In support of a multiagency project for assessing induction hazards, we present maps of extreme‐value geoelectric amplitudes over about half of the continental United States. These maps are constructed using a parameterization of induction: estimates of Earth surface impedance, obtained at discrete geographic sites from magnetotelluric survey data, are convolved with latitude‐dependent statistical maps of extreme‐value geomagnetic activity, obtained from decades of magnetic observatory data. Geoelectric amplitudes are estimated for geomagnetic waveforms having 240 s sinusoidal period and amplitudes over 10 min that exceed a once‐per‐century threshold. As a result of the combination of geographic differences in geomagnetic activity and Earth surface impedance, once‐per‐century geoelectric amplitudes span more than 2 orders of magnitude and are an intricate function of location. For north‐south induction, once‐per‐century geoelectric amplitudes across large parts of the United States have a median value of 0.26 V/km; for east‐west geomagnetic variation the median value is 0.23 V/km. At some locations, once‐per‐century geoelectric amplitudes exceed 3 V/km.
Key Points
White House releases National Space Weather Strategy and Action Plan
Federal interagency space weather policy articulates the Federal Government role in space weather
The strategy and action plan facilitate enhancement of national preparedness and resilience
The National Oceanic and Atmospheric Administration, on behalf of the National Science and Technology Council, published two notices in the Federal Register seeking public comment on draft products from the National Space Weather Action Plan: Space weather benchmarks and an operations‐to‐research plan.
An extreme space weather event has the potential to disrupt or damage infrastructure systems and technologies that many societies rely on for economic and social well-being. Space weather events occur regularly, but extreme events are less frequent, with a small number of historical examples over the last 160 years. During the past decade, published works have (1) examined the physical characteristics of the extreme historical events and (2) discussed the probability or return rate of select extreme geomagnetic disturbances, including the 1859 Carrington event. Here we present initial findings on a unified framework approach to visualize space weather event probability, using a Bayesian model average, in the context of historical extreme events. We present disturbance storm time (Dst) probability (a proxy for geomagnetic disturbance intensity) across multiple return periods and discuss parameters of interest to policymakers and planners in the context of past extreme space weather events. We discuss the current state of these analyses, their utility to policymakers and planners, the current limitations when compared to other hazards, and several gaps that need to be filled to enhance space weather risk assessments.
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