Three-Dimensional Energetic Ion Sounding of the Magnetopause Using Cluster/RAPID
K. Oksavik 1, T. A. Fritz 2, Q. G. Zong 2, F. Søraas 1, and B. Wilken 3*
1 Department of Physics, University of Bergen, Bergen, Norway
2 Center for Space Physics, Boston University, Boston, MA, USA
3 Max Planck Institut für Aeronomie, Katlenburg-Lindau, Germany
2002, Geophys. Res. Lett., 29 (9), doi:10.1029/2001GL014265.
We present new results using energetic particles to remotely sound the high-latitude magnetopause in three-dimensions. Less than two gyro radii away from an absorbing boundary a trapped particle distribution will get non-gyrotropic, as particles start to cross the boundary. Knowing the magnetic field and the particle mass and energy, it is possible to derive the direction and distance to the magnetopause just by examining the azimuthal distribution of locally mirroring particles. Combining observations from at least three spacecrafts gives a three-dimensional picture of the magnetopause surface. We have performed this analysis for a high-latitude boundary layer crossing on January 14, 2001. The very first results give a consistent overall picture of how the magnetopause boundary is coming torwards, just passing, and then retreating away from the spacecrafts. This clearly illustrates that the magnetopause ion sounding technique can be used to remotely study the three-dimensional orientation and location of the magnetopause surface.