The effect of solar proton events on ozone and other constituents

Solar proton events (SPEs) can cause changes in constituents in the Earth's middle atmosphere. The highly energetic protons cause ionizations, excitations, dissociations, and dissociative ionizations of the background constituents. Complicated ion chemistry leads to HO* production and dissociation of N, leads to NO, production. Both the HO" and NO, increases can result in changes to ozone in the stratosphere and mesosphere. The HO* increases lead to short-lived ozone decreases in the mesosphere and upper stratosphere due to the short life- times of the HO* constituents. The NO, increases lead to long-lived stratospheric ozone changes because of the long lifetime of NO, constituents in this region. The NOr-induced ozone changes are generally decreases, however, the NO, con- stituents can interfere with chlorine and bromine radicals in the lowest part of the stratosphere and cause ozone increases. Temperature changes have been predict- ed to occur as a result of the larger SPEs. Atmospheric changes have been observed as a result of eleven SPEs since 1969. Neutral wind variations were measured shortly after the July 1982 and April 1984 SPEs. The recent July 2000 SPE, caused NO" increases that lasted for two months past the event. The two peri- ods of largest SPEs (August 1912 and October 1989) caused ozone decreases that lasted for several weeks past the events.