Background separation in the upstream of a magnetised, collisionless shock.*

Magnetized, collisionless shocks are observed throughout the universe including within supernova remnants and at Earth’s magnetopause. These shocks have the potential to accelerate particles to far greater energies than many other astrophysical processes and may provide a source of high-energy cosmic rays. One challenge, yet to be addressed, is determining the exact mechanism of the energy dissipation by these shock waves. Designing a laboratory-based experiment that can create and investigate these shocks is advantageous for testing different theories and developing our knowledge of this phenomena. The results assist in benchmarking HANE (High Altitude Nuclear Explosion) models, as well as supporting HYDRA simulations, to develop a better understanding of the underlying physics.

 

The experiments were conducted using the Omega laser where a gas jet provides a pre-ionized, pre-magnetized background plasma within a MIFED assembly, through which the shock is driven. We diagnose the effect of the background magnetic fields on the shock formation using Thomson scattering. This allow us to measure the plasma conditions, as well as identify where the background and shock piston material are spatially located. In addition, we diagnose the evolving electromagnetic field structures using proton probing. These diagnostics have led to the clear identification of the shock’s development stages as well as the initial separation of the shock piston and background material.