The space radiation environment poses a critical threat to spacecraft electronics, with single-event upset (SEU) being one of the most representative transient radiation effects. Understanding the spatial distribution and driving mechanisms of SEUs is essential for improving radiation-hardened design and mission reliability.

This study aims to systematically investigate the relationship between on-orbit SEUs and space environment parameters, and to quantify the contribution of high-energy protons to SEU occurrence.

On-orbit SEU monitoring data from static random-access memory (SRAM) devices were analyzed in conjunction with particle flux measurements, geomagnetic parameters, and proton energy spectra. The spatial distribution of SEUs was mapped in L-shell coordinates, and statistical correlation analysis was performed between the flux of protons at or above 10 MeV and on-orbit soft error rate (SER). Theoretical SER was calculated using ground-based proton irradiation cross sections and compared with observed values.

A total of 97.5% of SEU events were concentrated within the South Atlantic Anomaly (SAA), with a peak at L ≈ 1.24−1.25, coinciding with enhanced the flux of protons at or above 10 MeV regions. A significant power-law correlation (R ≈ 0.73) was found between the flux of protons at or above 10 MeV and SER, confirming high-energy protons as the dominant driver of SEUs. The calculated SER agreed with observations within one order of magnitude but was systematically lower, indicating the need for extending the spectral range to improve prediction accuracy. No SEUs were detected during three minor solar proton events, while geomagnetic storms caused significant SER decreases due to proton flux depletion in the SAA.

This study systematically elucidates the spatial distribution characteristics and primary driving mechanisms of on-orbit SRAM SEUs, demonstrating that high-energy proton flux is the dominant contributor to SEU occurrence. These findings advance the understanding of space radiation effects and provide essential theoretical and experimental support for radiation effect modeling, radiation-hardened design, and mission reliability assessment.