On the anomalous ion temperatures observed at high latitude ionization troughs by AE-C satellite

Simultaneous measurements of electron and ion concentrations and their temperatures from AE-C satellite have shown anomalously large ion temperatures, far exceeding the electron temperatures, in the so-called high latitude ionization trough at an altitude of 400 km. It has also been observed that there is a very good correlation between the occurrence of excess ion temperatures and magnetic activity. The results are explained in terms of Joule heating which is enhanced at the trough due to large ion drag time constants caused by extremely low ion concentrations. This effect obviously prevails over the low Pedersen conductivity associated with low ion/electron densities.