The orientation of plasma structure in the solar wind

Data from the ISEE 3, IMP 8, and WIND spacecraft are used to find the average east‐west orientation of plasma structures in the solar wind. We determine the lags which, after radial propagation effects are removed, give the best correlations between data sets. These lags, when combined with the spacecraft positions and solar wind speeds, are then used to calculate the front angles of the propagating plasma. The average front normals are neither radial nor perpendicular to the magnetic field, but are roughly halfway between. Front angle distributions peak at lower angles near solar maximum than at solar minimum. These results may indicate that time‐dependent changes in the solar wind source are as important as longitudinal variations of the source in producing the solar wind structure observed near Earth.