Geomagnetically Induced Currents: Power Grid Risk

When a Coronal Mass Ejection slams into Earth's magnetosphere, the ground-level magnetic field doesn't just get stronger — it fluctuates rapidly, and that rate of change (dB/dt) is what actually matters. This simulator shows the real chain of physics behind a space-weather power-grid emergency: solar wind particles compress the magnetosphere, Faraday's law converts the resulting dB/dt into a telluric electric field in the crust, that field drives a quasi-DC geomagnetically induced current (GIC) into a long-distance transmission line, and the current flows into a transformer's grounded neutral where — past roughly 75 amps — it risks half-cycle core saturation. Tune the storm's intensity, the line's length and the underlying ground geology (resistive igneous rock versus a conductive sedimentary basin) to see which combinations push a transformer from normal operation into real saturation risk, the same mechanism that took down Hydro-Québec's grid during the March 1989 storm.