Abstract
This study examines the influence of the El Niño–Southern Oscillation (ENSO) on the ionospheric total electron content (TEC) diurnal eastward 3 (DE3) and stationary planetary wave 4 (SPW4) which are the major components of the ionospheric wave-4 longitudinal structure. The TEC is the integration of electron density from 200 to 800 km sounded by the GPS radio occultation experiment onboard the FORMOSAT-3/COSMIC satellites during the period of January 2007–December 2015. The results show that the TEC DE3 and SPW4 amplitudes respond to the ENSO signature in the thermospheric wind DE3 in the Northern Hemisphere during the lower-solar-activity period. The contribution of the ENSO cold phase in 2010 and 2011 to the quasi-biennial oscillation in the TEC DE3 and SPW4 amplitudes is not negligible.
Highlights
Ionospheric plasma density structures are highly variable on broad range of temporal and spatial scales, and the solar activity and lower atmosphere forcing are the major drivers
This study conducts the zonal wind diurnal eastward 3 (DE3) amplitude observed by Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED)/TIMED Doppler Interferometer (TIDI) at 100 km altitude to suggest a causal mechanism for the ionospheric tide/SPW response to the El Niño–Southern Oscillation (ENSO) phases
The agreement reveals that, besides the effect of the solar radiation and ionosphere/thermosphere composition changes, the ENSO-related wind DE3 variation contributes to the quasi-biennial oscillation (QBO) in the total electron content (TEC) DE3 and stationary planetary wave 4 (SPW4) during the strong 2010/2011 ENSO cold phase
Summary
Ionospheric plasma density structures are highly variable on broad range of temporal and spatial scales, and the solar activity and lower atmosphere forcing are the major drivers. During the 2010/2011 strong ENSO cold phase, enhanced forcing from below during the winter months causes a ~ 70% increase in the zonal wind DE3 tide in the MLT region. This study conducts the zonal wind DE3 amplitude observed by Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED)/TIMED Doppler Interferometer (TIDI) at 100 km altitude to suggest a causal mechanism for the ionospheric tide/SPW response to the ENSO phases. The ENSO can modulate the stratospheric QBO (Taguchi 2010) as well as the QBO components in the temperature DW1 and DE3 in the MLT (Sun et al 2018) Both the wind DE3 in the lower thermosphere and solar activity can affect the QBO in the TEC tidal/SPW amplitudes (Chang et al 2016; Wang et al 2018). 1998) is applied to show an overall feature of the temporal variation in the tidal amplitudes on various scales
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