Investigation of Lightning Distributions over Mt. Cimone using LINET and ISS-LIS Data for the Gamma-Flash Program

The typical features of the lightning distribution on the top of Mt. Cimone (2165 m a.s.l. - Northern-Central Italy) have been studied through detections provided by the ground-based LIghtning NETwork data (LINET) in the context of the Gamma-Flash program. Gamma-Flash is an innovative program funded by the Italian Space Agency (ASI) and lead by the National Institute for Astrophysics (INAF), with the collaboration of numerous institutions and universities. It involves an in situ measurement campaign (starting operations in late summer / fall 2021) dedicated to the observation of high-energy phenomena in the atmosphere, such as radiation (e.g., Terrestrial Gamma-ray Flashes, TGFs, and gamma-ray glows) and possible associated particle emissions (e.g., neutrons). The payload is set to be placed at the Osservatorio Climatico O. Vittori on the top of Mt. Cimone. The innovative aspect is the continuous monitoring at high altitude supported by meteorological data and analysis on local scale. In this perspective, annual and daily lightning distributions over the Mt. Cimone region have been considered. The LINET network exploits VLF/LF measurements, allowing detection of both cloud-to-ground (CG) and intra-cloud (IC) strokes (those recognized as being most likely associated with TGFs). The lightning distribution around the top of Mt. Cimone showed that locally also both CGs and ICs exhibit an impressive local clustering in the immediate surroundings of the observatory, likely driven by the orography. On the other hand, optical emissions can be related to other features of a flash not seen in VLF/LF. In order to provide a more complete picture of lightning processes, exploring the relationships between radio waves and optical emissions, an investigation of the LINET flashes optical counterparts by means of the Lightning Imaging Sensor (LIS) onboard the ISS data was also performed. The results allow a complementary analysis to Gamma-flash numerical simulations on the propagation of radiation and particles in the atmosphere: their combination gives a quantitative indication of the expected occurrence of lightning and ionizing radiation emissions in the region of interest.