Does the butterfly diagram indicate a solar flux-transport dynamo?

Max-Planck-Institut für Sonnensystemforschung (Formerly: Max-Planck-Institut für Aeronomie.) , Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany e-mail: [schuessler,schmitt]@linmpi.mpg.de

Corresponding author: M. Schüssler, msch@linmpi.mpg.de

Received: 26 February 2004
Accepted: 17 March 2004

Abstract

We address the question whether the properties of the observed latitude-time diagram of sunspot occurrence (the butterfly diagram) provide evidence for the operation of a flux-transport dynamo, which explains the migration of the sunspot zones and the period of the solar cycle in terms of a deep equatorward meridional flow. We show that the properties of the butterfly diagram are equally well reproduced by a conventional dynamo model with migrating dynamo waves, but without transport of magnetic flux by a flow. These properties seem to be generic for an oscillatory and migratory field of dipole parity and thus do not permit an observational distinction between different dynamo approaches.