Estimating lightning current moment waveforms 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. The remaining 2 events had anomalously large scaling factors of ∼3 and ∼8 MR/kAkm. The concurrent images showed two coincident bright cores of lightning, which suggests complex in‐cloud lightning processes may sometimes affect the optical‐radio relationship.