TESTING THE FORMULATION OF PARK AND DEJNAKARINTRA TO CALCULATE THUNDERSTORM DC ELECTRIC-FIELDS

Park and Dejnakarintra [1973] presented a formulation to calculate hig h-altitude electric fields due to electrified clouds, taking into acco unt the presence of the ionosphere. Calculation of these fields is nec essary to test the hypothesis that whistler ducts might be caused by p lasma interchange of geomagnetic flux tubes driven by thundercloud ele ctrostatic fields, To test the accuracy of the formulation, the calcul ated de electric fields are compared with those measured during a thun derstorm campaign reported by Holzworth et al, [1985]. Using a conduct ivity profile measured during their campaign, it is shown that the for mulation of Park and Dejnakarintra produces electric field predictions which are consistent with the measurements of Holzworth et al. This i ndicates the formulation developed by Park and Dejnakarintra is valid. The comparisons agree with measurements which show that large negativ e screening charges commonly exist around the top of thunderclouds, re ducing the high altitude fields. These calculations indicate that the effective thunderstorm charge used in such calculations needs to be si gnificantly reduced to account for screening charges. Such reductions lead to serious increases (up to a factor of 10) in the time required for high-altitude thunderstorm electric fields to produce whistler duc ts.