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Ann. Geophys., 19, 1367-1398, 2001
www.ann-geophys.net/19/1367/2001/
© European Geosciences Union 2001
Coordinated ground-based, low altitude satellite and Cluster observations on global and local scales during a transient post-noon sector excursion of the magnetospheric cusp
H. J. Opgenoorth1,7, M. Lockwood2, D. Alcaydé3, E. Donovan4, M. J. Engebretson5, A. P. van Eyken6, K. Kauristie7, M. Lester8, J. Moen9, J. Waterman10, H. Alleyne11, M. André1, M. W. Dunlop12, N. Cornilleau-Wehrlin13, A. Masson14, A. Fazerkerley15, H. Rème3, R. André14, O. Amm7, A. Balogh12, R. Behlke1, P. L. Blelly3, H. Boholm6, E. Borälv1, J. M. Bosqued3, S. Buchert1, M. Candidi21, J. C. Cerisier16, C. Cully1,4, W. F. Denig26, P. Eglitis1, R. A. Greenwald17, B. Jackal4, J. D. Kelly18, I. Krauklis15, G. Lu19, I. R. Mann20, M. F. Marcucci21, I. W. McCrea2, M. Maksimovic13, S. Massetti21, P. M. E. Décréau27, D. K. Milling20, S. Orsini21, F. Pitout1,3, G. Provan8, J. M. Ruohoniemi17, J. C. Samson22, J. J. Schott23, F. Sedgemore-Schulthess24, R. Stamper2, P. Stauning10, A. Strømme25, M. Taylor15, A. Vaivads1, J. P. Villain14, I. Voronkov22, J. A. Wild8, and M. Wild2
1Swedish Institute of Space Physics, S-75121 Uppsala, Sweden
2Rutherford Appleton Lab., Dept. Space Sci., Didcot OX11 0QX, Oxon, UK
3CNRS, CESR, F-31028 Toulouse 04, France
4Univ. Calgary, Dept. Phys. & Astron., Calgary, AB T2N 1N4, Canada
5Augsburg Coll., Dept. Phys., Minneapolis, MN 55454 USA
6EISCAT Scientific Assoc., N-9171 Longyearbyen, Norway
7Finnish Meteorological Institute, FIN-00101 Helsinki, Finland
8University of Leicester, Dept. Phys. and Astron., Leicester LE1 7RH, UK
9University of Oslo, Dept. Phys., POB 1048, N-0316 Oslo, Norway
10Danish Meteorol. Inst., Lyngbyvej 100, DK-2100 Copenhagen, Denmark
11University of Sheffield, Sheffield S1 3JD, S Yorkshire, UK
12Imperial College, Blackett Lab., London SW7 2BZ, UK
13CETP, Centre Etud. Env. Terr. & Planetaires, F-78140 Velizy, France
14Space Science Division, ESTEC, Noordwijk, The Netherlands
15Univ. College, Mullard Space Sci. Lab., Dorking RH5 6NT, Surrey, UK
16CETP, F-94107 St. Maur, France
17Johns Hopkins Univ., Appl. Phys. Lab., Laurel, MD 20723, USA
18SRI International, Menlo Park, CA 94025 USA
19Natl. Ctr. Atmosph. Res., High Alt. Observ., Boulder, CO 80307, USA
20York University, Dept. Phys., York Y01 5DD, N Yorkshire, UK
21CNR, IFSI, Via Fosso Cavaliere 100, I-00133 Rome, Italy
22Univ. of Alberta, Dept. Phys., Edmonton, AB T6G 2J1, Canada
23EOST, Ecole & Observ. Sci. Terre, F-67084 Strasbourg, France
24DSRI, Danish Space Res. Inst., DK-2100 Copenhagen O, Denmark
25University of Tromsø, Dept. Phys., Tromsø, Norway Oslo, Norway
26AFRL, Boston, USA
27CNRS, Lab. Phys. & Chim. Environm., F-45071 Orleans, France
Abstract. On 14 January 2001, the
four Cluster spacecraft passed through the northern magnetospheric mantle in
close conjunction to the EISCAT Svalbard Radar (ESR) and approached the
post-noon dayside magnetopause over Green-land between 13:00 and 14:00 UT.
During that interval, a sudden reorganisation of the high-latitude dayside
convection pattern occurred after 13:20 UT, most likely caused by a direction
change of the Solar wind magnetic field. The result was an eastward and
poleward directed flow-channel, as monitored by the SuperDARN radar network and
also by arrays of ground-based magnetometers in Canada, Greenland and
Scandinavia. After an initial eastward and later poleward expansion of the
flow-channel between 13:20 and 13:40 UT, the four Cluster spacecraft, and the
field line footprints covered by the eastward looking scan cycle of the Söndre
Strömfjord incoherent scatter radar were engulfed by cusp-like precipitation
with transient magnetic and electric field signatures. In addition, the EISCAT
Svalbard Radar detected strong transient effects of the convection
reorganisation, a poleward moving precipitation, and a fast ion flow-channel in
association with the auroral structures that suddenly formed to the west and
north of the radar. From a detailed analysis of the coordinated Cluster and
ground-based data, it was found that this extraordinary transient convection
pattern, indeed, had moved the cusp precipitation from its former pre-noon
position into the late post-noon sector, allowing for the first and quite
unexpected encounter of the cusp by the Cluster spacecraft. Our findings
illustrate the large amplitude of cusp dynamics even in response to moderate
solar wind forcing. The global ground-based data proves to be an invaluable
tool to monitor the dynamics and width of the affected magnetospheric regions.
Key words. Magnetospheric cusp,
ionosphere, reconnection, convection flow-channel, Cluster, ground-based
observations
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