Auroral source region: Plasma properties of the high-latitude plasma sheet

Statistical results from a survey of 93 passes through the high-latitude extension of the plasma sheet of electron data from the Hydra instrument on the Polar spacecraft show that the values for electron density can range from 0.01 to 0.5 cm^-3 with an average value around 0.1 cm^-3 on the poleward side and 0.3 cm^-3 on the equatorward side. Electron mean energy is found to have an average value near 900 eV on the equatorward side and 400 eVon the poleward side but varies from 100 eV to 4 keV. These values for density and mean energy are similar to those reported for measurements made in the equatorial plasma sheet by several previous spacecraft. The character of the electron distributions has been compared with Maxwellian and κ-distributions with the result that the κ-distribution with κ, ≤ 10 yields an acceptable fit to the data twice as often as a Maxwellian distribution. This is similar to results found in the equatorial plasma sheet for both electrons and ions. The variation of electron density and mean energy around their average values have been compared with several solar wind parameters which have been developed to correlate solar wind variation with magnetospheric activity level. Few of these parameters are found to provide significant correlation with high-latitude plasma sheet electron density or temperature with the notable exception of solar wind density and solar wind particle flux which correlate with plasma sheet density.