Whistlers and VLF noises propagating just outside the plasmapause

Ground-based recordings have been made of broadband whistler mode signals propagating along the plasmasphere outer surface, i.e., beyond the region of steep plasmapause density gradients. In contrast to features found in other field line regions, the extension of signal frequencies into the 0.5-0.8 f(Heq) range is observed, (where f(Heq) is the equatorial electron gyrofrequency of the path). The effects are exhibited by the fine structure of the knee trace and other plasmapause irregularities, amplitude peaks and emissionlike behavior above the nose frequency, whistler mode echoing above 0.5 f(Heq), and narrowband noises and noise bursts propagating along the plasmapause outer surface.