HR: 17:00h
AN: SM32D-05    [PDF]
TI: Cluster Observations of the Flank Boundary Layer Under Northward IMF Conditions
AU: * Fairfield, D H
EM: Donald.H.Fairfield@nasa.gov
AF: Laboratory for Extratresstrial Physics, NASA/GSFC, Code 695 NASA/GSFC, Greenbelt, MD 20771 United States
AU: Balogh, A
AF: The Blacket Laboratory, Imperial College, London, SW7 2BZ United Kingdom
AU: Dunlop, M W
AF: Space Sciences Division, SSTD, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX United Kingdom
AU: Farrugia, C J
AF: Space Science Center, University of New Hampshire, Durham, NH 03824 United States
AU: Fazakerley, A N
AF: Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT United Kingdom
AU: Gratton, F T
AF: Instituto de Fisica del Plasma,CONICET and FCEyN, University of Buenos Aires, Buenos Aires, 1428 Argentina
AU: Kistler, L M
AF: Space Science Center, University of New Hampshire, Durham, NH 03824 United States
AU: Mouikis, C
AF: Space Science Center, University of New Hampshire, Durham, NH 03824 United States
AU: Owen, C J
AF: Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT United Kingdom
AU: Reme, H
AF: CESR, BP4346 31028, Toulouse Cedex, 4 France
AB: The four Cluster spacecraft made observations near the dusk flank boundary layer during a north-to-south passage at a location near X=-5 Re on November 20-21, 2001. The IMF remained quite steady and northward while a decreasing solar wind kinetic pressure moved the boundary outward and kept it near Cluster for almost 20 hours. Magnetic field and plasma measurements revealed repeated traversals between a higher-density tailward-flowing magnetosheath plasma with cool isotropic ~ 30 eV electrons and a lower density, lower-tailward-velocity boundary layer plasma with anisotropic field aligned electrons nearer 80 eV. Transitions from the boundary layer to the magnetosheath were characterized by rotations to a more northward external magnetic field. These outbound crossings were invariably better defined than those in the opposite direction. For these outbound crossings, boundary normals were determined from a minimum variance analysis on the magnetic field; these normals generally agreed within ~5 degrees at the 4 spacecraft and showed tilting of the normal toward the sunward direction as is typical for waves on the boundary. Individual transitions were seen successively at the four spacecraft with 5-20 s delays at spacecraft separation distances up to ~2000 km. The transitions back to the boundary layer occurred gradually over a period of several minutes until the next abrupt entry to the magnetosheath. This recurrence periodicity of a few minutes is that often seen for Kelvin-Helmholtz waves in this boundary region. Determinations of Kelvin-Helmholtz instability criteria will be compared with these observations.
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2748 Magnetotail boundary layers
DE: 2752 MHD waves and instabilities
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting