Indices of Global Geomagnetic Activity
The planetary three-hour-range Kp index was introduced by J. Bartels in 1949 and is derived from the standardized K index (Ks) of 13 magnetic observatories. It is designed to measure solar particle radiation by its magnetic effects.
The geomagnetic ap, Ap, Cp and C9 and the classification of international Q-days and D-days are derived from the Kp index.
This service contributes to the "International Service of Geomagnetic Indices" (ISGI) of the IAGA.
Planetary magnetic three-hour-range indices, shown in old style musical diagram.