Abstract: A strong storm occurred on January 19, 2026, triggering a series of coupled responses across the magnetosphere–ionosphere–ground system. The magnetosphere, serving as a crucial natural shield surrounding the Earth, plays an essential role in space physics research. In this study, we perform a comprehensive analysis of the storm-time responses based on multi-instrument observations from the Zhangheng-1 (CSES) satellite, combined with coordinated measurements from the GOES and MetOp satellites, as well as ground-based observations from the Yangbajing muon telescope. A strong storm occurred on 19 January 2026, producing a series of coupled responses across the magnetosphere-ionosphere-ground system. The magnetosphere is an important natural barrier around the Earth and plays a necessary role in space physics research. Using multi-payload observational data from the CSES, combined with coordinated observations from the GOES satellite, Metop satellite, and Yangbajing muon telescope, this paper systematically analyzes the responses during this storm. The results show that during the main phase of the geomagnetic storm, the solar wind dynamic pressure rapidly increased to 60 nPa, while the Dst index sharply dropped to −200 nT, indicating a significant compression of the magnetosphere. Concurrently, this was accompanied by enhanced fluxes of high-energy electrons in the radiation belts, with electrons > 1 MeV significantly increasing in the 2<L<4 region, penetrating the slot region and entering the inner radiation belt. Protons across multiple energy channels also showed simultaneous enhancements, with the most significant response observed in the low-energy protons population. Global distribution results indicate that the enhancements of both electrons and protons mainly occurred in high-latitudes regions and near the South Atlantic Anomaly, while variations at low latitudes remain relatively weak. Meanwhile, enhanced low-frequency electromagnetic wave activity observed by satellites during the storm may promote electron acceleration and precipitation through wave-particle interactions. In addition, the electron temperature, electron density, and O⁺ density in the ionosphere all exhibited complex dynamic variations, reflecting the effective transport of energy from the magnetosphere to the ionosphere. Ultimately, this energy transport process propagates downward to the ground, where a significant Forbush decrease is observed by the Yangbajing muon telescope. Comprehensive analysis suggests that this storm produced a clear coupled response across the magnetosphere-ionosphere-ground system, reflecting the multi-scale coupling effects of intense solar activity on the near-Earth space environment.