Neutral Atom Emission in the Direction of the High-Latitude Magnetopause for Northward IMF: Simultaneous Observations From IMAGE Spacecraft and SuperDARN Radar

During a northward interplanetary magnetic field on 27 March 2001, the Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft in the magnetosphere observed an enhanced emission in the direction of the very high-latitude magnetopause. Simultaneous observations from IMAGE/LENA and SuperDARN radar show that the LENA emission appears concurrently with the enhancement of the sunward flow of the reverse convection in the ionosphere. The field line mapping from the magnetosphere to the ionosphere suggests that the source ions for the LENA emission are in the sunward flow region. Although the direction of the emission is relatively stable, its direction gradually changes so that the emission may shift poleward and then return equatorward. From these observations, we suggest that LENA can monitor the ion entry caused by cusp reconnection and that the reconnection site moves on a time scale of several minutes. Such motion is discussed in terms of the solar wind variations.