Analytic Calculation of Late-Time Source-Region EMP Fields below the Earth's Surface

An analytic technique is presented for calculating late-time source-region EMP fields in the earth. The radial electric field is found to result from the near-cancellation of two competing effects. Despite the sensitivity suggested by this circumstance, the present results are in reasonable agreement with LEMP-SUBL computer code predictions. Results are also obtained for a layered earth.