FORTE Perspectives on the Timing of Optical and Radio-Frequency Signals from Lightning

Coordinated optical and RF measurements of lightning have shown differences in the timing of transient lightning events; this can lead to events that are captured in one phenomenology but missed in another. At the individual pulse level, optical signals a re delayed on the order of 10s to 100s of microseconds by scattering through the cloud layer between the source and satellite. While on longer flash - level scales, strong RF activity from Narrow Bipolar Events (NBEs) may precede the first optical emissions by more than tens of milliseconds. To understand differences in detection efficiency between instruments, we use multi - phenomenology clustered lightning data from the FORTE satellite to examine the joint time evolution of lightning signals. This data set of linked events recorded by each FORTE instrument is used to generate statistics on optical / RF coincidence at both the pulse - level and the flash - level. These statistics show how often the RF signals in a flash precede the optical signals and by how long of a time period. We also use this data set to compare the optical / RF waveforms to evaluate scattering delays in various types of lightning events.