HR: 0830h
AN: SM31C-1117    [PDF]
TI: The Effects of the IMF Bx Component on the Earth's Magnetosphere
AU: * Ogino, T
EM: ogino@stelab.nagoya-u.ac.jp
AF: Solar-Terrestrial Environment Laboratory, Nagoya University, 3-13 Honohara, Toyokawa, Aic 442-8507 Japan
AU: Walker, R J
EM: rwalker@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Hilgard Ave., Los Angeles, CA 90095-1567 United States
AB: We have used a 3-dimensional global magnetohydrodynamic (MHD) simulation of the interaction between the solar wind and the magnetosphere to study the effects of the IMF Bx component on magnetospheric structure and dynamics. In the upstream solar wind, we assumed that the IMF field lines are in the plane of the Parker spiral which is inclined by 45 degrees to the y-z plane. We found that including an IMF Bx component in the simulation creates transient phenomenon with dawn-dusk and north-south asymmetry in the earth's magnetosphere and that the asymmetric structure is maintained even when the magnetosphere reaches a quasi-steady state. The asymmetries persist when Bx is small. The asymmetric structure in the magnetosheath and magnetosphere is enhanced when the IMF is large and the Alfven Mach number becomes small ($<$2). Since the IMF grows at the expense of the flow across the bow shock the flow is easily influenced by the IMF asymmetry in the magnetosheath. The existence of the IMF Bx component as well as the IMF By and Bz components precludes any symmetry in the magnetospheric structure. Thus an asymmetric configuration appears in the magnetosphere and this tendency is enhanced for strong IMF. For non-zero IMF Bx magnetopause magnetic reconnection occurs differently on the dawn and dusk sides. IMF lines on the dusk side are straighter than those on the dawn side. This increases the magnetic pressure and pushes the plasma sheet toward dawn. On the other hand, the IMF lines on the dawn side are bent sharply. This decreases the magnetic pressure. This dawn-dusk asymmetry in dayside reconnection and the related magnetospheric convection are the main reasons the plasma sheet is inclined, and the magnetotail is rotated about the sun-earth line. This also causes asymmetric plasma flows.
DE: 2700 MAGNETOSPHERIC PHYSICS
DE: 2731 Magnetosphere--outer
DE: 2740 Magnetospheric configuration and dynamics
DE: 2753 Numerical modeling
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting