Our Sun is a remarkably stable energy source, crucial for life on Earth. However, the Sun exhibits variations over a wide range of timescales. Occasionally, violent eruptions on the Sun’s surface, known as solar storms, release energetic particles that can disrupt modern technological systems. For example, one of the largest known solar storms, the “Carrington Event,” occurred in 1859, significantly affecting the telegraph system, one of the few systems dependent on electricity at that time. Historical observations and indirect proxy data demonstrate that the Sun can produce solar storms orders of magnitude larger than those observed during the space era. Presently, we do not know the recurrence rate of large solar storms or how these events are linked to solar activity. Mapping these linkages may help us understand the underlying processes and predict the risks of future events. To fill this important knowledge gap, cosmogenic radionuclides (e.g., Be-10,Cl-36 and C-14) measured in ice cores and tree-rings could serve as “natural detectors” of past solar activity. However, significant uncertainties remain in using those cosmogenic radionuclides as reliable solar proxies. These radionuclides are produced in the atmosphere, but measurements are taken from ground archives. It is therefore essential to quantify how post-production processes modify cosmogenic radionuclide signals between their atmospheric generation and their preservation in natural archives. Supported by my ERC Advanced Grant (2025-2029), titled "Past Solar Storms: The Links Between Solar Storms and Solar Activity," our group will employ a suite of state-of-the-art global models to simulate the transport and fate of cosmogenic radionuclides. Specifically, ECHAM6.3-HAM2.3 (https://redmine.hammoz.ethz.ch/projects/hammoz), GEOS-Chem (https://geoschem.github.io/), and the Community Earth System Model (CESM; https://www.cesm.ucar.edu/) will be applied. While ECHAM6.3-HAM2.3 and GEOS-Chem focus primarily on atmospheric transport, with non-atmospheric components prescribed, CESM simulates radionuclides interactively across multiple Earth system components, including carbon-cycle propagation of C-14. Control simulations covering the recent ~70 years will be conducted to model the transport and deposition of Be-10, Cl-36, as well as the atmospheric distribution and carbon-cycle redistribution of C-14, with selected simulations driven by reanalysis meteorology. In addition, a series of sensitivity experiments and paleo-event simulations will be performed to reassess theoretical expectations of solar storm signatures, including hemispheric differences, contrasts between Be-10, Cl-36 and C-14 responses, regional dependencies, and the influence of accumulation rates, volcanic eruptions and carbon-cycle processes. Together, these simulations will substantially improve our understanding of how transport, deposition, and carbon-cycle dynamics shape cosmogenic radionuclide signals, thereby reducing uncertainties in their application as robust indicators of past solar activity.