Kinetic Corrections to Heat-flow and Nernst advection for Laser Heated Plasmas

TL;DR

This paper develops and tests reduced kinetic models for heat and magnetic field transport in laser-heated plasmas, improving agreement with detailed kinetic simulations and relevant for fusion experiments.

Contribution

It introduces flux limiter modifications for thermal and Nernst advection that incorporate electron collisions and magnetic effects, enhancing model accuracy.

Findings

Harmonic flux limiter improves agreement with kinetic data.

Magnetic field effects require gyroradius-based modifications.

Simulations show sensitivity to flux limiter details.

Abstract

Reduced models for approximating the impact of kinetic electron behavior on the transport of thermal energy and magnetic field are investigated. The thermal flux limiter has improved agreement with Vlasov-Fokker-Planck data when a harmonic form is used that adjusts the electron mean free path to account for electron-electron collisions; these results apply to both unmagnetized and magnetized plasmas. Once a magnetic field is incorporated, the mean free path should also be modified using the electron gyroradius. A flux limiter on Nernst advection of magnetic field is also required; a form that limits Nernst by the same fraction as the thermal heat-flow best reproduces kinetic simulations. A flux limiter form for the cross terms (Righi-Leduc and cross-gradient-Nernst) are also suggested. Hohlraum simulations relevant to fusion experiments on the National Ignition Facility are found to be sensitive to all of these details.