On the usefulness of <i>E</i> region electron temperatures and lower <i>F</i> region ion temperatures for the extraction of thermospheric parameters: a case study

Abstract

Using EISCAT data, we have studied the behavior of the i region electron temperature and of the lower p region ion temperature during a period that was particularly active geomagnetically. We have found that the i region electron temperatures responded quite predictably to the eective electric ®eld. For this reason, the i region electron temperature correlated well with the lower p region ion temperature. However, there were several instances during the period under study when the magnitude of the i region electron temperature response was much larger than expected from the ion temperature observations at higher altitudes. We discovered that these instances were related to very strong neutral winds in the 110±175 km altitude region. In one instance that was scrutinized in detail using i region ion drift measurement in conjunction with the temperature observations, we uncovered that, as suspected, the wind was moving in a direction closely matching that of the ions, strongly suggesting that ion drag was at work. In this particular instance 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 indication of strong upper p region neutral winds at the time; this might have been because the event was uncovered around noon, at a time when, in the p region, the E Â B drift was strongly westward but the pressure gradients strongly northward in the p region. Our study indicates that both the lower p region ion temperatures and the i region electron temperatures can be used to extract useful geophysical parameters such as the neutral density (through a determination of ion-neutral collision frequencies) and Joule heating rates (through the direct connection that we have con®rmed exists between temperatures and the eective electric ®eld).

The role played by thermal feedback in heated Farley-Buneman waves at high latitudes

“…6. The area thus covered is based on the`normal' data recently presented by St.-Maurice et al (1999) and is also in basic agreement with the numbers given by Robinson (1986).…”

Structure functions and intermittency in ionospheric plasma turbulence

“…We use a value for the electron temperature which is consistent with the present observations. Evidence can be found for anomalous electron temperature enhancements for increasing dc electric field in the ionospheric Eregion (St.-Maurice et al, 1999;Noël et al, 2005), where the effective electric field needs to be considered in case we have neutral winds. Unfortunately, we have no means for obtaining information concerning neutral winds for the ROSEexperiment.…”

Ion and neutral temperature distributions in the E-region observed by the EISCAT Tromsø and Svalbard radars

“…The maximum of the ion temperature during the night was explained from the location of the radar relative to the largescale ion convection pattern. Since both the ion frictional heating rate and neutral heating rate due to the Joule dissipation of electric currents are proportional to the square of the relative velocity between ions and neutrals (Banks, 1980;St.-Maurice et al, 1999), it is inferred that the neutral heating at latitudes lower than about 70 • occurs mainly on the night side, in contrast to the heating within the polar cap.…”