This data set contains IMP 8 LANL 12-s solar wind plasma parameters from the magnetotail. Parameters included are proton density flow speed and azimuthal direction, and min and max temperatures; alpha particle parameters are given relative to protons: Abundance and temperature ratios, and relative flow speeds and directions. Alpha temperature anisotropy, and azimuthal angles of both proton and alpha pressure tensor symmetry axis are also given.