Atmospheric electrical discharges in the presence of water and ice particles

Abstract

A variety of electrical discharges were photographically examined in a preliminary survey of water‐involving discharge phenomena that occurred in simulations of the thunderstorm environment. The investigation was limited to situations showing no clear evidence of water drop disruption. Discharges between oppositely charged falling drops of water exhibit a luminosity distribution that suggests electron emission from the negative drop. Measurements indicate that the current density in this discharge may be 20 amp/cm2 or more as is the case with metallic cathode glow discharges. It is conceivable that a comparable emission occurs in clouds whenever a positive streamer comes within 40 μ of a particle's surface, and that this emission quenches weak streamers. Photographs show weak streamers that terminate on either ice or water surfaces, and stronger streamers and sparks that glide over the surface of a water drop. These latter observations demonstrate that in the arclike discharge produced by an intense spark, a water surface does not supply charge as copiously as a metallic one. Positive streamers are attracted to water and ice particles, which facilitates charge transfer across the air‐water interface whether it occurs by ion capture or by electron emission. Since long sparks are often preceded by streamers, the paths of sparks in an atmosphere containing water or ice particles should be modified by charges deposited on the particles by the streamers. Paths were observed in several situations involving 50‐ to 70‐cm‐long impulsive sparks and target volumes nonuniformly populated with either fog droplets or with falling cloudburst densities of 2‐mm‐diameter drops. Effects on the paths were slight, and they could be detected only statistically; but in all situations there was, if anything, a slight tendency for the sparks to avoid wet regions of the target volume. Just the opposite tendency was found in a situation involving 2‐cm‐long sparks and a much denser distribution of drops. The assorted observations are related by citation to various published discussions of the lightning path, the rain gush, the transfer of charge from precipitation elements to the lightning channel, and the radio noise from clouds.

Coordinated lightning, balloon‐borne electric field, and radar observations of triggered lightning flashes in North Florida

“…This tendency has traditionally been attributed to both precipitation and the charge tapped by lightning being transported similarly, but it is also possible that the detailed microphysics of spark development in the presence of precipitation has an effect. Several investigators have observed that water particles subjected to strong electric fields produce streamers [e.g., Pišler and Atkinson , ]. Pišler and Atkinson [] found that sparks tended to connect a stream of falling drops and suggested that this was caused by streamers charging the drops and the charge then causing the particles to attract the spark.…”

“…Several investigators have observed that water particles subjected to strong electric fields produce streamers [e.g., Pišler and Atkinson , ]. Pišler and Atkinson [] found that sparks tended to connect a stream of falling drops and suggested that this was caused by streamers charging the drops and the charge then causing the particles to attract the spark. Whether this process influences the propagation path of lightning in a thunderstorm is unclear. The charge had moved too far away to support continued vertical propagation, so the IS could not reach the layer of substantial charge density.…”

DC positive discharge performance of rod-plane short air gap under rain conditions

“…And then, the form of the drop will be an ellipsoid of revolution extended along the external field, which is more of advantage to initiate the corona emission from surface of water drop owing to the smaller radius of curvature at its two ends of long axis. Some research on the effect of electric field on the distortion and deformation of droplet and corona emission performance can be found in [14][15][16][17][18][19]. In [15], it is pointed out that positive corona can occur in the field of 2.5 kV/cm when a pair of water drops with a relative speed of 5.8 m/s and with an equivalent radius of 2.7 mm and 0.65 mm are colliding into a long filament.…”

The effect of electrical conductivity on the growth of the electric field in a thunderstorm

“…Supposedly the cloud droplets capture the free ions, effectively lowering the number of mobile charges, and reducing the electrical conductivity. However, the high electrical field within the thunderstorm is responsible for the formation of space charge due to point discharge at the ground and assorted discharge effects from irregular particles (ice crystals) and effects during the interactions of water drops (see Dawson, 1970;Pisler & Atkinson, 1971). Hence one might expect an increase in the electrical conductivity as the field builds.…”