SATELLITE-OBSERVATIONS OF LIGHTNING-INDUCED ELECTRON-PRECIPITATION

Lightening-induced electron precipitation (LEP) from the Earth's radia tion belt has been observed on numerous occasions with detectors on th e low-altitude S81-1/SEEP satellite. A sequence of seven LEP events on September 9, 1982, and eight events on October 20, 1982, are correlat ed on a one-to-one basis with one-hop whistlers at Palmer, Antarctica. The temporal profile within a LEP burst has a remarkable fine structu re. It is shown to be associated with bunches of magnetically guided a nd focused 100-to-200 keV electrons that are repeatedly scattered by t he atmosphere and bounce between the northern and southern hemispheres . The delay time between the lightning sferic and the arrival of the f irst electron bunch increases with increasing L as predicted by the fi rst-order gyroresonance theory. The global distribution of strong LEP events observed with the SEEP payload correlates with lightning activi ty and shows a preferred distribution at 2<L<3. This L shell range cor responds to the slot region in the electron radiation belt. A single L EP burst (10-3 erg s-1cm-2) in the slot region is estimated to deplete &SIM;0.001% of the particles in the region covered by the burst magne tic field lines. The evidence supports the production of structured LE P by ducted rather than nonducted whistlers. It is found that ducted w histlers can be an important pitch angle diffusion mechanism for 100-2 50 keV electrons in the 2<L<3 range although a number of uncertainties in the various parameters remain to be resolved. It is suggested that observations of LEP can be a new tool to measure the presence and tra nsverse dimensions of plasmapheric whistler mode ducts.