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| Titel |
Pulsed flows at the high-altitude cusp poleward boundary, and associated ionospheric convection and particle signatures, during a Cluster - FAST - SuperDARN- Søndrestrøm conjunction under a southwest IMF |
| VerfasserIn |
C. J. Farrugia, E. J. Lund, P. E. Sandholt, J. A. Wild, S. W. H. Cowley, A. Balogh, C. Mouikis, E. Möbius, M. W. Dunlop, J.-M. Bosqued, C. W. Carlson, G. K. Parks, J.-C. Cerisier, J. D. Kelly, J.-A. Sauvaud, H. Rème |
| 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 ; 22, no. 8 ; Nr. 22, no. 8 (2004-09-07), S.2891-2905 |
| Datensatznummer |
250014973
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| Publikation (Nr.) |
 copernicus.org/angeo-22-2891-2004.pdf |
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| Zusammenfassung |
| Particle and magnetic field observations during a
magnetic conjunction Cluster 1-FAST-Søndrestrøm within the field of view
of SuperDARN radars on 21 January 2001
allow us to draw a detailed, comprehensive and self-consistent picture at
three heights of signatures
associated with transient reconnection under a steady south-westerly
IMF (clock angle ≈130°).
Cluster 1 was outbound through the high altitude (~12RE) exterior northern cusp
tailward of the bifurcation line (geomagnetic Bx>0)
when a solar wind dynamic pressure release
shifted the spacecraft into a boundary layer
downstream of the cusp.
The centerpiece of the investigation is a series of flow bursts observed
there by the spacecraft, which were accompanied by strong
field perturbations and tailward flow deflections.
Analysis shows these to be Alfvén waves.
We interpret these flow events as being due to a sequence
of reconnected flux tubes,
with field-aligned currents
in the associated Alfvén waves carrying stresses
to the underlying ionosphere, a
view strengthened by the other observations.
At the magnetic footprint of the region of Cluster flow bursts,
FAST observed an ion energy-latitude
disperison of the stepped cusp type, with individual cusp ion steps corresponding to
individual flow bursts. Simultaneously, the SuperDARN Stokkseyri radar
observed very strong poleward-moving radar auroral forms
(PMRAFs)
which were conjugate to the flow bursts at Cluster.
FAST was traversing these PMRAFs when it observed the cusp ion
steps.
The Søndrestrøm radar observed pulsed ionospheric flows
(PIFs)
just poleward of the convection reversal boundary. As at Cluster, the flow was
eastward (tailward), implying a coherent
eastward (tailward) motion of the hypothesized open flux tubes.
The joint Søndrestrøm and FAST observations indicate that the
open/closed field line boundary was equatorward of the
convection reversal boundary by ~2°.
The unprecedented accuracy of the conjunction argues strongly for
the validity of the interpretation of the various
signatures as resulting from
transient reconnection. In particular, the cusp ion steps arise
on this
pass from this origin, in consonance with the original pulsating cusp
model. The observations point to the need of extending current
ideas on the response of the ionosphere to transient reconnection. Specifically,
it argues in favor of re-establishing the high-latitude boundary layer
downstream of the cusp as an active site
of momentum transfer. |
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