Impact of different energies of precipitating particles on NO sub(x) generation in the middle and upper atmosphere during geomagnetic storms

• Published in: Journal of atmospheric and solar-terrestrial physics 2009-07, Vol.71 (10-11), p.1176-1189
• Main Authors: Turunen, E, Verronen, P T, Seppala, A, Rodger, C J, Clilverd, MA, Tamminen, J, Enell, C F, Ulich, T
• Format: Article
• Language: English
• ISSN: 1364-6826
• DOI: 10.1016/j.jastp.2008.07.005

Energetic particle precipitation couples the solar wind to the Earth's atmosphere and indirectly to Earth's climate. Ionisation and dissociation increases, due to particle precipitation, create odd nitrogen (NO sub(x)) and odd hydrogen (HO sub(X)) in the upper atmosphere, which can affect ozone chemistry. The long-lived NO sub(x) can be transported downwards into the stratosphere, particularly during the polar winter. Thus, the impact of NO sub(x) is determined by both the initial ionisation production, which is a function of the particle flux and energy spectrum, as well as transport rates. In this paper, we use the Sodankyla Ion and Neurtal Chemistry (SIC) model to simulate the production of NO sub(x) from examples of the most representative particle flux and energy spectra available today of solar proton events (SPE), auroral energy electrons, and relativistic electron precipitation (REP). Large SPEs are found to produce higher initial NO sub(x) concentrations than long-lived REP events, which themselves produce higher initial NO sub(x) levels than auroral electron precipitation. Only REP microburst events were found to be insignificant in terms of generating NO sub(x). We show that the Global Ozone Monitoring by Occultation of Stars (GOMOS) observations from the Arctic winter 2003-2004 are consistent with NO sub(x) generation by a combination of SPE, auroral altitude precipitation, and long-lived REP events.