  We investigate the significance of large scale azimuthal, magnetic and
velocity modes for the MRI turbulence in accretion disks. We perform 3D global
ideal MHD simulations of global stratified proto-planetary disk models. Our
domains span azimuthal angles of \pi/4, \pi/2, \pi and 2\pi. We observe up to
100% stronger magnetic fields and stronger turbulence for the restricted
azimuthal domain models \pi/2 and \pi/4 compared to the full 2\pi model. We
show that for those models, the Maxwell Stress is larger due to strong
axisymmetric magnetic fields, generated by the \alpha \Omega dynamo. Large
radial extended axisymmetric toroidal fields trigger temporal magnification of
accretion stress. All models display a positive dynamo-\alpha in the northern
hemisphere (upper disk). The parity is distinct in each model and changes on
timescales of 40 local orbits. In model 2\pi, the toroidal field is mostly
antisymmetric in respect to the midplane. The eddies of the MRI turbulence are
highly anisotropic. The major wavelengths of the turbulent velocity and
magnetic fields are between one and two disk scale heights. At the midplane, we
find magnetic tilt angles around 8-9 degree increasing up to 12-13 degree in
the corona. We conclude that an azimuthal extent of \pi is sufficient to
reproduce most turbulent properties in 3D global stratified simulations of
magnetised accretion disks.
