Observation of high‐frequency turbulence induced by an artificial ion beam in the ionosphere

Abstract

High‐frequency electrostatic waves have been studied during the injection into the ionosphere of an artificial xenon ion beam in a direction quasi‐perpendicular to the magnetic field. The xenon ion plasma source was situated on a small ejectable payload, and the main characteristics of the beam were recorded on the central payload when the separation distance was increasing. Both active and passive methods of observation have been used. The electron density and temperature inside the beam have been derived from the active method of measurement, based on the propagation of artificial waves. The high‐frequency turbulence, detected with the passive method, appeared to be mainly electrostatic and was localized in two main different regions. At small distances from the source the strongest signals were recorded in the region of large‐density gradients situated in the leading edge of the beam. Then the spiky structure of the high‐frequency turbulence can be interpreted as resulting from the coupling between the lower hybrid drift instability and the Langmuir plasma waves. At larger distances from the source, another type of high‐frequency turbulence was set up in regions of low density situated in front of the beam. This last turbulence resulted from the destabilization of electron cyclotron harmonic waves and was localized inside a well‐defined density dip situated in front of the beam.