Incoherent scatter measurements of ion‐neutral collision frequencies and temperatures in the lower thermosphere of the auroral region

Incoherent scatter observations performed in March and November 1978 at Chatanika have been used for studying the lower thermosphere in the auroral region. Neutral temperatures and densities have been found during periods without Joule heating. We present mean profiles of temperatures and collision frequencies (approximately proportional to neutral densities) for each month and profiles obtained during four specific nights. Between 93 km and 110 km the mean profiles of temperature are in good agreement with the Jacchia (1971) model, and the profiles of collision frequency are similar to those deduced from the model. Consistency checks between these collision frequencies and temperatures were performed, as were various simulations of the data. Neutral temperature profiles between 90 km and 140 km on the four specific nights show variations from one night to another that are not correlated to magnetic activity. However, there are systematic variations during each night that we suggest are due to atmospheric tides.