Current moment waveforms in sprite/halo producing lightning derived from satellite optical measurements

From July 2004 to June 2007, the FORMOSAT-2/ISUAL spectrophotometer and Duke magnetometer observed clear optical and radio signatures of 12 sprite-producing lightning events. In 10 of these, 777.4-nm luminosity normalized to a distance of 3000 km was almost linearly correlated with current moment with a scaling factor of ~0.82 MR/kAkm. This finding provides a possible new way to remotely measure lightning current moment, which is critical for understanding the production of sprites, through satellite-based optical measurements. Using the scaling factor obtained, we further analyzed ISUAL-observed 85 lightning events producing TLEs. Out of 85 cases, 24 events produced pure haloes, 22 events produced pure sprites, and 39 events produced the combinations of a halo and sprites. The average timescale and charge moment of lightning were <1 ms and ~300 C-km in pure halo events, ~1 ms and ~600 C-km in halo-sprite events, and >>1 ms and ~600 C-km in pure sprite events, respectively. The charge moment values estimated were somewhat smaller than the previous results of Adachi et al. [2008], but the overall tendency was clearly consistent. In order to further discuss their generation processes, we will compare the observational results with theoretical calculations using self-consistent quasi-electrostatic model.