Evaluating higher moments in the transverse Kelvin-Helmholtz instability by full kinetic simulation

Abstract

Approximated forms of the third and fourth moments of a velocity distribution function are derived by using a perturbed velocity distribution function around a characteristic spatial scale on the gyroradius derived by Thompson [Rep. Prog. Phys. 24, 363-424 (1961)]. Then, they are evaluated by using a two-dimensional full kinetic Vlasov simulation result of the transverse Kelvin-Helmholtz instability. It is shown that the derived form of the fourth moment is in agreement with the one calculated from the distribution function data of the Vlasov simulation. On the other hand, the derived form of the third moment is quite different from the one (i.e., heat flux tensor) calculated from the distribution function data of the Vlasov simulation. The results suggest that the perturbed velocity distribution function of Thompson needs an improvement.