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Abstract: We present three-dimensional nonlinear magnetohydrodynamic simulations of theinteriors of fully convective M-dwarfs. Our models consider 0.3 solar-massstars using the Anelastic Spherical Harmonic code, with the sphericalcomputational domain extending from 0.08-0.96 times the overall stellar radius.Like previous authors, we find that fully convective stars can generatekG-strength magnetic fields in rough equipartition with the convective flowswithout the aid of a tachocline of shear. Although our model stars areeverywhere unstably stratified, the amplitudes and typical pattern sizes of theconvective flows vary strongly with radius, with the outer regions of the starshosting vigorous convection and field amplification while the deep interiorsare more quiescent. Modest differential rotation is established in hydrodynamiccalculations, but - unlike in some prior work -strongly quenched in MHDsimulations because of the Maxwell stresses exerted by the dynamo-generatedmagnetic fields. Despite the lack of strong differential rotation, the magneticfields realized in the simulations possess significant mean axisymmetriccomponents, which we attribute partly to the strong influence of rotation uponthe slowly overturning flows.

Autor: Matthew Browning U. Chicago-UC Berkeley


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