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William W. Hager
,
John S. Nisbet
,
John R. Kasha
, and
Wei-Chang Shann

Abstract

Numerical simulations based on a three-dimensional model for the electric fields in a thunderstorm are presented. In some of the simulations, we solve problems with known analytical solutions in order to determine the relevant physical properties that must be incorporated in a thunderstorm model. We then examine the inverse problem: Given measurements for the electric fields in a thunderstorm what are the associated current generators? Fits based on an analytic formula that neglects conduction currents give approximations to the current generators while simulations based on the thunderstorm model yield refinements to the generators. As a specific illustration, we obtain estimates for current generators associated with a storm observed at the Kennedy Space Center on 11 July 1978. Finally, we explore qualitative properties of our method used to simulate lightning. It is observed that as the charged particles associated with the thunderstorm are spread over a larger and larger volume, the flesh rate decreases while the charge transfer associated with each flash increases. Also, it is seen that a series of intracloud flashes can produce a charge imbalance in the cloud that will eventually lead to a cloud-to-ground discharge.

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