EDP Sciences
Free access
Volume 427, Number 3, December I 2004
Page(s) 1019 - 1030
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20041199

A&A 427, 1019-1030 (2004)
DOI: 10.1051/0004-6361:20041199

Full-sphere simulations of a circulation-dominated solar dynamo: Exploring the parity issue

P. Chatterjee1, D. Nandy2 and A. R. Choudhuri1

1  Department of Physics, Indian Institute of Science, Bangalore-560012, India
    e-mail: [piyali;arnab]@physics.iisc.ernet.in
2  Department of Physics, Montana State University, Bozeman, MT 59717, USA
    e-mail: nandi@mithra.physics.montana.edu

(Received 30 April 2004 / Accepted 23 July 2004 )

We explore a two-dimensional kinematic solar dynamo model in a full sphere, based on the helioseismically determined solar rotation profile and with an  $\alpha$ effect concentrated near the solar surface, which captures the Babcock-Leighton idea that the poloidal field is created from the decay of tilted bipolar active regions. The meridional circulation, assumed to penetrate slightly below the tachocline, plays an important role. Some doubts have recently been raised regarding the ability of such a model to reproduce solar-like dipolar parity. We specifically address the parity issue and show that the dipolar mode is preferred when certain reasonable conditions are satisfied, the most important condition being the requirement that the poloidal field should diffuse efficiently to get coupled across the equator. Our model is shown to reproduce various aspects of observational data, including the phase relation between sunspots and the weak, diffuse field.

Key words: Sun: activity -- Sun: magnetic fields -- Sun: sunspots

© ESO 2004