Solar wind electron characteristics inside and outside coronal mass ejections

We present a study of 9 months of data from the solar wind plasma electron instrument on the ACE spacecraft. Electron pitch angle distributions were u sed to identify intervals of counterstreaming halo electrons, which were ob served similar to 16% of the time that the spacecraft was not magnetically connected to the Earth's bow shock. Counterstreaming electrons presumably i ndicate a closed magnetic field topology and thus indicate the passage of c oronal mass ejections (CMEs) in the solar wind. In this study, we separatel y examine electron moments at times with and without counterstreaming elect rons, including both magnetic clouds and noncloud CMEs. The properties of b oth the core and halo electron populations were nearly identical at times w ith and without counterstreaming electrons. Both low and high electron dens ities and temperatures were observed in either type of event. In contrast, magnetic clouds, on average, showed increased densities and reduced tempera tures. The core/halo density ratio and the total electron density were anti correlated in all cases, indicating that the halo contributes more to the t otal electron density at low density times, regardless of magnetic topology . Total electron temperature anal density were anticorrelated in all types of events. This consistent anticorrelation implies that such single-spacecr aft measurements of temperature and density cannot be used to determine a p olytropic index for solar wind electrons. Instead, the anticorrelation may be due to pressure balance of the solar wind plasma or may be a remnant of coronal conditions.