Accession Number:

ADP002236

Title:

Lightning Initiation in Thunderclouds,

Descriptive Note:

Corporate Author:

UNIVERSITY OF MANCHESTER INST OF SCIENCE AND TECHNOLOGY (ENGLAND)

Personal Author(s):

• Latham,J.

Report Date:

1983-01-01

Pagination or Media Count:

4.0

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 Vm 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 R2.7mm and r0.65mm, collided with a relative velocity of 5.8ms. Values of Ec ranged from approx. 500,000 ms for head-on collisions to approx. 250,000 ms 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

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE