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 ~2 ms, and the current lowers ~60 C from cloud to ground within the first ~10 ms of the discharge. The subsequent continuing current exhibits a decay time constant of ~40 ms and lowers ~170 C from cloud to ground within the next ~100 ms of the discharge. The total charge transfer ~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 ~10-5 J/m3 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 $gtrsim$100 ms which can be observed with radio waves at frequencies $lesssim$10 Hz.