Observation of the neutral‐ion coupling through 6 day planetary wave

Abstract

A westward 6 day oscillation with zonal wave number 1 is identified in the global maps of the ionospheric total electron content (TEC) during May 2003. This signature coincides with the wave activities in the mesosphere and lower thermosphere (MLT) region with a similar zonal structure and period, deduced from the temperature and wind observations from the Thermosphere Ionosphere and Mesosphere Electric Dynamics (TIMED) satellite. The vertical wavelength of this 6 day wave is estimated to be~65 km, which enables it to propagate up into the lower thermosphere and therefore modulate the ionosphere through E region wind dynamo. The zonal wind perturbations of the 6 day wave maximize in the equatorial region with an amplitude of~30 m/s and the meridional wind perturbations peak at middle latitudes with an amplitude of 15-20 m/s. The 6 day oscillation in TEC peaks at the geomagnetic equatorial ionization anomaly (EIA) crests in both hemispheres with a deep minimum at the equator. The absolute TEC perturbations maximize at~1400-1800 LT with an amplitude of~9 (~7) total electron content unit (TECU; 1 TECU = 10 16 m À2 ) in the southern (northern) hemisphere, which account for~16% (~10%) of the background TEC. Larger relative TEC perturbations of~20% are found at 0200-0400 LT. The similar wave number-period spectra and the consistent temporal variations of the 6 day periodical signatures in both neutral atmosphere and ionosphere suggest a strong neutral-ion coupling through planetary wave.

Climatology of the Quasi‐6‐Day Wave in the Mesopause Region and Its Modulations on Total Electron Content During 2003–2017

“…The International Global Navigation Satellite System Service uses data from global GPS network to generate the global maps of TEC at 2.5° × 5° latitude‐longitude grids and 2‐hr universal time intervals (Mannucci et al, ). TEC data are broadly utilized to investigate ionospheric responses to the lower atmosphere through the planetary waves and solar tide waves (Chang et al, ; Gu, Dou, et al, ; Gu, Liu, et al, ; Liu et al, ; Wan et al, , ). The TEC during every Q6DW event recorded in section is analyzed to study the ionospheric responses.…”

“…This is because the ionospheric parameters are governed by geomagnetic lines and strongly influenced by solar fluxes, which makes the extraction of planetary wave signals more complicated. Therefore, the TEC observations at different local times are analyzed separately to exhibit the planetary wave signal more clearly, following Gu, Dou, et al (), Gu, Liu, et al (), and Liu et al ().…”

“…Therefore, the research on this aspect is a focus of space physics research at the present. The westward quasi‐6‐day planetary wave (Q6DW) with zonal wave number 1 (W1) has been reported many times in different atmospheric variables during the last few years (Gu et al, ; Jiang et al, ; Lieberman et al, ; Liu et al, ; Miyoshi & Hirooka, ; Pancheva et al, ; Riggin et al, ; Talaat et al, ; Wu et al, ). Wu et al () reported the 5‐day planetary wave in the horizontal winds measured by High‐Resolution Doppler Imager aboard the Upper Atmosphere Research Satellite in the mesosphere and lower thermosphere (MLT) region and first declared that the 5‐ to 7‐day planetary wave may be Rossby (1,1) wave mode because of the similarities in their horizontal structure.…”

Variability and predictability of the space environment as related to lower atmosphere forcing

“…Oscillations of F region electron density with periods 2 and 6.5days are identified from midlatitude ground‐based observations and are assumed to be caused by TPWs [ Altadill and Apostolov , ]. Analyses of concurrent neutral dynamics and ionospheric observations provided further evidence linking planetary‐scale waves with ionospheric variability: Pancheva et al [] related QTDW observed in MLT neutral wind measurements to quasi‐2day oscillations of both F region electron density and ionospheric current; Gu et al [] found clear correspondence between 6day wave from temperature and wind measurements by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) and TIMED Doppler Interferometer (TIDI) on NASA's Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellites with 6day oscillation in total electron content (TEC). Ionospheric variabilities have also been related to TPWs (and also UFKWs) with periods between 5 and 6days identified in MLT neutral winds and in National Centers for Environmental Prediction (NCEP) reanalysis data [ Pancheva et al , ].…”

Short‐term variability in the ionosphere due to the nonlinear interaction between the 6 day wave and migrating tides

“…By diagnosing global data materials, Gu et al . [] showed 6 day oscillations in the total electron content (TEC), concurrent with the 6 day wave event in the mesosphere in May 2003. Meanwhile, Gan et al .…”