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| Titel |
Relative brightness of the O+(2D-2P) doublets in low energy aurora |
| VerfasserIn |
D. K. Whiter, B. S. Lanchester, N. I. B. Jallo, B. Gustavsson, N. Ivchenko |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068055
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| Zusammenfassung |
| The ratio of the emission line doublets from O+ at 732.0Â nm (I732) and 733.0Â nm (I733) has
been measured in auroral conditions of low energy electron precipitation from Svalbard
(78.20° north, 15.83° east) during two winters between 2003 and 2006. The value
obtained for R = I732-I733 for the 2003–2004 season is 1.38 ± 0.02. This result is
slightly higher than theoretical values, and values obtained in airglow, but is lower
than earlier measurements in similar auroral conditions. Most of the data from
2003–2004 were from 06Â UT to 13Â UT, which straddles the time when Svalbard is under
the magnetospheric cusp region. The value obtained for the 2005–2006 season is
R = 1.45 ± 0.08. The data from this season have lower spectral resolution, and contain much
more scatter than those from the earlier season. Higher ratio values mostly occur
between 14Â UT and 17Â UT, when Svalbard is outside the cusp, and when more
energetic precipitation may dominate. One of the motivations of the work is the
need for accurate modelling of the emission doublet at 732.0Â nm. It is one of the
emissions measured by the Auroral Structure and Kinetics (ASK) instrument, which is
also located at Svalbard. Accurate determination of R = I732-I733 provides a
powerful method for separating the density of the upper 2P states, information which is
needed for ionospheric modelling of emissions. This work is especially relevant
for studies of plasma flows in the ionosphere utilising the long lifetime of the O+
emission. Although the present work is a statistical study, the work shows that it is
necessary to determine whether there are significant variations in the ratio resulting
from auroral energy deposition, large electric fields, and changes in composition. |
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