PolyPIC: the Polymorphic-Particle-in-Cell Method for Fluid-Kinetic Coupling

TL;DR

PolyPIC introduces a unified particle-in-cell framework with polymorphic particles that can switch between fluid and kinetic states, enabling adaptive fluid-kinetic plasma simulations within a single method.

Contribution

This work presents the first PIC method that combines fluid and kinetic particles with dynamic switching capabilities in a unified framework.

Findings

Successfully modeled Landau damping of plasma waves

Simulated two-stream instability effectively

Demonstrated fluid-kinetic coupling in sheath formation

Abstract

Particle-in-Cell (PIC) methods are widely used computational tools for fluid and kinetic plasma modeling. While both the fluid and kinetic PIC approaches have been successfully used to target either kinetic or fluid simulations, little was done to combine fluid and kinetic particles under the same PIC framework. This work addresses this issue by proposing a new PIC method, PolyPIC, that uses polymorphic computational particles. In this numerical scheme, particles can be either kinetic or fluid, and fluid particles can become kinetic when necessary, e.g. particles undergoing a strong acceleration. We design and implement the PolyPIC method, and test it against the Landau damping of Langmuir and ion acoustic waves, two stream instability and sheath formation. We unify the fluid and kinetic PIC methods under one common framework comprising both fluid and kinetic particles, providing a tool for adaptive fluid-kinetic coupling in plasma simulations.