Analytical derivation of the H.F. electrostatic potential created by an oscillating point source in a streaming water-bag plasma

The purpose of this paper is to demonstrate the possibility of measuring the drift velocity of a thermal plasma with an H.F. quadrupole probe. The plasma is assumed to be isotropic and collisionless. A hydrodynamic model is used without restrictive assumptions on the magnitude of the drift velocity, which can be made smaller or larger than the thermal velocity. Some curves are presented for velocities parallel or anti-parallel to the emission-reception axis of the probe.