ANOMALOUS MERIDIONAL THERMOSPHERIC NEUTRAL WINDS IN THE AE-E NATE DATA - EFFECTS OF THE EQUATORIAL NIGHTTIME PRESSURE BULGE

The work described here makes it possible to identify anomalous wind b ehavior such as the nighttime meridional wind abatements that occur at F-region heights. A new analysis technique uses a simple empirical wi nd model to simulate measurements of ''normal'' winds (as measured by the Neutral Atmosphere and Temperature Experiment (NATE) that flew on the Atmosphere Explorer-E (AE-E)) to highlight anomalous wind measurem ents made by the satellite while in circular orbits at 270-290 km alti tude. Our approach is based on the recognition that the ''in orbit'' w ind variation must show the combined effects of the diurnal wind varia tion as seen from the ground with the latitude variation of the satell ite orbit. For the data period 77250-78035 examined thus far, the wind abatement always occurred with a corresponding pressure or temperatur e maximum, and was detected on 12 out of the 36 nights with data. This study has revealed that the wind abatements occur only during or shor tly after increases in solar EUV flux, as indicated by daily radio flu x measurements. In the past, nighttime wind reversals at mid-latitudes have been associated with increased geomagnetic activity. This study indicates that intensified solar EUV heating may be responsible for an omalous thermospheric nighttime winds at mid-latitudes.