On the usefulness of E region electron temperatures and lower F region iontemperatures for the extraction of thermospheric parameters: a case study

Using EISCAT data, we have studied the behavior of the E region electron te mperature and of the lower F region ion temperature during a period that wa s particularly active geomagnetically. We have found that the E region elec tron temperatures responded quite predictably to the effective electric fie ld. For this reason, the E region electron temperature correlated well with the lower F region ion temperature. However, there were several instances during the period under study when the magnitude of the E region electron t emperature response was much larger than expected from the ion temperature observations at higher altitudes. We discovered that these instances were r elated to very strong neutral winds in the 110-175 km altitude region. In o ne instance that was scrutinized in detail using E region ion drift measure ment in conjunction with the temperature observations, we uncovered that, a s suspected, the wind was moving in a direction closely matching that of th e ions, strongly suggesting that ion drag was at work. In this particular i nstance the wind reached a magnitude of the order of 350 m/s at 115 km and of at least 750 m/s at 160 km altitude. Curiously enough, there was no indi cation of strong upper F region neutral winds at the time; this might have been because the event was uncovered around noon, at a time when, in the F region, the E x B drift was strongly westward but the pressure gradients st rongly northward in the F region. Our study indicates that both the lower F region ion temperatures and the E region electron temperatures can be used to extract useful geophysical parameters such as the neutral density (thro ugh a determination of ion-neutral collision frequencies) and Joule heating rates (through the direct connection that we have confirmed exists between temperatures and the effective electric field).