Magnetic field generation by convective flows in a plane layer: the dependence on the Prandtl numbers

• Published in: Geophysical and astrophysical fluid dynamics 2008-08, Vol.102 (4), p.409-433
• Main Author: Podvigina, O. M.
• Format: Article
• Language: English
• Subjects: Attractors; Bifurcations; Magnetic field generation; Thermal convection
• ISSN: 0309-1929; 1029-0419
• DOI: 10.1080/03091920701841945

Investigation of magnetic field generation by convective flows is carried out for three values of kinematic Prandtl number: P = 0.3, 1 and 6.8. We consider Rayleigh-Bénard convection in Boussinesq approximation assuming stress-free boundary conditions on horizontal boundaries and periodicity with the same period in the x and y directions. Convective attractors are modelled for increasing Rayleigh numbers for each value of the kinematic Prandtl number. Linear and non-linear dynamo action of these attractors is studied for magnetic Prandtl numbers P m ≤ 100. Flows, which can act as magnetic dynamos, have been found for all the three considered values of P, if the Rayleigh number R is large enough. The minimal R, for which of magnetic field generation occurs, increases with P. The minimum (over R) of critical P m for magnetic field generation in the kinematic regime is admitted for P = 0.3. Thus, our study indicates that smaller values of P are beneficial for magnetic field generation.