Experimental Validation of Analytic Models of the Coupling of a Laser-Driven and Background Plasma in Mini-Magnetosphere Experiments on the Large Plasma Device*

Supersonic plasmas expanding through magnetized, collisionless plasmas are ubiquitous, from supernova remnants and coronal mass ejections to laser-driven plasmas in laboratory experiments. Key to understanding these interactions is the collisionless coupling between the expanding and background plasmas. A specific system of interest is the formation of laboratory mini-magnetospheres through the interaction of a fast laser-driven plasma generated by the Phoenix Laser Laboratory with the background magnetized plasma of the Large Plasma Device (LAPD) at UCLA [1].  We present results from an investigation into the coupling physics for these experiments, using experimental data to validate analytic coupling models extracted from particle-in-cell simulations [2].  We find reasonable agreement for some parameters of the model, but discrepancies for others, suggesting that the coupling models do not fully capture the physics of the experiments. We discuss the limitations of the current models and propose improvements.

[1] Schaeffer, et al., “Laser-drive, ion-scale magnetospheres in laboraotety plasmas. I. Experimental platform and first results.” Physics of Plasmas 29, 042901 (2022).

[2] Cruz, et al., “Strong collisionless coupling between an unmagnetized driver plasma and a magnetized background plasma.” Physics of Plasmas 30, 052901 (2023).