Kp Index

The Kp index (planetarische Kennziffer, or "planetary index") is a 0–9 logarithmic scale measuring global geomagnetic activity caused by solar wind and coronal mass ejections interacting with Earth's magnetosphere. It is derived from magnetometer readings at 13 ground stations. Kp 0–1 is quiet; 4 is active; 5+ is a geomagnetic storm (G1); 7+ is severe (G3+). Geomagnetic storms increase atmospheric drag on LEO satellites, cause satellite surface charging, degrade GPS accuracy, and produce visible auroras at lower latitudes.