Energetic plasma sheet electrons and their relationship with the solar wind: A Cluster and Geotail study

The statistical relationship between tens of kiloelectron volts plasma sheet electrons and the solar wind, as well as > 2 MeV geosynchronous electrons, is investigated using plasma sheet measurements from Cluster (2001-2005) and Geotail (1998-2005) and concurrent solar wind measurements from ACE. Plasma sheet selection criteria from previous studies are compared, and this study selects a new combination of criteria that are valid for both polar-orbiting and equatorial-orbiting satellites. Plasma sheet measurements are mapped to the point of minimum vertical bar B vertical bar, using the Tsyganenko T96 magnetic field model, to remove measurements taken on open field lines, which reduces the scatter in the results. Statistically, plasma sheet electron flux variations are compared to solar wind velocity, density, dynamic pressure, interplanetary magnetic field (IMF) B-z, and solar wind energetic electrons, as well as > 2 MeV electrons at geosynchronous orbit. Several new results are revealed: (1) There is a strong positive correlation between energetic plasma sheet electrons and solar wind velocity, (2) this correlation is valid throughout the plasma sheet and extends to distances of X-GSM = -30 R-E,, (3) there is evidence of a weak negative correlation between energetic plasma sheet electrons and solar wind density, (4) energetic plasma sheet electrons are enhanced during times of southward interplanetary magnetic field (IMF), (5) there is no clear correlation between energetic plasma sheet electrons and solar wind electrons of comparable energies, and (6) there is a strong correlation between energetic electrons (> 38 keV) in the plasma sheet and > 2 MeV electrons at geosynchronous orbit measured 2 days later.