Quasi-two-day wave structure, interannual variability, and tidal interactions during the 2002-2011 decade

In this paper we employ Thermosphere Ionosphere Mesosphere Energetics Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry temperature measurements from 20 to 120 km and between about 72 degrees latitude to investigate several aspects of the quasi-two-day wave (QTDW) during the 2002-2011 decade, including interannual variability of its seasonal-latitudinal structure, its penetration into the lower thermosphere, and various wave-wave interactions. We focus on two components of the QTDW: the westward-propagating component with zonal wave number s=3 (TDW3), and the eastward-propagating component with s=-2 (TDE2). TDW3(TDE2) has maximum amplitudes during 2003, 2004, and 2011(2006 and 2011) and both waves have their lowest amplitudes during the deep solar minimum years of 2008-2009. TDW3 and to some degree TDE2 penetrate with significant amplitudes up to 120 km altitude, well into the region where neutral winds generate electric fields through the dynamo mechanism. A new longitude subdivision method (LSM) is presented that enhances temporal resolution of TDW3 and enables the determination of 9.6 h and 16 h waves that result from nonlinear interaction between TDW3 and/or TDE2 and diurnal migrating (DW1) and semidiurnal migrating (SW2) tides. Evidence is presented for westward-propagating 9.6 h and 16 h waves with s=5 and s=4, respectively, and a zonally symmetric (s=0) 9.6 h wave. The s=5(s=0) wave only occurs as a result of nonlinear interaction between SW2 and TDW3(TDE2), whereas the s=4 wave can result from interaction of TDW3 with DW1 or of TDE2 with SW2. We payed special attention to possible aliasing between different waves. Key Points The QTDW exhibits significant interannual variability The QTDW extends into the dynamo region with significant amplitudes QTDW-tide interactions produce 9.6h and 16h secondary waves