Abstract. While the Cluster spacecraft were located near the high-latitude magnetopause, between 11:30-13:00 UT on 1 April 2004, a series of medium to large scale (40 nT, 0.6-1.2 Re) FTEs were observed. During this pass, simultaneous and conjugated SuperDARN measurements are available that show a global flow pattern which is consistent with the expected (mapped) north-west motion of (predominantly subsolar) reconnected, magnetic flux at the magnetopause. We focus on analysing the local response of three FTEs, tracking their magnetopause motion via the four-spacecraft measurements together with their corresponding ground mapped motions. For two of these FTEs, where the tracking is strongly coordinated with the ionospheric flow at each footprint of the implied flux tubes in the Northern Hemisphere, conditions corresponded to stable, increasing (>100 • ) clock angle, while the third event, where the correspondence is less strong, coincided with low (<100 • ) clock angle. Flux tube motion, both measured and modeled from the inferred Xline, qualitatively matches the clear velocity enhancements in ionospheric convections with northward and westward flow at each location in the Northern Hemisphere, measured simultaneously by SuperDARN, and also roughly matches the observed, south-eastward ionospheric flow in the Southern Hemisphere at the time of these events. The time periods of these velocity enhancements infer that the evolution time of the FTEs is about 4-6 min from its origin on magnetopause to its addition to the polar cap. However, the ionospheric response time in the Southern Hemisphere might be Correspondence to: Q.-H. Zhang (zhangqinghe@pric.gov.cn) 2 min longer for the 12:31 UT FTE (and 6 min longer for the 12:51 UT FTE) than the response time in the Northern Hemisphere.

[1] Ground observations of Pc3 ULF waves at high latitude show enhanced pulsation activity near the cusp. To investigate this, typical Pc3 pulsation events from 0920 to 1010 UT on 1 April 2004 have been selected that are simultaneously observed by the Cluster satellites and Zhongshan, Davis, and Mawson magnetometers, Antarctica. When Cluster was located on closed field lines equatorward of the exterior northern cusp, Zhongshan and Davis were near the ionospheric footprint of the southern cusp. Assuming linear phase variation between the four Cluster spacecraft, the Pc3 waves with a frequency of $25 mHz have a wavelength of $5200 ± 2400 km and wave vector directed almost perpendicular to the geomagnetic field (94.6°± 10.4°) pointing toward the Earth. The Pc3 waves are transverse waves over the interval and different from the broadband perturbations and compressional waves generally observed in the cusp and the magnetosheath, respectively. The wave Poynting flux indicates energy is transported predominantly along the magnetic field line toward the ionosphere. These results indicate that Pc3 waves near the cusp are shear Alfvénic waves guided by closed field lines in the low-latitude boundary of the cusp and reflected from the ionosphere. We suggest that the waves may result from incoming compressional fast waves from the upstream solar wind that couple to shear Alfvén waves guided by the magnetic field at high latitudes and excite field line resonance in various harmonics at middle and low latitudes.

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