GEOMAGNETIC-FIELD INTENSITY AND REVERSALS DURING THE PAST 4 MILLION YEARS

A long and continuous record of the geomagnetic field intensity shows that intensity variations are dominated by two modes. Major episodes of field regeneration prevail on timescales of a few thousand years immediately after most reversals, whereas stable polarity states are characterized by a slow (approximately 0.5 Myr) relaxation process. Reversals can be seen as the consequence of a progressive degradation of the dipole field.