3D power-law index ﹩| \alpha | ﹩ of turbulence vs. the range of length scales where the turbulent power spectrum is measured in the Milky Way (Armstrong et al. 1995; Chepurnov & Lazarian 2010), Hydra A galaxy cluster (Vogt & Enßlin 2005), the Coma galaxy cluster (Schuecker et al. 2004), and in the IGM taken from this work. The shaded region indicates the uncertainty. The dashed line marks the Kolmogorov index.