The electron foreshock: strahl-driven anisotropy and acceleration beyond fast Fermi

We present the results of two studies of foreshock electrons and associated Langmuir waves, using wave and particle measurements from the Wind and STEREO spacecraft. Using a statistical survey of Wind data, we find that the presence of a strong strahl in the upstream solar wind leads to an increase in the occurrence of Langmuir wave activity in the sunward wing of the electron foreshock, creating asymmetry between the sunward and antisunward wings. Using a Liouville mapping technique with measured STEREO solar wind and foreshock electrons, we show evidence for electron acceleration above the levels predicted by the fast Fermi model. We demonstrate that this enhancement begins at energies where the assumption of adiabatic mirror reflection breaks down.; Sunward and anti-sunward wings of the foreshock. The presence of the strahl population creates asymmetry in Langmuir wave occurrence between the two wings. ; STE data showing enhanced electron spectra above levels predicted from fast Fermi.