  We have studied forced turbulence of compressible magnetohydrodynamic (MHD)
flows through two-dimensional simulations with different numerical resolutions.
First, hydrodynamic turbulence with Mach number $<M_s >_{\rm init} \equiv < v
>_{\rm rms}/ c_s = 1$ and density compression ${< \delta\rho / \rho >}_{\rm
rms} \simeq 0.45$ was generated by enforcing a random force. Then, initial,
uniform magnetic fields of various strengths were added with Alfv\'enic Mach
number $<M_A >_{\rm init} \equiv < v >_{\rm rms} / c_{A, {\rm init}} \gg 1$. An
isothermal equation of state was employed, and no explicit dissipation was
included. After the MHD turbulence is saturated, the resulting flows are
categorized as very weak field (VWF), weak field (WF), and strong field (SF)
classes, which have $<M_A > \equiv < v >_{\rm rms} / < c_A >_{\rm rms} \gg 1$,
$<M_A > > 1$, and $<M_A > \sim 1$, respectively. Not only in the SF regime but
also in the WF regime, turbulent transport is suppressed by the magnetic field.
In the SF cases, the energy power spectra in the inertial range, although no
longer power-law, exhibit a range with slopes close to $\sim1.5$, hinting the
Iroshnikov-Kraichnan spectrum. Our simulations were able to produce the SF
class behaviors only with high resolution of at least $1024^2$ grid cells. The
specific requirements for the simulation of the SF class should depend on the
code (and the numerical scheme) as well as the initial setup, but our results
do indicate that very high resolution would be required for converged results
in simulation studies of MHD turbulence.
