Hydromagnetic dynamos in rotating spherical fluid shells in dependence on the Prandtl number, density stratification and electromagnetic boundary conditions

Abstract

We present an investigation of dynamo in a simultaneous dependence on the
non-uniform stratification, electrical conductivity of the inner core and the Prandtl number.
Computations are performed using the MAG dynamo code. In all the investigated
cases, the generated magnetic fields are dipolar. Our results show that the dynamos, especially
magnetic field structures, are independent in our investigated cases on the electrical
conductivity of the inner core. This is in agreement with results obtained in previous
analyses. The influence of non-uniform stratification is for our parameters weak, which is
understandable because most of the shell is unstably stratified, and the stably stratified
region is only a thin layer near the CMB. The teleconvection is not observed in our study.
However, the influence of the Prandtl number is strong. The generated magnetic fields
do not become weak in the polar regions because the magnetic field inside the tangent
cylinder is always regenerated due to the weak magnetic diffusion.