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Ground-satellite relationships of Pc 5 pulsations observed in the morning sector

*Tohru Sakurai[1] ,Yutaka Tonegawa [1],Susumu Kokubun [2]
Ousuke Saka [3],‚s‚�‚“‚ˆ‚‰‚†‚•‚�‚‰ ‚l‚•‚‹‚�‚‰ [4]
Tokai�@University[1]
Solar-Terrestrial Environment Laboratory, Nagoya University[2]
Institute of Space and Aeronautical Science[4]

Our recent studies based on the Geotail satellite observations of Pc 5 pulsations in the outer magnetosphere are summarized and examined in relation to excitation of Pc 5 pulsations, which depends on several important factors, such as solar wind conditions, magnetic activity, magnetospheric convection, substorm activity, distributions of low and high energy plasmas and etc. These coditions are found to be all important for excitation of Pc 5 pulsations. Detail examinations are discussed in this report.

Our recent studies based on the Geotail satellite observations in the outer magnetosphere reveal occurrence characteristics of Pc 5 pulsations in the magnetosphere as follows; 1)Large amplitude Pc 5 pulsations with clear resonance oscillations were observed only in the morning sector and their occurrences were restricted in the very quiet magnetic condition with the northward IMF. 2)They were observed during the period of high density low energy background plasmas. 3)They were observed in association with substorm injected remnant plasmas. 4)The corresponding resonance regions of these Pc 5 pulsations on the ground occurred in the very narrow latitudinal width. 5)More activated Pc 5 pulsations and magnetopause oscillations appeared in association with the enhanced magnetospheric convection due to the IMF directional changes even when the solar wind velocity and dynamic pressure were steady. 6)However, the amplification of the Pc 5 pulsations occurred in the period of substorm injected remnant plasmas. 7)The corresponding occurrences of the Pc 5 pulsations on the ground were observed over the extended latitudes. 8)Some of the Pc5 pulsations observed on the ground were triggered with the FTE events, which occurred in association with the impulse events observed in the low latitude boundary region near the magnetopause, where the impulses were very frequently observed. Although some of these conditions above mentioned seem to be coincident with the previous work by Saka, et al., (1992), excitation of Pc 5 pulsations depends on several factors occurring in the magnetosphere. In this report wave characteristics and ground-satellite relationships of Pc 5 pulsations, and several conditions in the solar wind and in the magnetosphere for Pc 5 excitation are discussed in detail.