The Geomagnetic Kp Index and Derived Indices of Geomagnetic Activity

The geomagnetic Kp index is one of the most extensively used indices of geomagnetic activity, both for scientific and operational purposes. This article reviews the properties of the Kp index and provides a reference for users of the Kp index and associated data products as derived and distributed by the GFZ German Research Centre for Geosciences. The near real‐time production of the nowcast Kp index is of particular interest for space weather services and here we describe and evaluate its current setup. Key Points Production and distribution of nowcast and definitive Kp index and derived products Kp is estimated to have decreased from 1932 to 2020 by one third of a unit due to geomagnetic secular variation Improved agreement between nowcast and definitive Kp since August 2020