Solar Proton Events Enhance Polar Upper Stratospheric Downward Transport: Evidence From Ozone‐Traced Descent

Abstract The Brewer‐Dobson circulation (BDC) is a fundamental driver of trace gas transport in the middle atmosphere. Direct quantification of its descent rate remains observationally challenging. Here, we leverage wintertime solar proton events (SPEs) as natural experiments and use ozone‐depletion trajectories as dynamical tracers to quantify polar stratospheric descent. Derived velocities range from 150 to 570 m/day, consistent with CO/NO tracer studies and WACCM simulations. We find a strong relationship between descent velocity and integrated proton flux (CC = 0.54, p = 0.01), indicating that stronger particle precipitation is associated with enhanced polar descent of ozone‐depletion tracers. This relationship is accompanied by coherent changes in ozone, temperature, zonal wind, and planetary‐wave forcing. We further show that the SPE‐related dynamical responses differ between quasi‐biennial oscillation (QBO) phases, with stronger planetary‐wave forcing during the QBO westerly phase. These results provide observational constraints on the linkage between energetic particle precipitation and stratospheric dynamical variability.