[ 1] The mean lightning current waveform of particularly intense lightning discharges is inferred from 52,510 radio wave recordings in the frequency range 1 - 200 Hz. The current waveform decays initially with a time constant of similar to 2 ms, and the current lowers similar to 60 C from cloud to ground within the first similar to 10 ms of the discharge. The subsequent continuing current exhibits a decay time constant of similar to 40 ms and lowers similar to 170 C from cloud to ground within the next similar to 100 ms of the discharge. The total charge transfer similar to 230 C from cloud to ground deposits electrical energy into the stratosphere resulting from quasi-static ( Joule) heating. The energy deposition is dominated by the lightning continuing current, and it is similar to 10(-5) J/m(3) at 30 km height. It is speculated that the initiation of blue jets and gigantic jets in the stratosphere may result from lightning continuing current greater than or similar to 100 ms which can be observed with radio waves at frequencies less than or similar to 10 Hz.
Fullekrug, M., Ignaccolo, M., & Kuvshinov, A. (2006). Stratospheric Joule heating by lightning continuing current inferred from radio remote sensing. Radio Science, 41(2). https://doi.org/10.1029/2006rs003472