Abstract
Magnetic fields can be generated in plasmas by the Biermann battery when the electric field produced by the electron pressure gradient has a curl. The commonly employed magnetohydrodynamic (MHD) model of the Biermann battery breaks down when the electron distribution function is distorted away from Maxwellian. Using both MHD and kinetic simulations of a laser-plasma interaction relevant to inertial confinement fusion we have shown that this distortion can reduce the Biermann-producing electric field by around 50%. More importantly, the use of a flux limiter in an MHD treatment to deal with the effect of the non-Maxwellian electron distribution on electron thermal transport leads to a completely unphysical prediction of the Biermann-producing electric field and so results in erroneous predictions for the generated magnetic field.This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 2)’.
Highlights
The simple interpretation of the Biermann battery being caused by the curl of the electric field due to the electron pressure gradient only holds for plasmas where the electrons are in local thermodynamic equilibrium (LTE)
We showed that varying the electron flux limiter between reasonable values led to more than a factor of six change in the instantaneous peak electric field in 1D
We have shown that kinetic effects modify the Biermann battery under conditions relevant to current laser plasma experiments
Summary
Magnetic fields can be generated in plasmas by the Biermann battery when the electric field produced by the electron pressure gradient has a curl. The commonly employed magnetohydrodynamic (MHD) model of the Biermann battery breaks down when the electron distribution function is distorted away from Maxwellian. Using both MHD and kinetic simulations of a laser-plasma interaction relevant to inertial confinement fusion we have shown that this distortion can reduce the Biermann-producing electric field by around 50%. The use of a flux limiter in an MHD treatment to deal with the effect of the nonMaxwellian electron distribution on electron thermal transport leads to a completely unphysical prediction of the Biermann-producing electric field and so results in erroneous predictions for the generated magnetic field. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 2)’
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