Radar Diagnosis of the Thundercloud Electron Accelerator

Thunderstorm Ground Enhancements (TGEs) refer to correlated enhancements in surface electric field and gamma ray flux that are manifestations of electron runaway the storm overhead. The can be positive or negative polarity. In this study, altitude-resolved S-band radar observations graupel used demonstrate distinct differences structure linked with these “positive” “negative” TGEs. physical interpretation rests on well-established temperature-dependent tripole thunderstorms, main charge acting as an repeller. This is supported by case studies showing altitude-stable convection, shallow (deep) development (“negative”) TGEs, collapsing storms show upper dipole dominance early lower inverted later when particles descend from a colder warmer temperature domain. many TGEs Mt Aragats (3.2 km MSL), altitude downward acceleration avalanching may sufficiently distant (>500 m) detectors energetic electrons (1–10 MeV) not likely avalanche/runaway electrons. Instead, they Compton-scattered pair-produced bremsstrahlung radiation emanating high-field avalanche region aloft. These inferences consistent GEANT4 calculations identify origins at surface.