Michal Rozyczka

Spiral Shocks in Accretion Disks: A Preliminary Numerical Study

The response of accretion disks to tidal forces is studied numerically with the help of a 2-D, second order hydrodynamical code. The code is tested on analytical self-similar models of spiral shocks and proven capable of maintaining them stationary in the grid. The disks are assumed to reside in potential wells of primary components of binary systems. The models are not structured perpendicularly to the orbital plane, and only the flow in the orbital plane is studied. A uniform inflow condition applied to the outer boundary of the disk invariably leads to the formation of two-armed spiral waves resembling the analytical similarity solutions. Provided the disk approaches the Roche lobe, fairly strong shocks are observed even for mass ratios (secondary to primary) as small as 0.01. Stopping the inflow at the outer boundary modifies the spiral pattern and causes the disk to shrink rapidly.

Driving Protostellar Jets

Magnetized gas is readily lifted from accretion disks by magnetic buoyancy or Parker instability. We follow the evolution of buoyant elements after they have reached the disk surface, using axisymmetric magneto-hydrodynamic calculations. The ambient medium above the disk in our calculations is unmagnetized, differentially rotating, and in hydrostatic balance (see Figure 1).