Observed effects of solar proton events and sudden stratospheric warmings on odd nitrogen and ozone in the polar middle atmosphere

Abstract

Here we use satellite observations from the ACE-FTS, MLS/Aura and SABER/TIMED to study the effects of solar proton events (SPEs) and strong sudden stratospheric warmings (SSWs) on the middle atmospheric odd nitrogen (NO x) and ozone levels in the Northern Hemispheric polar region. Three winters (January-March) are considered: (1) 2005 (SPE), (2) 2009 (SSW), and (3) 2012 (SPEs and SSW). These different cases provide a good opportunity to study the roles that transport from the mesosphere-lower thermosphere region and in situ production due to particle precipitation have on stratospheric NO x levels and the consequent effects on the middle atmospheric ozone. The observations show increases in NO x after both the SPEs (days to weeks) and SSWs (weeks to months) by up to a factor of 25 between 40 and 90 km. The largest mesospheric NO x increases are observed following the SSW in late January 2009, but the most substantial effects in the upper stratosphere are seen when both an SSW and in situ production by SPEs take place (2012), even though the in situ NO x production in 2012 was relatively weak in magnitude compared to periods of much higher solar activity. In 2012, both short-term (days, due to SPEs and odd hydrogen) depletion and longer-term (months, due to several drivers) depletion of ozone of up to 90% are observed in the mesosphere and upper stratosphere, coinciding with the enhanced amounts of NO x. Key Points Middle atmospheric composition significantly affected by SPEs and major SSWs NOx increases by a factor of 1-25 between 40-90km after both types of events SPEs enhanced the effects of major SSWs on middle atmosphere chemistry © 2013. American Geophysical Union. All Rights Reserved.