Star B2

Introduction
Evolution of Density Profile and Poloidal Magnetic Field Lines
Evolution of Lagrangian Matter Tracers


Introduction


Fig. 1-1 Initial Shape of the Rotating Star

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/M0,sup=0.85 where M0,sup is the rest-mass limit for uniformly rotating polytropes. Figure 1.1 shows the initial shape of the star, a normal star.


Evolution of the Density Profile and Poloidal Magnetic Field Lines

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.


Fig. 2-1 Density profile at t/M = 0

Fig. 2-2 Density profile at t/M = 4860

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Evolution of Lagrangian Matter Tracers

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.


Fig. 3-1 Lagrangian matter tracers with full field at t/M = 0

Fig. 3-2 Field line at t/M = 0

Fig. 3-3 Lagrangian matter tracers at t/M = 4860

Fig. 3-4 Field lines at t/M = 4860

Fig. 3-5 Top view of field lines at t/M = 4860

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last updated 12 Nov 14 by SEC

Center for Theoretical Astrophysics---University of Illinois at Urbana-Champaign

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