Star B2

Evolution is performed on a 400x400 grid, with outer boundaries at r/M=36.4, where M is the initial mass of the star. In this simulation, the spin parameter is J/M²=0.38, and M₀/M_0,sup=0.85 where M_0,sup is the rest-mass limit for uniformly rotating polytropes. Figure 1.1 shows the initial shape of the star, a normal star.

In the meridional clip, the density is plotted on a logarithmic scale normalized to the maximum central density, which occurs at excision.

At t/M=0, the star has an oblate density profile and rapid differential rotation (Fig. 2-1). Poloidal magnetic field lines are indicated by the closed loops. Rotational to gravitational potential energy is T/|W|=0.040. Magnetic braking and MRI destroy differential rotation and transfer angular momentum to the outer layers. The star evolves to a uniformly rotating configuration without much change to its density profile (Fig. 2-2), at which point magnetic winding and MRI cease.

In these clips, we place 20,000 Lagrangian matter tracers that represent fluid elements. The initial distribution of Lagrangian tracers is proportional to the initial rest-mass density. We then calculate the trajectories of the tracers by integrating fluid velocities. The red lines trace representative magnetic field lines.

last updated 12 Nov 14 by SEC