Imaging gamma-ray glows

Gamma-ray glows are persistent (seconds to minutes) gamma-ray emissions from thunderclouds associated to intense large-scale electric fields. Results from the ALOFT flight campaign in 2023 over Florida and the Gulf of Mexico [1,2] have shown that tropical thunderclouds can glow in gamma-rays for hours and over thousands of square kilometres, pointing at particle acceleration as a fundamental and ubiquitous phenomenon in thundercloud electrodynamics, likewise cloud electrification and lightning discharge. Moreover, ALOFT measurements evidence a significant intrinsic time variability of gamma-ray glows, likely matching the dynamics of large scale thundercloud electric fields. Despite earlier attempts, there is no direct measurement of gamma-ray glow spatial extent. With the ENLIGHTEN project we have the ambition to measure directly the spatial extent of glows in gamma-rays and their spatio-temporal evolution. We will use diverse gamma-ray imaging systems hosted onboard a high-altitude aircraft from NASA flying over active thunderclouds. The ENLIGHTEN flight campaign is currently scheduled for July 2028. Here we present the preliminary design of the gamma-ray imagers and their expected performance based on Monte Carlo simulations informed by the ALOFT gamma-ray glow measurements.

[1] Lang, T. J., et al., 2025: Hunting for Gamma Rays above Thunderstorms: The ALOFT Campaign. Bull. Amer. Meteorol. Soc., https://doi.org/10.1175/BAMS-D-24-0060.1.

[2] Marisaldi, M., et al., 2024: Highly dynamic gamma-ray emissions are common in tropical thunderclouds. Nature 634, https://doi.org:10.1038/s41586-024-07936-6