Three-Dimensional Global MHD Simulations of Accretion Disks and Jet Formation

R. Matsumoto (Dept. Physics, Chiba University, Email : matumoto@c.chiba-u.ac.jp)

Global 3D MHD Simulations of Differentially Rotating, Cylindrical Plasma
- Simulation Code : 3D MHD code in a Cylindrical Geometry
- Grid Points : (N_r,N_p,N_z)=(129,65,120)
- Numerical Results
  - Numerical results for a constant angular momentum cylindrical plasma initially threaded by weak vertical magnetic fields (beta_0=P_gas/P_mag=100). Small amplitude, random perturbations are imposed at t=0. The top panel shows magnetic field lines at t=12.1r_0/v_K0. The color scale in the bottom panel shows magnetic field strength.
  - Numerical results for a cylindrical plasma with nearly Keplerian initial angular momentum distribution (L = L_0 r^0.45) threaded by weak vertical magnetic fields (beta_0=P_gas/P_mag=100). Small amplitude, random perturbations are imposed at t=0. Numerical results at t=15.1r_0/v_K0 are shown.
  - Numerical results for a cylindrical plasma with nearly Keplerian initial angular momentum distribution (L = L_0 r^0.45) threaded by weak toroidal magnetic fields (B_toroidal = B_0/r, beta_0=P_gas/P_mag=10). Small amplitude, random perturbations are imposed at t=0. Numerical results at t=43.1r_0/v_K0 are shown.
Global 3D MHD Simulations of a Torus Threaded by Vertical Magnetic Fields
- Simulation Code : 3D MHD code in a Cylindrical Geometry
- Grid Points : (N_r,N_p,N_z)=(101,33,101) - (241,65,240)
- Numerical Results
  - Numerical results for a constant angular momentum torus threaded by vertical magnetic fields. The model parameters are E_th=0.05 and E_mg=0.001 (the same as model B3 in Matsumoto et al. 1996). At t=0, small amplitude, m=2 non-axisymmetric perturbations are imposed for rotation speed. The number of grid points is (101,33,101). The left panels show volume rendered image of density distribution. The right panels show magnetic field lines.
    Magnetic Field lines and their projection onto the equatorial plane at t=12.3r_0/v_K0.
  - Numerical results for a constant angular momentum torus threaded by uniform, vertical magnetic fields. The model parameters of the torus are the same as those in model B3. Small amplitude, m=1 perturbations are imposed at t=0. The number of grid points used for this simulation is (129,33,120)
  - GIF movie for the time evolution of magnetic field lines and density distribution by high-resolution numerical simulation, The number of grid points is (N_r,N_p,N_z)=(201,65,240). The model parameters of the torus are the same as those in model B3. We imposed m=1 perturbation at t=0.
Global 3D MHD Simulations of a Torus Threaded by Toroidal Magnetic Fields
- Simulation Code : 3D MHD code in a Cylindrical Geometry
- Grid Points : (N_r,N_p,N_z)=(201,65,240)
- Numerical Results
  - Numerical results for a torus threaded by weak toroidal magnetic fields. The model parameters of the torus are the same as those in model B3. The initial plasma beta is beta=100 inside the torus. Random perturbations for the rotation speed are imposed at t=0.
    - Initial condition. Color scale shows density distribution. Red curves show magnetic field lines.
    - Magnetic field lines and density distribution at t=67.8r_0/v_K0. Magnetic field lines are tangled inside the torus.
    - Isosurface of plasma beta (=P_gas/P_mag). The brue surface and green surface show the isosurface of beta=100 and beta=10, respectively. The yellow surface show the isosurface of beta=1. Note that spirally shaped, low-beta (beta < 1) regions are created inside the torus.
  - GIF movie of the time evolution of the isosurface of plasma beta for a model starting with a constant angular momentum torus threaded by toroidal magnetic fields. The model parameters of the torus are the same as those in model B3. The initial plasma beta is beta=10 inside the torus. The green surface and yellow surface show the isosurface of beta=10 and beta=1, respectively.