  The magnetorotational instability (MRI) has been suggested to have an
important role on the dynamics of accretion disks. We investigate MRI as an
alternative way for guiding the plasma from the disk to the funnel flow at the
disk-magnetosphere boundary of classical T Tauri stars (CTTSs) by considering
the diamagnetic effects. We solve the magnetohydrodynamic equations by
including the effect of both the magnetic field gradient and the perpendicular
(to the field) velocity gradient produced by the magnetization current at the
disk-magnetosphere boundary for the first time. Diamagnetic current modified
MRI produces a non-propagating mode which may lift the plasma from the disk
towards the vertical magnetic field lines. Our model also shows that the
diamagnetic effects play an important role in triggering the MRI. The
instability becomes more powerful with the inclusion of the gradient in the
magnetic field and the perpendicular velocity.
