G-Scale (Geomagnetic Storm Scale)

The official 1-to-5 scale used by NOAA's Space Weather Prediction Center to classify the severity of geomagnetic storms, from G1 (minor) to G5 (extreme). Each level corresponds to real, observable effects — G1 storms can cause weak power grid fluctuations and push aurora to high latitudes, while G5 storms can trigger widespread voltage control problems, satellite drag, and aurora visible as far as the tropics.