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| Titel |
Are there optical differences between storm-time substorms and isolated substorms? |
| VerfasserIn |
R. A. Hoffman, J. W. Gjerloev, L. A. Frank, J. W. Sigwarth |
| 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. 5 ; Nr. 28, no. 5 (2010-05-28), S.1183-1198 |
| Datensatznummer |
250016836
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| Publikation (Nr.) |
 copernicus.org/angeo-28-1183-2010.pdf |
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| Zusammenfassung |
We have performed an extensive analysis of auroral optical events
(substorms) that occurred during the development of the main phase of
magnetic storms. Using images from the Earth Camera on the Polar spacecraft
(Frank et al., 1995), we compared the optical emission features of substorms
occurring during 16 expansion phases of magnetic storms with the features of
isolated substorms occurring during non-storm times. The comparison used two
techniques, visual inspection and statistical comparisons. The comparisons
were based on the common characteristics seen in isolated substorms that
were initially identified by Akasofu (1964) and quantified by Gjerloev et
al. (2008). We find that when auroral activity does occur during main phase
development the characteristics of the aurora are very dissimilar to those
of the classical isolated substorm. The primary differences include the lack
of a surge/bulge, lack of bifurcation of the aurora, much shorter expansion
phases, and greater intensities.
Since a surge/bulge and bifurcation of the aurora are characteristics of the
existence of a substorm current wedge, a key component of the
magnetosphere-ionosphere current system during substorms, the lack of this
component would indicate that the classical substorm model does not apply to
the storm time magnetosphere-ionosphere current system. Rather several of
the analyses suggest that the storm-time substorms are associated more
closely with the auroral oval, at least spatially, and, therefore, probably
with the plasma sheet dynamics during the main phase development. These
results then must call into question the widely held assumption that there
is no intrinsic difference between storm-time substorms and classical
isolated substorms. |
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