The CHAOS-8 geomagnetic field model

Abstract We present CHAOS-8, an extension of the CHAOS field model series that describes the time-dependent near-Earth geomagnetic field, valid from 1999 to 2025. It is estimated from magnetic measurements collected by multiple low-earth-orbit satellites, such as CHAMP and Swarm , and ground observatories. An initial version of this model, CHAOS-8.1, served as the parent model for constructing DTU’s candidate models for the 14th generation International Geomagnetic Reference Field. CHAOS-8 comprises a time-dependent internal field up to spherical harmonic degree 20, a static internal field that merges with the LCS-1 lithospheric field model above degree 25, a model of the magnetospheric field and its induced…