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Ann. Geophys., 21, 2031-2041, 2003
www.ann-geophys.net/21/2031/2003/
© European Geosciences Union 2003
Cusp structures: combining multi-spacecraft observations with ground-based observations
K. J. Trattner1,3, S. A. Fuselier1, T. K. Yeoman2, A. Korth3, M. Fraenz3, C. Mouikis4, H. Kucharek4, L. M. Kistler4, C. P. Escoubet5, H. R` eme6, I. Dandouras6, J. A. Sauvaud6, J. M. Bosqued6, B. Klecker7, C. Carlson8, T. Phan8, J. P. McFadden8, E. Amata9, and L. Eliasson10
1Lockheed-Martin Advanced Technology Center, Palo Alto, California, USA
2Department of Physics and Astronomy, University of Leicester, UK
3Max-Planck-Institut für Aeronomie, Katlenburg-Lindau, Germany
4Institute for Study of Earth, Oceans and Space, University of New Hampshire, Durham, USA
5Space Science Deptment of ESA. ESTEC, Noordwijk, The Netherlands
6CESR, Toulouse, France
7Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
8University of California, Berkeley, CA, USA
9IFSI, Rome, Italy
10IRF, Kiruna, Sweden
Abstract. Recent simultaneous
observations of cusp structures with Polar, FAST and Interball revealed
remarkably similar features at spacecraft crossing the cusp. Such stable cusp
structures could be observed up to several hours only during stable solar wind
conditions. Their similarities led to the conclusion that for such conditions
large-scale cusp structures are spatial structures related to a global
ionospheric convection pattern and not the result of temporal variations in
reconnection parameters. With the launch of the Cluster fleet we are now able
to observe precipitating ion structures in the cusp with three spacecraft and
identical instrumentation. The orbit configuration of the Cluster spacecraft
allows for delay times between spacecraft of about 45 min in crossing the cusp.
The compact configuration of three spacecraft at about the same altitude allows
for the analysis of cusp structures in great de-tail and during changing solar
wind conditions. Cluster observations on 25 July 2001 are combined with
SuperDARN radar observations that are used to derive a convection pattern in
the ionosphere. We found that large-scale cusp structures for this Cluster cusp
crossing are in agreement with structures in the convection pattern and
conclude that major cusp structures can be consistent with a spatial
phenomenon.
Key words. Magnetospheric physics
(energetic particles, precipitating, magnetopause, cusp arid and boundary
layers; solar wind-magnetosphere interactions)
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