Laser-Driven, Ion-Scale Magnetospheres in Laboratory Plasmas. II. Particle-in-cell Simulations

TL;DR

This paper uses particle-in-cell simulations to study ion-scale magnetospheres created in laboratory plasma experiments, revealing magnetic cavity formation, current structures, and the effects of varying parameters on magnetospheric features.

Contribution

It provides the first detailed simulation analysis of laser-driven ion-scale magnetospheres, connecting experimental observations with kinetic-scale plasma physics insights.

Findings

Magnetic cavity and compression form in simulated ion-scale magnetospheres.

Two main current structures identified: diamagnetic and magnetopause currents.

Magnetospheric features depend on dipolar magnetic moment and plasma driver length.

Abstract

Ion-scale magnetospheres have been observed around comets, weakly-magnetized asteroids, and localized regions on the Moon, and provide a unique environment to study kinetic-scale plasma physics, in particular in the collisionless regime. In this work, we present the results of particle-in-cell simulations that replicate recent experiments on the Large Plasma Device at the University of California, Los Angeles. Using high-repetition rate lasers, ion-scale magnetospheres were created to drive a plasma flow into a dipolar magnetic field embedded in a uniform background magnetic field. The simulations are employed to evolve idealized 2D configurations of the experiments, study highly-resolved, volumetric datasets and determine the magnetospheric structure, magnetopause location and kinetic-scale structures of the plasma current distribution. We show the formation of a magnetic cavity and a magnetic compression in the magnetospheric region, and two main current structures in the dayside of the magnetic obstacle: the diamagnetic current, supported by the driver plasma flow, and the current associated to the magnetopause, supported by both the background and driver plasmas with some time-dependence. From multiple parameter scans, we show a reflection of the magnetic compression, bounded by the length of the driver plasma, and a higher separation of the main current structures for lower dipolar magnetic moments.