Thunderstorm-induced muon event on 20 March 2020: Insights from the Ooty muon telescope, INSAT-3DR, and lightning observations

We report a thunderstorm-induced muon event (TIME) observed on 20 March 2020 using the GRAPES-3 muon telescope in Ooty, India. This event was investigated using complementary data from the INSAT-3DR satellite, the Indian lightning location network, and ground-based electric field measurements. A 1.4% suppression in muon flux ($12.4\ensuremath{\sigma}$ significance) was detected in the southeast sector, coinciding with intense upward-directed electric fields ($\ensuremath{-}5\text{ }\text{ }\mathrm{kV}/\mathrm{m}$) and elevated lightning activity. These observations support the hypothesis that upward electric fields cause energy losses in positive muons, resulting in reduced ground-level flux. The event provides evidence for the directional sensitivity of cosmic-ray secondaries to storm-time electric fields and highlights the unique capability of muon telescopes in probing high-altitude atmospheric electrodynamics. This study illustrates the value of integrating particle physics with atmospheric science, leveraging ground- and space-based observations to deepen our understanding of energetic atmospheric processes and their connections to space weather phenomena.