Coronal Magnetic Field Modulates Giga-electronvolt Solar Disk Gamma Rays

Solar disk gamma rays, theorized to originate from hadronic galactic cosmic-ray interactions, exhibit many puzzling features. At 1 giga-electronvolts (GeV), these features include high flux and anti-correlation with the solar activity cycle. Between 10 and 50 GeV, it also displays an unexpected time- and energy- dependent morphology. A key question is how solar magnetic fields could affect solar disk gamma rays. The magnetic field in solar corona, in particular, is complex in structure, variable in time, and difficult to probe. Here we present the first model of time-dependent gamma-ray flux across an entire solar cycle, produced using simulation toolkit G4SOLAR and incorporating state-of-the-art coronal magnetic field models. Our result produces good agreement with observations in both flux and time variation between 0.1 and 1 GeV, showing the open coronal fields as the dominant cause. We further predict distinct morphological signatures linked to coronal magnetic field structures, which can be verified by future gamma-ray telescopes. These findings establish a clear connection between coronal field and GeV gamma-ray emission, positioning solar gamma rays as a novel tool to study solar physics.