Scattering of terrestrial kilometric radiation at very high altitudes

Abstract

On a number of occasions during the 3.5‐yr operating lifetime of Rae 2, we observed strong terrestrial kilometric radiation when the spacecraft was over the far side of the moon and when the low‐altitude terrestrial magnetosphere was completely obscured from view. If these deep lunar occultation events are used to infer radio source locations, then we find that the apparent source must sometimes be situated at geocentric distances of 10–40 RE or more. From an analysis of these events, we show that they are probably due to propagation effects rather than the actual generation of the emission at such large distances. The kilometric radiation can be generated near the earth at auroral latitudes and subsequently strongly scattered in the magnetosheath and nearby solar wind to produce the large apparent distances. The most likely scatterers are density inhomogeneities in the magnetosheath plasma and ion plasma waves in the magnetosheath and the upstream solar wind.