Resonance scattering by auroral N 2 + : steady state theory and observations from Svalbard
Studies of auroral energy input at high latitudes often depend on observations of emissions from the first negative band of ionised nitrogen. However, these emissions are affected by solar resonance scattering, which makes photometric and spectrographic measurements difficult to interpret. This work...
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ftdoajarticles:oai:doaj.org/article:049cce0271e842b1a8897bd65cc603d0 2023-05-15T17:08:31+02:00 Resonance scattering by auroral N 2 + : steady state theory and observations from Svalbard O. Jokiaho B. S. Lanchester N. Ivchenko 2009-09-01T00:00:00Z https://doi.org/10.5194/angeo-27-3465-2009 https://doaj.org/article/049cce0271e842b1a8897bd65cc603d0 EN eng Copernicus Publications https://www.ann-geophys.net/27/3465/2009/angeo-27-3465-2009.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-27-3465-2009 0992-7689 1432-0576 https://doaj.org/article/049cce0271e842b1a8897bd65cc603d0 Annales Geophysicae, Vol 27, Pp 3465-3478 (2009) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2009 ftdoajarticles https://doi.org/10.5194/angeo-27-3465-2009 2022-12-31T01:35:13Z Studies of auroral energy input at high latitudes often depend on observations of emissions from the first negative band of ionised nitrogen. However, these emissions are affected by solar resonance scattering, which makes photometric and spectrographic measurements difficult to interpret. This work is a statistical study from Longyearbyen, Svalbard, Norway, during the solar minimum between January and March 2007, providing a good coverage in shadow height position and precipitation conditions. The High Throughput Imaging Echelle Spectrograph (HiTIES) measured three bands of N 2 + 1N (0,1), (1,2) and (2,3), and one N 2 2P band (0,3) in the magnetic zenith. The brightness ratios of the N 2 + bands are compared with a theoretical treatment with excellent results. Balance equations for all important vibrational levels of the three lowest electronic states of the N 2 + molecule are solved for steady-state, and the results combined with ion chemistry modelling. Brightnesses of the (0,1), (1,2) and (2,3) bands of N 2 + 1N are calculated for a range of auroral electron energies, and different values of shadow heights. It is shown that in sunlit aurora, the brightness of the (0,1) band is enhanced, with the scattered contribution increasing with decreasing energy of precipitation (10-fold enhancements for energies of 100 eV). The higher vibrational bands are enhanced even more significantly. In sunlit aurora the observed 1N (1,2)/(0,1) and (2,3)/(0,1) ratios increase as a function of decreasing precipitation energy, as predicted by theory. In non-sunlit aurora the N 2 + species have a constant proportionality to neutral N 2 . The ratio of 2P(0,3)/1N(0,1) in the morning hours shows a pronounced decrease, indicating enhancement of N 2 + 1N emission. Finally we study the relationship of all emissions and their ratios to rotational temperatures. A clear effect is observed on rotational development of the bands. It is possible that greatly enhanced rotational temperatures may be a signature of ion upflows. Article in Journal/Newspaper Longyearbyen Svalbard Directory of Open Access Journals: DOAJ Articles Longyearbyen Norway Svalbard Annales Geophysicae 27 9 3465 3478 |
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Open Polar |
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Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
spellingShingle |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 O. Jokiaho B. S. Lanchester N. Ivchenko Resonance scattering by auroral N 2 + : steady state theory and observations from Svalbard |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
Studies of auroral energy input at high latitudes often depend on observations of emissions from the first negative band of ionised nitrogen. However, these emissions are affected by solar resonance scattering, which makes photometric and spectrographic measurements difficult to interpret. This work is a statistical study from Longyearbyen, Svalbard, Norway, during the solar minimum between January and March 2007, providing a good coverage in shadow height position and precipitation conditions. The High Throughput Imaging Echelle Spectrograph (HiTIES) measured three bands of N 2 + 1N (0,1), (1,2) and (2,3), and one N 2 2P band (0,3) in the magnetic zenith. The brightness ratios of the N 2 + bands are compared with a theoretical treatment with excellent results. Balance equations for all important vibrational levels of the three lowest electronic states of the N 2 + molecule are solved for steady-state, and the results combined with ion chemistry modelling. Brightnesses of the (0,1), (1,2) and (2,3) bands of N 2 + 1N are calculated for a range of auroral electron energies, and different values of shadow heights. It is shown that in sunlit aurora, the brightness of the (0,1) band is enhanced, with the scattered contribution increasing with decreasing energy of precipitation (10-fold enhancements for energies of 100 eV). The higher vibrational bands are enhanced even more significantly. In sunlit aurora the observed 1N (1,2)/(0,1) and (2,3)/(0,1) ratios increase as a function of decreasing precipitation energy, as predicted by theory. In non-sunlit aurora the N 2 + species have a constant proportionality to neutral N 2 . The ratio of 2P(0,3)/1N(0,1) in the morning hours shows a pronounced decrease, indicating enhancement of N 2 + 1N emission. Finally we study the relationship of all emissions and their ratios to rotational temperatures. A clear effect is observed on rotational development of the bands. It is possible that greatly enhanced rotational temperatures may be a signature of ion upflows. |
format |
Article in Journal/Newspaper |
author |
O. Jokiaho B. S. Lanchester N. Ivchenko |
author_facet |
O. Jokiaho B. S. Lanchester N. Ivchenko |
author_sort |
O. Jokiaho |
title |
Resonance scattering by auroral N 2 + : steady state theory and observations from Svalbard |
title_short |
Resonance scattering by auroral N 2 + : steady state theory and observations from Svalbard |
title_full |
Resonance scattering by auroral N 2 + : steady state theory and observations from Svalbard |
title_fullStr |
Resonance scattering by auroral N 2 + : steady state theory and observations from Svalbard |
title_full_unstemmed |
Resonance scattering by auroral N 2 + : steady state theory and observations from Svalbard |
title_sort |
resonance scattering by auroral n 2 + : steady state theory and observations from svalbard |
publisher |
Copernicus Publications |
publishDate |
2009 |
url |
https://doi.org/10.5194/angeo-27-3465-2009 https://doaj.org/article/049cce0271e842b1a8897bd65cc603d0 |
geographic |
Longyearbyen Norway Svalbard |
geographic_facet |
Longyearbyen Norway Svalbard |
genre |
Longyearbyen Svalbard |
genre_facet |
Longyearbyen Svalbard |
op_source |
Annales Geophysicae, Vol 27, Pp 3465-3478 (2009) |
op_relation |
https://www.ann-geophys.net/27/3465/2009/angeo-27-3465-2009.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-27-3465-2009 0992-7689 1432-0576 https://doaj.org/article/049cce0271e842b1a8897bd65cc603d0 |
op_doi |
https://doi.org/10.5194/angeo-27-3465-2009 |
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Annales Geophysicae |
container_volume |
27 |
container_issue |
9 |
container_start_page |
3465 |
op_container_end_page |
3478 |
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