MAGNETOHYDRODYNAMIC JET FORMATION

Numerical solution of the time-dependent equations for ideal magnetohy drodynamics shows that jet formation can be a natural consequence of t he rotation of an accretion disc in a magnetic field. The accretion di sc loses angular momentum and falls into the gravitational well. Press ure builds up near the centre of the well and ejects a jet along the r otation axis. The jet is collimated partly by hydrodynamic funnelling and partly by the magnetic field. The magnetic field component paralle l to the rotation axis is compressed and amplified by the infalling di sc, and plays an essential part in the collimation process.