Belgian
Institute
for Space
Aeronomy
Wave observations on the Cluster II Spacecraft:
Probing Structure and Dynamics of the Magnetopause
Welcome to the home page of the Beligan Institute
for Space Aeronomy Cluster II project.
The
Belgian Institute for Space Aeronomy (Brussels, Belgium) has set
up the project Wave observations on the Cluster
II Spacecraft:Probing Structure and Dynamics of the
Magnetopause. In this framework the Institute's Space Physics
group participates in the experiment teams:
- WHISPER
PI is Dr. Pierrette Décréau (LPCE et
Université d'Orléans, Orléans, France)
BISA Co-Investigator: Dr. Joseph Lemaire
- STAFF
PI is Dr. Nicole Cornilleau-Wehrlin (CETP/UVSQ, Vélizy,
France)
BISA Co-Investigator: Dr. Michel Roth
The project will focus on the magnetopause region and its adjacent solar wind and magnetospheric plasmas. The magnetopause is the thin plasma layer that separates the solar wind plasma from the Earth's magnetic field. It is the locus where the plasma and magnetic pressure of the solar wind is in equilibrium with the magnetic and plasma pressure inside the magnetosphere. Due to a continuous variation of the solar wind pressure, this boundary moves continuously. Cluster, with its four-point measurements, will help to characterize this motion. Although to first order impermeable to the solar wind, the magnetopause lets some plasma from the solar wind enter the magnetosphere. Various processes have been proposed to account for this penetration of plasma, but there is still no consensus on their relative importance. Impulsive penetration of solar wind, first proposed by Lemaire and Roth is one of these processes aimed at explaining the penetration of solar wind plasma into the magnetosphere. The Cluster spacecraft will measure the three-dimensional size and motion of the structures observed at the magnetopause and will therefore make it possible to distinguish between the various mechanisms proposed to account for the penetration of the solar wind. The contribution of the WHISPER (Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation) wave experiment is its capability to measure simultaneously the absolute value of the total density in four points which are close to each other. To test the impulsive penetration scenario, WHISPER will provide more precise information about the structure and velocity of the plasmoids in the solar wind and magnetosheath region as well as during some low-latitude boundary-layer crossings planned at the flanks of the magnetosphere. In addition, correlated multi-satellite and ground-based observations will be needed.
The objective of the STAFF (Spatio-Temporal Analysis of Field Fluctuations) wave experiment is to assess the role that plasma waves play in affecting and controlling the physical processes by which mass and momentum are transferred through the magnetopause, from the solar wind to the magnetosphere. Many experiments aboard single spacecraft have shown that a very high level of fluctuations is observed in all frequency ranges during magnetopause crossings. The question of the origin of these fluctuations has seldom been addressed in the literature. Two different hypotheses are generally considered: either they are due to local instabilities of the current layer, or they are generated in the magnetosheath and are amplified at the magnetopause. Modeling the plasma wave distribution in the vicinity of the magnetopause will help to test the first hypothesis.
The research at the Belgian Institute for Space Aeronomy
is funded by PRODEX. We acknowledge the support of the Belgian Federal
Office for Science and Technology Policy.
Magnetospheric
research at the Belgian Institute for Space Aeronomy
Solar wind - magnetosphere interaction
Space
Physics research at the Belgian Institute for Space Aeronomy
Related
sites
Staff
Cluster Workshop 2001 : Remote sensing of magnetopause motion on 2001 April 23 (powerpoint)
Author: J. De Keyser and M. Roth Curator: J. De Keyser Johan.DeKeyser@oma.be
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