Q. Wu et al., DYNAMICS EXPLORER-2 OBSERVATIONS OF EQUATORIAL THERMOSPHERIC WINDS AND TEMPERATURES - LOCAL TIME AND LONGITUDINAL DEPENDENCES, J GEO R-S P, 99(A4), 1994, pp. 6277-6288
We have analyzed a large database of Dynamics Explorer 2 (DE 2) measur
ements of equatorial (< +/-9-degrees latitude) thermospheric neutral t
emperatures and horizontal wind components in the altitude range from
200 to 400 km for quiet and active geomagnetic conditions (Kp < 3 and
Kp > 3, respectively). Local time variations and longitudinal dependen
ces on the duskside, dayside, and nightside have been separately exami
ned. The dayside hourly averaged neutral zonal winds are relatively in
sensitive to variations in geomagnetic activity and appear to show an
inverse dependence (lower zonal wind speed for higher Kp) in the midni
ght-dawn local time sector. The duskside neutral temperatures show a r
egion of enhancement (by approximately 60 K) over the South Atlantic m
agnetic anomaly. The quiet time zonal winds are weaker than the corres
ponding active time zonal winds on the dayside near the South Atlantic
magnetic anomaly. Enhanced ionization in the region, which increases
the ion drag on the neutral gas, is suggested as the causal mechanism
for these effects. The DE 2 averaged measurements have also been compa
red with MSIS-86/HWM90 and VSH models. The data and models are in good
general agreement, though, the MSIS-86/HWM90 model predicts stronger
dayside zonal winds than are observed under active conditions and the
VSH model appears to underestimate the magnitude of the dayside zonal
winds for both high and low Kp cases.