Flux Separation in Stellar Magnetoconvection

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Abstract
The effect of a strong magnetic field on photospheric convection in a cool star like the Sun can be established by relating high-resolution solar observations to results from nonlinear models that rely on computation. The patterns of motion in numerical experiments on three-dimensional, compressible magnetoconvection depend not only on the strength of the imposed vertical magnetic field but also on the aspect ratio λ of the computational box. In a wide box (λ=8) with a moderately strong field, the flow organizes itself so that magnetic flux is separated from the motion. There are regions with strong fields and small-scale oscillatory convection next to almost field-free regions with clusters of broad and vigorous convective plumes. In the solar photosphere, this corresponds to the difference between the patterns of granulation in plage regions (with fields greater than 100 G) and in the adjacent quiet Sun.