Spectral analysis of individual Terrestrial Gamma-ray Flashes using Fermi Gamma-ray Burst Monitor data and lightning leader models
Abstract
Due to high photon rates and low number of counts, studying individual Terrestrial Gamma-ray Flashes (TGFs) can be challenging. Gamma-ray Burst Monitor (GBM) onboard Fermi spacecraft has observed tens of sufficiently bright events, which are suitable for the individual analysis. Mailyan et al., [JGR, 121, 11346, 2016] for the first time fit individual, bright TGFs with Relativistic Runaway Electron Avalanche (RREA) models [Dwyer, GRL, 30, 2055, 2003]. RREA models assume that the TGF-producing electron acceleration takes place in a large-scale electric field in thunderclouds. Alternatively, lightning leader models consider the acceleration of the electrons at smaller spatial scales, at the tips of lightning leaders [Celestin et al., JGR, 120, 10712, 2015]. The predictions of the latter models for the TGF beaming geometry show some differences from estimations of the RREA models in homogeneous fields. In this work, we will analyze a large sample of bright Fermi-GBM TGFs in the framework of lightning leader models, making comparisons with previous results from the homogeneous-field RREA models. In addition, we will introduce more precise corrections for the instrumental effects caused by pulse pileup by considering a variable photon rate.