Core electron drift in the solar wind: measurements and instability thresholds

We describe an analysis of solar wind electron measurements from the Wind/3DP experiment. We have fitted several hundred thousand electron distribution functions to a three component (core, halo, strahl) distribution function. Here we show statistically that the (Maxwellian) core drifts with respect to the solar wind protons and that this drift speed is a simple function of the collision rate, as expected. In the collisionless limit, the electron-proton drift is large (200 km/s) and may be limited by a core-proton or 'heat flux' instability and could be a source of Alfven or whistler waves.