EMP/GMD Phase 0 Report, A Review of EMP Hazard Environments and Impacts

Down to Earth With Nuclear Electromagnetic Pulse: Realistic Surface Impedance Affects Mapping of the E3 Geoelectric Hazard

“…are such that the E3 signal is of nearly maximum amplitude [e.g., Rivera et al, 2016, their Figure 23], but the assumed explosion altitude and yield are not usually specified. The parameterizations are generic, but they serve as useful benchmarks for comparison.…”

“…These impacts were the results of electromagnetic pulses (EMPs) interacting with the atmosphere, the geomagnetic field, and the solid Earth. A nuclear explosion of several hundred kilotons set at altitudes of several hundred kilometers generates an EMP having three semi‐distinct phases (Gombosi et al., 2017; Legro et al., 1985; Rivera et al., 2016). The first, called E1, lasts for less than a microsecond.…”

“…This period band corresponds, roughly, to that of lightning, and since many terrestrial technological systems are lightning hardened, it is often assumed that E2 would not be especially impactful. As a consequence, it is not very well studied (Gombosi et al., 2017, their Chapter 2.2; Rivera et al., 2016, their Section 3.2).…”

“…This phase covers a period band from a tenth of a second to a few hundred seconds. It consists of a two‐part jerking of the Earth's magnetic field (Gombosi et al., 2017; Legro et al., 1985; Rivera et al., 2016). During the first part, E3A, the blast creates a diamagnetic plasma bubble that pushes outwards against ambient geomagnetic field lines.…”

“…After about 10 s, however, the ionization begins to subside, and diffusion permits the amplitude of E3A geomagnetic field variation to increase at the Earth's surface. During the second part, E3B, the ionized and heated atmosphere below the explosion buoyantly rises, a heaving that brings the field lines beneath the explosion hypocenter back together (e.g., Gombosi et al., 2017; Legro et al., 1985; Rivera et al., 2016). E3 geomagnetic disturbance induces geoelectric fields in the electrically conducting solid Earth, and these, in turn, drive uncontrolled currents in grounded electric‐power grids that can interfere with transmission operations and damage high‐voltage transformers (e.g., Electric Power Research Institute, 2019; Tesche et al., 1991).…”