Electron velocity distribution functions from the solar wind to the corona

Typical electron velocity distribution functions observed at 1 AU from the Sun by the 3DP instrument onboard Wind are used as boundary conditions to d etermine the electron velocity distribution function at 4 solar radii in th e corona. The velocity distribution functions (VDFs) at low altitude are ob tained by solving the Fokker-Planck equation, using two different sets of b oundary conditions. The first set typically corresponds to a VDF observed i n a low-speed solar wind flow (i.e., characterized by "core" and "halo" ele ctrons); the second one corresponds to highspeed solar wind (i.e., characte rized by "core," "halo,", and "strahl" populations). We use the observed el ectron VDFs as test particles, which are submitted to external forces and C oulomb collisions with a background plasma. Closer to the Sun, the relative density of the core electrons is found to increase compared to the density of the halo population. Nevertheless, we find that in order to match the o bserved distributions at 1 AU, suprathermal tails have to be present in the VDF of the test electron at low altitudes in the corona.