Reactive nitrogen (NO_<i>y</i>) and ozone responses to energetic electron precipitation during Southern Hemisphere winter

• Main Authors: P. Arsenovic, A. Damiani, E. Rozanov, B. Funke, A. Stenke, T. Peter
• Format: Article
• Language: English
• Published: Copernicus Publications 2019-07-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://www.atmos-chem-phys.net/19/9485/2019/acp-19-9485-2019.pdf

<p>Energetic particle precipitation (EPP) affects the chemistry of the polar middle atmosphere by producing reactive nitrogen (<span class="inline-formula">NO_<i>y</i></span>) and hydrogen (<span class="inline-formula">HO_<i>x</i></span>) species, which then catalytically destroy ozone. Recently, there have been major advances in constraining these particle impacts through a parametrization of <span class="inline-formula">NO_<i>y</i></span> based on high-quality observations. Here we investigate the effects of low (auroral) and middle (radiation belt) energy range electrons, separately and in combination, on reactive nitrogen and hydrogen species as well as on ozone during Southern Hemisphere winters from 2002 to 2010 using the SOCOL3-MPIOM chemistry-climate model. Our results show that, in the absence of solar proton events, low-energy electrons produce the majority of <span class="inline-formula">NO_<i>y</i></span> in the polar mesosphere and stratosphere. In the polar vortex, <span class="inline-formula">NO_<i>y</i></span> subsides and affects ozone at lower altitudes, down to 10&thinsp;hPa. Comparing a year with high electron precipitation with a quiescent period, we found large ozone depletion in the mesosphere; as the anomaly propagates downward, 15&thinsp;% less ozone is found in the stratosphere during winter, which is confirmed by satellite observations. Only with both low- and middle-energy electrons does our model reproduce the observed stratospheric ozone anomaly.</p>