Evidence for stratosphere sudden warming‐ionosphere coupling due to vertically propagating tides

Abstract

Observations of the Global Positioning System (GPS) total electron content (TEC) are used to study the coupling between the 2009 sudden stratospheric warming (SSW) and ionospheric perturbations. The observations reveal both migrating and nonmigrating perturbations to the semidiurnal tide in the equatorial ionization anomaly crest region that are associated with changes in electric fields induced by the tidal dynamo. In particular, a significant enhancement is observed in the nonmigrating semidiurnal westward propagating tide with zonal wavenumber 1 (SW1) in GPS TEC during the SSW. The SW1 perturbations in the low‐latitude ionosphere are found to oscillate with a similar period as planetary wave‐1 activity in the Northern Hemisphere stratosphere. This connection is attributed to the nonlinear interaction between tides and planetary waves and strongly supports the theory that planetary wave‐tide interaction is the primary mechanism coupling SSWs to ionospheric variability. Enhancements are also observed in the nonmigrating semidiurnal tide with zonal wavenumber 0 (S0) during this time period and may be related to the nonlinear interaction between the migrating semidiurnal tide and planetary wave‐2. The connection between planetary wave‐2 and S0 is, however, less clear which may be attributed to differences in the zonal mean zonal winds in the mesosphere and lower thermosphere during the times of peak planetary wave‐1 and planetary wave‐2 activity. We conclude that the changing zonal winds during SSWs play an important role in the coupling between ionospheric variability and the forcing from planetary waves of lower atmospheric origin during SSWs.