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Rapidly rotating α 2 ‐dynamo models
Author(s) -
Rüdiger G.
Publication year - 1980
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.2103010407
Subject(s) - dynamo , physics , eigenvalues and eigenvectors , equator , rotational symmetry , rotation (mathematics) , tensor (intrinsic definition) , classical mechanics , magnetic field , dipole , plane (geometry) , dynamo theory , solar dynamo , quantum electrodynamics , mechanics , quantum mechanics , geometry , mathematics , astronomy , latitude
We present numerical calculations for a special α 2 ‐dynamo basing on an α‐tensor proportional to (δ im + α 3 ω i ω m /ω 2 ). ( gω ). For α 3 = – 1 this non‐linear expression reflects the inducting action of (weakly) inhomogeneous stochastic motions for very rapid rotation, ω > ω c . As far as the natural cosmic objects are concerned we do not know, however, the frequency ω c of the fluctuating mide with which the rotational rate Ω has to be compared. The calculations provide the non‐axisymmetric but equatorially symmetric magnetic S 1‐mode to be a preferred one, the poloidal part of which is similar to a dipolar system lying in the equator plane. For α 3 = o … – 1 its eigenvalue remains nearly unchanged whereas the eigenvalues of the other modes strongly increase. In the case of very rapid rotation, finally, this mode possesses the lowest eigenvalue. Therefore, the generation of global magnetic fields by the α‐effect is not substantially obstructed by fast rotation. The realized magnetic rotator should be expected to be a non‐axisymmetric but equatorially symmetric one, which sems to correspond with the observations. From the discussion of the time‐related eigenvalue we obtain the information that the longitudinal drifting of the nonaxisymmetric fields has always a westward direction.