Constraining Downward Terrestrial Gamma Ray Flashes Using Ground‐Based Particle Detector Arrays

Abstract

Until recently, there were only a few ground‐based observations of terrestrial gamma ray flashes (TGFs). Since the Telescope Array in Utah, USA, started reporting detections of high‐energy particles correlated with lightning, their number has greatly increased. Ground observations of TGFs represent a valuable addition to space‐borne detectors. The proximity to the event and the ability to observe an event with several detectors may reveal new information about the production of TGFs. In this paper, we study downward directed TGFs using Monte Carlo modeling of photon transport through the atmosphere. The Telescope Array‐observed pulses of gamma rays spread over periods of a few hundred microseconds. We predict such structures to be observable at satellite altitude, given sufficient time resolution. Additionally, we demonstrate how various source spectra would lead to different number of photons reaching ground, which impacts the conclusions one can draw using observational data.

High‐Energy Radiation From Natural Lightning Observed in Coincidence With a VHF Broadband Interferometer

“…Based on these considerations, it is reasonable to think that observed X-rays are a very small fraction compared to those actually produced by lightning leaders. This conclusion is in agreement with Monte Carlo simulations and absorption models (Berge & Celestin, 2019;Celestin et al, 2015;Østgaard et al, 2008).…”

“…The observed energy deposit of the gamma ray shower found is consistent with a fluence of 10 12 –10 14 photons. Simulations on the beaming geometries, the fluence, and the time dispersion were discussed by (Berge & Celestin, 2019). These downward TGF observations show that it is particularly interesting and promising to study high‐energy emissions also from ground‐based instruments.…”

A Study on TGF Detectability at 2165 m Altitude: Estimates for the Mountain-Based Gamma-Flash Experiment

“…Such estimate ends up with a total fraction of survived photons equal to ∼10 −6 out of those emitted at the source. This value is strongly model dependent, and it is about one order of magnitude smaller than that obtained by [40] using a RREA model, pointing out that, although providing a reliable spatial extent of the region from which TGFs can be detected, our analytical treatment may result in an underestimation of the amount of survived photons at ground.…”

“…where K is a normalization constant. As pointed out in [40], the spectrum plays a crucial role in estimating the number of survived photons at the target. Due to the dependence of the radiation cross-section, and radiation-matter interaction, on energy, different spectral energy distributions would result in different survived fluxes, strongly affecting the TGF detectability of a given gamma-ray detection facility.…”

TGFs, Gamma‐Ray Glows, and Direct Lightning Strike Radiation Observed During a Single Flight of a Balloon‐Borne Gamma‐Ray Spectrometer

“…Results from this campaign may offer valuable insights into TGFs and high‐energy radiation phenomena in tropical storms. Ground‐based assets, such as lightning arrays (Berge & Celestin, 2019; Hare et al., 2016; Lu et al., 2010; Lyu et al., 2021; Shao et al., 2010), have also contributed information into storm charge structure, various radio frequency emissions, and the temporal nature of radiation events; these surface‐based platforms often validate and enhance data collected by space‐based observation systems (Bankert et al., 2011; Erdmann et al., 2020; Peterson & Rudlosky, 2018).…”