The Spectral Slope and Kolmogorov Constant of MHD turbulence
  The spectral slope of strong MHD turbulence has recently been a matter of
controversy. While Goldreich-Sridhar model (1995) predicts Kolmogorov's -5/3
slope of turbulence, shallower slopes were often reported by numerical studies.
We argue that earlier numerics was affected by driving due to a diffuse
locality of energy transfer in MHD case. Our highest-resolution simulation
(3072^2x1024) has been able to reach the asymptotic -5/3 regime of the energy
slope. Additionally, we found that so-called dynamic alignment, proposed in the
model with -3/2 slope, saturates and therefore can not affect asymptotic slope.
The observation of the asymptotic regime allowed us to measure Kolmogorov
constant C_KA=3.2+-0.2 for purely Alfv\'enic turbulence and C_K=4.1+-0.3 for
full MHD turbulence. These values are much higher than the hydrodynamic value
of 1.64. The larger value of Kolmogorov constant is an indication of a fairly
inefficient energy transfer and, as we show in this Letter, is in theoretical
agreement with our observation of diffuse locality. We also explain what has
been missing in numerical studies that reported shallower slopes.
