Electrical breakdown of soil about earthed conductors resulting from late time EMP effects

EMP/EMC-related transient electromagnetic phenomenology has historically focused on source time scales on the order of 10/sup -9/-10/sup -6/ after the onset of the pulse. This is the domain of the standard EMP wave assumed propagating within a region. Earthed conductors, however, may be subject to a secondary electromagnetic excitation of longer duration caused by the resulting negative charge combining through the earth. The currents and charge densities developed about buried conductors in this regime have temporal durations greater than 30 mu s and are shown to permit the onset of corona. The authors investigate the effects that the formation of corona may have on the late-time transient electrodynamics associated with earthed conductors. This is done by formulating the soil conductivity as a function of yield intensity and characterizing the transient phenomenology in the vicinity of an earthed conducting right circular cylinder. The results of the investigation indicate that the presence of corona tends to increase the current on the conductor and thereby worsen the late-time EMP hazard.<
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