  We study the stability properties of Rayleigh unstable flows both in the
purely hydrodynamic and magnetohydrodynamic (MHD) regimes for two different
values of the shear $q=2.1, 4.2$ ($q = - d\ln\Omega / d\ln r$) and compare it
with the Keplerian case $q=1.5$. We find that the $q>2$ regime is unstable both
in the hydrodynamic and in the MHD limit (with an initially weak magnetic
field). In this regime, the velocity fluctuations dominate the magnetic
fluctuations. In contrast, in the $q<2$ (magnetorotational instability (MRI))
regime the magnetic fluctuations dominate. This highlights two different paths
to MHD turbulence implied by the two regimes, suggesting that in the $q>2$
regime the instability produces primarily velocity fluctuations that cause
magnetic fluctuations, with the causality reversed for the $q<2$ MRI unstable
regime. We also find that the magnetic field correlation is increasingly
localized as the shear is increased in the Rayleigh unstable regime. In
calculating the time evolution of spatial averages of different terms in the
MHD equations, we find that the $q>2$ regime is dominated by terms which are
nonlinear in the fluctuations, whereas for $q<2$, the linear terms play a more
significant role.
