Current Problems of Electrodynamics of a Thunderstorm Cloud

Abstract

Electrodynamics of a thunderstorm cloud is considered with allowance for recirculation and multiflow motion of charged intracloud particles. In this simulation, the large-scale electric-field emerges due to the charge separation at the process of air convection and develops through the oscillation regime in the initial and final stages of the thunderstorm evolution. These oscillations qualitatively explain the observed behavior of the electric field of a thunderstorm. On the other hand, the multiflow convection is unstable and leads to generation of small-scale electrostatic waves (wavelength from 1 to 100 m) with amplitude reaching the conventional breakdown value. Such an instability can initiate microdischarge intracloud activity at the preliminary stage of the lightning discharge and between individual return strokes. We propose a three-dimensional cellular automata model which describes the main features of the preliminary stage of the lightning.

Initiation of positive streamer corona in low thundercloud fields

“…One is 2 km × 0.1 km × 0.8 km from Proctor [], and another one is 10 m × 10 m × 10 m. The 10 m is chosen to illustrate a situation when electric field is enhanced only in a very localized region. According to Babich et al [], streamers in thunderstorms originate near hydrometeors in local electric field regions with very small spatial extent where the ambient electric thundercloud field is amplified either by the RREA mechanism seeded by the background cosmic rays flux [ Dwyer , ; Babich et al , , ] or by cloud charge fluctuations arising from a local assemblage of charged hydrometeors [ Trahtenhertz and Iudin , ]. We use R = 2 N 0 / N mm as particle dimension at 3.5 km leading to actual particle radius R ≃3 mm to calculate collision frequency since for this case the minimum thunderstorm electric field shown in Figures a and b is just slightly above based on the Qin's method.…”

Profuse activity of blue electrical discharges at the tops of thunderstorms

“…The fact they are generated at the screening layer altitude is perhaps not surprising, as the threshold electric field at 18 km is only ~10% of its value at sea level. They may be related to turbulence in the cloud top layer and to the 1–100 m microdischarges created by instabilities in the convective flow of the cloud [ Trakhtengerts and Iudin , ; Bruning and MacGorman , ]. However, the observed scale size of a few kilometer is larger than that of the microdischarges.…”

The Mechanism of the Origin and Development of Lightning From Initiating Event to Initial Breakdown Pulses (v.2)

“…Similar processes should also occur in the cloud during random motion among differently charged hydrometeors (Iudin, 2017;Iudin et al, 2019). This movement of hydrometeors leads to a broad spectrum of amplitude oscillations in E. Rare, small-volume, large-amplitude oscillations of E should be added to larger scale oscillations of hydrodynamic changes in E. These statistical waves of oscillations of E are estimated to have a scale of 1-30 cm (Iudin, 2017;Iudin et al, 2019;Trakhtengerts & Iudin, 2005). Ordinary metal electrodes have a similar scale (1-30 cm) during high-voltage discharges.…”

“…Following the hypotheses of Trakhtengerts (1989), Trakhtengertz et al (1997Trakhtengertz et al ( , 2002, and Trakhtengerts and Iudin (2005), we assume that discharges in a thundercloud are fundamentally different from the laboratory discharges from metal electrodes precisely because the E is created by statistically located charges in the cloud, which create small-scale variations in E. These small-scale variations of the field do not exist in the physics of a classical electrode gas discharge. For several decades, an approach has been developed for the possible local enhancement of E in a thunderstorm on scales from tens of centimeters to hundreds of meters.…”