Turbulent electromagnetic fields at sub-proton scales: two-fluid and full-kinetic plasma simulations

TL;DR

This study compares fully kinetic and two-fluid plasma simulations to evaluate how well simplified models capture turbulence at sub-proton scales, highlighting strengths and limitations of each approach.

Contribution

The paper provides a detailed benchmarking of two-fluid and fully kinetic plasma models focusing on sub-proton scale turbulence, emphasizing the accuracy and limitations of fluid approximations.

Findings

Two-fluid models capture large-scale dynamics well.

Hall physics is reasonably represented at smaller scales.

Electron-scale features differ from fully kinetic models.

Abstract

Plasma dynamics is a multi-scale problem that involves many spatial and temporal scales. Turbulence connects the disparate scales in this system through a cascade that is established by nonlinear interactions. Most astrophysical plasma systems are weakly collisional, making a fully kinetic Vlasov description of the system essential. Use of reduced models to study such systems is computationally desirable but careful benchmarking of physics in different models is needed. We perform one such comparison here between fully kinetic Particle-In-Cell (PIC) model and a two-fluid model that includes Hall physics and electron inertia, with a particular focus on the sub-proton scale electric field. We show that in general the two fluid model captures large scale dynamics reasonably well. At smaller scales the Hall physics is also captured reasonably well by the fluid code but electron features show departures from the fully kinetic model. Implications for use of such fluid models are discussed.