Geomagnetic storms drive geomagnetically induced currents (GICs) in high-voltage power transmission systems. GICs thus carry information about the near-space environment conditions. The U.S. high-voltage power transmission system was used as an extremely large antenna to extract unprecedented spatiotemporal space physical and geological information from distributed GIC observations.
GICs are measured using a differential magnetometer technique involving one fluxgate magnetometer under a transmission line, and another reference magnetometer station nearby. GICs carry information about near-space phenomena, which is of interest to NASA science. GICs can be harmful to the power grid, so the information is valuable to transmission system operators.
A reference station allows subtraction of the natural field from the line measurement, leaving only the GIC-related Biot-Savart field, allowing inversion of the GIC amplitude. The magnetometer stations are designed to be autonomous and low cost, allowing large-scale application with many measurement locations.