E-mode and B-mode power spectra, C^EE and C^BB, calculated from synthetic dust polarization. Top panel: the power spectra C^EE and C^BB computed from synthetic dust polarization maps. The gray solid line indicates a reference slope of −2.54, which was the C^BB spectral slope measured by Planck at 353 GHz. The subscripts “353” and “150” represent two distinct frequencies: 353 and 150 GHz. k_inj is the injection wavenumber of turbulence, and k_dis is the numerical dissipation wavenumber. The shaded area represents the standard deviation. Bottom panel: same as the top panel, but for C^EE and C^BB, calculated from dust polarization in WNM, UNM, and CNM, respectively.