Magnetohydrodynamic jet formation

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