Measurement of charge transfer in sprite-producing lightning using ELF radio atmospherics

Transient high altitude optical emissions referred to as ''sprites'' are believed to occur as a result of the transfer of large amounts of charge (similar to 100-300 C) from cloud altitudes of 5-10 km to the ground. Using a general subionospheric ELF propagation model, we quantitatively interpret magnetic field waveforms of ELF radio atmospherics originating in mid-western U.S. lightning discharges and observed at Stanford (similar to 1800 km range) to determine the temporal variation of the lightning current and thereby measure the charge transfer during the stroke. For 6 sprite-producing lightning current waveforms observed on July 24, 1996, we find that 25 to 325 coulombs of charge was transferred during the first 5 ms of the discharges, assuming a 10 km altitude for the initial charge.