Geostrophic balance and reversals of the geomagnetic field

Abstract

The 3D geodynamo model in the rapidly rotating spherical shell with heating from below is considered. We show that correlation of the geomagnetic dipole with total magnetic energy in the core depends on the forces balance in the dynamo system. As a result, reversals of the field not always reflect essential changes of the magnetic energy in the core. This result is closely related to the slow decay of the magnetic spectrum at the surface of the core, and in the bulk of the liquid core, especially.

The mean-field dynamo model in geodynamo

“…The simplified form of the vacuum boundary condition for A is well adopted in dynamo community, and presents a good approximation of the boundary with the non-conductive medium [9]. The reason why the vacuum boundary condition is used at the inner core boundary is discussed in [20] and concerned with the weak influence of the inner core on the reversals statistics of the magnetic field [23].…”

“…Such a catastrophic event is hardly believed to happen in the liquid core if the geomagnetic reversals is treated like the trivial redistribution of the energy between the harmonics in the Figure 3: Evolution of the root mean square value of α (upper plane), normalized magnetic dipole g 0 1 (middle plane), and the averaged magnetic spectra S l (lower plane) for the three regimes: C = 1 (red), 7 (green), and 50 (blue). The corresponding amplitudes for g 0 1 : 0.31, 0.32, 1.27, and for S l : 1 500, 9 900, 124 000. white spectrum [20].…”