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Ann. Geophys., 19, 1641-1653, 2001
www.ann-geophys.net/19/1641/2001/
© European Geosciences Union 2001
Observations of the cusp region under northward IMF
F. Pitout1,2, J.-M. Bosqued2, D. Alcaydé2, W. F. Denig3, and H. Rème2
1Swedish Institute of Space Physics, Box 537, 751 21 Uppsala, Sweden
2Centre d’Etude Spatiale des Rayonnements, 9 avenue du Colonel Roche, F-31028 Toulouse Cedex 4, France
3Air Force Research Laboratory, Space Vehicles Directorate, Hanscom AFB, Massachusetts, USA
Abstract. We present a comparative
study of the cusp region using the EISCAT Svalbard Radars (ESR) and the Cluster
spacecraft. We focus in this paper on 2 February 2001, over the time period
from 07:30 UT to 12:00 UT when the oblique ESR antenna pointing northward at a
low elevation recorded latitudinal motions of the cusp region in response to
the IMF. Meanwhile, the Cluster satellites were flying over the EISCAT Svalbard
Radar field-of-view around local magnetic noon. The spacecraft first flew near
ESR, northeast of Svalbard and then passed over the field-of-view of the
antenna at about 11:30 UT. From 08:00 UT to 09:00 UT, the IMF remains primarily
southward yet several variations in the Z-component are seen to move the
cusp. Around 09:00 UT, an abrupt northward turning of the IMF moves the cusp
region to higher latitudes. As a result, the Cluster satellites ended up in the
northernmost boundary of the high-altitude cusp region where the CIS instrument
recorded highly structured plasma due to ion injections in the lobe of the
magnetosphere. After 09:00 UT, the IMF remains northward for more than two
hours. Over this period, the ESR records sunward plasma flow in the cusp region
due to lobe reconnection, while Cluster spacecraft remain in the high-altitude
cusp.
Key words. Magnetospheric physics
(magnetopause, cusp, and boundary layers; plasma convection) Ionosphere (polar
ionosphere)
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