Top and middle panels: Histograms of the distance distributions between neighboring SF regions and giant molecular clouds for different spiral arms. Bottom panel: Distribution of instability wavelengths, which are shown on the right side of Fig. 1. The blue histogram includes only those pixels with both Σ_H2 > 30 M_⊙/pc² and $S({\sigma }_{\mathrm{s}}^{\varphi ,\min })<1$. Solid lines represent the Fourier analysis of the GMC spacings, its range of values is shown on the right y-axis.