During geomagnetic storms, Joule heating is a major heating source of the upper atmosphere that is not well estimated, due to a lack of measurements. This leads to uncertainties in orbital calculations. We present simulations with commonly used physics-based models and empirical models that provide measurements of Joule heating. The results show great discrepancies, pointing to the need for measurements in the Earth's Lower Thermosphere-Ionosphere at altitudes where Joule heating maximizes.

Comparisons of wind measurements using two different techniques (ground-based radar and satellite) in Brazil during 2006 were made in order to point out the advantages of each instrument for studies in the mesosphere and upper thermosphere. (i) For short-period variations, the measurements of the satellite were more advantageous. (ii) The monthly climatology using the radar was more appropriate. (iii) For long periods (longer than a few months), both instruments responded satisfactorily.

The midnight temperature maximum (MTM) is a phenomenon resulting from the constructive interference of the atmospheric tides. This paper brings the analysis of a long data set (846 nights) from the NATION network along with new analysis techniques (harmonic background removal and 2-D temperature interpolation) to detect the MTM in the mid-latitude range.

For subauroral polarization streams (SAPS) commencing at different universal times (UT), the strongest westward neutral winds exhibit large variations in amplitudes. The effect of a sine-wave oscillation of SAPS on the neutral wind also exhibits UT variations in association with the solar illumination. The reduction in the electron density and enhancement in the air mass density are strongest when the maximum solar illumination collocates with the SAPS.

The Global Ionosphere Thermosphere Model has been validated against flight data. The validation shows a linear dependency of the neutral density values with respect to the solar activity. In particular, the thermosphere model shows an over-predicting or under-predicting behaviour under high or low solar activity respectively. The reasons for such behaviour can be attributed to an erroneous implementation of the chemical processes or the gas transport properties in the model.