Authors: Julian Toczylowski (Andrews University), Jay Johnson (Andrews University), Simon Wing (Johns Hopkins University), and Thierry Dudok de Wit (ISSI)

To better understand the dynamics of the solar cycle, we analyze sunspot area data (solarcyclescience.com/AR_Database/bflydata.txt) organized by Carrington rotation, focusing on latitudinal and interhemispheric interactions over 14 solar cycles (1874 to 2024). We use information theoretic measures, mutual information (MI) and transfer entropy (TE), to establish nonlinear correlations and to quantify directional information flow between high- and low-latitude temporal modes across and between hemispheres. Our results reveal a helical TE structure near 15° latitude reflecting an evolution of the intrahemispheric coupling. Additionally, TE shows that apparent low-latitude interhemispheric coupling is substantially mediated through polar field modes, consistent with Babcock-Leighton flux-transport dynamics. We further identify significant cross-scale information cascades: decomposing each mode into four non-overlapping period bands (0–1.3 to 5–10 yr), we find that transfer entropy is directed preferentially from low-frequency to high-frequency modes across both hemispheres and both latitude bands. This indicates that slow modes modulate fast ones rather than the reverse. This suggests a directed, cross-scale coupling that cannot be explained by the source band’s spectral content alone. Together, these results provide new, largely model-independent constraints on cross-scale and interhemispheric coupling in the solar dynamo.