  An evolution of a magnetic reconnection in a collisionless accretion disk is
investigated using a 2.5 dimensional hybrid code simulation. In astrophysical
disks, magnetorotational instability (MRI) is considered to play an important
role by generating turbulence in the disk and contributes to an effective
angular momentum transport through a turbulent viscosity. Magnetic
reconnection, on the other hand, also plays an important role on the evolution
of the disk through a dissipation of a magnetic field enhanced by a dynamo
effect of MRI. In this study, we developed a hybrid code to calculate an
evolution of a differentially rotating system. With this code, we first
confirmed a linear growth of MRI. We also investigated a behavior of a
particular structure of a current sheet, which would exist in the turbulence in
the disk. From the calculation of the magnetic reconnection, we found an
asymmetric structure in the out-of-plane magnetic field during the evolution of
reconnection, which can be understood by a coupling of the Hall effect and the
differential rotation. We also found a migration of X-point whose direction is
determined only by an initial sign of J_0 \times \Omega_0, where J_0 is the
initial current density in the neutral sheet and \Omega_0 is the rotational
vector of the background Keplerian rotation. Associated with the migration of
X-point, we also found a significant enhancement of the perpendicular magnetic
field compared to an ordinary MRI. MRI-Magnetic reconnection coupling and the
resulting magnetic field enhancement can be an effective process to sustain a
strong turbulence in the accretion disk and to a transport of angular momentum.
