The lightning‐TGF relationship on microsecond timescales

[1] We analyze the count rates of two terrestrial gamma‐ray flashes (TGFs) detected by the Fermi Gamma‐ray Burst Monitor (GBM) with the broadband magnetic fields (1 to 300 kHz) produced by the simultaneous lightning processes. The microsecond‐scale absolute time accuracy for these data, combined with independent geolocations of the source lightning, enable this analysis with higher accuracy than previously possible. In both events, fast discharge‐like processes occur within several tens of microseconds of the gamma‐ray generation, although not with a consistent relationship. The magnetic field data also show a slower signal component produced by a source current that in both events mirrors the gamma‐ray count rate closely in shape and time. This indicates electromagnetic radiation directly associated with the gamma‐ray generation process and thus provides a new means for probing the internal physics of this enigmatic phenomenon. Citation: Cummer, S. A., G. Lu, M. S. Briggs, V. Connaughton, S. Xiong, G. J. Fishman, and J. R. Dwyer (2011), The lightning‐TGF relationship on microsecond timescales, Geophys. Res. Lett., 38, L14810, doi:10.1029/2011GL048099.