Accession Number : ADP002236

Title :   Lightning Initiation in Thunderclouds,

Corporate Author : UNIVERSITY OF MANCHESTER INST OF SCIENCE AND TECHNOLOGY (ENGLAND)

Personal Author(s) : Latham,J.

Report Date : 1983

Pagination or Media Count : 4

Abstract : Experiments have been carried out to determine the electric field, E sub c, required to obtain corona from both ice particles and cooling drop-pairs. In the former case it was found that corona currents of about 0.1 microA and above could be obtained from ice particles a few millimetres in length for C sub c approx. 4 x 100,000 V/m for values of temperature and pressure likely to occur in the mid-regions of a thundercloud. These currents were drastically reduced if temperature was below -18 deg C, owing to the reduction in surface conductivity suffered by the ice sample. In the second set of experiments, a pair of water drops, of radii R=2.7mm and r=0.65mm, collided with a relative velocity of 5.8m/s. Values of Ec ranged from approx. 500,000 m/s for head-on collisions to approx. 250,000 m/s for glancing collisions which produce, momentarily, long liquid filaments. (Author)

Descriptors :   *Coronas, *Hydrometeors, Theory, Lightning, Clouds, Ice, Particles, Raindrops, Collisions, Electric fields, Measurement, Laboratory tests

Distribution Statement : APPROVED FOR PUBLIC RELEASE