Observations and Simulations of Eddy Diffusion and Tidal Effects on the Semiannual Oscillation in the Ionosphere

Wu, Qian; Schreiner, William S.; Ho, Shu‐Peng; Liu, Hanli; Qian, Liying

doi:10.1002/2017ja024341

Cited by 11 publications

(10 citation statements)

References 31 publications

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“…The lower atmosphere can also contribute to the latitudinal dependency of the summer‐to‐winter difference in ∑ O/N 2 . Seasonal and latitudinal variations in wave/tidal activity, turbulent mixing, and residual circulations in the mesosphere and lower thermosphere region strongly impact the seasonal and latitudinal variations of thermosphere composition (e.g., Jones et al., 2017 , 2014 ; Wu et al., 2017 ; Yamazaki & Richmond, 2013 ). For example, the lower thermospheric residual circulation reduces the summer‐to‐winter gradient of O/N 2 (Qian & Yue, 2017 ).…”

Section: Discussionmentioning

confidence: 99%

Seasonal Variation of Thermospheric Composition Observed by NASA GOLD

et al. 2022

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We examine characteristics of the seasonal variation of thermospheric composition using column number density ratio ∑O/N2 observed by the NASA Global Observations of Limb and Disk (GOLD) mission from low‐mid to mid‐high latitudes. We also use ∑O/N2 derived from the Global Ultraviolet Imager (GUVI) limb measurements onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite and estimated by the NRLMSISE‐00 empirical model to aid our investigation. We found that the ∑O/N2 seasonal variation is hemispherically asymmetric: in the southern hemisphere, it exhibits the well‐known annual and semiannual pattern, with highs near the equinoxes, and primary and secondary lows near the solstices. In the northern hemisphere, it is dominated by an annual variation, with a minor semiannual component with the highs shifting toward the wintertime. We also found that the durations of the December and June solstice seasons in terms of ∑O/N2 are highly variable with longitude. Our hypothesis is that ion‐neutral collisional heating in the equatorial ionization anomaly region, ion drag, and auroral Joule heating play substantial roles in this longitudinal dependency. Finally, the rate of change in ∑O/N2 from one solstice season to the other is dependent on latitude, with more dramatic changes at higher latitudes.

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Section: Discussionmentioning

confidence: 99%

Seasonal Variation of Thermospheric Composition Observed by NASA GOLD

et al. 2022

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“…

{n}_{{O}_{2}^{+}}

decreases continuously for the entire 27‐day solar rotation period, which is also due to the accumulation of O + (decreased loss). Under realistic conditions, variations of the eddy diffusion are smaller (Salinas et al., 2016; Wu et al., 2017) and therefore a smaller influence on the delay is expected. The effect on the neutral components must also be considered when variations in eddy diffusion occur (Qian et al., 2009, 2013).…”

Section: Simulation Of the Height‐dependent Delayed Ionospheric Responsementioning

confidence: 99%

The Height‐Dependent Delayed Ionospheric Response to Solar EUV

et al. 2022

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Based on the analysis of electron density Ne profiles (Grahamstown ionosonde), a case study of the height‐dependent ionospheric response to two 27‐day solar rotation periods in 2019 is performed. A well‐defined sinusoidal response is observed for the period from 27 April 2019 to 24 May 2019 and reproduced with a Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model simulation. The occurring differences between model and observations as well as the driving physical and chemical processes are discussed based on the height‐dependent variations of Ne and major species. Further simulations with an artificial noise free sinusoidal solar flux input show that the Ne delay is defined by contributions due to accumulation of O+ at the Ne peak (positive delay) and continuous loss of O2+ ${\mathrm{O}}_{2}^{+}$ in the lower ionosphere (negative delay). The neutral parts' 27‐day signatures show stronger phase shifts. The time‐dependent and height‐dependent impact of the processes responsible for the delayed ionospheric response can therefore be described by a joint analysis of the neutral and ionized parts. The return to the initial ionospheric state (and thus the loss of the accumulated O+) is driven by an increase of downward transport in the second half of the 27‐day solar rotation period. For this reason, the neutral vertical winds (upwards and downwards) and their different height‐dependent 27‐day signatures are discussed. Finally, the importance of a wavelength‐dependent analysis, statistical methods (superposed epoch analysis), and coupling with the middle atmosphere is discussed to outline steps for future analysis.

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“…Recently, Wu et al (2017) showed that imposing the Qian et al (2009) IAVs in K zz in the TIE-GCM improved the model's capability of reproducing observed IAVs in electron density measured by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. Analogous to the TIME-GCM results presented in Jones et al (2017), Wu et al (2017) demonstrated that tidal dissipation in the MLT region damps the ionospheric SAO in the TIE-GCM. Examination of both observed and modeled IAVs in TEC, N m F 2 , and electron density peak height (h m F 2 ) strongly suggests that the ionospheric SAO is largely driven in direct response to the SAO in thermospheric O/N 2 , as demonstrated by Rishbeth, Müller-Wodarg, et al (2000).…”

Section: Introductionmentioning

confidence: 99%

“…In particular, Rishbeth, Müller-Wodarg, et al (2000) expounded on the physical discussion of the TSM presented by Fuller-Rowell (1998) stating that IAVs in O/N 2 at low and middle latitudes driven by IAVs in the large-scale thermospheric meridional and vertical circulation directly forced an ionospheric SAO in the peak electron density (N m F 2 ). Recently, Wu et al (2017) showed that imposing the Qian et al (2009) IAVs in K zz in the TIE-GCM improved the model's capability of reproducing observed IAVs in electron density measured by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. Analogous to the TIME-GCM results presented in Jones et al (2017), Wu et al (2017) demonstrated that tidal dissipation in the MLT region damps the ionospheric SAO in the TIE-GCM.…”

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confidence: 99%

Origins of the Thermosphere‐Ionosphere Semiannual Oscillation: Reformulating the “Thermospheric Spoon” Mechanism

et al. 2018

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We demonstrate how Earth's obliquity generates the global thermosphere‐ionosphere (T‐I) semiannual oscillation (SAO) in mass density and electron density primarily through seasonally varying large‐scale advection of neutral thermospheric constituents, sometimes referred to as the “thermospheric spoon” mechanism (TSM). The National Center for Atmospheric Research thermosphere‐ionosphere‐mesosphere‐electrodynamics general circulation model (TIME‐GCM) is used to isolate the TSM forcing of this prominent intraannual variation (IAV) and to elucidate the contributions of other processes to the T‐I SAO. An ∼30% SAO in globally averaged mass density (relative to its global annual average) at 400 km is reproduced in the TIME‐GCM in the absence of seasonally varying eddy diffusion, tropospheric tidal forcing, and gravity wave breaking. Artificially, decreasing the tilt of Earth's rotation axis with respect to the ecliptic plane to 11.75° reduces seasonal variations in insolation and weakens interhemispheric pressure differences at the solstices, thereby damping the global‐scale, interhemispheric transport of atomic oxygen (O) and molecular nitrogen in the thermosphere and reducing the simulated global mass density SAO amplitude to ∼10%. Simulated T‐I IAVs in mass density and electron density have equinoctial maxima at all latitudes near the F2 region peak; this phasing and its latitude dependence agree well with empirically inferred climatologies. When tropospheric tides and gravity waves are included, simulated IAV amplitudes and their latitudinal dependence also agree well with empirically inferred climatologies. Simulated meridional and vertical transport of O due to the TSM couples to the upper mesospheric circulation, which also contributes to the T‐I SAO through O chemistry.

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Observations and Simulations of Eddy Diffusion and Tidal Effects on the Semiannual Oscillation in the Ionosphere

Cited by 11 publications

References 31 publications

Seasonal Variation of Thermospheric Composition Observed by NASA GOLD

Seasonal Variation of Thermospheric Composition Observed by NASA GOLD

The Height‐Dependent Delayed Ionospheric Response to Solar EUV

Origins of the Thermosphere‐Ionosphere Semiannual Oscillation: Reformulating the “Thermospheric Spoon” Mechanism

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