3D Evolution of the Boundary Layer Formed During the Expansion of a Laserplasma in a Magnetic Field in Vacuum

Summary form only given. Explosive sub-Alfvenic plasma expansions occur in a variety of space and astrophysical events. A laboratory simulation was performed to investigate such interactions. The plasma flow was created by ablation of a solid CH₂ target with up to 0.1 PW/cm² pulses of the "Tomcat" Nd:glass laser. It expanded in vacuum in the azimuthal magnetic fields with strength up to 20 T generated by high current discharges of the "Zebra" pulsed-power generator. The expanding plasma was diagnosed with two-frame laser interferometry and schlieren imaging. The plasma expansion was asymmetric in directions parallel and perpendicular to the magnetic field. A dynamic boundary layer with steep density gradient formed at the plasma-field interface. The density modulations observed at the interface in schlieren images suggest the onset of instabilities in this high beta plasma. Comparing the growth in planes parallel and perpendicular to the field indicates flute-like instabilities (with k _parallel=0). As the expansion proceeds, the space-scale of the modulation appears to decrease. We will present experimental observations pointing to the instability growth. We will make detailed comparison between experiment and theory