No abstract

The increasing power of computers makes it possible to model the nonlinear interaction between magnetic elds and convection at the surfaces of solar-type stars in ever greater detail. We present the results of idealized numerical experiments on twodimensional magnetoconvection in a fully compressible perfect gas. We rstvary the aspect ratio of the computational box and show that the system runs through a sequence of convective patterns, and that it is only for a su ciently wide box( 6) that the ow becomes insensitive to further increases in . Next, setting =6,we decrease the eld strength from a value strong enough to halt convection and nd transitions to small-scale steady convection, next to spatially modulated oscillations ( rst periodic, then chaotic) and then to a new regime of ux separation, with regions of strong eld (where convection is almost completely suppressed) separated by broad convective plumes. We also explore the e ects of altering the boundary conditions and show that this sequence of transitions is robust. Finally, we relate these model calculations to recent high-resolution observations of solar magnetoconvection, in plage regions as wellasinlight bridges and the umbrae of sunspots.

No abstract

The increasing power of computers makes it possible to model the nonlinear interaction between magnetic elds and convection at the surfaces of solar-type stars in ever greater detail. We present the results of idealized numerical experiments on twodimensional magnetoconvection in a fully compressible perfect gas. We rstvary the aspect ratio of the computational box and show that the system runs through a sequence of convective patterns, and that it is only for a su ciently wide box( 6) that the ow becomes insensitive to further increases in . Next, setting =6,we decrease the eld strength from a value strong enough to halt convection and nd transitions to small-scale steady convection, next to spatially modulated oscillations ( rst periodic, then chaotic) and then to a new regime of ux separation, with regions of strong eld (where convection is almost completely suppressed) separated by broad convective plumes. We also explore the e ects of altering the boundary conditions and show that this sequence of transitions is robust. Finally, we relate these model calculations to recent high-resolution observations of solar magnetoconvection, in plage regions as wellasinlight bridges and the umbrae of sunspots.