Stratosphere NO y Species Measured by MIPAS and GOMOS Onboard ENVISAT During 2002–2010: Influence of Plasma Processes onto the Observed Distribution and Variability

Abstract

We present observations of stratosphere NO y species from 2002 to 2010 taken by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and by the Global Ozone Monitoring by Occultation of Stars (GOMOS) instruments on board ENVISAT. We jointly used observations of MIPAS NO2, HNO3, N2O5, ClONO2 and N2O, and GOMOS NO2 and NO3. MIPAS results are part of the MIPAS2D database retrieved adopting a full 2D tomographic approach. We describe the mean distribution and variability of NO y species in the stratosphere, identifying changes induced by plasma processes. Beside enhancements due to sporadic solar proton events, we show that winter polar NO2 has an almost linear relationship with the geomagnetic activity index Ap down to about 10 hPa. This indicates a dominant role of energetic precipitating particles in the production of upper atmosphere NO y . The correlation has clear signatures extending to mid latitudes. Partitioning of the NO y reservoir species are also traced, with HNO3 and N2O5 showing a correlation with Ap extending to lower altitude within the polar regions. We found no large signatures of an impact of thunderstorm-induced plasma processes onto monthly means of NO y species in the stratosphere.