We explore the arguments presented in the past linking changes in the angular momentum modulus , | { \bf L } | , of the Sun ’ s barycentric orbit , with the discharges of Po River in Europe and Paraná River in South America , looking for any evidence regarding to a possible underlying physical mechanism .
We clarify the planetary effect on solar torque presenting new analyses and results ; we also improve prior results on Paraná River ’ s cycles finding significant spectral lines around 6.5 yr , 7.6 yr , 8.7 yr , and 10.4 yr. We show that the truly important dynamical parameter in this issue is the vectorial planetary torque .
Moreover , following the variations of { \bf L } respect to the Sun ’ s spin axis of rotation ( i.e. , a LS relationship ) , we found virtually the same Paraná River discharge peaks : 6.3 yr , 7.7 yr , 8.6 yr and 9.9 yr. An analisys based on Magnitude Squared Coherence and Wavelet Coherence between Paraná River discharge and our LS relationship shows significant , although intermittently , coherence near 8-yr periodicities .
Wavelet Coherence also shows big and significant regions of coherence inside 12-19 yr band .
Our results ruled out classical tidal effects in this problem ; but suggest that , if these rivers are trully related to solar barycentric motion , the physical origin of this connection might be related to a working solar spin-orbit interaction .