Articles | Volume 19, issue 10/12
Ann. Geophys., 19, 1367–1398, 2001

Special issue: CLUSTER

Ann. Geophys., 19, 1367–1398, 2001

  30 Sep 2001

30 Sep 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. Opgenoorth7,1, 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. Cully4,1, 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. Pitout3,1, 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 H. J. Opgenoorth et al.
  • 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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