Study on the Solar Wind-Magnetosphere Interaction Based on Remote Sensing Data From IMAGE Spacecraft

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Observations by the Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft show that emission in the direction of the high-latitude magnetosheath is modulated in such a manner that the source shifts equatorward/poleward in the high-latitude sheath. A model based on the distributions of the sheath flux and of the number density of the hydrogen exosphere has explained these characteristics as a result of the motion of the magnetopause having an indentation at the cusp, suggesting a means for monitoring the cusp motion using IMAGE/LENA. Simultaneous observations from IMAGE/LENA and SuperDARN radar have given evidence for the means. Detailed analyses of an event of simultaneous observations from IMAGE and Polar have revealed that the high-latitude sheath emission consists of two parts : the stable emission at the higher-latitudes, and the lower-latitude emission that occurs on and off, and that that the entry of the cusp ions happens in concurrence with the appearance of the lower-latitude LENA emission. This strongly suggests that LENA monitors the entry of the ions in the cusp as well as the cusp indentation, and that the significant flux of the cusp ion entry occurs equatorward of, and separately from the cusp indentation. LENA also sometimes observes an enhanced emission in the direction of the very high-latitude magnetopause. Simultaneous observations from IMAGE/LENA and SuperDARN radar have shown that the LENA emission appears concurrently with the enhancement of the sunward flow of the reverse convection in the ionosphere. This shows that LENA can monitor the ion entry caused by cusp reconnection, and that the reconnection site moves on a time scale of several minutes. The reconnection "spot" mapped on a sphere having a radius of 8 Re shifts by approximately 1 Re over 10 minutes while fluctuating.