Temperature and composition of the ionosphere: diurnal variations and waves

Abstract

This work reports ion temperature, electron temperature and the relative concentration of atomic ions (O +) to molecular ions (NO + and O 2 +), derived from Thomson scatter measurements in the height range 115–430 km above Arecibo, Puerto Rico. A double pulse measurement technique was employed, permitting autocorrelation functions of the ion component of the Thomson scatter signal to be obtained with an altitude resolution of 15 km. In general, only two of the three unknowns could be determined directly from each measured autocorrelation function and two alternative methods of supplying the other parameter were used, viz. ion temperature models and ion composition models. The use of an ion composition model was appropriate when wave-like variations in ion temperature were found to be present in addition to the expected diurnal ion temperature variation due to solar heating. On occasions when the temperature waves were absent, temperature models were used to derive the diurnal ion composition variation. The average ion composition was substantially in agreement with rocket measurements. Daytime electron and ion temperatures were equal at 130 km while at greater heights the electrons were hotter than the ions. Above approximately 200 km the shape of the electron temperature profile was strongly influenced by the electron density.