Observation of Variations in Cosmic Ray Showers During Thunderstorms and Implications for Large-Scale Electric Field Changes

This work presents the first observation by the Telescope Array Surface Detector (TASD) of the effect of thunderstorms on the development of the cosmic ray showers. Observations of variations in the cosmic ray showers, using the TASD, allows us to study the electric field inside thunderstorms on a large scale without dealing with all the limitation of narrow exposure in time and space using balloons and aircraft detectors. In this work, observations of variations in the cosmic ray shower intensity (Delta N/N) using the TASD, was studied and found to be on average at the (1-2)% level. These observations where found to be both negative and positive in polarity. They were found to be correlated with lightning but also with thunderstorms. The size of the footprint of these variations on the ground ranged from (4-24) km in diameter and lasted for 10s of minutes. Dependence of (Delta N/N) on the electric field inside thunderstorms, in this work, is derived from CORSIKA simulations.