Hydromagnetic dynamos at the low Ekman and magnetic Prandtl numbers

0472505 - GFÚ 2017 RIV SK eng J - Článek v odborném periodiku
Šimkanin, Ján
Hydromagnetic dynamos at the low Ekman and magnetic Prandtl numbers.
Contributions to Geophysics & Geodesy. Roč. 46, č. 3 (2016), s. 221-244. ISSN 1335-2806
Grant CEP: GA MŠMT(CZ) LG13042
Institucionální podpora: RVO:67985530
Klíčová slova: hydromagnetic dynamo * magnetic Prandtl number * inertial forces
Obor OECD: Physical geography
https://www.degruyter.com/downloadpdf/j/congeo.2016.46.issue-3/congeo-2016-0014/congeo-2016-0014.pdf

Hydromagnetic dynamos are numerically investigated at low Prandtl, Ekman and magnetic Prandtl numbers using the PARODY dynamo code. In all the investigated cases, the generated magnetic fields are dominantly-dipolar. Convection is small-scale and columnar, while the magnetic field maintains its large-scale structure. In this study the generated magnetic field never becomes weak in the polar regions, neither at large magnetic Prandtl numbers (when the magnetic diffusion is weak), nor at low magnetic Prandtl numbers (when the magnetic diffusion is strong), which is a completely different situation to that observed in previous studies. As magnetic fields never become weak in the polar regions, then the magnetic field is always regenerated in the tangent cylinder. At both values of the magnetic Prandtl number, strong polar magnetic upwellings and weaker equatorial upwellings are observed. An occurrence of polar magnetic upwellings is coupled with a regenaration of magnetic fields inside the tangent cylinder and then with a not weakened intensity of magnetic fields in the polar regions. These new results indicate that inertia and viscosity are probably negligible at low Ekman numbers.
Trvalý link: http://hdl.handle.net/11104/0269802