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Long-term middle atmospheric influence of very large solar proton events

Jackman, C. H., D. R. Marsh, F. M. Vitt, R. R. Garcia, C. E. Randall, E. L. Fleming, and S. M. Frith (2009), Long-term middle atmospheric influence of very large solar proton events, J. Geophys. Res., 114, D11304, doi:10.1029/2008JD011415.

The Whole Atmosphere Community Climate Model (WACCM3) has been used to study the long-term (more than a few months) effects of solar proton events (SPEs). Extremely large solar proton events occurred in 1972, 1989, 2000, 2001, and 2003 and caused some longer-lasting atmospheric changes. The highly energetic solar protons produced odd hydrogen (HOx) and odd nitrogen (NOy), which then led to ozone variations. Some statistically significant long-term effects on mesospheric ozone were caused by the HOx increases due to a very active time period for SPEs (years 2000–2004), even though the HOx increases were short-lived (days). The long-term stratospheric ozone effects were caused by the NOy enhancements. Very large NOy enhancements lasted for months in the middle and lower stratosphere after a few of the largest SPEs. SPE-caused NOy increases computed with WACCM3 were statistically significant at the 95% level throughout much of the polar stratosphere and mesosphere in the recent solar maximum 5-year period (2000–2004). WACCM3-computed SPE-caused polar stratospheric ozone decreases of >10% continued for up to 5 months past the largest events; however, statistically significant ozone decreases were computed for only a relatively small fraction of this time in relatively limited altitudes in the lower mesosphere and upper stratosphere. Annually averaged model output showed statistically significant (to 95%) stratospheric ozone loss in the polar Northern Hemisphere for years 2000–2002. The computed annually averaged temperature and total ozone change in these years were not statistically significant.

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Atmospheric Composition Modeling and Analysis Program (ACMAP)