Laboratory evidence for proton energization by collisionless shock surfing

Detailed characterization of laboratory magnetized super-critical collisionless shock and of the associated proton energization

“…We have also modelled the formation of the shocks using macroscopic hydrodynamic simulations and the associated particle acceleration using kinetic particle-in-cell simulations. As a companion paper of Yao et al 1 , here we show additional results of the experiments and simulations, providing more information to reproduce them and demonstrating the robustness of our interpreted proton energization mechanism to be shock surfing acceleration.…”

“…7 with red dots and blue error bars. Comparing it to the analytical thermal proton spectra (200 eV in red dash-dotted lines, as is observed in 1 through TS), it is clear that the proton energization is non-thermal. The cutoff energy reaches to about 80 keV.…”

“…For the shocked plasma, the electron number density is n e1 = 2n e0 = 2.0 × 10 18 cm −3 , and the temperature is T e1 = 100 eV and T i1 = 200 eV, all inferred from the TS characterization 1 . The boundary conditions for both particles and fields are open, and enough room is left between the boundary and the shock, so that the boundary conditions do not affect the concerned physics.…”

“…Particle dynamics of a high-velocity shock (as well as the comparison with the low-velocity case) and of the subsequent shock surfing proton energization is detailed in our previous paper 1 , while here we focus on demonstrating the robustness of the SSA mechanism that is at play in our experiment via 2D simulations, taking the non-stationarity 64 into considera-tion. Due to the limitation of the computational resources, we reduce the 2D simulation scale to an acceptable level: the simulation box size are L x = 8 mm, L y = 0.8 mm, the simulation time t end = 0.7 ns, and the resolution is d x = 0.4d e .…”

“…In our experimental campaigns at JLF/Titan and LULI2000 1 , we investigated shock formation combining laser-produced plasmas, a background medium and a strong ambient magnetic field (as detailed below). We chose to have an expanding plasma to drive a shock into an ambient gas in the presence of a strong external magnetic field.…”