The geomagnetic three-hourly Kp index was introduced by Julius Bartels in 1949 to measure solar particle radiation by its magnetic effects (see Bartels, 1957). Today Kp is an important measure for the energy input from the solar wind to Earth and it is used by space weather services in near real-time. Kp goes back to 1932 and is an important parameter to investigate long-term climate change in the upper atmosphere, in geospace, in the solar wind and on the sun. Kp is based on the data of 13 geomagnetic observatories around the globe.
GFZ provides Kp and its derived indices and the figures on this website with the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Please refer to GFZ German Research Centre for Geosciences as data source. GFZ contributes with Kp to the International Service of Geomagnetic Indices (ISGI) of IAGA. The indices and their provision (including a data publication with DOI) are described in Matzka et al. (2021).
Next to Kp, this website also provides the new Hpo-indices Hp30 and Hp60.
GFZ also offers a Kp prediction.