Development of an Updated Geoelectric Field Benchmark: Understanding the Magnetosphere to Secure the Grid

During extreme space weather events, ground-level electromagnetic disturbances result from a combination of global, regional, and localized effects. These effects are fundamentally related through the magnetosphere's response to extreme forcing, presenting us with a conundrum - we need to understand the magnetosphere's behavior during yet-unobserved events in order to properly characterize the expected hazards. Significant dynamical variability can exist even between storms of similar magnitude as measured by Kp or Dst, and extrapolation based upon the small sample size of historical events may lead us to misleading or even dangerous conclusions. In this work, we present results from a study of stormtime geoelectric fields that seeks to characterize the magnitude of extreme disturbances in a manner that respects the observed dynamics of the magnetosphere and while permitting extrapolation to unobserved events within credible bounds.