Particle-in-cell simulations of shockwaves in plasma

Plasma shocks are a ubiquitous phenomenon that occur in dynamically driven inertial confinement fusion and dense Z-pinch experiments, as well as in many areas of astrophysics. The structure of a shockwave in a plasma is more complicated than that in a neutral gas because of the disparity between the electron and ion masses and their mean free paths, the latter of which is sensitive to the charge state Z. Here, we present fully kinetic results of shockwaves in plasmas ranging from Z=1 (hydrogen) to Z=10 (neon). The simulations are performed using the energy- and charge-conserving particle-in-cell algorithm in PICNIC. In contrast to some theories for shocks in plasmas with Z>5, where the classical electron viscosity can exceed that of the ions, the electron heating in the viscous sublayer is insignificant compared to that for the ions for all values of Z considered. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and was supported by the LLNL-LDRD Program under Project No. 23-ERD-007.