Fig. 3

Magnetic variance versus radius, for the 100 dynamo states before and after the assimilation of geomagnetic observations. The unconstrained ensemble refers to 100 decorrelated independent dynamo states extracted from a 70,000-year-long free run integration of the coupled Earth Dynamo. The ensemble in 2019.0 is obtained after applying a Kalman filter to adjust the magnetic field in the core interior for each ensemble member, given the constraints provided by the initial field model constructed at epoch 2019.0 from one year of Swarm data. The variance ratio is the ratio of the variances of the adjusted ensemble to the unconstrained ensemble