  Accretion disks around compact stars are formed due to turbulence driven by
magnetorotational instability. Despite over thirty years of numerous
computational studies on magnetorotational turbulence, the properties of
fluctuations in the inertial range -- where cross-scale energy transfer
dominates over energy injection -- have remained elusive, primarily due to
insufficient numerical resolution. Here, we report the highest-resolution
simulation of magnetorotational turbulence ever conducted. Our simulations
reveal a constant cross-scale energy flux, a hallmark of the inertial range. We
found that as the cascade proceeds to smaller scales in the inertial range, the
kinetic and magnetic energies tend toward equipartitioning with the same
spectral slope, and slow-magnetosonic fluctuations dominate over Alfv\'enic
fluctuations, possessing twice the energy. These findings align remarkably with
the theoretical expectations from the reduced magnetohydrodynamic model, which
assumes a near-azimuthal mean magnetic field. Our results provide important
implications for interpreting the radio observations by the Event Horizon
Telescope.
