MEASUREMENT OF CHARGE-TRANSFER IN SPRITE-PRODUCING LIGHTNING USING ELF RADIO ATMOSPHERICS

Transient high altitude optical emissions referred to as ''sprites'' a re believed to occur as a result of the transfer of large amounts of c harge (similar to 100-300 C) from cloud altitudes of 5-10 km to the gr ound. Using a general subionospheric ELF propagation model, we quantit atively interpret magnetic field waveforms of ELF radio atmospherics o riginating in mid-western U.S. lightning discharges and observed at St anford (similar to 1800 km range) to determine the temporal variation of the lightning current and thereby measure the charge transfer durin g the stroke. For 6 sprite-producing lightning current waveforms obser ved on July 24, 1996, we find that 25 to 325 coulombs of charge was tr ansferred during the first 5 ms of the discharges, assuming a 10 km al titude for the initial charge.