Generation of plasma current under arbitrary strong direct current electric field

Abstract

The generation of plasma current and the evolution of electron distribution under arbitrarily strong direct current electric fields have been studied by Fokker-Planck simulation. It is found that the behaviors of plasma are different under different fields: in the weak field, Spitzer’s law is suitable for describing the relationship between plasma current and electric field, and the response time to generate current is approximately equal to the relaxation time to reduce current after switching off the electric field; in the moderate field, the electron distribution is well represented by the sum of a stationary and drifting Maxwellian, and the relaxation time is much longer than the response time. According to the detailed knowledge of electron distributions, a set of hydrodynamic-like equations, similar to Spitzer’s but without the weak-field limit, is given for calculating the current. It is more suitable for application in hybrid particle-in-cell simulations.