Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...289..949f&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 289, no. 3, p. 949-956
Astronomy and Astrophysics
Astronomy
89
Dynamo Theory, Electric Fields, Magnetic Flux, Magnetohydrodynamics, Solar Convection (Astronomy), Solar Magnetic Field, Solar Rotation, Stability, Equilibrium Equations, Linear Transformations, Stellar Models, Turbulence
Scientific paper
We show that a non-axisymmetric instability of toroidal magnetic flux tubes in a rotating star provides a dynamo effect. The instability occurs in the form of propagating helical waves; their growth in amplitude causes a phase shift between the perturbations of magnetic field and velocity, which leads to an electric field (anti)parallel to the direction of the unperturbed field. Together with differential rotation, this effects is capable of driving a dynamo of the alpha omega-type. In contrast to the conventional alpha-effect in cyclonic convention, this dynamo effect operates in strong (super-equipartition) magnetic fields which resist against distortion by convective flows. We calculate the induced electric field using results from linear stability and a model of the solar convection zone which consistently includes an overshoot layer. We find that for growing magnetic field the dynamo effect occurs first in high latitudes (near the poles) in a region of weak instability which moves towards the equator as the field strength increases further. The dependence of the dynamo effect on the location of the flux tubes (in depth and latitude) and on the rotation rate is discussed.
Ferriz-Mas Antonio
Schmitt Denis
Schuessler Manfred
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