COMPUTED CONDITIONS OF CORONA EMISSION FROM 2 INTERACTING RAINDROPS

The conditions of corona emission from two interacting drops located i n a vertical ambient field parallel to their line of centres are estab lished by combining the corona experimental results obtained by Dawson (1969) with the distortion model from Georgis ct al. (1995). Given th e drop shapes and electrical fields at any points on the surface then, thanks to the distortion model, it is possible to calculate the altit ude of corona occurrence from a fitting of Dawson's data. Unexpectedly it was found that an increase in the ambient field and/or a decrease in the distance between the two drops is not always equivalent to a lo wering of the altitude of the corona occurrence, thus confirming that distortion plays a key part in this highly nonlinear mechanism. Nevert heless, corona emission is now generally possible at quite realistic a ltitudes in permanent ambient fields provided that the drops are close enough to each other. The mutual approach of the two drops certainly favours corona emission at low altitudes, but it also entails such a r eduction in the ambient field for corona onset that conditions may be no longer propitious for corona propagation.