HR: 1330h
AN: SM32B-1154    [PDF]
TI: Conductivity Depdendence of Cross-Polar Potential Saturation
AU: * Nagatsuma, T
EM: tnagatsu@crl.go.jp
AF: Communications Research Laboratory, 4-2-1 Nukui-kita, Koganei, 184-8795 Japan
AB: The cross-polar potential tended to be saturated when the value of the merging electric field (Em) was high. Using data from the Wind and ACE satellites and the northern polar cap index (PCN) as a proxy for cross polar potential, Nagatsuma [2002] have shown that the degree of saturation does not depend on the intensity of the interplanetary magnetic field on GSM Y-Z plane (BT) but depends on that of Em. This result supports the idea that the enhancement of Region 1 current plays a significant role for regulating the efficiency of solar wind - magnetosphere interaction [Hill,1976; Siscoe et al.,2002]. If the enhancement of the Region 1 current plays a significant role for regulating solar wind - magnetosphere interaction, the intensity of ionospheric conductivity controls the degree of saturation since the Region 1 current system is a voltage generator. We have examined that the solar zenith angle (SZA) dependence of PCN saturation. Our statistical results show that the degree of saturation is increasing with decreasing solar zenith angle under the sunlit condition, and opposite trend is seen during the darkness period. These characteristics can be explained as a SZA dependence of total ionospheric conductivity in northern and southern polar caps. This result confirms that the development of Region 1 currents plays a significant role for regulating solar wind - magnetosphere interaction. Further, it is suggested that this conductivity dependence of solar wind - magnetosphere interaction produces diurnal and seasonal changes of geomagnetic activity.
DE: 2463 Plasma convection
DE: 2475 Polar cap ionosphere
DE: 2708 Current systems (2409)
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting