Energetic Radio Emissions and Possible Terrestrial Gamma-Ray Flashes Associated With Downward Propagating Negative Leaders

Abstract

A study of negative polarity energetic in-cloud pulses (−EIPs) during thunderstorms reveals that −EIPs occur during two distinct stages of downward negative leader development. The first group is observed at the beginning of downward negative leaders, with estimated average source altitude of ~5.9 km between main negative and lower positive charge regions. The second and new group are observed at the very end of downward negative leaders and appear to be produced at low altitudes close to the ground, where image charges amplify the electric field between the leader tip and conducting ground. Negative EIPs appear to occur only in these two scenarios, suggesting that their production require a high background electric field. Their radio emission signatures and occurrence contexts are similar with +EIPs, which are known to be connected to terrestrial gamma-ray flashes. We thus suggest that these two types of −EIPs may be associated with downward terrestrial gamma ray flashes.