Exploring the influence of the non-dipole field on magnetic records for field reversals and excursions

Abstract

We have used the model CALS7K.2 to explore the possible influence of the time-varying non-dipole components of the geomagnetic field during field reversals and excursions. Our findings suggest that non-dipole components could add significant structure to the field during the reversal and excursion processes. Globally, the main polarity reversal is variable in duration and rapid reversals on subdecadal timescales are seen for a small number of locations. The model generates variable reversal paths; however, there is a longitudinal preference both spatially and, more weakly, temporally. Directional reversal features are not globally synchronous: some polarity changes finish before they start elsewhere. Global intensity variations, however, appear more coherent. We also find support for the idea that field intensity changes occur some time before and after the major directional changes of the reversal. Large excursions appear naturally when the axial dipole has been reduced to 20 per cent for the whole time period; however, they are not globally synchronous or uniform. © 2006 The Authors Journal compilation © 2006 RAS.