Radio Frequency Emissions Associated With Multi-Pulsed Terrestrial Gamma-Ray Flashes

Terrestrial Gamma-ray Flashes (TGFs) with multiple pulses have been observed many times since their discovery in the 1990s. The BATSE sample of TGFs had a large fraction of multi-pulsed TGFs. It was not until later instruments, such as RHESSI, that the sample of detected TGFs consisted mostly of single-peaked, sub-millisecond events. Recent research has focused chiefly on these common single pulsed events, but several questions can be answered by analyzing multi-pulse TGFs. One is the relationship between very low frequency (VLF) radio signals and the gamma-ray pulses of TGFs. This paper discusses multi-pulsed TGFs observed by Fermi Gamma-ray Burst Monitor and their associated radio frequency pulses. In our data set of 29 multi-pulse TGFs, 22 have a VLF association only with the last gamma-ray pulse. However, unlike previous studies, we identified several events having radio matches with the first or both gamma-ray pulses of double-pulse TGFs. The absence of a VLF signal can be due to detection efficiency. On the other hand, the lack of correlation between radio and gamma-ray intensities for some TGFs, cannot be explained by existing models. The models should be revised taking into account recent observations.

Duke Scholars

Author Steven A. Cummer Electrical and Computer Engineering