Simultaneous Cluster and CUTLASS Observations of FTEs on 11 February 2004

Abstract

AbstractThis paper analyzes the simultaneous observations of the Flux Gate Magnetometer (FGM) and Plasma Electron and Current Experiment (PEACE) on Cluster Spacecraft, and the CUTLASS Finland radar between 11:00 and 11:40 UT on 11 February 2004. In this interval, the Cluster spacecraft array encountered the northern hemisphere high altitude cusp, and crossed the magnetopause into the magnetosheath at about 11:18 UT. A large number of flux transfer events (FTEs) were observed by all 4 Cluster spacecraft. It is found that these FTEs appeared quasi‐periodically with a period of about 130 s. Since all 4 Cluster spacecraft observed these FTEs, we applied the four‐spacecraft techniques “Minimum Directional Derivative (or Difference)” (MDD) and “Spatio‐temporal Difference” (STD) to calculate the dimension, motion and scale of these FTEs. The inferred northwardly reconnected flux tubes for these FTEs are shown to move northward or north‐east and tailward with a quasi‐2‐D structure and a scale of (0.87 ~ 1.81)RE. The ionospheric footprint of the Cluster spacecraft during the boundary passage is shown to map centrally within the field‐of‐view of the CUTLASS Finland radar. It is shown that the backscatter power of CUTLASS data is enhanced in synchronously with the magnetospheric FTEs at the latitude of the Cluster footprint. These radar auroral features in the radar subsequently propagated poleward, forming classic “poleward‐moving radar auroral form” structures at higher latitudes. The FTE motions meanwhile are shown to be consistent with the expected motion of reconnected magnetic flux tubes over the surface of the magnetopause, arising from a predominantly sub‐solar reconnection site during the prevailing upstream conditions.