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Numerical simulations of rotating sunspots

G.J.J. Botha,
A.M.Rucklidge
F.H. Busse
N.E. Hurlburt
Abstract. A numerical model of idealized, axisymmetric, rotating sunspots is presented. The model contains a compressible plasma described by the nonlinear MHD equations, with density and temperature gradients simulating the upper layer of the sun's convection zone. The solution forms a central flux tube in the cylindrical numerical domain, with convection cells pushing the magnetic field to the axis. When the numerical domain is rotated with a constant angular velocity, the umbra rotates as a rigid body while the surrounding convection cells show a swirling, vortical flow. As a result, the azimuthal velocity and magnetic field have their maximum values close to the flux tube, inside the innermost convection cell.

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