Anisotropic 2D noise map (left) and its 1D Fourier power spectra averaged over all rows and columns (right). The term “PA” means “power anisotropy”, that is, the ratio of the power in the perpendicular to parallel wave number at the highest wave number. The terms r_⊥ and r_∥ are the array indices in the noise map perpendicular and parallel to the magnetic field, respectively. The amplitude of the noise map is shown in arbitrary units.