Forced oscillations generated by a point antenna in a drifting plasma

Abstract

Drift effects on forced oscillations generated by an oscillating antenna are analysed in two cases. First, a Water Bag model with temperature T>or=0 is considered using a mixed analytical and numerical method. The numerical part is shown to be necessary to obtain results outside the perpendicular and parallel directions to the drift and radiation diagrams at different distances from the antenna give the behaviour of the potential. The existence of a radiation cone of the Cherenkov type is pointed out, and whilst outside of a cone centred on the drift direction with angle alpha , the potential is independent of the temperature, the bulk of the thermal effects are concentrated in an inner cone of smaller angle. Secondly a Maxwellian plasma represented by a Multi Water Bag (MWB) model with 60 bags is used and the normalisation of the distances is made classically in terms of the Debye length. The integration is performed by the same analytico-numerical method as used in the first case and the authors discuss the topology of the poles and the problems introduced by the choice of model. Radiation diagrams for low drift velocity (vD=0.35 vT) and w=1.2 wp are given at various distances from the source.