Estimating the Impact of the Magnetometer Network on the SWPC Geoelectric Field Model

We performed a leave-one-out analysis in order to study the impact of the operational network of magnetometers on the SWPC Geoelectric field model. The Geoelectric field model has two main components: 1) the magnetic interpolator (MI), which uses geomagnetic data from the magnetometer network and the Spherical Elementary Currents (SECS) method to evaluate the magnetic field disturbance everywhere, and 2) the geoelectric field calculator,  which combines the SECS model output with information about the ground conductivity. In this study we create an ensemble of SECS and Geoelectric field model runs: one reference run in which all magnetometers are included, and many test runs in which one magnetometer is excluded from the SECs interpolation. The main goal of this study is to compare geomagnetic and geoelectric response time series at the test location and characterize the differences between the reference run and the test runs. This methodology only accounts for the uncertainties introduced in the model by the geographical configuration of the magnetometer network. Our results show that both geomagnetic and geoelectric field vector correlations are higher when the distance to the closest station is smaller. In particular, SWPC Geoelectric Field models appear to produce geoelectric fields with high reliability for grid points located at less than 200 km from a magnetometer. However, this distance displays some dependence on the test site’s geographical location (longitude and latitude). The magnetometer network currently used in the nowcasting (operational) SWPC Geoelectric field model (a combination of USGS and NRCan stations) is in a configuration such that any given model grid point over CONUS is, on average, 484 km to the nearest magnetometer. Our results suggest the addition of magnetic observatories to the operational network is needed.