Electric discharges between hydrometeors

The phenomenon of the microdischarge between small conductors (simulating hydrometeors) is experimentally investigated. The study consists in directly measuring the electric current signature of the discharge under various initial conditions and for two different sets of conductors: sphere‐sphere and sphere‐needle. The second system produces an important initial streamer phase prior to the leader one. The characteristics of the current signatures are strongly dependent on gap length. The shorter the gap, the higher the current intensity and the narrower the pulse. Measurements made with real water drops provide comparable results. On the other hand, the radiated electric field generated by a microdischarge between two conducting spheres located within an intense electrostatic field has also been measured. The temporal characteristics of the field signatures obtained agree with those of the current pulses. Risetimes of the order of a few nanoseconds have been measured. The derived spectral content shows that the electromagnetic energy of this elementary phenomenon radiates within the VHF range. A numerical model based on the current dependence of the air conductivity contributes to the explanation of the mechanism.