Magnetic Reconnection in the Earth's Magnetosphere

T. Ogino (Nagoya Univ.)

The configuration of magnetic field lines in the earth's magnetosphere is
determined by magnetic reconnection between the interplanetary magnetic field
(IMF) and the geomagnetic field. That is, the IMF determines where magnetic
reconnection occurs, and how the reconnected field lines move. Two conditions
determine where magnetic reconnection occurs at the magnetopause: The extent to
which the antiparallel field condition is satisfied and the relative velocity of
the reconnected field lines in the direction perpendicular to the magnetic
field. The IMF lines flow radially from the subsolar point in the magnetosheath.
Their velocity can easily exceed the local Alfven speed. Therefore, magnetopause
reconnection occurs in regions where the antiparallel field condition is well
satisfied and magnetosheath plasma flow is relatively small (closest areas to
the subsolar point). We will demonstrate the complicated structure and dynamics 
of the earth's magnetosphere due to magnetic reconnection by using a 
3-dimensional global MHD simulation when the dipole tilt of geomagnetic field 
and the IMF with various orientations are included.