Spectral Analysis of Terrestrial Gamma-ray Flashes and Their Connection to Lightning Discharges

This PhD thesis consists of three papers published in the Journal of Geophysical Research: Atmospheres. The thesis provides a new method to identify TGFs, detected from space, that are associated with radio-sferics. The method provided an independent diagnostics tool to validate and correct the absolute timing accuracy of the AGILE satellite. The new TGF catalog confirms and improves previous results about duration, geographical and local time distributions. Using data from several space missions combined with ground-detected sferics data and optical data from the ASIM mission, it is shown that the TGFs occur in the beginning of the lightning flash and that there is an increased sferics activity within a few hundreds of milliseconds after the TGFs. The thesis also provides spectral analysis of individual TGFs from the ASIM instrument. The work put constraints on space-based instrumental design aimed at TGF spectroscopy and shows that radio detection capabilities should be prioritized. Doktorgradsavhandlin