The quasi 2 day wave and spatial‐temporal variability of the OH emission and ionosphere

Abstract

The quasi 2 day wave (QTDW) during January 2006 is investigated using Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) observations of OH airglow and temperature in the mesosphere and lower thermosphere (MLT) and CHAMP in situ electron density observations at an altitude of ∼360 km. The zonal structure of the QTDW during early 2006 in the Southern Hemisphere MLT and low‐latitude ionosphere is dominated by westward propagating zonal wave number 3 (W3) and eastward propagating zonal wave number 2 (E2) components. However, the observed longitude variability is not fully described by the E2 and W3 components of the QTDW. The remaining longitude variability is attributed to the presence of nonmigrating tides and secondary waves generated by the nonlinear interaction of the QTDW with migrating tides. The nonmigrating tides are a combination of those that are generated in situ by QTDW‐tide nonlinear interactions and those of tropospheric origin that propagate upward into the MLT. The results presented demonstrate that nonmigrating tides and secondary waves are of considerable importance for determining the total longitude variability during periods of enhanced QTDW activity. The general similarity between the QTDW in OH airglow and temperature indicates that variations in atomic oxygen concentrations due to vertical winds during the QTDW are the primary driver of the QTDW in the OH airglow emission. However, there are some differences in the OH airglow and temperature that we consider to be connected to changes in eddy diffusion due to changes in gravity waves during the QTDW. Last, although similar zonal structure of the QTDW is observed in the ionosphere, the observed longitude variations are not well represented by the QTDW components, indicating that nonmigrating tides play a critical role in determining longitudinal variability in the ionosphere during the QTDW. The importance of nonmigrating tides in the ionosphere may be related to the relative efficiency of the QTDW and different nonmigrating tides in the generation of electric fields.