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

Opgenoorth, H. J. and Lockwood, M. and Alcaydé, D. and Donovan, E. and Engebretson, M. J. and van Eyken, A. P. and Kauristie, K. and Lester, M. and Moen, J. and Watermann, J. and Alleyne, H. and André, M. and Dunlop, M. W. and Cornilleau-Wehrlin, N. and Masson, A. and Fazerkerley, A. and Rème, H. and André, R. and Amm, O. and Balogh, A. and Behlke, R. and Blelly, P. L. and Boholm, H. and Borälv, E. and Bosqued, J. M. and Buchert, S. and Candidi, M. and Cerisier, J. C. and Cully, C. and Denig, W. F. and Eglitis, P. and Greenwald, R. A. and Jackal, B. and Kelly, J. D. and Krauklis, I. and Lu, G. and Mann, I. R. and Marcucci, M. F. and McCrea, I. W. and Maksimovic, M. and Massetti, S. and Décréau, P. M. E. and Milling, D. K. and Orsini, S. and Pitout, F. and Provan, G. and Ruohoniemi, J. M. and Samson, J. C. and Schott, J. J. and Sedgemore-Schulthess, F. and Stamper, R. and Stauning, P. and Strömme, A. and Taylor, M. and Vaivads, A. and Villain, J. P. and Voronkov, I. and Wild, J. A. and Wild, M. (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. Annales Geophysicae, 19 (10-12). pp. 1367-1398. ISSN 0992-7689

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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 Greenland between 13:00 and 14:00 UT. During that interval, a sudden reorganisation of the high-latitude dayside convection pattern accurred 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 Sondre Stromfjord 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.