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Abstract.This paper presents coherent scatter radar observations of plasma irregularities in the equatorial F region ionosphere made with the JULIA (Jicamarca unattended long-term studies of the ionosphere and atmosphere) radar and discusses model equations and simulations pertinent to their interpretation. The data set shows that bottom-type and bottomside scattering layers are prevalent throughout solar minimum equinox. Bottom-type layers are undifferentiated and relatively weak layers confined to a narrow range of altitudes falling within regions of the ionosphere driven by the E region dynamo. These layers are often precursors to large-scale radar plumes as well as to bottomside layers, which are broader, more structured, and more intense layers than the bottom-type variety. Bottomside layers are the source of intermediate-scale plasma depletions that can ascend and penetrate through to the topside. Fluid simulations of the collisional interchange instability suggest that dynamo theory explains why one kind of layer emerges at a given time and altitude.

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BackgroundThis paper presents new coherent backscatter radar observations of plasma irregularities in the midlatitude E region ionosphere. The meter-scale irregularities are thought to be generated by gradient-drift instabilities forming in sporadic E ionization layers. Gradient-drift and modified two-stream instabilities have long been known to exist in the auroral E region, where they are driven by strong convection electric fields, and in the equatorial zone, where they are driven by the vertical polarization electric field responsible for the equatorial electrojet. Numerous observing programs exist for studying E region plasma instabilities at low and high latitudes, facilitated by the long-standing presence of strategically placed coherent and incoherent scatter

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