On the red line emission in nighttime observed from ISIS-II spacecraft and implied thermospheric winds

Abstract

Downward looking vertical observations at 6300 Å and the F-layer critical frequency from the ISIS-II spacecraft at equatorial, middle and high latitudes in the American zone are use to derive F-layer peak height (<i>h</i>_mF2). The observations refer to nighttime periods (2315 to 0250 hrs LT) in September 1972 for geomagnetically quite and disturbed conditions during low solar activity. The <i>h</i>_mF2 values are entered into vector spherical harmonic model of the thermospheric dynamics to find winds in F-region. The equatorial ionospheric anomaly (EIA) in the emission are observed to move closer to the magnetic equator with time, and sometimes are not collocated with EIA in peak electron density (<i>n</i>_mF2) during disturbed conditions. Also the observed intensities do not always indicate the presence of gravity waves or oscillations during disturbed periods as expected.