Helioseismic Data Inclusion in Solar Dynamo Models

The Astrophysical Journal (Impact Factor: 5.99). 06/2009; 698:461-478. DOI: 10.1088/0004-637X/698/1/461
Source: arXiv


An essential ingredient in kinematic dynamo models of the solar cycle is the internal velocity field within the simulation domain – the solar convection zone. In the last decade or so, the field of helioseismology has revolutionized our understanding of this velocity field. In particular, the internal differential rotation of the Sun is now fairly well constrained by helioseismic observations almost throughout the solar convection zone. Helioseismology also gives us some information about the depth-dependence of the meridional circulation in the near-surface layers of the Sun. The typical velocity inputs used in solar dynamo models, however, continue to be an analytic fit to the observed differential rotation profile and a theoretically constructed meridional circulation profile that is made to match the flow speed only at the solar surface. Here we take the first steps towards the use of more accurate velocity fields in solar dynamo models by presenting methodologies for constructing differential rotation and meridional circulation profiles that more closely conform to the best observational constraints currently available. We also present kinematic dynamo simulations driven by direct helioseismic

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Available from: Andres Munoz-Jaramillo,
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    • "In the first approach, since we are aiming to reproduce fairly basic features of the PC curves, the details of the exact interaction between the layers are neglected. This approach is validated by a comparison with kinetic simulations of the dynamo models taking into account the meridional circulation as derived from the helioseimology measurements (Munoz-Jaramillo et al., 2009), which showed the separation of meridional flows and the appearance of the region between them with zero flow. This region with zero flow, in fact, can be considered as the boundary between the two layers with meridional circulation, and this boundary can be accepted as non-interactive one as proposed in the current study. "
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    The Astrophysical Journal 12/2009; 707(2):1852. DOI:10.1088/0004-637X/707/2/1852 · 5.99 Impact Factor
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    ABSTRACT: A revision to the flux-transport dynamo model for the solar sunspot cycle is proposed and is demonstrated by using the axisymmetric kinematic simulations. The flux-transport dynamo has succeeded to explain the general cyclic behaviors of the sunspots. It has been known, however, that previous models failed to avoid the strong polar surface field and the strong toroidal field at the base in the high latitude, both of which are not consistent with observations. We propose a new regime of the flux-transport dynamo model by assuming an additional intense diffusivity profile near the surface. The surface poloidal field generated by the α effect is transported down to the base of the convection zone not by the meridional flow but by the surface diffusion mainly in the mid-latitude. With a moderate α quenching, this prevents the concentration of the polar surface field and the amplification of the toroidal field at the high latitude. The condition to obtain the proper magnetic field strength near the pole is ηsurf/u 0>2 × 109 cm, where ηsurf and u 0 are the surface diffusivity and the meridional flow speed, respectively. We also do some parameter studies to ensure the importance of the surface strong diffusivity. In addition, the dependence of the cycle period on free parameters, the speed of meridional flow and the surface diffusivity, is investigated.
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