Study of early-stage, quasi-parallel, collisionless shock formation in the high Alfvénic Mach number regime*

Collisionless shocks that form in the presence of an ambient magnetic field are the likely source of the highest energy cosmic rays in our universe. Both the magnetic field amplitude, through the Alfvénic Mach number (M_A), and the field orientation relative to the plasma flow will dictate the formation mechanism of the collisionless shocks. The quasi-parallel configuration has shown to produce efficient particle acceleration in satellite measurements [Johlander ApJ 914 (2021)] and in numerical studies [Caprioli ApJ 783 (2014)]. Laser-based experiments provide a unique means to create relevant plasma conditions to study the microphysics associated with electromagnetic field generation relevant to quasi-parallel collisonless-shock formation. To this end, we have developed a new experimental platform at the Omega Laser Facility to study the early stages of quasi-parallel collisionless shock formation by studying the streaming instabilities generated during the interpenetration of magnetized, asymmetric plasma flows at high M_A (>100). The interaction region is characterized using time-resolved Thomson scattering to fully characterize the plasma flows and short-pulse proton radiography to visualize the B-field structures driven by ion streaming instabilities. Recent experimental results will be shown and discussed.