Estimating the global production rate of TGFs
Abstract
Terrestrial gamma-ray flashes (TGFs) are short sub-millisecond bursts of high energy gamma radiation, bremsstrahlung from the negative charges brought upwards from positive intracloud lightning. They were first detected by the Burst and Transient Source Experiment (BATSE) in 1991 and were thought to be a rare phenomena. However with new and improved satellites and more sophisticated data search algorithms, they have been found to be more and more common. This begs the question; how common are TGFs? We have previously used the World Wide Lightning Location Network (WWLLN) in addition to RHESSI to extract 100ms interval of RHESSI data centred at the time of each lightning flash. By superposing the RHESSI intervals of data (excluding already identified TGFs) between August 2002 and December 2015, we found a 9.39σ increase in gamma-rays at the time of lightning. This indicates that there exists a population of observationally faint TGFs that cannot be identified by current RHESSI search algorithms. Comparing the detected counts at the time of lightning to the background over all events, we find a significant and continuous signal down to 3 counts in the detector. We do not see a clear cutoff in the signal, as has been suggested by others. This could indicate that a potential signal cutoff happens below this level in RHESSI. In this work we will deadtime correct the faint TGF-WWLLN events so that we can fit a power law function to their fluence. Comparing this with the fluence distribution of TGFs without WWLLN matches should enable us to estimate the global production rate of TGFs.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMAE33B2539A
- Keywords:
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- 3304 Atmospheric electricity;
- ATMOSPHERIC PROCESSES;
- 3324 Lightning;
- ATMOSPHERIC PROCESSES;
- 4301 Atmospheric;
- NATURAL HAZARDS