Ionospheric signatures of magnetospheric boundaries in the post-noon sector

Spatial structures in ionospheric electron density revealed in a tomographi c image have been identified with auroral forms and related to their source s in precipitating particles observed by DMSP satellites. The observations of plasma enhancements relate to discrete auroral arcs seen in the post-noo n sector, identified by both red- and green-line emissions measured by a me ridional scanning photometer. The features lie within a very narrow latitud inal band on L-shells where the satellite detectors observed electron preci pitation classified as from the boundary plasma sheet (BPS). The harder par ticles are identified with an E-region structure, while further north the p recipitation is softer, resulting in a localised F-layer blob and 630.0 nm emissions. A steep gradient in plasma density represent a signature in the ionosphere of the central plasma sheet (CPS)/BPS boundary. A transition to a less-structured F-layer is found on crossing the convection reversal boun dary.