Induced enhancement of the plasma line in the backscatter spectrum by ionospheric heating

Abstract

Summary. Recent results from ionospheric modification experiments at the Arecibo Ionospheric Observatory show an enhanced plasma line temperature of approximately 4000°K due to excitation of the ion acoustic parametric instability. Recent theories on the saturation spectrum of the plasma waves excited in this experiment predict that the bulk of the wave energy is associated with waves propagating in a very narrow angular cone centered on the geomagnetic field. The intensity of the plasma waves responsible for the scattering that are propagating parallel to the probing radar beam, i.e., at 40° to the geomagnetic field, is weaker than the intensity of the parallel propagating plasma waves by orders of magnitude. It is shown here that the intensity is still sufficient to account for the experimental results.