HR: 15:05h
AN: SA23B-05    [Abstracts]
TI: Direct Solar Wind-Thermosphere Coupling
AU: * Siscoe, G
EM: siscoe@bu.edu
AF: Center for Space Physics Boston University, 725 Commonwealth Ave., Boston, MA 02215 United States
AB: It has long been known that the solar wind induces motion in the thermosphere at high latitudes and that this motion is sensitive to the direction and strength of the interplanetary magnetic field (IMF). It has also long been known that this coupling almost certainly occurs by means of drag between ionospheric ions set in motion by solar wind induced magnetospheric convection and thermospheric neutrals. However, until now the discussion has focused largely on the ionosphere/thermosphere end of the process. Here we focus on the system-wide aspects of the process and show that under conditions of strong southward IMF the solar wind and the thermosphere are in effect directly coupled by means of the region 1 current system. The magnetosphere plays a passive role as the conduit through which the region 1 current flows to couple the solar wind to the thermosphere. Said differently, when the solar wind hits the bow shock, the force that slows and deflects it around the magnetosphere is applied against the thermosphere and not against the earth's dipole. Moreover this force - which is the total force that the solar wind exerts against the terrestrial system - appears to be too small to account for observed thermospheric winds. Thus, there appears to be a missing force. The explanation to this apparent paradox comes automatically from considering the interaction between the region current system and the geomagnetic dipole. Surprisingly (but obviously once considered), this interaction entails a force stronger than the solar wind's that drives the thermosphere antisunward over the poles (i.e., in the usual convection sense of magnetospheric convection), thus providing the missing force, while shoving the geomagnetic dipole compensatingly sunward.
DE: 2409 Current systems (2721)
DE: 2431 Ionosphere/magnetosphere interactions (2736)
DE: 2437 Ionospheric dynamics
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005