The Karzas-Latter-Seiler Model of a High-Altitude Electromagnetic Pulse: A New Numerical Code for an Old Model

A high-altitude nuclear blast can produce an electromagnetic pulse (EMP) capable of disrupting electronics on Earth. The basic phenomenology of the initial (E1) phase of the EMP was initially worked out in the 1960s by Longmire, Karzas, and Latter, and although more accurate and sophisticated EMP models have since been devised, the Karzas-Latter model is particularly simple and amenable to implementation as a numerical code. This paper accompanies the release of a new software implementation of an approximation of the Karzas-Latter model due to Seiler. This is, as far as we are aware, the only such publicly available numerical EMP code. After reviewing the physics and assumptions of the model, the numerical results for EMP simulations under a range of conditions are presented. It is shown how the results from multiple line of sight integrations of the field equations can be assembled to form a map of the EMP intensity across a broad geographic region. The model predictions are at least qualitatively correct and in general agreement with other simulation results, including the characteristic "smile" pattern in the spatial variation of the EMP intensity.