Longitudinal structure in electron density at mid-latitudes: Upward-propagating tidal effects 3. Space science

Abstract

This work studies the upward-propagating migrating and non-migrating tidal effects from the lower atmosphere on the longitudinal variation of electron density (ΔN e) in both the E and F regions at mid-latitudes during the 2002 March equinox. A total of 12 runs are conducted using the Thermosphere Ionosphere Electrodynamic General Circulation model for theoretical investigation. The Δ N e at altitudes above 200 km is affected by upward-propagating tides, with maximum values attained around 300 km. Migrating tides result in reduced longitudinal differences in the Δ N e over North America and in the Southern Hemisphere, while non-migrating tides induce a wave-4 pattern in both hemispheres. The non-migrating effect is weaker than the migrating effect after penetrating into the F region. The neutral composition (i.e., ratio of atom oxygen to molecular nitrogen) is dominant in regulating the Δ N e in both the migrating (accounting for approximately 64%) and non-migrating (about 60%) tidal penetration processes. The Δ N e caused by the tidal meridional wind (accounting for approximately 70%) is stronger than the tidal zonal wind (about 30%) under both the migrating and non-migrating tidal conditions, except in the Southern Hemisphere under migrating tidal input. This work contributes to our understanding of the mechanisms for the longitudinal modulation of the Δ Ne at mid-latitudes.