Threshold atmospheric electric fields for initiating relativistic runaway electron avalanches: theoretical estimates and CORSIKA simulations

Abstract. We examine the threshold atmospheric electric field (Eth) required to initiate a runawayavalanche in Earth's atmosphere. We compare the traditional, thirty-year-old theoretical threshold with its recently updated value and with the threshold derived from CORSIKA-simulated avalanches (Ez). The altitude dependence of these thresholds is analyzed, considering how changes in air density affect avalanche development. This study is vital for understanding high-energy atmospheric phenomena in both the lower and upper atmosphere, including thunderstorm ground enhancements (TGEs) and gamma glows, and for refining atmospheric electric field (AEF) models based on particle flux measurements.