Formation of decimeter-scale, long-lived elevated ionic conductivity regions in thunderclouds

Abstract

We propose a scenario in which elevated ionic conductivity regions (EICRs) with dimensions of the order of 0.1-1 m are formed in the turbulent thundercloud environment. The starting point in this scenario is the occurrence of electron avalanches in the vicinity of colliding hydrometeors, leading to the formation of ion production centers. Their dimensions are of the order of 10 À3 À 10 À2 m, and their lifetime is of the order of 10 À4 À 10 À3 s. When a new ion production center is created inside the decimeter-scale residual ion concentration spot left behind by a previously established center, the local ion concentration steadily increases, which leads to the formation of decimeter-scale EICRs whose lifetime is measured in seconds. The relatively high conductivity of EICRs (up to 10 À9 S/m or so) relative to the background conductivity (10 À14 S/m or less) ensures their polarization in external electric field within a few milliseconds or so. The EICR formation mechanism requires only one condition: the rate of occurrence of ion production centers per unit time in a unit volume should exceed the percolation-theory-based critical level of 10 À1 m À3 s À1 . Hydrometeor collision rates three and even four orders of magnitude higher than this value have been reported from observations. Presence of EICRs in the cloud provides local electric field enhancements and pre-ionization levels that will lead to the formation of additional ion production centers and may be sufficient for the initiation and development of streamers and, eventually, lightning.npj Climate and Atmospheric Science (2019) 2:46 ; https://doi.

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

“…One molecule cannot affect a larger particle that is a million times heavier, but in an ensemble there are always fluctuations proportional to molecules to produce Brownian motion in a larger particle. 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 .…”

“…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.…”

“…Some cells are E str + volumes, capable of supporting the movement of positive streamers (as defined in t8). Furthermore, Trakhtengerts and Iudin (2005), Iudin (2017), and Iudin et al (2019) have shown that additional E enhancements at even smaller scales may be possible due to the random statistical motion of a multitude of charged particles of different sizes in the cloud, and it is inside these very small volumes that breakdown electric fields can occur. Unfortunately, these approaches rely on theoretical work, and it is difficult to verify them experimentally.…”

“…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.…”

“…">Colgate (1967) suggested that turbulence in a thundercloud can significantly enhance the local E on scales of about 100 m. Trakhtengerts with coauthors theoretically showed that, due to hydrodynamic instabilities, E in a thunderstorm can fluctuate over about 100 m (Iudin et al, 2003; Mareev et al, 1999; Trakhtengerts, 1989; Trakhtengertz et al, 1997). Trakhtengerts and Iudin (2005), Iudin (2017), and Iudin et al (2019) theoretically estimated that more significant amplifications of E on a smaller scale (10–100 cm) are possible due to the statistical movement of hydrometeors of different sizes and charges in a cloud. Many studies have connected lightning initiation with turbulent air motions in thunderstorms.…”