Solar Wind Core Halo and Strahl Electrons at 1 AU: New insights into their Properties, Regulation & Constraints

Abstract:

We present a review of our latest work based on statistical analysis of solar wind electrons at 1AU using a newly developed dataset of (several years of) accurate measurements of core, halo and strahl electron parameters from the 3D-Plasma experiment on Wind. We investigate the properties of these different populations and the physical processe(s) that likely act to control and regulate them. We review new results obtained on (1) the electron temperature anisotropies and their variation with collisions and/or solar wind fluctuations and instabilities, (2) the properties of core and halo drifts in the solar wind proton frame, (3) the electron heat flux, and (4) the electron strahl. These new observations emphasize the non-negligible role of Coulomb collisions in shaping the electron distribution function and regulating of the thermal and supra thermal electrons, but that the solar wind electron expansion and compression are limited fundamentally by some instabilities under certain conditions.