  Magnetohydrodynamic instabilities play an important role in accretion disks
systems. Besides the well-known effects of the magnetorotational instability
(MRI), the Parker-Rayleigh-Taylor instability (PRTI) also arises as an
important mechanism to help in the formation of the coronal region around an
accretion disk and in the production of magnetic reconnection events similar to
those occurring in the solar corona. In this work, we have performed
three-dimensional magnetohydrodynamical (3D-MHD) shearing-box numerical
simulations of accretion disks with an initial stratified density distribution
and a strong azimuthal magnetic field with a ratio between the thermal and
magnetic pressures of the order of unity. This study aimed at verifying the
role of these instabilities in driving fast magnetic reconnection in turbulent
accretion disk/corona systems. As we expected, the simulations showed an
initial formation of large-scale magnetic loops due to the PRTI followed by the
development of a nearly steady-state turbulence driven by both instabilities.
In this turbulent environment, we have employed an algorithm to identify the
presence of current sheets produced by the encounter of magnetic flux ropes of
opposite polarity in the turbulent regions of both the corona and the disk. We
computed the magnetic reconnection rates in these locations obtaining average
reconnection velocities in Alfv\'en speed units of the order of $0.13 \pm 0.09$
in the accretion disk and $0.17 \pm 0.10$ in the coronal region (with mean peak
values of order of $0.2$), which are consistent with the predictions of the
theory of turbulence-induced fast reconnection.
