) are characterized for non- Maxwellian ions in the presence of charge-exchange collisions. It is found that the nonlinear plasma response considerably modifies the plasma-grains interaction. Unlike the stationary plasma case, for two identical grains separated by a distance in the presence of streaming ions, the electrostatic force is neither repulsive for all grain separations nor equivalent to the force due to one isolated grain. Inadequacy of the linear response formalism in dealing with the systems having very large grain charges is also discussed. The smallest inter-grain separation for which the role of the shadow effect can be ignored is reported.