Solar wind velocity estimation from multi‐station IPS

Three‐station and four‐station observations at 74 MHz are used to study the spatial structure and temporal rearrangement of the intensity pattern of interplanetary scintillations (IPS) in weak scattering. Velocity estimators from three models, two of which include rearrangement, are applied to the data and evaluated. It is shown that for certain radio sources the spatial anisotropy of the pattern is determined by elongated source structure. An upper bound on the average pattern axial ratio for an isotropic ecliptic source is 1.3 for data of mid‐1972. An upper bound on the average random velocity for the same period is 40% of the bulk velocity. We discuss a simple velocity estimator that is independent of the spatial anisotropy and has a low sensitivity to the random velocity.