Direct observation of magnetospheric electron precipitation stimulated by lightning

Plasmaspheric electron precipitation bursts stimulated by observed lightning flashes have been studied using in situ rocket techniques under night-time conditions at Wallops Island, Virginia, on 23 August 1984. In one case, the rocket-observed ligntning flash was located by a ground-based network to be off the coast of Virginia at 74.8°W, 35.9°N, which was approximately 200km southeast of the rocket. Electron precipitation (> 40 keV) caused by simultaneous 21.4 kHz coded transmissions from a VLF radio transmitter at Annapolis, Maryland, was found to be negligible compared with the observed fluxes and energies of precipitating electrons stimulated by lightning. The results confirm that lightning (which can occur up to 100 times per second globally) can activate ionizing radiation sources within the magnetosphere, and that these may affect local middle atmospheric electrical structure in a measurable way.