Correlative study of neutral winds and scintillation drifts measured near the magnetic equator

Abstract

Measurements of the thermospheric neutral wind at Arequipa, Peru, and observations of the drift of the irregularities at Ancon, Peru, are used to study the coupling that exists between ions and neutrals at equatorial latitudes and the variability of this coupling as a function of the occurrence of scintillations. This study is based on data collected at the Arequipa and Ancon stations between 1996 and 1998. Our comparative analysis indicates that the relative wind-drift values vary depending on season and the solar flux level. We found that during the equinoxes and low solar flux values, the averaged zonal drift is larger than the wind by 15 m s−1, but for solar flux values above 130 units, the average wind exceeds the drift values by 10 to 20 m s−1. We suggest that the occurrence of larger equinoctial drifts can be explained by the existence of altitude gradients in the zonal wind during that season. During the June solstice the zonal wind seems to exceed the irregularity drift by ∼10–20 m s−1 independent of the solar flux. We also find that the meridional wind shows a modest dependence on the scintillation activity during the June solstice. During scintillation events and between 2000 and 2400 LT the averaged meridional wind observed to the south and north of Arequipa exceeds their corresponding no-scintillation values by 20 m s−1. We present likely explanations of this effect.