The three-dimensional evolution of rising, twisted magnetic flux tubes in a gravitationally stratified model convection zone

We present three-dimensional numerical simulations of the rise and fragment ation of twisted, initially horizontal magnetic flux tubes that evolve into emerging Omega-loops. The flux tubes rise buoyantly through an adiabatical ly stratified plasma that represents the solar convection zone. The MHD equ ations are solved in the anelastic approximation, and the results are compa red with studies of Aux-tube Fragmentation in two dimensions. We find that if the initial amount of field line twist is below a critical value, the de gree of fragmentation at the apex of a rising Omega-loop depends on its thr ee-dimensional geometry: the greater the apex curvature of a given Omega-lo op, the lesser the degree of fragmentation of the loop as it approaches the photosphere. Thus, the amount of initial twist necessary for the loop to r etain its cohesion can be reduced substantially from the two-dimensional li mit. The simulations also suggest that, as a fragmented flux tube emerges t hrough a relatively quiet portion of the salar disk, extended crescent-shap ed magnetic features of opposite polarity should form and steadily recede f rom one another. These features eventually coalesce after the fragmented po rtion of the Omega-loop emerges through the photosphere.