Fe⁺ ions in the high latitude F‐region

Ion mass spectrometer measurements on Atmosphere Explorer C orbits from December 1974 to December 1976 were surveyed poleward of ±30°Λ for instances in which the Fe + number density exceeded the spectrometer threshold sensitivity of 30/cm³. The occurrences of Fe + within the altitude range covered by the orbit, 220 to 320km, revealed a distinct pattern apparently associated with regions of upward plasma transport. At night a band of such events occurred between 50° and 60°Λ which typically corresponded to the location of the main ionospheric trough. In this region large upward ion drifts due to the drag of an equatorward blowing neutral wind are expected. The Fe + band extends past 06 MLT to ∼11MLT during the summer, but is not observed in the afternoon. The dayside distributions possibly result from the upward drifts of F‐region ions detected by back‐scatter techniques after dawn during summer. At higher latitudes patches of Fe + were detected in regions where strong plasma drifts often prevail and hence where poleward motions and atmospheric expansion through Joule heating can lift the ions upwards.