On the induced charge density distribution in streaming plasmas

Abstract

Motivated by experiments on the generation of streaming plasmas in high energy density facilities,
industrial setups, and fundamental dusty plasma research, the plasma polarization around a test charge in
streaming plasmas is considered in this work. The induced charge density distribution of the plasma
constituents is discussed for the subsonic, sonic, and supersonic regime taking into account the non-
Maxwellian distribution of the flowing ions. It is shown that the plasma polarization (the plasma
wakefield) in the vicinity of the test charge shows different scaling in the subsonic and supersonic
regimes, where Mach number is defined as the ratio of the ion streaming velocity and the ion sound
speed. In contrast to the wake potential, the density decays strongly monotonically in the plasma wake
and does not exhibit an oscillatory pattern or trailing maxima. Therefore, the picture of an ion focusing
effect creating a separated ion region downstream was not confirmed.