A Model for Positive Corona Inception From Charged Ellipsoidal Thundercloud Hydrometeors

Lightning is observed to incept in thundercloud electric fields below the threshold value Ek for discharge initiation. To explain this, local enhancement of field by hydrometeors considered. The conditions onset positive corona discharges are studied air ellipsoidal geometries. A hydrometeor simulated as an individual charged conductor zero ambient field; there only a generated charge on surface. By doing so, feasibility inception from can be formulated based self-sustaining condition electron avalanches. For dimensions few millimeters and typical pressure, values above 2.4 found at tip ellipsoid. From simulations required uncharged then derived. This results between 0.07 0.8 semiaxes aspect ratios 0.01 1. surface pressures minimum increasing 0.12 0.22 decreasing volume 42 4.2 mm3. representative hydrometeors, charges 495 2,430 pC. mm3 comparable measured precipitation 0.16 0.32. it concluded that realistic achieved certain ratios.