MHD simulations of spherical accretion to a star in the propeller regime

MHD SIMULATION OF SPHERICAL ACCRETION TO A STAR IN THE "PROPELLER" REGIME

Authors: Romanova M.M., Toropina O.D., Toropin Yu.M., Lovelace R.V.E.

	Spherical accretion to a rapidly rotating star. Matter flow in the "propeller" regime for a star rotating at W_=0.5 W_K_ The axes are measured in units of the star's radius. The background represents the density and the length of the arrows is proportional to the poloidal velocity. The thin solid lines are magnetic field lines.
	Enlarged view of Figure 1. Bold solid lines show the streamlines of the matter flow.
	The radial dependences of the angular velocity in the equatorial plane for different values of W_. If the rotation rate is smaller, then the matter outflow become less intense. For W_< 0.16, no equatorial outflow is observed and the shock wave becomes more nearly spherical as it is in the non-rotating case. On the other hand the shock wave becomes more a more flattened ellipsoid for larger W_*.
[return]	The radial dependences of the different radial forces in the equatorial plane. One can see that for r>3.5 R_, the centrifugal force becomes dominant in accelerating the matter outward. However, at larger distances, r > 5.5 R_, the pressure gradient force become larger and determines acceleration of matter. Thus, centrifugal and pressure gradient forces accelerate matter in the radial direction. Note, that in most of the region r >4.3 R_* the magnetic force is negative so that it opposes the matter outflow.

	Spherical accretion to a rapidly rotating star. Matter flow in the "propeller" regime for a star rotating at W_=0.5 W_K_ The axes are measured in units of the star's radius. The background represents the density and the length of the arrows is proportional to the poloidal velocity. The thin solid lines are magnetic field lines.
	Enlarged view of Figure 1. Bold solid lines show the streamlines of the matter flow.
	The radial dependences of the angular velocity in the equatorial plane for different values of W_. If the rotation rate is smaller, then the matter outflow become less intense. For W_< 0.16, no equatorial outflow is observed and the shock wave becomes more nearly spherical as it is in the non-rotating case. On the other hand the shock wave becomes more a more flattened ellipsoid for larger W_*.
[return]	The radial dependences of the different radial forces in the equatorial plane. One can see that for r>3.5 R_, the centrifugal force becomes dominant in accelerating the matter outward. However, at larger distances, r > 5.5 R_, the pressure gradient force become larger and determines acceleration of matter. Thus, centrifugal and pressure gradient forces accelerate matter in the radial direction. Note, that in most of the region r >4.3 R_* the magnetic force is negative so that it opposes the matter outflow.