Fully kinetic simulations of collisional plasma shocks

We discuss fully kinetic simulations of steady-state high Mach number planar shocks in a Hydrogen plasma with kinetic electrons and ions, and compare to hybrid simulations with kinetic ions coupled to a fluid electron model [1]. The simulations are independently performed by two different fully kinetic codes, namely the Vlasov-Fokker-Planck code iFP and the particle-in-cell code VPIC. We find that, while kinetic electrons do not change the shock structure observed in the hybrid simulation at a fundamental level, the preheat layer experiences an appreciable rearrangement. This modification is associated with kinetic electron effects, namely nonlocal electron heat transport. We find that the kinetic electron heat flux exhibits significant nonlocality, and agrees well with the Luciani-Mora-Virmont nonlocal electron heat flux closure [2]. Finally, the fully kinetic simulations show a significant collapse in the ‘precursor’ electric-field shock at the edge of the preheat layer, which contrasts with the classical hydrodynamic picture [3].

References:

[1]  S. E. Anderson, et. al, “Fully kinetic simulations of strong steady-state collisional planar plasma shocks”, arXiv:2106.13108 (2021), preprint submitted to Phys. Rev. Lett.

[2]  J. F. Luciani et. al, “Nonlocal heat transport due to steep temperature gradients,” Phys. Rev. Lett. 51, 1664 (1983)

[3]. M. Y. Jaffrin and R. F. Probstein, “Structure of a plasma shock wave,” Phys. Fluids 7, 1658 (1964)