Magnetopause Motions, DP-2, and the Growth Phase of Magnetospheric Substorms.
CALIFORNIA UNIV LOS ANGELES PLASMA PHYSICS GROUP
Pagination or Media Count:
A southward shift of the solar wind magnetic field enhances field-cutting at the dayside magnetopause and internal magnetospheric convection. The magnetopause is connected to highly conducting dayside auroral oval ionosphere where large Pederson currents flow in response to convection electric fields. When field-cutting starts, internal magnetic flux cannot return freely to the magnetopause, but flows at a line-tied limited rate determined by the ionospheric conductivity. If the line-tied flux return rate is less than the field-cutting rate, the magnetopause shrinks in size. The distorted magnetopause forces more current into the ionospheric Pederson circuit, which then self-consistently permits a larger flux return rate. For typical magnetospheric parameters, the time constant for the establishment of equal flux return and field cutting rates is 20-40 minutes the magnetopause shrinkage is 1-2 R sub E the missing flux adds roughly 10 to the geomagnetic tail flux. The time constant for convection establishment is consistent with DP-2 and the growth phase of magnetospheric substorms. Author
- Atmospheric Physics