First simultaneous measurements of neutral and ionized iron densities in the upper mesosphere

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Abstract
We report on the results of a multi‐instrument study of a sporadic Fe layer and a sporadic E layer which took place in the night of September 20, 1991, at the Andøya Rocket Range (69°N, 16°E). A ground‐based lidar was used to measure mesospheric Fe densities, while simultaneously rocket‐borne probes and an ion mass spectrometer measured the profile of total ion density and ion composition, respectively. All instruments observed the sporadic layers near 97 km altitude. Radar tracking of chaff clouds established the wind field in the 90‐ to 100‐km region with high spatial resolution, while the EISCAT incoherent scatter radar measured the E fields in the F region. The major ion in the sporadic E layer turned out to be Mg+. The narrow Fe+ layer was 1 km lower than the sporadic Fe+ layer. The ratio of densities [Fe+]/[Fe] in the peaks of the sporadic layers was found to be 1.75.