Magnetic field confinement by meridional flow and the solar tachocline

¹ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482, Potsdam, Germany e-mail: [gruediger; lkitchatinov]@aip.de
² Institute for Solar-Terrestrial Physics, PO Box 4026, Irkutsk 664033, Russian Federation e-mail: kit@iszf.irk.ru

Received: 17 January 2006
Accepted: 1 March 2006

Abstract

We show that the MHD theory that explains the solar tachocline by an effect of the magnetic field can work with the decay modes of a fossil field in the solar interior if the meridional flow of the convection zone penetrates slightly the radiative zone beneath. An equatorward flow of about 10 m/s penetrating to a maximum depth of 1000 km below the convection zone is able to generate almost horizontal field lines in the tachocline region so that the internal field is almost totally confined to the radiative zone. The theory of differential solar rotation indeed provides meridional flows of about 10 m/s and a penetration depth of 1000 km for viscosity values that are characteristic of a stable tachocline.