Laboratory Studies of Laser-Driven, Ion-Scale Magnetospheres on the Large Plasma Device

Magnetospheres are a ubiquitous feature of magnetized bodies embedded in a plasma flow. Large planetary magnetospheres in the heliosphere have been studied for decades by spacecraft, while ion-scale "mini" magnetospheres have been observed around comets, weakly-magnetized asteroids, and localized regions on the Moon. These mini-magnetospheres provide a unique environment to study kinetic-scale plasma physics, in particular in the collisionless regime, but are difficult to study directly. Laboratory experiments on mini-magnetospheres can thus provide a controlled and reproducible platform for understanding fundamental magnetospheric physics while helping to validate models of larger, planetary magnetospheres. In this work [1,2], we present the results from experiments on ion-scale magnetospheres performed on a new high-repetition-rate (1 Hz) experimental platform developed on the Large Plasma Device (LAPD) at UCLA. The experiments utilize a high-energy laser to drive a supersonic plasma flow into a pulsed dipole magnetic field embedded in a uniform background magnetic field. 2D maps of "dayside" magnetic field with high spatial and temporal resolution are measured with magnetic flux probes and examine the evolution of local and global magnetosphere and current density structures for a range of dipole and upstream parameters. The results are compared to PIC simulations to further identify the magnetospheric structure, kinetic-scale structures of the plasma current distribution, and dynamics of the laser-driven plasma.

The experiments were supported by the DOE FES, the NSF/DOE Partnership in Basic Plasmas Science and Engineering, and the Defense Threat Reduction Agency and Lawrence Livermore National Security LLC. The simulations were supported by the European Research Council and FCT.

[1] Schaeffer, et al., Physics of Plasmas 29, 042901 (2022).

[2] Cruz, et al., Physics of Plasmas 29, 032902 (2022).