[SEM22-P04] Investigation of equatorial symmetry of the flow and magnetic fields in numerical dynamos with dipolar reversal
Keywords:Geomagnetic field, Geodynamo, Polarity reversals, Equatorial symmetry
In the present study, we perform dynamo simulations in order to discuss dynamical processes of the reversal, using a geodynamo code Calypso [Matsui et al., 2014]. In particular, we investigate how equatorial flow asymmetry contributes reversal processes. In the present study, we fix aspect ratio, Ekman, Prandtl and magnetic Prandtl numbers of ri/ro = 0.15,E = 10-3,Pr = 1 and Pm = 5, respectively. The simulations are performed to 4 times of the magnetic diffusion time (td) with various Rayleigh number of Ra = 980, 1100, 1200 and 1300. Then we examine the dipole tilt angle. Generally, with increasing Ra, the tilt angle became more unstable. In Ra = 980 case, during simulation time, dipole field was stable without reversal. In Ra = 1100 case, dipole field tilts to vicinity of the opposite polarity at near the end of simulation (t = 4.0td). In Ra = 1200 case, dipole field keeps the normal polarity at 2.0 td < t < 3.5 td, and flips to the reverse polarity to the end of the simulation. In Ra = 1300 case, the dipole field has reverse polarity at 2.0 td < t < 3.5td, and has normal polarity at 1.0 td < t < 2.0td and 3.5 td < t < 4.0td. And we are performing with aspect ratio of the current Earth's outer and inner cores (i.e. ri/ro = 0.35), and we analyze the amplitude of symmetric and asymmetric components of flow and magnetic field respectively. For further research, we will also discuss how the equatorial antisymmetric flow component with respect to the equator is generated and maintained, focusing on the energy transfer between the flow and the magnetic field.