ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-8679-2012 Influence of a Carrington-like event on the atmospheric chemistry, temperature and dynamics Calisto M. 1 Verronen P. T. 2 Rozanov E. 3 4 Peter T. 4 International Space Science Institute (ISSI), Bern, Switzerland Finnish Meteorological Institute, Helsinki, Finland Physical-Meteorological Observatory/World Radiation Center, Davos, Switzerland Institute for Atmospheric and Climate Science ETH, Zurich, Switzerland 26 09 2012 12 18 8679 8686 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/12/8679/2012/acp-12-8679-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/8679/2012/acp-12-8679-2012.pdf

We have modeled the atmospheric impact of a major solar energetic particle event similar in intensity to what is thought of the Carrington Event of 1–2 September 1859. Ionization rates for the August 1972 solar proton event, which had an energy spectrum comparable to the Carrington Event, were scaled up in proportion to the fluence estimated for both events. We have assumed such an event to take place in the year 2020 in order to investigate the impact on the modern, near future atmosphere. Effects on atmospheric chemistry, temperature and dynamics were investigated using the 3-D Chemistry Climate Model SOCOL v2.0. We find significant responses of NO<sub>x</sub>, HO<sub>x</sub>, ozone, temperature and zonal wind. Ozone and NO<sub>x</sub> have in common an unusually strong and long-lived response to this solar proton event. The model suggests a 3-fold increase of NO<sub>x</sub> generated in the upper stratosphere lasting until the end of November, and an up to 10-fold increase in upper mesospheric HO<sub>x</sub>. Due to the NO<sub>x</sub> and HO<sub>x</sub> enhancements, ozone reduces by up to 60–80% in the mesosphere during the days after the event, and by up to 20–40% in the middle stratosphere lasting for several months after the event. Total ozone is reduced by up to 20 DU in the Northern Hemisphere and up to 10 DU in the Southern Hemisphere. Free tropospheric and surface air temperatures show a significant cooling of more than 3 K and zonal winds change significantly by 3–5 m s<sup>−1</sup> in the UTLS region. In conclusion, a solar proton event, if it took place in the near future with an intensity similar to that ascribed to of the Carrington Event of 1859, must be expected to have a major impact on atmospheric composition throughout the middle atmosphere, resulting in significant and persistent decrease in total ozone.

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