Ion Acceleration by Quasi-Parallel Magnetized Collisionless Shocks

Magnetized collisionless shocks are ubiquitous in heliospheric and astrophysical environments, including planetary shocks, the heliopause, supernova remnants, and galaxy clusters. Additionally, magnetized shock dynamics are highly dependent on the angle $ heta_B$ between the upstream magnetic field and the shock propagation direction, with different physical processes active in quasi-perpendicular (θ_B > 45°) and quasi-parallel (θ_B < 45°) geometries. Of particular interest are quasi-parallel shocks, in which the shock propagates primarily along the background magnetic field and which have been associated with efficient particle energization and extremely high-energy cosmic rays. However, we currently lack an understanding of key aspects of how these ions are accelerated to extreme energies, with multiple competing theories and incomplete hints from satellite observations of shocks in space. Recent advances have enabled collisionless shocks to be created experimentally using high-powered lasers, but quasi-parallel shocks have yet to be created in the laboratory. We present a new experimental platform to study particle acceleration by quasi-parallel shocks that combines large magnetized plasmas with strongly driven plasma flows uniquely available on the National Ignition Facility. Particle-in-cell simulations indicate the experimental conditions under which quasi-parallel shocks can form and accelerate ions.