FLUX SEPARATION IN STELLAR MAGNETOCONVECTION

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 compu tation. The patterns of motion in numerical experiments on three-dimen sional, compressible magnetoconvection depend not only on the strength of the imposed vertical magnetic field but also on the aspect ratio l ambda of the computational box. In a wide box (lambda = 8) with a mode rately strong field, the flow organizes itself so that magnetic flux i s separated from the motion. There are regions with strong fields and small-scale oscillatory convection next to almost field-fret regions w ith clusters of broad and vigorous convective plumes. In the solar pho tosphere, this corresponds to the difference between the patterns of g ranulation in plage regions (with fields greater than 100 G) and in th e adjacent quiet Sun.