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| Titel |
The pulsed nature of the nightside contribution to polar cap convection: repetitive substorm activity under steady interplanetary driving |
| VerfasserIn |
P. E. Sandholt, Y. L. Andalsvik, C. J. Farrugia |
| 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 ; 30, no. 10 ; Nr. 30, no. 10 (2012-10-12), S.1539-1553 |
| Datensatznummer |
250017282
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| Publikation (Nr.) |
 copernicus.org/angeo-30-1539-2012.pdf |
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| Zusammenfassung |
| The aim of this study is to
investigate the relative contributions of
dayside and nightside processes to
the spatial and temporal structure of polar cap
plasma convection. The central parameter is the cross-polar cap potential
(CPCP). Selecting a 10-h-long interval of stable
interplanetary driving by an interplanetary CME (ICME),
we are able to distinguish between the dayside and nightside
sources of the convection. The event was initiated by
an abrupt enhancement of the magnetopause (MP) reconnection rate
triggered by a southward turning of the ICME magnetic field.
This was followed by a long interval (10 h) of steady
and strong driving. Under the latter condition a long series of
electrojet intensifications
was observed which recurred at 50 min intervals.
The detailed temporal structure of polar cap convection in
relation to polar cap contraction events
is obtained by combining continuous
ground observations of convection-related magnetic
deflections (including polar cap magnetic indices
in the Northern and Southern Hemispheres, PCN and PCS)
and the more direct, but lower-resolution ion drift data
obtained from a satellite (DMSP F13) in polar orbit.
The observed PCN enhancements combined with DMSP satellite observations
(F13 and F15 data) of polar cap contractions during the evolution of selected
substorm expansions allowed us to estimate the
CPCP enhancements (25%)
associated with individual events in the series.
Ground-satellite conjunctions are further
used to investigate the spatial structure of polar cap convection,
i.e., the homogeneous plasma flow in the centre (Vi ≤ 1 km s−1) versus
channels of enhanced antisunward flows (Vi ≥ 1 km s−1)
along the periphery of the polar cap. We emphasise the
temporal structure of these polar cap flow phenomena
in relation to the prevailing solar wind forcing
and the repetitive substorm activity. |
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