Magneto-Ionic Process for Cloud Electrification

This paper presents a theory of cloud electrification by geomagnetic control. In the atmosphere, when ion-pairs produced by collision between cloud-particles are drifted in the W-E direction by the horizontal wind, the ions of opposite polarity get separated from each other under the influence of earth's magnetic field. Lorentz forces urge these ions to move in semi-circular trajectories at different altitudes, creating the positive bipolar charged structure of the thundercloud. The continuous charging process actuated by the magneto-ionic separation and the drift of the charged cloud-particles or snow crystals generate high electric fields in both vertical and horizontal planes within the cloud; as a result, Cloud-to-Ground (CG), Intra-Cloud (IC) both vertical and horizontal, and Cloud-to-Cloud (CC) discharges occur. The nature and frequency of these discharges are determined by the geomagnetic (CM) latitude of the place of observation. Maximum thunderstorm activity is expected to occur at intermediate CM latitude stations. During violent winter thunderstorms in the northern hemisphere, the direction of wind drift within the cloud becomes E-W; then a negative dipolar charge structure develops, with its N-region lying near the crest and the P-region near the bottom of the cloud. Leader strokes from such a negative dipolar cloud contribute positive charges to ground via CG discharges. This paper also includes explanations for the cause of occurrence of IC flashes at a level higher than the N-region in a positive dipolar cloud, and the role of the IC flash preceding the CG discharge, which neutralizes a part of the positive charge in the P-region. Consequently, an equal amount of negative charge becomes unbounded in the N-region, which actuates the CG leader stroke.