A study of the numerical heating in electrostatic particle simulations

Abstract

We study the nonphysical increase of kinetic energy observed in electrostatic particle simulations. Quantitative analysis of the numerical heating is of vital importance in obtaining reliable results in simulation studies. The numerical heating caused by electrostatic fields is discussed with an emphasis on a couple of simulation parameters, such as the ratios of the number of particles Np to that of grid points Nx, and Debye length λD to the grid size Δx. In this paper a measure called "heating rate" is used for this purpose, which is defined by the relative magnitude of the kinetic energy increment in unit time to the initial energy. The present numerical experiments have revealed that the heating rate may vary in proportion to ( Np Nx)-1 and ( λD Δx)-3. The heating mechanisms are discussed in terms of nonphysical electric fields as observed in the fluctuation spectra of electric fields. © 1994.