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Дата последнего поиска статьи во внешних источниках: 29 мая 2015 г.
Аннотация:We investigate linear and nonlinear dynamo models for a galactic disk embedded in a halo, assuming a relatively strong magnetic diffusivity and a nonvanishing alpha effect in the halo. We take the halo to be spherical and embedded in a vacuum. The field is assumed to be axisymmetric, but we do not impose symmetry conditions at the equatorial plane. In one parameter regime we find mixed parity solutions. However, it is argued that the regular magnetic field in the galactic halo can hardly reach a steady-state configuration during the galactic lifetime. In the regime that is observably relevant the field can have an even parity within and near the disk and an odd one in the halo. This may have implications for explaining the occurrence of a neutral sheet above the galactic plane. During certain time intervals the rotation measure of these models shows a doubly peaked azimuthal variation, which could be falsely interpreted as an indication of a bisymmetric field structure.