On Gamma-Ray and Radio-Frequency Radiation from Thunderstorms
Abstract
The occurrence context, characteristics, and physical mechanism of terrestrial gamma ray flashes (TGFs) continue to remain subjects of debate in the area of atmospheric electricity. In this study, we analyze a large dataset of more than 2000 TGFs whose energetic-radiation and radio signatures were simultaneously measured using space- and ground-based detectors, respectively, over a five-year period. The Gamma-ray Burst Monitor (GBM) on board the Fermi spacecraft provided the energetic radiation measurements and the radio signatures were obtained from the Global Lightning Dataset (GLD360). We examine two categories of TGFs - those that were accompanied by quasi-simultaneous electromagnetic pulses (EMPs) detected by the GLD360 and those without such simultaneous EMPs. We analyze the dependence of GLD360-estimated peak currents (which are proportional to their distance-normalized magnetic field peak amplitudes) for TGF-associated EMPs on the horizontal offset distance between the Fermi spacecraft and the TGF source. TGFs detected by GBM with sources at farther horizontal distances are expected be intrinsically brighter. These TGFs were also found to be associated with EMPs with larger median peak amplitudes. This provides independent evidence that the EMPs and TGFs are produced by the same phenomena, rather than EMPs being from lightning in the TGF-producing thunderstorm. Additionally, we examine the relationship between GLD360-estimated peak currents for EMPs, with GBM-measured TGF-associated energetic particle characteristics. TGFs with simultaneous EMPs exhibit shorter gamma-ray pulse durations, lower particle counts, and higher proportion of particles with higher energies, indicating a possibly that such TGFs originated deeper within the thundercloud (farther away from the spacecraft). The impact of GBM-instrument-characteristics such as pulse pile-up and dead-time on these results will be discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMAE41A..01M
- Keywords:
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- 3304 Atmospheric electricity;
- ATMOSPHERIC PROCESSES;
- 3324 Lightning;
- ATMOSPHERIC PROCESSES;
- 4301 Atmospheric;
- NATURAL HAZARDS