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Upper thermospheric meridional wind data at midlatitudes and for low magnetic activity are examined for solar activity variations following an analysis scheme suggested by a Coordinated Analysis of the Thermosphere workshop. Wind data from incoherent scatter, Fabry-Perot, and F2 peak heights show decreasing diurnal amplitudes with increasing solar activity during all seasons, except for Saint Santin data, which show a slight increase in summer. Equivalent winds from F2 peak height data have strong decreases in diurnal amplitude in all seasons. The coupled thermosphere ionosphere model and thermosphere ionosphere global circulation model predictions of diurnal amplitude, while differing considerably in magnitude, also show decreasing amplitudes during all seasons except summer, while the HWM90 empirical model amplitudes increase slightly with solar activity during all seasons. The diurnal mean wind trends with solar activity are fairly weak, except for Millstone Hill incoherent scatter radar, which shows a shift from strong southward to near zero or northward wind with increasing activity. Model results for the mean generally fall within the band of measurements. Near midnight, most of the data also show that the typically southward winds weaken with increasing solart activity in all seasons except summer, when results are mixed. There are significant differences between the trends and between absolute values for the various data sets and models which need further investigation.

The meridional neutral winds at 300 km altitude have been calculated from the data obtained during 15 years of measurements by the incoherent scatter facility at Saint-Santin (France). The analysis is based on the classical technique: the meridional neutral wind is given by the difference between the measured ion velocity and the computed diffusion velocity. This relies on knowledge of the O+-O collision frequency, which is still the subject of some controversy. A simple but reasonable expression is given and has been agreed upon with workers at Millstone Hill, so that comparisons may be made. This expression gives values consistent with the equations used elsewhere, which are more complicated but no more reliable. The whole set of data gives 223 twenty-four-hour periods of measurements from which the average meridional winds are computed for a range of conditions. A statistical analysis shows how the diurnal variations depend on season, solar flux, and geomagnetic activity. It is shown that these variations are well represented by four harmonic components, of which amplitudes and phases are given.

Empirical scaling factors between the height-integrated joule heating rate deduced from measurements of the Chatanika incoherent scatter radar and the square of magnetic perturbation at College are derived. These relationships, calculated for different situations (the eastward and westward electrojects and daytime) are then used to estimate the joule heating rate along the latitudinal extent of the auroral oval on the basis of magnetometer data from the IMS Alaska meridian chain of observations. The total heat input for a disturbed day (April 12, 1978) is estimated to be 2.8 x 10/sup 15/ J.