Initial results of high‐latitude magnetopause and low‐latitude flank flux transfer events from 3 years of Cluster observations

Abstract

We present initial results from a statistical study of Cluster multispacecraft flux transfer event (FTE) observations at the high‐latitude magnetopause and low‐latitude flanks from February 2001 to June 2003. Cluster FTEs are observed at both the high‐latitude magnetopause and low‐latitude flanks for both southward and northward IMF. Among the 1222 FTEs, 36%, 20%, 14%, and 30% are seen by one, two, three, and four Cluster satellites, respectively. There are 73% (27%) of the FTEs observed outside (inside) the magnetopause, which might be caused by the motion of FTEs toward the magnetosheath when they propagate from subsolar magnetopause to the midlatitude and high‐latitude magnetopause and low‐latitude flanks. We obtain an average FTE separation time of 7.09 min, which is at the lower end of the previous results. The mean BN peak‐peak magnitude of Cluster FTEs is significantly larger than that from low‐latitude FTE studies. FTE BN peak‐peak magnitude clearly increases with increasing absolute magnetic latitude (MLAT), it has a weaker dependence on magnetic local time (MLT) with a peak near the magnetic local noon, and it has a complex dependence on Earth dipole tilt with a peak at around zero. FTE periodic behavior is found to be controlled by MLT, with a general increase of FTE separation time with increasing MLT, and by Earth dipole tilt, with a peak FTE separation time at around zero Earth dipole tilt. There is no clear dependence of FTE separation time on MLAT. There is a weak increase of FTE BN peak‐peak magnitude with increasing FTE separation time, and we see no clear dependence of it on FTE BN peak‐peak time. When no FTE identification thresholds are used, more accurate calculations of some FTE statistical parameters, including the mean BN peak‐peak time, can be obtained. Further, comparing results with different thresholds can help obtain useful information about FTEs.