Rapid, highly structured meridional winds and their modulation by non migrating tides: Measurements from the Streak mission

Measurements of the Earth's low latitude thermosphere returned by the ionization gauge on the Streak mission are reported and discussed. The measurements are of the amount of gas rammed into the sensor by its passage through the thermospheric medium. They were obtained in the dusk sector in the altitude range 130-330 km and are shown to be strongly structured by the geomagnetic field. Similarities to the structure of the equatorial ionization anomaly are discussed. The structure is interpreted as being due to rapid (several hundred meters per second) meridional winds having an antisymmetric pattern with respect to the geomagnetic equator. The measurements are interpreted in light of results from other missions and are shown to fit well with ideas based on complementary measurements from the Dynamics Explorer 2 mission discussed as the Equatorial Temperature and Wind Anomaly. Several features of these winds are described and discussed, including their altitude dependence, how they form convection cells that extend to high latitude, and how the wind amplitudes vary with geographic longitude with an apparent wavenumber one variation. The latter characteristic is shown to be consistent with being the signature of tidal variations observed by others. Approximate calculations utilizing published values for the pertinent parameters are used to show that heating from the dissipation due to ion drag within the ionospheric F region is a dominant driver of the inferred winds. Citation: Clemmons, J. H., R. L. Walterscheid, A. B. Christensen, and R. L. Bishop (2013), Rapid, highly structured meridional winds and their modulation by non migrating tides: Measurements from the Streak mission, J. Geophys. Res. Space Physics, 118, 866-877, doi: 10.1029/2012JA017661.