G-Scale Overview
NOAA uses a G-scale (G1–G5) for geomagnetic storms: G1 = minor, G2 = moderate, G3 = strong, G4 = severe, G5 = extreme. Each level is linked to a Kp range and to typical effects on power grids, satellites, and aurora.
Kp and G-Scale
Roughly: G1 ↔ Kp 5, G2 ↔ Kp 6, G3 ↔ Kp 7, G4 ↔ Kp 8, G5 ↔ Kp 9. Higher G means more likely voltage problems in power systems, satellite and radio impacts, and aurora at lower latitudes. G5 events are rare but can cause widespread grid stress and aurora deep into mid-latitudes. Cosmic Radar shows the daily Kp so you can relate it to the G-scale and possible effects.
Sources and further reading
- NOAA – G-scale – Geomagnetic storm scale (G1–G5)
- NOAA – Kp index – Kp and G-scale mapping