Probing the deviation from the Braginskii heat transport model due to kinetic effects in HED-relevant conditions*

Non-local heat transport caused by kinetic effects is expected to be prevalent in many high energy density (HED) plasma systems. While the impact of kinetic ions has been studied, less is known about the impact of kinetic electrons. Hydrodynamic and hybrid kinetic codes which are often used to simulate HED systems typically assume fluid electrons. While some non-local fluid heat flux models exist [1-3], a local Braginskii/Spitzer-Härm-type heat flux model is most commonly used in such codes. This model is only strictly valid in regimes where the electron Knudsen number, defined as the electron mean free path over the temperature gradient length scale, is small. In this study the fully kinetic code iFP [4,5] is used to quantify the deviation from the Braginskii model across a range of electron Knudsen numbers, including regimes with highly kinetic electrons. Systems are initialized in locally Maxwellian states with temperature gradients to allow for heat transport. The resulting heat flux is compared with the Braginskii model.

 

This work was performed under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory, managed by Triad National Security, LLC under contract 89233218CNA000001.

 

[1] Luciani et al., Phys. Rev. Lett., 51 (1983) 1664.

[2] Bendib et al., Phys. Fluids, 31 (1988) 711.

[3] Schurtz et al., Phys. Plasmas, 7 (2000) 4238.

[4] Taitano et al., Comp. Phys. Comm., 263 (2021) 107861.

[5] Anderson et al., J. Comp. Phys., 419 (2020) 109686.