HR: 1340h
AN: AE23A-0835    [Abstracts]
TI: The Corona Discharge Waves in Thunderclouds and Formation of Ionic Channels
AU: * Fomenko, A
AF: Institute of Geospheres Dynamics of Russian Academy of Sciences, 38 Leninsky pr. bldg.1, Moscow, 119334 Russian Federation
AU: Losseva, T V
EM: losseva@idg.chph.ras.ru
AF: Institute of Geospheres Dynamics of Russian Academy of Sciences, 38 Leninsky pr. bldg.1, Moscow, 119334 Russian Federation
AU: Nemtchinov, I V
EM: ivvan@idg.chph.ras.ru
AF: Institute of Geospheres Dynamics of Russian Academy of Sciences, 38 Leninsky pr. bldg.1, Moscow, 119334 Russian Federation
AB: Measurements of electric field strength in the thunderclouds persistently give values by an order of magnitude lower than the breakdown threshold of the pure air. Models of lightning propagation through the thundercloud usually start with existing highly conductive channel in the cloud of rather large length and rather thin, at the end of which the field is already enhanced due to charge redistribution along the channel and thus the channel may increase its length due to streamers and leader formation. It is not clear how such long highly conductive channel may be formed. It is well known that the droplets, ice particles, hailstones or snowflakes may enhance the electric field and produce corona discharge. We assume that in a small part of the thundercloud an exceptionally high concentration of large hailstones or (and) water drops is formed and the onset-strength of the corona discharge becomes smaller than the background electric field. Polarization of this "hot spot" (with high conductivity and high ionization rates) produces charges at opposite sides of this volume. The increased electric field initiates corona discharge in other parts of the cloud with "normal" sizes of large ice particles and water drops. The small ice particles and water droplets are removed in the direction perpendicular to the axis of the channel. The high conductivity channel increases its length. The corona discharge front moves as a wave with the velocity of the order of ion drift velocity and the electric field at the ends of the channel increases, until the breakdown conditions are reached. A simple analytical model of such a wave is developed and the results are compared with some observations and data of the laboratory experiments, and the results of 3D numerical simulations of the relevant electrodynamic problem (Poisson equations are solved simultaneously with equations of motion of ions and charged particles, and electrons, and with a set of kinetic equations).
DE: 3324 Lightning
DE: 3210 Modeling
DE: 3230 Numerical solutions
DE: 3304 Atmospheric electricity
DE: 0320 Cloud physics and chemistry
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting