Magnetic and velocity fields in a dynamo operating at extremely small Ekman and magnetic Prandtl numbers

0486241 - GFÚ 2018 RIV SK eng J - Journal Article
Šimkanin, Ján - Kyselica, Juraj
Magnetic and velocity fields in a dynamo operating at extremely small Ekman and magnetic Prandtl numbers.
Contributions to Geophysics & Geodesy. Roč. 47, č. 4 (2017), s. 261-276. ISSN 1335-2806
R&D Projects: GA MŠMT(CZ) LG13042
Institutional support: RVO:67985530
Keywords : hydromagnetic dynamo * magnetic Prandtl number * inertial forces
OECD category: Physical geography

Numerical simulations of the geodynamo are becoming more realistic because
of advances in computer technology. Here, the geodynamo model is investigated numerically at the extremely low Ekman and magnetic Prandtl numbers using the PARODY dynamo code. These parameters are more realistic than those used in previous numerical studies of the geodynamo. Our model is based on the Boussinesq approximation and the temperature gradient between upper and lower boundaries is a source of convection. This study attempts to answer the question how realistic the geodynamo models are. Numerical results show that our dynamo belongs to the strong-field dynamos. The generated magnetic field is dipolar and large-scale while convection is small-scale and sheet-like flows (plumes) are preferred to a columnar convection. Scales of magnetic and velocity fields are separated, which enables hydromagnetic dynamos to maintain the magnetic field at
the low magnetic Prandtl numbers. The inner core rotation rate is lower than that in
previous geodynamo models. On the other hand, dimensional magnitudes of velocity and magnetic fields and those of the magnetic and viscous dissipation are larger than those expected in the Earth’s core due to our parameter range chosen.
Permanent Link: http://hdl.handle.net/11104/0281123