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On radiation-zone dynamos

Published online by Cambridge University Press:  08 June 2011

Günther Rüdiger
Affiliation:
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany email: gruediger@aip.de, mgellert@aip.de, rarlt@aip.de
Marcus Gellert
Affiliation:
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany email: gruediger@aip.de, mgellert@aip.de, rarlt@aip.de
Rainer Arlt
Affiliation:
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany email: gruediger@aip.de, mgellert@aip.de, rarlt@aip.de
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Abstract

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It is shown that the magnetic current-driven (‘kink-type’) instability produces flow and field patterns with helicity and even with α-effect but only if the magnetic background field possesses non-vanishing current helicity B⋅ curl B by itself. Fields with positive large-scale current helicity lead to negative small-scale kinetic helicity. The resulting α-effect is positive. These results are very strict for cylindric setups without z-dependence of the background fields. The sign rules also hold for the more complicated cases in spheres where the toroidal fields are the result of the action of differential rotation (induced from fossil poloidal fields) at least for the case that the global rotation is switched off after the onset of the instability.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2011

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