Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations

摘要

Moments calculated from the ion distributions (~0–40 keV) measured bythe Cluster Ion Spectrometry (CIS) instrument are combined with data fromthe Cluster Flux Gate Magnetometer (FGM) instrument and used to characterisethe bulk properties of the plasma in the near-Earth magnetosphere over fiveyears (2001–2005). Results are presented in the form of 2-D xy, xz and yzGSM cuts through the magnetosphere using data obtained from the ClusterScience Data System (CSDS) and the Cluster Active Archive (CAA). Analysisreveals the distribution of ~0–40 keV ions in the inner magnetosphereis highly ordered and highly responsive to changes in solar wind velocity.Specifically, elevations in temperature are found to occur across the entirenightside plasma sheet region during times of fast solar wind. Wedemonstrate that the nightside plasma sheet ion temperature at a downtaildistance of ~12 to 19 Earth radii increases by a factor of ~2during periods of fast solar wind (500–1000 km s−1) compared to periodsof slow solar wind (100–400 km s−1). The spatial extent of theseincreases are shown in the xy, xz and yz GSM planes. The results from thestudy have implications for modelling studies and simulations ofsolar-wind/magnetosphere coupling, which ultimately rely on in situ observations ofthe plasma sheet properties for input/boundary conditions.