Turbulent magnetohydrodynamic dynamo for accretion disks using the cross-helicity effect

Accretion disks are studied using the concept of the turbulent magnetohydrodynamic (MHD) dynamo. Under this concept, the effect of cross helicity (magnetic-field/velocity correlation function) plays a key role as does the effect of turbulent viscosity and anomalous resistivity. In the presence of the cross helicity, the rotational motion of the disk can generate the toroidal magnetic field. The magnetic field produces the thrust for launching the jet which, in turn, induces the poloidal magnetic field under the cross-helicity effect. The close relationship between the magnetic field and the plasma velocity is a primary feature of the cross-helicity dynamo.