What is the Kp Index?
The Kp index is a planetary index of geomagnetic activity ranging from 0 (quiet) to 9 (extreme storm). It is derived from ground-based magnetometers around the world. Disturbances from the solar wind and CMEs change the magnetic field; the deviations at many stations are combined into a single global index (Kp). The scale is logarithmic: a one-unit increase means a clear rise in disturbance.
What the Levels Mean
- Kp 0–2: Quiet. Aurora mostly at high latitudes.
- Kp 3–4: Unsettled. Aurora possible at high latitudes.
- Kp 5–6: Geomagnetic storm. Aurora often visible at mid-latitudes.
- Kp 7+: Strong storm. Aurora can reach lower latitudes; possible impacts on power grids and satellites.
Kp 5 is often taken as the threshold for "storm" conditions. Cosmic Radar shows the daily Kp in the report and labels it (e.g. quiet, unsettled, storm) so you can see current activity.
Sources and further reading
- NOAA – Planetary K-index – Official Kp description and data
- GFZ Potsdam – Kp index – Kp derivation and history
- ESA Space Weather – Geomagnetic forecasts