Laser-Produced Plasmas as Drivers of Quasi-Parallel Collisionless Shock Formation in the Laboratory

Peter Ver Bryck Heuer, Christoph Niemann
2020 Zenodo  
Quasi-parallel collisionless shocks are objects of considerable interest in space and astrophysics, most notably as possible sites of cosmic ray acceleration. Such shocks occur naturally in systems such as supernova remnants and planetary bow shocks, where the complex and turbulent structures they form are commonly observed by spacecraft. However, \textit{in situ} spacecraft measurements have some inherent limitations, such as a moving reference frame and non-repeatable measurements. Generating
more » ... a quasi-parallel collisionless shock in a repeatable, well-diagnosed laboratory environment could therefore improve our understanding of their formation and structure. The quasi-parallel collisionless shocks observed in space and astrophysics are far too large to fit in a laboratory, but scaled versions of these systems can be created using smaller, denser plasmas with similar dimensionless parameters. However, quasi-parallel collisionless shocks are particularly challenging to scale to a feasible experiment. The shock formation process is mediated by several electromagnetic ion/ion beam instabilities which require long length scales ($>500$ ion-inertial lengths) to grow, so an experiment must include a long magnetized background plasma. This background plasma must be overlapped over the same length by a highly super-Alfv\'enic beam plasma. Matching the dimensionless parameters of the shocks observed in space sets demanding requirements on the densities of both plasmas as well as the background magnetic field strength. Laser-produced plasmas (LPPs) provide a promising beam plasma source (a "driver") for such experiments. A recent experimental campaign has been conducted at UCLA to investigate the potential of LPPs as drivers of quasi-parallel collisionless shocks. These experiments combine one of two high-energy lasers with the magnetized background plasma of the Large Plasma Device (LAPD) to drive the electromagnetic ion/ion beam instabilities responsible for shock formation. The experiments have observed electromagn [...]
doi:10.5281/zenodo.3875148 fatcat:ry7wu4q47resbiw4fa7nnbcz7m