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| Titel |
What can we tell about global auroral-electrojet activity from a single meridional magnetometer chain? |
| VerfasserIn |
K. Kauristie, T. I. Pulkkinen, R. J. Pellinen, H. J. Opgenoorth |
| 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 ; 14, no. 11 ; Nr. 14, no. 11, S.1177-1185 |
| Datensatznummer |
250012469
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| Publikation (Nr.) |
 copernicus.org/angeo-14-1177-1996.pdf |
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| Zusammenfassung |
| The AE indices are generally used for
monitoring the level of magnetic activity in the auroral oval region. In some
cases, however, the oval is either so expanded or contracted that the
latitudinal coverage of the AE magnetometer chain is not adequate. Then,
a longitudinal chain in the key region would give more information of the real
situation, but, of course, only during some limited UT-period. In order to find
out the UT coverage of a single meridional chain, we have compared the global AL
and AU indices with corresponding local indices determined using data
from the meridional part of the EISCAT Magnetometer Cross during the years
1985–1987. A statistical study shows that the local indices are close (within
relative error of 0.2) to the global AU and AL during periods
1500–2000 UT (~1730–2230 MLT) and 2130–0130 UT (~0000–0400 MLT), respectively.
In the middle of these optimal MLT-sectors the EISCAT Cross sees more than 70%
of the cases when the global AE chain records activity. Then, also the
correlation between the local and global indices is generally good (>0.7).
Thus we conclude that five to six evenly located meridional chains are needed
for covering all the UT-periods. On the other hand, already the combination of
IMAGE, CANOPUS, and the Greenland chains catches ~50% of the substorms.
Case-studies show that usually during 2130–1100 UT the AL achieved from
these chains reproduces the real AL with good timing, although it does
not follow all transient variations. |
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