Study to assess the effects of high-altitude electromagnetic pulse on electric power systems. Phase I, final report

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

“…In this regard, ORNL reports provide a parameterization of E3 electromagnetic variation that has had widespread influence. Here, the spatiotemporal form of horizontal‐component, ground‐level geoelectric field variation is represented by the multiplication of separate geographic and temporal functions for each of the blast and heave phases, (Legro et al., 1985, their Equation 6). The time‐invariant vector functions describe the geographic dependence of the amplitude and polarization of the induced E3 geoelectric field, and the geographically invariant functions describe the time dependence of E3 geoelectric field variation.…”

“…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 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).…”

“…Time‐dependent maps of E3 EMP geoelectric fields can, in principle, be obtained by convolving a model of bomb‐generated geomagnetic disturbance with estimates of the Earth‐surface impedance tensor field. In developing such maps, numerical methods pioneered in the 1980s by the Oak Ridge National Laboratory (ORNL) have been widely influential (Barnes, Rizy, et al., 1993; Legro et al., 1985, 1986). ORNL's methods have been used in numerous E3 scenario mapping projects across the conterminous United States (CONUS) (e.g., Electric Power Research Institute, 2017; Electromagnetic Pulse Commission, 2017; Gilbert et al., 2010; International Electrotechnical Commission, 1996; Lee et al., 2019; Rackliffe et al., 1988; Tesche et al., 1991), and these maps have been used in projects for assessing the vulnerability of power grids to the E3 hazard (e.g., Barnes, Tesche, et al., 1993; Electric Power Research Institute, 2019; Electromagnetic Pulse Commission, 2017; Tesche et al., 1991).…”