ARE VLF RAPID ONSET, RAPID DECAY PERTURBATIONS PRODUCED BY SCATTERINGOFF SPRITE PLASMA

Rapid onset, rapid decay perturbations (RORDs) of subionospheric VLF p ropagation require highly localized or laterally structured plasma at low altitudes to explain the wide angle scattering observed and the ra pid decay. Simultaneous occurrence of RORDs and red sprites, illustrat ed by a single event here, together with VLF phase and group delay mea surements from a pair of spaced receivers suggest that RORDs are produ ced by scattering from conducting columns at the position and with the lateral shape of the sprite. The sprite luminosity decays much faster than the RORDs which depend on the sprite conductivity and so plasma density. Plasma is also produced near the sprite plasma by energetic e lectrons precipitated from the magnetosphere by ducted whistlers and a fter the expected whistler and electron propagation delay. This whistl er-induced electron precipitation (WEP) plasma produces wide angle VLF scattering similar to that by sprite plasma, implying similar lateral fine structure. This suggests that the processes leading to sprites a lso produce whistler ducts in the magnetosphere.