Resolution of the discrepancy between experiment and theory of midlatitude F‐region structures

The Perkins instability has long been quoted as the explanation for midlatitude F ‐region structure. This notion has been called into question by a number of recent experimental results using airglow and incoherent scatter radar measurements. Here we attempt to reconcile experiment and theory by invoking polarization of the Perkins structures in the direction parallel to their long axis. The resulting northwest‐directed electric field causes the observed southwestward motion, thus resolving the apparent conflict. A simple dipole polarization electric field model is proposed and compared favorably with the observations.