HR: 14:05h
AN: SM43D-03 INVITED     [Abstracts]
TI: Solar Cycle Effects on Solar Wind-Magnetosphere Coupling
AU: * McPherron, R L
EM: rmcpherron@igpp.ucla.edu
AF: Robert L. McPherron, Inst. Geophys. Planet. Phys. Univ. of Calif. Los Angeles, Los Angeles, CA 900951567 United States
AB: It is well established that solar wind coupling to the magnetosphere is a maximum at the equinoxes. This is a geometric effect partially caused by the projection of the IMF onto the GSM Z-axis. In the Russell-McPherron effect activity is a maximum at equinox according to the rule "spring to fall away". Recently it has been shown that the equinoctial maximum is also a result of dipole tilt towards and away from the Sun. Coupling is less efficient when this angle departs from 90 degrees. The actual disturbance measured on the ground also depends on ionospheric conductivity so that it is unclear which factors are dominant is determining the strength of ground disturbances. Since conductivity depends on solar UV it is likely that coupling to the magnetosphere is modulated by the solar cycle. In addition we have recently found evidence that coupling depends on the Mach number of the solar wind. This property is modulated by the solar cycle through its dependence on the occurrence of CMEs. These considerations lead us to speculate that there should be an obvious solar cycle dependence of the coupling of the solar wind to the magnetosphere. We will investigate this hypothesis by calculating the prediction filters that relate the solar wind electric field to several different magnetic indices including AL, sym-H, and PC. Filters will be calculated at equinox and solstice for each year of the solar cycle. The sum of the filter coefficients will be used as a measure of coupling strength.
DE: 2722 Forecasting
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Storms and substorms
DE: 7839 Nonlinear phenomena
SC: SPA-Magnetospheric Physics [SM]
MN: 2005 Joint Assembly