Kp index live

What is the Kp index?

The Kp index sums up, in one number from 0 to 9 per three-hour interval, the disturbance of the Earth's magnetic field measured by thirteen observatories spread around the planet. Julius Bartels defined it in 1949 and GFZ Potsdam has computed it continuously since 1932. A Kp below 4 describes a quiet field; from 5 upwards a geomagnetic storm begins, rated G1 to G5 by NOAA, from minor to extreme.

A storm occurs when the solar wind, especially after a coronal mass ejection, compresses and shakes the magnetosphere. Auroras then reach unusual latitudes: a Kp of 7 makes them visible from northern France or the central United States. The chart overlays the near-real-time estimates from NOAA SWPC and the definitive GFZ series, with the quiet, active and storm bands in the background.

The Schumann resonance also responds to these storms: the disturbed ionosphere slightly shifts the frequency and power of the modes. Comparing the two Ultrastats pages shows that relationship day by day.