  We present a series of numerical simulations aimed at understanding the
nature and origin of turbulence in coronal loops in the framework of the Parker
model for coronal heating. A coronal loop is studied via reduced
magnetohydrodynamics simulations in Cartesian geometry. A uniform and strong
magnetic field threads the volume between the two photospheric planes, where a
velocity field in the form of a 1D shear flow pattern is present. Initially the
magnetic field which developes in the coronal loop is a simple map of the
photospheric velocity field. This initial configuration is unstable to a
multiple tearing instability which develops islands with X and O points in the
plane orthogonal to the axial field. Once the nonlinear stage sets in the
system evolution is characterized by a regime of MHD turbulence dominated by
magnetic energy. A well developed power law in energy spectra is observed and
the magnetic field never returns to the simple initial state mapping the
photospheric flow. The formation of X and O points in the planes orthogonal to
the axial field allows the continued and repeated formation and dissipation of
small scale current sheets where the plasma is heated. We conclude that the
observed turbulent dynamics are not induced by the complexity of the pattern
that the magnetic field-lines footpoints follow but they rather stem from the
inherent nonlinear nature of the system.
