Observationally weak TGFs in the RHESSI data

International audienceTerrestrial gamma‐ray Flashes (TGFs) are sub‐millisecond bursts of high energetic gamma radiation associated with intracloud flashes in thunderstorms. In this paper we use the simultaneity of lightning detections by WWLLN to find TGFs in the RHESSI data that are too faint to be identified by standard search algorithms. A similar approach has been used in an earlier paper, but here we expand the dataset to include all years of RHESSI+WWLLN data, and show that there is a population of observationally weak TGFs all the way down to 0.22 of the RHESSI detection threshold (3 counts in the detector). One should note that the majority of these are “normal” TGFs that are produced further away from the sub‐satellite point (and experience a 1/r2 effect) or produced at higher latitudes with a lower tropoause, and thus experience increased atmospheric attenuation. This supports the idea that the TGF production rate is higher than currently reported. We also show that, compared to lightning flashes, TGFs are more partial to ocean and coastal regions than over land