Abstract
Abstract. Energetic particle precipitation (EPP) affects the chemistry of the polar middle atmosphere by producing reactive nitrogen (NOy) and hydrogen (HOx) species, which then catalytically destroy ozone. Recently, there have been major advances in constraining these particle impacts through a parametrization of NOy 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 NOy in the polar mesosphere and stratosphere. In the polar vortex, NOy subsides and affects ozone at lower altitudes, down to 10 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 % 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.
Highlights
Energetic particles originating from the Sun, the magnetosphere, or outside the solar system continuously precipitate into the Earth’s atmosphere and can influence atmospheric processes
Ionization by solar protons (SP) is treated according to Jackman et al (2008) and ionization by middle-energy electrons (MEE) with energies between 30 and 300 keV is taken from the Atmospheric Ionization Module Osnabrück (AIMOS) v1.6 (Arsenovic et al, 2016; Wissing and Kallenrode, 2009)
Our results indicate that low-energy electrons (LEE) and MEE are responsible for the ozone anomaly in the mesosphere
Summary
Energetic particles originating from the Sun, the magnetosphere, or outside the solar system continuously precipitate into the Earth’s atmosphere and can influence atmospheric processes They ionize neutral air molecules, especially in the middle and upper polar atmosphere, and create odd nitrogen and hydrogen species, NOx ([N] + [NO] + [NO2]) and HOx ([H] + [OH] + [HO2]). Electrons of lower energies (< 30 keV, auroral) originate from the magnetosphere as well as the radiation belt electrons (Mironova et al, 2015), but they get accelerated in the magnetotail and precipitate into the lower thermosphere in the auroral ovals (55–70◦ geomagnetic latitude) (Baker et al, 2001; Barth et al, 2003) Their peak impact is above 90 km in the thermosphere (Turunen et al, 2009)
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