Ionization layers observed at middle latitudes by Atmosphere Explorer-C

In the early phases of the Atmosphere Explorer mission the highly elliptica l orbit with apogee near 4000 km and perigee near 135 km, allowed altitude profiles of the ion composition to be obtained over limited latitude extent s at middle latitudes. Data from consecutive orbits through the mid-latitud e ionosphere show the repeated appearance of ionization layers that are dis tributed in longitude, appearing at the same geographic location but differ ent geomagnetic locations. In this data set the layers appear at dip latitu des as high as 40 degrees and at these locations the magnetic declination c an be significant. Examination of the shape of these layers at different lo ngitudes supports the idea that both meridional and zonal winds may play a role in the field-aligned plasma transport that is primarily responsible fo r their formation. (C) 1999 Elsevier Science Ltd. All rights reserved.