From ground to space: high-energy atmospheric and astrophysics transient phenomena through a ground-based detector and a 8U CubeSat

High-energy transient phenomena, ranging from terrestrial gamma-ray flashes and gamma-ray glows in the Earth’s atmosphere to cosmological events such as gamma-ray bursts, are of remarkable interest due to their high-energy emission and extremely short duration. Despite their very different origins, these phenomena share key observational features: they produce impulsive gamma-ray emissions and require fast and sensitive detectors, robust trigger logic, and versatile analysis tools. This Thesis addresses these challenges through a combined ground-to-space approach. On the ground, two complementary detector systems, Gamma-Flash at Mt. Cimone (Sestola, Modena) and PIZ-Gamma at Mt. Piz Boé (Canazei, Trento), were developed, optimized, and operated to detect atmospheric gamma-ray transients in real conditions. Their characterization, calibration, and the creation of a data-analysis pipeline carried out in this work, enabled the identification of high-energy events. The strong dependence of detection efficiency on altitude, environment, and instrumental configurations is investigated in this work. Building on this experience, the Thesis also proposes a mission concept for an 8U CubeSat equipped with a wide-field 4π gamma-ray detector capable of observing both atmospheric and astrophysical transients. It shows how technologies developed for ground-based detectors can be translated into a compact orbital instrument, effectively using ground-based results to guide the design of a space-borne platform for the joint study of TGFs, GRBs, and other high-energy transient events.