Comparison of the Theoretical Collision Efficiency of Uncharged Cloud Droplets in Horizontal and Vertical Electric Fields

Abstract

The collision efficiency of two unchanged droplet pairs with radii combinations of (10; 9) ?m and (10; 2) ?m was computed for horizontal and vertical background electric fields ranging from 300 V m?1 to 300 kV?1. For horizontal fields, the trajectories strongly vary with azimuth; maximum attraction occurs when the smaller droplet starts in the vertical plane containing the center of the larger droplet and the direction of the field, maximum repulsion takes place perpendicular to it. There is azimuthal symmetry for vertical fields., for horizontal fields symmetry is only conserved in respect to the x and y axes. The collision efficiency, however, is only slightly varying within the measured range of atmospheric electric fields.