Observing magnetised, collisionless shocks using laser-driven platforms
Ellie Tubman (UC Berkley)
Wednesday 8th April 15:00-16:00
Maths 311B
Abstract
Magnetized, collisionless (λmfp>> Lshock) 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.
In this talk I will present exciting results from an experimental platform using the Omega laser facility. A gas jet and MIFED assembly provide a pre-ionized, pre-magnetized background plasma, through which a shock wave is launched. We diagnose the effect of the magnitude of the background magnetic fields on the shock formation using both temporally and spatially resolved 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 first, clear identification of the shock’s development stages as well as the initial separation of the shock piston and background material. The results assist in benchmarking particle-in-cell codes and hydrodynamic models as well as interpreting measurements from spacecrafts, to gain a better understanding of the underlying physics.
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