  The results of three-dimensional MHD numerical simulations are used to
investigate the characteristic properties of the magnetic-field structures in
the accretion disks of semi-detached binary systems. It is assumed that the
intrinsic magnetic field of the accretor star is dipolar. Turbulent diffusion
of the magnetic field in the disk is taken into account. The SS Cyg system is
considered as an example. The results of the numerical simulations show the
intense generation of a predominantly toroidal magnetic field in the accretion
disk. Magnetic zones with well defined structures for the toroidal magnetic
field form in the disk, which are separated by current sheets in which there is
magnetic reconnection and current dissipation. Possible observational
manifestations of such structures are discussed. It is shown that the
interaction of a spiral precessional wave with the accretor's magnetosphere
could lead to quasi-periodic oscillations of the accretion rate.
