Simultaneous observations of the polar-orbiting Wideband satellite at two auroral zone stations (separated by approximately 200 km along the geomagnetic meridian) were made during November 1977. The latitudinal distribution of the average scintillation occurrence at each station shows a local maximum at the point where the propagation vector lies within an L shell. This supports the hypothesis that the enhancement is a geometrical effect due to L shell aligned, sheetlike irregularities. The detailed structure of the average scintillation occurrence as well as the scintillation patterns on individual passes shows, however, that the source regions are confined in latitude. From a detailed analysis of total electron content data we were able to show that the local scintillation enhancements occur in a region of enhanced F region ionization with a steep gradient at its equatorward edge. The source region lies within the general confines of the diffuse aurora, often with too limited a latitudinal extent to cause an enhancement at both stations. These new results are discussed in light of recent theoretical analysis by Ossakow and Chaturvedi that shows that the current convective instability, which is essentially a stable E¿B configuration destabilized by moderate field-aligned currents, can explain the irregularities. The sheetlike structure is a result of the nonlinear saturation of the instability. The linearly unstable mode, which would give rise to meridional structures, is nonlinearly damped while the dominant nonlinearity favors the perpendicular modes that cause the sheetlike structures.