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| Titel |
Estimating the location of the open-closed magnetic field line boundary from auroral images |
| VerfasserIn |
N. Longden, G. Chisham, M. P. Freeman, G. A. Abel, T. Sotirelis |
| 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 ; 28, no. 9 ; Nr. 28, no. 9 (2010-09-10), S.1659-1678 |
| Datensatznummer |
250016879
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| Publikation (Nr.) |
 copernicus.org/angeo-28-1659-2010.pdf |
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| Zusammenfassung |
| The open-closed magnetic field line boundary (OCB) delimits the region of
open magnetic flux forming the polar cap in the Earth's ionosphere. We
present a reliable, automated method for determining the location of the
poleward auroral luminosity boundary (PALB) from far ultraviolet (FUV) images
of the aurora, which we use as a proxy for the OCB. This technique models
latitudinal profiles of auroral luminosity as both a single and double
Gaussian function with a quadratic background to produce estimates of the
PALB without prior knowledge of the level of auroral activity or of the
presence of bifurcation in the auroral oval. We have applied this technique
to FUV images recorded by the IMAGE satellite from May 2000 until August 2002
to produce a database of over a million PALB location estimates, which is
freely available to download. From this database, we assess and illustrate
the accuracy and reliability of this technique during varying geomagnetic
conditions. We find that up to 35% of our PALB estimates are made from
double Gaussian fits to latitudinal intensity profiles, in preference to
single Gaussian fits, in nightside magnetic local time (MLT) sectors. The
accuracy of our PALBs as a proxy for the location of the OCB is evaluated by
comparison with particle precipitation boundary (PPB) proxies from the DMSP
satellites. We demonstrate the value of this technique in estimating the
total rate of magnetic reconnection from the time variation of the polar cap
area calculated from our OCB estimates. |
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