Cumulative geomagnetic disturbances modulate global photosystem stoichiometry through temperature-dependent gating

1.Space weather exerts profound effects on Earths technological systems, yet its influence on the terrestrial biosphere remains largely unexplored at the global scale. Despite decades of research on solar-terrestrial interactions, most studies have focused on technological and atmospheric effects, while potential influences on biological regulation remain largely unexplored. While local experiments suggest magnetic sensitivity in plants (Galland and Pazur 2005; Belyavskaya 2004), observational evidence for a planetary-scale vegetative response to geomagnetic disturbances is lacking. In particular, it is unclear whether weak and intermittent geomagnetic disturbances can leave detectable signatures in ecosystem-scale physiological processes. Here, we analyze a decade of satellite-derived solar-induced chlorophyll fluorescence (SIF) data alongside geomagnetic indices to isolate non-seasonal physiological anomalies. Using temperature-stratified cumulative correlation analysis and multivariate models controlling for radiative and hydrological drivers, we identify a robust, cumulative, and thermally gated association between geomagnetic activity and vegetation fluorescence. We report a global-scale coherent modulation of photosystem balance, potentially inferred from the SIF757/SIF771 ratio, with recurrent geomagnetic disturbances, exhibiting maximal coherence under cold and moderate thermal conditions and weakening under Optimum and Warm Stress regimes. This response intensifies with increasing integration window length, indicating progressive physiological integration of repeated perturbations. Comparative analyses demonstrate that geomagnetic forcing is frequently comparable to or exceeds major climatic drivers in explaining fluorescence variability within biologically active regimes. We propose a mechanism consistent with magnetic modulation of radical pair spin dynamics in iron-sulfur clusters and cryptochromes, potentially influencing reactive oxygen species generation and redox-regulatory adaptation. Our findings suggest that plants have evolutionarily co-opted geomagnetic variability as an informational signal, integrating it into existing redox-regulatory networks. Rather than a passive mechanical perturbation, the observed response reflects an evolved sensitivity that operates near physiological criticality--a hypothesis that opens new frontiers in understanding magnetosphere-biosphere coupling.