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| Titel |
Towards a synthesis of substorm electrodynamics: HF radar and auroral observations |
| VerfasserIn |
A. Grocott, Mark Lester, M. L. Parkinson, T. K. Yeoman, P. L. Dyson, J. C. Devlin, H. U. Frey |
| 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 ; 24, no. 12 ; Nr. 24, no. 12 (2006-12-21), S.3365-3381 |
| Datensatznummer |
250015710
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| Publikation (Nr.) |
 copernicus.org/angeo-24-3365-2006.pdf |
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| Zusammenfassung |
| At 08:35 UT on 21 November 2004, the onset of an interval
of substorm activity was captured in the southern hemisphere by the Far
UltraViolet (FUV) instrument on board the IMAGE spacecraft. This was
accompanied by the onset of Pi2 activity and subsequent magnetic bays,
evident in ground magnetic data from both hemispheres. Further
intensifications were then observed in both the auroral and ground magnetic
data over the following ~3 h. During this interval the fields-of-view
of the two southern hemisphere Tasman International Geospace Enviroment
Radars (TIGER) moved through the evening sector towards midnight. Whilst
initially low, the amount of backscatter from TIGER increased considerably
during the early stages of the expansion phase such that by ~09:20 UT
an enhanced dusk flow cell was clearly evident. During the expansion phase
the equatorward portion of this flow cell developed into a narrow high-speed
flow channel, indicative of the auroral and sub-auroral flows identified in
previous studies (e.g. Freeman et al., 1992; Parkinson et al., 2003). At the
same time, higher latitude transient flow features were observed and as the
interval progressed the flow reversal region and Harang discontinuity became
very well defined. Overall, this study has enabled the spatial and temporal
development of many different elements of the substorm process to be
resolved and placed within a simple conceptual framework of magnetospheric
convection. Specifically, the detailed observations of ionospheric flows
have illustrated the complex interplay between substorm electric fields and
associated auroral dynamics. They have helped define the distinct nature of
different substorm current systems such as the traditional substorm current
wedge and the more equatorward currents associated with polarisation
electric fields. Additionally, they have revealed a radar signature of
nightside reconnection which provides the promise of quantifying nightside
reconnection in a way which has already proved extremely successful in
studies of the dayside magnetosphere. |
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