The correlations of energetic electron fluxes in the Earth’s central plasma sheet with solar wind variables and geomagnetic indices

Correlations between the electron fluxes in the Earth’s central plasma sheet and various solar wind and magnetospheric parameters are studied. Higher-energy fluxes (above approximately 2 keV) are the focus of the analysis. Flux measurements are taken during 950 current-sheet crossings in the central plasma sheet using 3-s-resolution electron measurements from the THEMIS-B and THEMIS-C spacecraft in the solar minimum years 2007–2010. The current-sheet crossings were from 10.8–30.6 R E downtail from the Earth. Plots of the Pearson linear correlation coefficient r corr as a function of the instrument channel energy are examined. Even though all the solar wind variables are intercorrelated, which complicates the situation, indications are that the same element in the solar wind that drives magnetospheric activity is also what drives the fluxes of energetic electrons in the magnetotail plasma sheet. The correlation curves show that the energetic electron fluxes are related to the electron bulk temperature of the central plasma sheet. Accounting for the fact that magnetospheric activity moves the plasma sheet plasma earthward and systematically and adiabatically heats the plasma as a function of downtail distance, it is found that the electron temperature at a given downtail distance from the Earth is related to the level of magnetospheric activity at the time that the temperature is measured. The correlations of energetic electron fluxes with various common solar wind coupling functions are examined. The impact of measurement shot noise in the data is examined, and future work is outlined.