Geomagnetic activity (planetary Kp index)

The planetary Kp index is a measure of how much Earth's magnetic field is being disturbed by space weather. It is derived from a network of ground-based magnetometers at mid-latitude observatories spread around the globe, each recording how far the local field strays from its quiet-day baseline over three-hour windows; those readings are combined into a single planetary figure, published and updated continuously by NOAA's Space Weather Prediction Center. Values run on a quasi-logarithmic scale from 0 to 9. Most of the time Kp sits between 0 and 3, reflecting a calm field; values of 5 and above mark storm conditions, when solar wind gusts or coronal mass ejections compress and stir the magnetosphere, pushing auroras towards the equator and occasionally disrupting satellites, radio links and power grids. One caveat: Kp summarises the whole planet in one number, so it can hide intense but localised disturbances, and it is a measure of magnetic shaking rather than of any single solar cause.

Record high

Kp 5.7, 4 Oct 2026, 18:00 UTC

Record low

Kp 0.3, 2 Oct 2026, 06:00 UTC

First measurement

2 Oct 2026, 00:00 UTC

Measurement cadence

several times a day

Measurements in this record

64