HR: 09:00h
AN: SM51C-05    [Abstracts]
TI: Motion of Solar Wind Ions in an Analytical Field-Line Model of the Magnetosheath
AU: * Chen, M W
EM: mchen@aero.org
AF: The Aerospace Corporation, P. O. Box 2957, M2-260, Los Angeles, CA 90009-2957, United States
AU: Schulz, M
EM: mike.schulz@lmco.com
AF: Lockheed Martin Advanced Technology Center, Dept. ADCS, B/255, 3251 Hanover Street, Palo Alto, CA 94304, United States
AU: Lemon, C L
EM: colby.lemon@aero.org
AF: The Aerospace Corporation, P. O. Box 2957, M2-260, Los Angeles, CA 90009-2957, United States
AU: McNab, M C
EM: michael.c.mcnab
AF: The Aerospace Corporation, P. O. Box 2957, M2-260, Los Angeles, CA 90009-2957, United States
AB: To investigate the transport of representative solar-wind ions within the Earth's magnetosheath, we trace their trajectories in an analytical model of the magnetosheath, based on the draping of plasma streamlines and magnetic field lines around a conducting magnetosphere that consists of a prolate ellipsoid, extending ~ 11 R_E upstream and ~ 65 R_E downstream from Earth, matched to a cylinder of radius ~ 28.4 R_E. The bow shock is well represented in our model by an axisymmetric paraboloid that intersects the Sun-Earth line about 26% farther upstream from the point dipole than the nose of the magnetopause does. For a uniform but arbitrarily directed interplanetary magnetic field (IMF), the magnetosheath magnetic field can be obtained by superposition of results for special cases in which the IMF is respectively parallel to and perpendicular to the solar-wind velocity. In this study we consider only the simplest case, in which the interplanetary magnetic field (IMF) is parallel to the solar-wind velocity. Under this condition magnetosheath magnetic-field lines are the same as plasma streamlines, and the magnetosheath magnetic field is derivable from Euler potentials. We express the magnetosheath magnetic field analytically as a function of ellipsoidal or cylindrical coordinates that scale inversely with the sixth root of solar-wind pressure, and we qualitatively compare the resulting field lines and streamlines with those obtained by Spreiter and Alksne [Rev. Geophys., 7, 11-50, 1969] from their hydrodynamic calculation. As an application of our analytical model magnetosheath, we trace the motion (gyration and gradient-curvature drift) of representative solar-wind ions through it. (There is no interplanetary or magnetosheath electric field for IMF purely in the B_x direction.) We identify regions in which the first adiabatic invariant breaks down for ions of various energies. This study constitutes a first step toward understanding the motion of solar-wind ions through the magnetosheath and their penetration into the magnetosphere for more general IMF configurations.
DE: 2728 Magnetosheath
DE: 2731 Magnetosphere: outer
DE: 2753 Numerical modeling
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly