HR: 11:35h
AN: SM42A-06    [Abstracts]
TI: The Effects of IMF Orientation and Dipole Tilt on the Configuration of the 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, Los Angeles, 3845 Slichter Hall, Los Angeles, CA 90095-1567 United States
AB: The response of the magnetosphere to changes in the interplanetary magnetic field (IMF) is determined by two factors: The extent to which the interplanetary magnetic field and the geomagnetic field are antiparallel and the relative velocity of the reconnected field lines in the direction perpendicular to the magnetic field. The first factor determines where the reconnection occurs while the second determines how the reconnected field lines move. We have used a three-dimensional global magnetohydrodynamic simulation of the interaction between the solar wind and magnetosphere to carry out a systematic investigation of the effects of the orientation of the IMF and dipole tilt on magnetospheric structure and dynamics. The combination of dipole tilt and finite IMF By and Bz leads to complex structures in the magnetosphere with no symmetry planes. Competition between antiparallel reconnection and the relative velocity of reconnected field lines determines the location of dayside reconnection. It frequently suppresses to occur in the subsolar region because the geomagnetic field is not weakest there. The reconnection maximizes where the fields are antiparallel. The addition of the Bx component to the IMF adds dawn-dusk and north-south asymmetry to the dayside magnetic reconnection. Open field lines on the dusk side are relatively straight. They increase the lobe magnetic pressure and compress the plasma sheet. Open field lines on the dawn side are bent sharply and decrease the lobe magnetic pressure. As a result tail reconnection occurs preferably on the dusk side. This tendency is largest when the solar wind Alfve'n Mach number is low. The dawn-dusk and north-south asymmetries cause an inclined plasma sheet, rotation of the magnetotail and asymmetric plasma flows in the tail.
DE: 2700 MAGNETOSPHERIC PHYSICS
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2740 Magnetospheric configuration and dynamics
DE: 2753 Numerical modeling
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting