Solar wind electron halo depletions at 90 degrees pitch angle

Strong depletions in solar wind electron halo distribution functions, cente red on and roughly symmetric about 90 degrees pitch angle, are present in a t least 10 % of data obtained by the Los Alamos SWEPAM experiment on the AC E spacecraft. Sunward-directed conics are also present in the electron data , occur in conjunction with the 90 degrees depletions, but are less common than depletions. We suggest that on open field lines both depictions and co nics arise from focusing and mirroring effects associated with field line c onnection to magnetic field enhancements further out in the heliosphere. Th e focusing and mirroring produces field-aligned, counterstreaming fluxes of suprathermal electrons somewhat similar to that observed on closed field l ines. Our observations provide strong evidence that the antisunward-directe d portion of the electron halo on open field lines at times results primari ly from mirroring of back scattered strahl and/or shock-heated electrons fr om far out in the heilosphere.