Calculation of Late-Time Surface Burst EMP (Electromagnetic Pulse) Fields Using a Time-Independent Numerical Method

摘要

A numerical solution was developed to find the quasi-static EMP fields resulting from a surface nuclear burst. By ignoring the time derivatives in Maxwell's equations and expanding the electrostatic potential in Legendre polynomials, a set of differential equations was obtained that was dependent on r only (r = radius from burst). By employing finite difference, a tri-diagonal matrix equation was obtained that was on-linear in the electric field. This equation was solved using an iterative scheme. Analytic curve fits based on Monte Carlo data were used to determine the air ionization rate and Compton current. This permitted the angular variation of these sources to be included in the calculations. In addition, the electron air chemistry parameters were allowed to vary with the local electric field and water vapor content of the air. This was accomplished by the use of previously developed equations for these terms. Field calculations were made and compared to previous analytic results. The differences were found to be as great as 50 percent for peak field values. A limited parametric study was performed to consider the effects of varying the time, the yield, and the water vapor content. (Author)