  The initial magnetic field of previous magnetorotational instability (MRI)
simulations has always included a significant system-scale component, even if
stochastic. However, it is of conceptual and practical interest to assess
whether the MRI can grow when the initial field is turbulent. The ubiquitous
presence of turbulent or random flows in astrophysical plasmas generically
leads to a small-scale dynamo (SSD), which would provide initial seed turbulent
velocity and magnetic fields in the plasma that becomes an accretion disc. Can
the MRI grow from these more realistic initial conditions? To address this we
supply a standard shearing box with isotropically forced SSD generated magnetic
and velocity fields as initial conditions, and remove the forcing. We find that
if the initially supplied fields are too weak or too incoherent, they decay
from the initial turbulent cascade faster than they can grow via the MRI. When
the initially supplied fields are sufficient to allow MRI growth and
sustenance, the saturated stresses, large-scale fields, and power spectra match
those of the standard zero net flux MRI simulation with an initial large scale
vertical field.
