Thin disc kinematic α ω-dynamo models
作者:
A.M. Soward,
期刊:
Geophysical & Astrophysical Fluid Dynamics
(Taylor Available online 1992)
卷期:
Volume 64,
issue 1-4
页码: 201-225
ISSN:0309-1929
年代: 1992
DOI:10.1080/03091929208228090
出版商: Taylor & Francis Group
关键词: α ω-dynamos;galactic discs;kinematic dynamos
数据来源: Taylor
摘要:
In thin disc kinematic dynamo theory there are two classes of dynamo mode. In the first class, the magnetic field generated has a radial length scale long compared with the short transverse length scale defined by the disc thickness. In the second class the radial length scale is short and comparable to the disc width. The former were investigated in Part I and Stix's (1975, 1978) α ω-galactic dynamo in an oblate spheroid with small aspect ratio, ε, was adopted as an illustrative example. Here we again investigate Stix's model but, in contrast, consider the most readily excited oscillatory dipole mode, which happens to have short radial length scale and so belongs to the latter class. It is shown that, in the limit ε ↓ 0, local theory, which ignores the radial structure of the disc, leads to a critical Dynamo number which is smaller than the actual value by about 20%. The explanation of this discrepancy is the main feature of the analysis.
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