Numerical heating in hybrid plasma simulations (Q1360402)

The numerical heating in hybrid particle-fluid simulations has been investigated with emphasis on the regime \(ZT_e/T_i\gg 1\), where \(Z\) is the charge state of the ions and \(T_e\) and \(T_i\) are the electron and ion temperatures, respectively. For the simple case of particle ions advanced in the ambipolar field due to quasineutral isothermal fluid electrons, the heating rate is observed to be weakly dependent on time step, inversely proportional to the number of simulation particles per grid cell and strongly increasing with increasing \(ZT_e/T_i\). Additional smoothing, due to finite Debye length, or introduced through numerical means such as higher order particle interpolation or smoothing of grid quantities, is observed to significantly reduce this heating. Both one- and two-dimensional results are presented.