Collisional interchange instability: 2. A comparison of the numerical simulations with the in situ experimental data

A two‐dimensional model applicable to F region ionosphere plasma instabilities has been developed and described in a companion paper. Here we apply the model to equatorial F region irregularities and in particular test the model against rocket and satellite data. As a diagnostic we create simulated data sets similar to the one‐dimensional measurements of plasma density performed by space probes and take the Fourier transform of these data in the same manner and used by the space experimentors. To our knowledge this is the first attempt to directly relate a simulation to in situ data in this way, diagnostic technique which resolves the ambiguity inherent to one‐dimensional measurements. The comparison is in excellent agreement with the in situ data. In particular, we have been able to resolve the apparent differences between satellite quasi‐sinusoidal observations with the shocklike observations made on rockets. Unlike previous simulations of this phenomenon we find an inherent anisotropy in the instability development which is mirrored in the in situ data. We also present evidence that the shallow spectral slopes which often characterize spread F rocket spectra near the F peak may be due to a change in the angle between the rocket velocity vector and the characteristic directions in the medium.