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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L11107, doi:10.1029/2005GL025460, 2006

Response of the mid-altitude cusp to rapid rotations of the IMF

F. Pitout

Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany


C. P. Escoubet

European Space Agency, Noordwijk, Netherlands


Y. V. Bogdanova

Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking, Surrey, UK


E. Georgescu

Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany


A. N. Fazakerley

Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking, Surrey, UK


H. Rème

Centre d'Études Spatiales des Rayonnements, Toulouse, France


Abstract

On 12 August 2003, the four Cluster spacecraft crossed the mid-altitude cusp one after the other a minute or two apart. Shortly after the cusp crossing, two of the Cluster observed three structures poleward of the cusp that appeared and grew in successive satellite passes. In these structures, high fluxes of low-energy magnetosheath-like ions and electrons are observed. The analysis of particle and magnetic field data reveals that it is the cusp region that moved back and forth over the spacecraft. We show that the cusp reacts extremely fast to rotations of the interplanetary magnetic field (IMF) and that each of the three northward turnings of the IMF is accompanied by a poleward displacement of the cusp. The latitudinal component of the cusp velocity at ∼5 Re altitude is estimated to be of the order of 30 km/s.

Received 12 December 2005; accepted 28 March 2006; published 10 June 2006.

Index Terms: 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions; 2740 Magnetospheric Physics: Magnetospheric configuration and dynamics; 2706 Magnetospheric Physics: Cusp.

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Citation: Pitout, F., C. P. Escoubet, Y. V. Bogdanova, E. Georgescu, A. N. Fazakerley, and H. Rème (2006), Response of the mid-altitude cusp to rapid rotations of the IMF, Geophys. Res. Lett., 33, L11107, doi:10.1029/2005GL025460.