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Ann. Geophys., 24, 1737-1758, 2006
www.ann-geophys.net/24/1737/2006/
© European Geosciences Union 2006
Analysis of plasmaspheric plumes: CLUSTER and IMAGE observations
F. Darrouzet1, J. De Keyser1, P. M. E. Décréau2, D. L. Gallagher3, V. Pierrard1, J. F. Lemaire1,4, B. R. Sandel5, I. Dandouras6, H. Matsui7, M. Dunlop8, J. Cabrera4, A. Masson9, P. Canu10, J. G. Trotignon2, J. L. Rauch2, and M. André11
1Belgian Institute for Space Aeronomy (IASB-BIRA), Brussels, Belgium
2Laboratoire de Physique et Chimie de l’Environnement (LPCE), CNRS and University of Orléans, Orléans, France
3Marshall Space Flight Center (MSFC), NASA, Huntsville, Alabama, USA
4Center for Space Radiation (CSR), Louvain la Neuve, Belgium
5Lunar and Planetary Laboratory (LPL), University of Arizona, Tucson, Arizona, USA
6Centre d’Etude Spatiale des Rayonnements (CESR), CNRS, Toulouse, France
7Space Science Center (SSC), University of New Hampshire, Durham, New Hampshire, USA
8Space Sciences Division (SSTD), Rutherford Appleton Laboratory (RAL), Chilton, Didcot, Oxfordshire, UK
9Research and Scientific Support Department (RSSD), ESTEC-ESA, Noordwijk, The Netherlands
10Centre d’étude des Environnements Terrestre et Planétaires (CETP), CNRS, Vélizy, France
11Swedish Institute of Space Physics (IRFU), Uppsala division, Uppsala, Sweden
Abstract. Plasmaspheric plumes have been routinely observed by CLUSTER and IMAGE. The
CLUSTER mission provides high time resolution four-point measurements of the
plasmasphere near perigee. Total electron density profiles have been derived
from the electron plasma frequency identified by the WHISPER sounder
supplemented, in-between soundings, by relative variations of the spacecraft
potential measured by the electric field instrument EFW; ion velocity is
also measured onboard these satellites. The EUV imager onboard the IMAGE
spacecraft provides global images of the plasmasphere with a spatial
resolution of 0.1 RE every 10 min; such images acquired near apogee
from high above the pole show the geometry of plasmaspheric plumes, their
evolution and motion. We present coordinated observations of three plume
events and compare CLUSTER in-situ data with global images of the
plasmasphere obtained by IMAGE. In particular, we study the geometry and the
orientation of plasmaspheric plumes by using four-point analysis methods. We
compare several aspects of plume motion as determined by different methods:
(i) inner and outer plume boundary velocity calculated from time delays of
this boundary as observed by the wave experiment WHISPER on the four
spacecraft, (ii) drift velocity measured by the electron drift instrument
EDI onboard CLUSTER and (iii) global velocity determined from successive EUV
images. These different techniques consistently indicate that plasmaspheric
plumes rotate around the Earth, with their foot fully co-rotating, but with
their tip rotating slower and moving farther out.
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