Scattering of Superthermal Solar Wind Electrons Inside 5 AU

Several theories invoke scattering of the outward propagating strahl electrons to populate the sunward directed part of the solar wind superthermal (halo) electron distribution. If such a scattering mechanism occurs then does it occur in the inner or outer heliosphere? We examine how the sunward moving and anti-sunward moving superthermal electrons vary with distance from the Sun and assess whether or not the source of sunward moving electrons lies between 1 and 5 AU. We use in-ecliptic Ulysses SWOOPS (Solar Wind Observations Over the Poles of the Sun) electron measurements from 1991 when Ulysses was on its way to Jupiter. We start with electron velocity distributions in magnetic coordinates, and determine if the magnetic field is pointing towards or away from the Sun. We then integrate daily average distributions to determine the relative populations of superthermal electrons moving towards and away from the Sun, and assess their variations with distance.