Non-migrating Tidal Influences on Longitudinal Structure of the Topside Ionosphere

Thursday, 17 December 2015
Poster Hall (Moscone South)
Jessica Hawkins and Phillip Charles Anderson, University of Texas at Dallas, Richardson, TX, United States
Recent evidence suggests that atmospheric tides can be significant drivers of the global ionospheric structure, especially at low latitudes. In particular, a wavenumber-4 (WN4) pattern has been observed in several parameters including total electron content (TEC), zonal winds, [O]/[N2] ratio, distribution of NO, the equatorial electrojet current density, and ion density. WN4 is thought to be a signature of the DE3 non-migrating tide, which originates in the troposphere and modifies the E-region electric field and equatorial ExB drifts, in order to re-distribute plasma at higher altitudes.

We present ionospheric measurements by DMSP showing longitudinal variations at low latitudes. Monthly averages of evening ion densities often clearly show a WN4 or WN3 pattern along the magnetic equator, although these patterns are not always consistent on a day-to-day basis. We examine how the WN4 pattern at DMSP altitudes varies across local time, season, and solar activity, and interpret these variations in terms of tides, composition, and field-aligned transport.