An advective solar-type dynamo without the effect^*

¹ Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany e-mail: seehafer@uni-potsdam.de
² Institute for Solar-Terrestrial Physics, Siberian Division of the Russian Academy of Sciences, 664033 Irkutsk, Russia e-mail: pip@iszf.irk.ru

Received: 1 June 2009
Accepted: 11 September 2009

Abstract

Context. Most solar and stellar dynamo models use the scenario where the magnetic field is generated by the interplay between differential rotation (the Ω effect) and a mean electromotive force due to helical turbulent convection flows (the α effect). There are, however, turbulent dynamo mechnisms that may complement the α effect or may be an alternative to it.

Aims. We investigate models of solar-type dynamos where the α effect is completely replaced by two other turbulent dynamo mechanisms, namely the effect and the shear-current effect, which both result from an inhomogeneity of the mean magnetic field.

Methods. We studied axisymmetric mean-field dynamo models containing differential rotation, the and shear-current effects, and a meridional circulation. The model calculations were carried out using the rotation profile of the Sun as obtained from helioseismic measurements and radial profiles of other quantities according to a standard model of the solar interior.

Results. Without meridional flow, no satisfactory agreement of the models with the solar observations can be obtained. With a sufficiently strong meridional circulation included, however, the main properties of the large-scale solar magnetic field, namely, its oscillatory behavior, its latitudinal drift towards the equator within each half cycle, and its dipolar parity with respect to the equatorial plane, are correctly reproduced.

Conclusions. We have thereby constructed the first mean-field models of solar-type dynamos that do not use the α effect.