The influence of solar proton events on the ozone layer

Our two-dimensional chemistry and transport atmospheric model was used to simulate the influence of solar proton events (SPEs) over the 1965 to 1995 time period. Extremely large particle events with huge fluxes of very high energy protons occurred in August 1972 and October 1989 and caused large increases in long-lived NO(y) constituents, which affected ozone for several months to years past the events. Our simulations show that the SPE-produced NO(y) constituents in the upper stratosphere caused direct ozone losses. However, interference of the NO(y) constituents with the halogen loss cycles for ozone destruction actually led to some total ozone production. We predict a seasonal dependence for the impact on polar ozone, with larger (smaller) decreases predicted for SPEs occurring in the fall or winter (spring or summer).