ELF hiss generation at lower edge of inner radiation belt

Abstract

An attempt has been made to investigate the possibility of generation of ELF hiss emissions (a few hundred Hz ≤ f ≤ 3 kHz) at the lower edge of inner radiation belt (L = 1.2) by calculating their equatorial magnetic field intensities in terms of incoherent and coherent Cerenkov radiation mechanisms. The results indicate that ELF hiss emissions can not be generated by incoherent Cerenkov radiation mechanism at this location, because the intensities calculated in terms of this mechanism are found to be much lower than the observed intensities. The intensities calculated in terms of coherent Cerenkov radiation mechanism, being several orders of magnitude higher than the observed ones, indicate that the conditions are propitious for the generation of ELF hiss emissions (other than the plasmaspheric hiss) having large wave normal angles at the lower edge of inner radiation belt (L = 1.2) through partially coherent Cerenkov radiation mechanism. This is not, however, true in the case of plasmaspheric hiss (f < 1 kHz), which is thought to be originated in the vicinity of the plasmapause through electron-cyclotron resonance instability mechanism and reaching the lower L-shells after several magnetospheric reflections from there.