Laboratory model of magnetosphere created by strong plasma perturbation with frozen-in magnetic field

TL;DR

This study demonstrates laboratory creation of a magnetosphere using laser-produced plasma with frozen-in magnetic fields, revealing collisionless coupling, shock formation, and electric potential penetration similar to natural magnetospheres.

Contribution

It introduces a novel laboratory setup for simulating magnetosphere formation with frozen-in magnetic fields, highlighting differences from vacuum expansion.

Findings

Formation of a strong compressive perturbation propagating super-Alfvenically.

Generation of a transverse electric field comparable to induction expectations.

Deep penetration of electric potential inside the magnetosphere with Alfvenic velocity.

Abstract

Transient interaction of magnetic dipole with plasma flow carrying southward magnetic field is studied in laboratory experiment. The flow with transverse frozen-in field is generated by means of laser-produced plasma cross-field expansion into background plasma which fills vacuum chamber along externally applied magnetic field prior to interaction. Probe measurements showed that at realized plasma parameters effective collisionless Larmor coupling takes place resulting in formation of strong compressive perturbation which propagates in background with super-Alfvenic velocity and generates in laboratory frame transverse electric field comparable in value to expected induction one. Compression pulse with southward field after short propagation interacts with dipole and creates well defined magnetosphere. Comparison of magnetospheres created by laser-produced plasma expanding in vacuum field and in magnetized background revealed fundamental differences in structure and behavior of electric potential in plasma. In presence of frozen-in southward field direct {\guillemotleft}sub-solar{\guillemotright} penetration of outside electric potential deep inside of magnetosphere was observed taking place with velocity close to upstream Alfven speed.