On the persistence of geomagnetic flux lobes in global Holocene field models

To investigate the longevity and robustness of high-latitude flux patches in the geomagnetic field at the core-mantle boundary, we present time-dependent models of the geomagnetic field for the past 7000 years. Our models use the same data set as previously used for time-dependent archaeomagnetic field modelling, but constrained with additional priori models from time averages of field models covering the last 150, 400 and 3000 years. We find that the data are consistent with flux patches existing in both north and south hemispheres for the past 7000 years, and that the northern hemisphere patches at least have highly dynamic behaviour. Simple averaging of the historical field may not be appropriate to obtain a characteristic time-averaged model of the field for comparison with other geophysical observables. Our results should inform geodynamo studies of thermal core-mantle coupling, and of possible long-term structure in the geomagnetic field.