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| Titel |
Ionization and NO production in the polar mesosphere during high-speed solar wind streams: model validation and comparison with NO enhancements observed by Odin-SMR |
| VerfasserIn |
S. Kirkwood  , A. Osepian, E. Belova, J. Urban, K. Pérot, A. K. Sinha |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 33, no. 5 ; Nr. 33, no. 5 (2015-05-26), S.561-572 |
| Datensatznummer |
250121197
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| Publikation (Nr.) |
 copernicus.org/angeo-33-561-2015.pdf |
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| Zusammenfassung |
| Precipitation of high-energy electrons (EEP) into the polar middle atmosphere
is a potential source of significant production of odd nitrogen, which may
play a role in stratospheric ozone destruction and in perturbing large-scale
atmospheric circulation patterns. High-speed streams of solar wind (HSS) are
a major source of energization and precipitation of electrons from the
Earth's radiation belts, but it remains to be determined whether these
electrons make a significant contribution to the odd-nitrogen budget in the
middle atmosphere when compared to production by solar protons or by
lower-energy (auroral) electrons at higher altitudes, with subsequent
downward transport. Satellite observations of EEP are available, but their
accuracy is not well established. Studies of the ionization of the atmosphere
in response to EEP, in terms of cosmic-noise absorption (CNA), have
indicated an unexplained seasonal variation in HSS-related effects and have
suggested possible order-of-magnitude underestimates of the EEP fluxes by the
satellite observations in some circumstances. Here we use a model of
ionization by EEP coupled with an ion chemistry model to show that published
average EEP fluxes, during HSS events, from satellite measurements
(Meredith et al., 2011), are fully consistent with the published average CNA
response (Kavanagh
et al., 2012). The seasonal variation of CNA response
can be explained by ion chemistry with no need for any seasonal variation in
EEP. Average EEP fluxes are used to estimate production rate profiles of
nitric oxide between 60 and 100 km heights over Antarctica for a series of
unusually well separated HSS events in austral winter 2010. These are
compared to observations of changes in nitric oxide during the events, made
by the sub-millimetre microwave radiometer on the Odin spacecraft. The
observations show strong increases of nitric oxide amounts between 75 and 90 km heights, at all latitudes poleward of 60° S, about 10 days after the
arrival of the HSS. These are of the same order of magnitude but generally
larger than would be expected from direct production by HSS-associated EEP,
indicating that downward transport likely contributes in addition to direct
production. |
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