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

Abstract

Gamma-Flash is an Italian program devoted to the realization of both a ground-based and an airborne gamma-ray and neutron detection system, for in situ measurements of high-energy phenomena correlated to thunderstorm activity, such as Terrestrial Gamma-ray Flashes (TGFs), gamma-ray glows, and associated neutron emissions. The ground-based Gamma-Flash experiment is currently under installation at the Osservatorio Climatico “Ottavio Vittori” (CNR-ISAC) on Mt. Cimone, in Northern-Central Italy (2165 m a.s.l.), and it will be operational starting in Summer 2022. We studied the detectability of TGFs in the surroundings of the ground-based Gamma-Flash experiment, to identify an investigable spatial region around the detectors from which typical TGFs can survive and be revealed onground. We carried out numerical simulations of gamma-ray propagation in the mid-latitude atmosphere, and we developed a qualitative analytical model to integrate the results. This analysis allows one to identify a spatial region extending up to 4 km distance on ground and up to 10 km altitude a.s.l., considering typical TGFs emitting ∼1018 gamma-ray photons at the source. Lightning sferics data acquired by the LINET network demonstrate that such a region is interested by frequent cloud-to-ground and intra-cloud lightning, pointing out the suitability of the location for the purposes of the Gamma-Flash program.

Estimates of Lightning Activity and Terrestrial Gamma-ray Flash Detectability at Mount Etna for the ESTHER Project

“…The ESTHER project takes advantage of the long-term experience in TGF studies achieved with the AGILE satellite [21][22][23] and with the Gamma-Flash program [24][25][26]. Moreover, it is worth mentioning that it offers the interesting side opportunity of monitoring environmental high-energy background spectrum variations before, during, and after volcanic eruptions, from a favored point of view.…”

“…Etna is affected by frequent and intense lighting activity, we evaluated the detectability of possibly emitted Terrestrial Gamma-ray Flashes (TGFs) from the two proposed installation sites (i.e., OE and RC). We followed the same approach already adopted in [24] for the estimate of the TGF detectability region in the surroundings of the Gamma-Flash experiment installation site.…”

“…All TGF emission cones are considered to point directly toward the installation site in order to test the best source-target configuration. Adopting the same method used in [24] and considering the average attenuation undergone by gamma-ray radiation in the air for the considered energies, we evaluated the number of surviving photons at the installation site for each TGF source of the grid.…”