Results of the cross-spectra analysis in the core of the Perseus Cluster shown in Fig. 4. Left: results from the entire central r ∼ 3.5 arcmin (∼70 kpc) region. Right: results from the selected dotted region (Fig. 4). Top row: amplitude of the volume emissivity fluctuations in the soft and hard bands, cross-amplitudes, measured coherence C and ratio R. Bottom row: the corresponding C and R maps. Notation and colour coding are the same as in Fig. 3. The ellipses show a range of parameters that lead to the observed values of C and R. The sizes of the ellipses reflect statistical and systematic uncertainties. Black ellipse: the entire r = 3.5 arcmin region, white ellipse: the selected dotted region (Fig. 4). The fluctuations in the central region are predominantly isobaric.