Browsing by Author "Geis, Paul B."

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    An analysis of lightning and the limitations it imposes on a global model of thunderstorm electricity
    (1990) Geis, Paul B.; Few, Arthur A., Jr.
    I report here on preliminary work incorporating transient effects from lightning into a global thunderstorm electricity model. First, E, the electric field produced by a lightning return stroke, is analytically derived. Second, a determination is made of the model's ability to handle the quickly varying fields produced by lightning. In solving for the conduction current and other quantities of interest in the atmosphere the contribution to E from the vector potential is ignored. This approximation is most likely to be invalidated by the electric fields associated with lightning. We calculate the electric field component due to the vector potential, and the conduction current this electric field drives. The conduction current driven by the lightning flash is small compared to the other currents present for the time scales of importance in the model, and can be ignored. Therefore the model is able to include the effect of lightning on the global electric circuit even though the radiation component of the lightning is explicitly absent. A test of the model's accuracy, the continuity of current test, shows the model's results are self-consistent to within 9%-17%, depending upon the region being studied.
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    The electrical environment of thunderstorm models and measurements
    (1994) Geis, Paul B.; Few, Arthur A., Jr.
    A model describing a thunderstorm's interaction with the global electric circuit is presented. The model includes a thunderstorm, the surrounding atmospheric and ionospheric region, and the magnetically conjugate atmospheric and ionospheric region. The model is time-dependent, and includes lightning and thundercloud evolution. A method of using experimental data to more accurately simulate observed thunderstorms has been developed. Of the upward current generated by a thunderstorm, about 50% flows through the Earth's magnetosphere to the conjugate hemisphere. This percentage is fairly constant over the storm's active life, and varies little with storm size or structure. Infrequent lightning activity (less than one flash/minute) within a thunderstorm does not appear to greatly affect the thunderstorm's efficiency in transferring separated charge to the global circuit. Lightning does limit the magnitude of the electric fields and resulting currents within and below the storm.