Source Region EMP Coupling to Long Lines

The results discussed in this paper can be summarized as follows: 1. Early-time (less than a microsecond) response of aerial lines are apparently highly dependent upon details of the time-dependent air conductivity. Transmission line results do not agree well with finite-difference calculations for this case. 2. For buried cables, early-time results from both transmission line and finite-difference calculations seem to be in fair agreement. This is probably due to partial isolation of the line from the Compton current driver by the conducting ground. 3. Late-time transmission line calculations (for both aerial and buried cables) indicate that large currents may flow at late times. This large current is due to the predicted slow decay of the radial electric field generated by a nuclear burst, combined with a decreasing line impedance as fields diffuse into the ground. As a result, large currents can persist for hundreds of microseconds. 4. Quasi-static analytic solutions for certain cases have also been given. These expressions point out the importance of assumed loads at the end of the line. (A low impedance at each end can result in very large late-time currents.) Such solutions also provide checks of the late-time accuracy of transmission line calculations.