Open AccessNon‐linear αω ‐dynamos driven by magnetic buoyancy
Author(s) -
Thelen J.C.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03420.x
Subject(s) - dynamo , physics , buoyancy , solar dynamo , magnetic field , mechanics , dynamo theory , classical mechanics , magnetohydrodynamics , convection , convection zone , astrophysics , quantum mechanics
It is now widely accepted that the large‐scale solar magnetic field is generated by some kind of non‐linear αω ‐dynamo. However, these dynamos have the disadvantage that the non‐linearities, and in particular the α ‐effect, are chosen in an ad hoc fashion and are only vaguely related to the underlying physical processes. Here, on the other hand, an αω ‐dynamo with an α ‐effect based on magnetic buoyancy instabilities is described. This α ‐effect has one main advantage over previous descriptions, namely that it is derived from a numerical model of the physical processes that are thought to occur at the base of the convection zone. In this paper we investigate a one‐dimensional and a two‐dimensional αω ‐dynamo in a cylindrical and a spherical shell, respectively. In both models the ω ‐effect is described by a simple shear flow, while α is proportional to the radial gradient of the magnetic field because, simply speaking, this gradient determines when magnetic buoyancy instabilities occur and hence when the α ‐effect sets in.