Bibliography

Seasonal Variation of Thermospheric Composition Observed by NASA GOLD

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.

Qian, Liying; Gan, Quan; Wang, Wenbin; Cai, Xuguang; Eastes, Richard; Yue, Jia;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2022     DOI: 10.1029/2022JA030496

annual variation; GOLD observation; MSIS; seasonal variation; semiannual variation; thermosphere composition

Climatology of Mesosphere and Lower Thermosphere Residual Circulations and Mesopause Height Derived From SABER Observations

In the mesosphere and lower thermosphere (MLT) region, residual circulations driven by gravity wave breaking and dissipation significantly impact constituent distribution and the height and temperature of the mesopause. The distribution of CO2 can be used as a proxy for the residual circulations. Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) CO2 volume mixing ratio (VMR) and temperature measurements from 2003 to 2020 are used to study the monthly climatology of MLT residual circulations and the mesopause height. Our analyses show that (a) mesopause height strongly correlates with the CO2 VMR vertical gradient during solstices; (b) mesopause height has a discontinuity at midlatitude in the summer hemisphere, with a lower mesopause height at mid-to-high latitudes as a result of adiabatic cooling driven by strong adiabatic upwelling; (c) the residual circulations have strong seasonal variations at mid-to-high latitudes, but they are more uniform at low latitudes; and (d) the interannual variability of the residual circulations and mesopause height is larger in the Southern Hemisphere (SH; 4–5 km) than in the Northern Hemisphere (NH; 0.5–1 km).

Wang, Ningchao; Qian, Liying; Yue, Jia; Wang, Wenbin; Mlynczak, Martin; Russell, James;

Published by: Journal of Geophysical Research: Atmospheres      Published on:

YEAR: 2022     DOI: 10.1029/2021JD035666

climatology; interannual variation; MLT region; residual circulation; seasonal variation

Pronounced Suppression and X-Pattern Merging of Equatorial Ionization Anomalies After the 2022 Tonga Volcano Eruption

Following the 2022 Tonga Volcano eruption, dramatic suppression and deformation of the equatorial ionization anomaly (EIA) crests occurred in the American sector ∼14,000 km away from the epicenter. The EIA crests variations and associated ionosphere-thermosphere disturbances were investigated using Global Navigation Satellite System total electron content data, Global-scale Observations of the Limb and Disk ultraviolet images, Ionospheric Connection Explorer wind data, and ionosonde observations. The main results are as follows: (a) Following the eastward passage of expected eruption-induced atmospheric disturbances, daytime EIA crests, especially the southern one, showed severe suppression of more than 10 TEC Unit and collapsed equatorward over 10° latitudes, forming a single band of enhanced density near the geomagnetic equator around 14–17 UT, (b) Evening EIA crests experienced a drastic deformation around 22 UT, forming a unique X-pattern in a limited longitudinal area between 20 and 40°W. (c) Thermospheric horizontal winds, especially the zonal winds, showed long-lasting quasi-periodic fluctuations between ±200 m/s for 7–8 hr after the passage of volcano-induced Lamb waves. The EIA suppression and X-pattern merging was consistent with a westward equatorial zonal dynamo electric field induced by the strong zonal wind oscillation with a westward reversal.

Aa, Ercha; Zhang, Shun-Rong; Wang, Wenbin; Erickson, Philip; Qian, Liying; Eastes, Richard; Harding, Brian; Immel, Thomas; Karan, Deepak; Daniell, Robert; Coster, Anthea; Goncharenko, Larisa; Vierinen, Juha; Cai, Xuguang; Spicher, Andres;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2022     DOI: 10.1029/2022JA030527

EIA suppression and X-pattern; Equatorial ionization anomaly; GNSS TEC; GOLD UV images; ICON MIGHTI neutral wind; Tonga volcano eruption

Comparison of GOLD nighttime measurements with total electron content: Preliminary results

The National Aeronautics and Space Administration (NASA) Global‐scale Observations of the Limb and Disk (GOLD) has been imaging the thermosphere and ionosphere since

Cai, Xuguang; Burns, Alan; Wang, Wenbin; Coster, Anthea; Qian, Liying; Liu, Jing; Solomon, Stanley; Eastes, Richard; Daniell, Robert; McClintock, William;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2020     DOI: 10.1029/2019JA027767

Annual and Semiannual Oscillations of Thermospheric Composition in TIMED/GUVI Limb Measurements

The Global UltraViolet Imager (GUVI) onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite provides a data set of vertical thermospheric composition (O, N₂, and O₂ densities) and temperature profiles from 2002\textendash2007. Even though GUVI sampling is limited by orbital constraint, we demonstrated that the GUVI data set can be used to derive the altitude profiles of the amplitudes and phases of annual oscillation (AO) and semiannual oscillation (SAO), thereby providing important constraints on models seeking to explain these features. We performed a seasonal and interannual analysis of GUVI limb O, O₂, and N₂ densities and volume number density ratio O/N₂ at constant pressure levels. These daytime observations of O and O/N₂ in the lower thermosphere show a strong AO at midlatitudes and a clear SAO at lower latitudes. The global mean GUVI O/N₂ number density ratio shows the AO, with slightly larger values in January than in July and a SAO with O/N₂ greater during equinoxes than at the solstices. O and N₂ densities on fixed pressure levels in the upper thermosphere are anticorrelated with solar extreme ultraviolet flux. On the other hand, O/N₂ is smaller during solar minimum and larger during solar maximum. The thermospheric AO and SAO in composition have a constant phase with altitude throughout the thermosphere.

Yue, Jia; Jian, Yongxiao; Wang, Wenbin; Meier, R.R.; Burns, Alan; Qian, Liying; Jones, M.; Wu, Dong; Mlynczak, Martin;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2019

YEAR: 2019     DOI: 10.1029/2019JA026544

Composition Changes Around the Equinoxes

Burns, Alan; Cai, Xuguang; Wang, Wenbin; Qian, Liying; Zhang, Yongliang; Eastes, Richard; McClintock, William;

Published by:       Published on:

YEAR: 2019     DOI:

Development and Validation of the Whole Atmosphere Community Climate Model With Thermosphere and Ionosphere Extension (WACCM-X 2.0)

Key developments have been made to the NCAR Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X). Among them, the most important are the self-consistent solution of global electrodynamics, and transport of O⁺ in the F-region. Other ionosphere developments include time-dependent solution of electron/ion temperatures, metastable O⁺ chemistry, and high-cadence solar EUV capability. Additional developments of the thermospheric components are improvements to the momentum and energy equation solvers to account for variable mean molecular mass and specific heat, a new divergence damping scheme, and cooling by O(³P) fine structure. Simulations using this new version of WACCM-X (2.0) have been carried out for solar maximum and minimum conditions. Thermospheric composition, density, and temperatures are in general agreement with measurements and empirical models, including the equatorial mass density anomaly and the midnight density maximum. The amplitudes and seasonal variations of atmospheric tides in the mesosphere and lower thermosphere are in good agreement with observations. Although global mean thermospheric densities are comparable with observations of the annual variation, they lack a clear semiannual variation. In the ionosphere, the low-latitude E \texttimes B drifts agree well with observations in their magnitudes, local time dependence, seasonal, and solar activity variations. The prereversal enhancement in the equatorial region, which is associated with ionospheric irregularities, displays patterns of longitudinal and seasonal variation that are similar to observations. Ionospheric density from the model simulations reproduces the equatorial ionosphere anomaly structures and is in general agreement with observations. The model simulations also capture important ionospheric features during storms.

Liu, Han-Li; Bardeen, Charles; Foster, Benjamin; Lauritzen, Peter; Liu, Jing; Lu, Gang; Marsh, Daniel; Maute, Astrid; McInerney, Joseph; Pedatella, Nicholas; Qian, Liying; Richmond, Arthur; Roble, Raymond; Solomon, Stanley; Vitt, Francis; Wang, Wenbin;

Published by: Journal of Advances in Modeling Earth Systems      Published on: 01/2018

YEAR: 2018     DOI: 10.1002/jame.v10.210.1002/2017MS001232

Temporal Variability of Atomic Hydrogen From the Mesopause to the Upper Thermosphere

We investigate atomic hydrogen (H) variability from the mesopause to the upper thermosphere, on time scales of solar cycle, seasonal, and diurnal, using measurements made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere Ionosphere Mesosphere Energetics Dynamics satellite, and simulations by the National Center for Atmospheric Research Whole Atmosphere Community Climate Model-eXtended (WACCM-X). In the mesopause region (85 to 95\ km), the seasonal and solar cycle variations of H simulated by WACCM-X are consistent with those from SABER observations: H density is higher in summer than in winter, and slightly higher at solar minimum than at solar maximum. However, mesopause region H density from the Mass-Spectrometer-Incoherent-Scatter (National Research Laboratory Mass-Spectrometer-Incoherent-Scatter 00 (NRLMSISE-00)) empirical model has reversed seasonal variation compared to WACCM-X and SABER. From the mesopause to the upper thermosphere, H density simulated by WACCM-X switches its solar cycle variation twice, and seasonal dependence once, and these changes of solar cycle and seasonal variability occur in the lower thermosphere (~95 to 130\ km), whereas H from NRLMSISE-00 does not change solar cycle and seasonal dependence from the mesopause through the thermosphere. In the upper thermosphere (above 150\ km), H density simulated by WACCM-X is higher at solar minimum than at solar maximum, higher in winter than in summer, and also higher during nighttime than daytime. The amplitudes of these variations are on the order of factors of ~10, ~2, and ~2, respectively. This is consistent with NRLMSISE-00.

Qian, Liying; Burns, Alan; Solomon, Stan; Smith, Anne; McInerney, Joseph; Hunt, Linda; Marsh, Daniel; Liu, Hanli; Mlynczak, Martin; Vitt, Francis;

Published by: Journal of Geophysical Research: Space Physics      Published on: 01/2018

YEAR: 2018     DOI: 10.1002/2017JA024998

Physical processes driving the thermospheric variations during the March 2015 St. Patrick's day major geomagnetic storm

Wang, Wenbin; Qian, Liying; Burns, Alan; Liu, Jing;

Published by: 42nd COSPAR Scientific Assembly      Published on:

YEAR: 2018     DOI:

Impact of the lower thermospheric winter-to-summer residual circulation on thermospheric composition

Gravity wave forcing near the mesopause drives a summer-to-winter residual circulation in the mesosphere and a reversed, lower thermospheric winter-to-summer residual circulation. We conducted modeling studies to investigate how this lower thermospheric residual circulation impacts thermospheric composition (O/N₂). We found that the upwelling associated with the residual circulation significantly decreases O/N₂ in winter and the downwelling in summer slightly increases O/N₂. Consequently, the residual circulation reduces the summer-to-winter latitudinal gradient of O/N₂, which causes the simulated latitudinal gradient of O/N₂ to be more consistent with observations. The smaller summer-to-winter latitudinal gradient of O/N₂ would decrease the ionosphere winter anomaly in model simulations, which would bring the simulated winter anomaly into better agreement with ionospheric observations. The lower thermospheric residual circulation may be a process that has been largely ignored but is very important to the summer-to-winter latitudinal gradients, as well as annual/semiannual variations in the thermosphere and ionosphere.

Qian, Liying; Yue, Jia;

Published by: Geophysical Research Letters      Published on: 05/2017

YEAR: 2017     DOI: 10.1002/2017GL073361

How the circulation can affect neutral composition at solar minimum: possible implications for the F2 region and topside ionosphere

Burns, Alan; Wang, Wenbin; Zhang, Yongliang; Qian, Liying;

Published by:       Published on:

YEAR: 2017     DOI:

Longitudinal variations of thermospheric composition at the solstices

O/N₂, measured by the Global Ultraviolet Imager on board the Thermosphere Ionosphere Mesosphere Energetics Dynamics satellite, has large longitudinal variations at the solstices, which are simulated well in upper atmosphere general circulation models. These longitudinal variations are caused by the displacement of the Earth\textquoterights magnetic poles from the geographic ones. The location of a magnetic pole affects the latitude at which the winds, driven by heating in summer, converge in the subauroral region of the winter hemisphere. In the magnetic pole\textquoterights longitude sector, this convergence occurs at relatively low latitudes, which results in the maximum values of O/N₂ also occurring at relatively low latitudes. These latitudes have a relatively small solar zenith angle, contributing to a strong winter anomaly. In the zonally opposite longitude sector, maximum values of O/N₂ occur at relatively high latitudes because the summer-to-winter wind convergence also occurs at relatively high latitudes. These high latitudes have a relatively large solar zenith angle, so ionization is weak, contributing to a weak winter anomaly. Therefore, the displacement between the magnetic and geographic poles not only results in a strong longitudinal variation of O/N₂ but also results in a strong longitudinal variation of the ionosphere winter anomaly.

Qian, Liying; Burns, Alan; Wang, Wenbin; Solomon, Stanley; Zhang, Yongliang;

Published by: Journal of Geophysical Research: Space Physics      Published on: 06/2016

YEAR: 2016     DOI: 10.1002/2016JA022898

Solar cycle variations of thermospheric composition at the solstices

We examine the solar cycle variability of thermospheric composition (O/N₂) at the solstices. Our observational and modeling studies show that the summer-to-winter latitudinal gradient of O/N₂ is small at solar minimum but large at solar maximum; O/N₂ is larger at solar maximum than at solar minimum on a global-mean basis; there is a seasonal asymmetry in the solar cycle variability of O/N₂, with large solar cycle variations in the winter hemisphere and small solar cycle variations in the summer hemisphere. Model analysis reveals that vertical winds decrease the temperature-driven solar cycle variability in the vertical gradient of O/N₂ in the summer hemisphere but increase it in the winter hemisphere; consequently, the vertical gradient of O/N₂ does not change much in the summer hemisphere over a solar cycle, but it increases greatly from solar minimum to solar maximum in the winter hemisphere; this seasonal asymmetry in the solar cycle variability in the vertical gradient of O/N₂ causes a seasonal asymmetry in the vertical advection of O/N₂, with small solar cycle variability in the summer hemisphere and large variability in the winter hemisphere, which in turn drives the observed seasonal asymmetry in the solar cycle variability of O/N₂. Since the equatorial ionization anomaly suppresses upwelling in the summer hemisphere and strengthens downwelling in the winter hemisphere through plasma-neutral collisional heating and ion drag, locations and relative magnitudes of the equatorial ionization anomaly crests and their solar cycle variabilities can significantly impact the summer-to-winter gradients of O/N₂ and their solar cycle variability.

Qian, Liying; Burns, Alan; Solomon, Stanley; Wang, Wenbin; Zhang, Yongliang;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2016

YEAR: 2016     DOI: 10.1002/2016JA022390

Thermospheric hydrogen response to increases in greenhouse gases

We investigated thermospheric hydrogen response to increase in greenhouse gases and the dependence of this response to solar activity, using a global mean version of the National Center for Atmospheric Research Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model. We separately doubled carbon dioxide (CO₂) and methane (CH₄) to study the influence of temperature and changes to source species for hydrogen. Our results indicate that both CO₂ cooling and CH₄ changes to the source species for hydrogen lead to predicted increases in the upper thermospheric hydrogen density. At 400 km, hydrogen increases ~30\% under solar maximum and ~25\% under solar minimum responding to doubling of CH₄, indicating that hydrogen response to the source variation due to CH₄ increase is relatively independent of solar activity. On the other hand, hydrogen response to doubling of CO₂ highly depends on solar activity. At 400 km, doubling of CO₂ results in an ~7\% hydrogen increase at solar maximum, whereas it is ~25\% at solar minimum. Consequently, at solar maximum, the predicted ~40\% increase in atomic hydrogen in the upper thermosphere is primarily due to the source variation as a result of doubling of CH₄, whereas at solar minimum, both cooling due to doubling of CO₂ and the source variation due to doubling of CH₄ have commensurate effects, resulting in an approximate 50\% increase in the modeled upper thermospheric hydrogen.

Nossal, S.; Qian, L.; Solomon, S.; Burns, A.; Wang, W.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 03/2016

YEAR: 2016     DOI: 10.1002/2015JA022008

Effects of the Equatorial Ionosphere Anomaly on the Inter-Hemispheric Circulation in the Thermosphere

We investigate the interhemispheric circulation at the solstices, in order to understand why O/N₂\ is larger in the northern hemisphere winter than in the southern hemisphere winter. Our studies reveal that the equatorial ionosphere anomaly (EIA) significantly impacts the summer-to-winter wind through plasma-neutral collisional heating, which changes the summer-to-winter pressure gradient, and ion drag. Consequently, the wind is suppressed in the summer hemisphere as it encounters the EIA but accelerates after it passes the EIA in the winter hemisphere. The wind then converges due to an opposing pressure gradient driven by Joule heating in auroral regions and produces large O/N₂\ at subauroral latitudes. This EIA effect is stronger near the December solstice than near the June solstice because the ionospheric annual asymmetry creates greater meridional wind convergence near the December solstice, which in turn produces larger O/N₂\ in the northern hemisphere winter than in the southern hemisphere winter.

Qian, Liying; Burns, Alan; Wang, Wenbin; Solomon, Stanley; Zhang, Yongliang; Hsu, V.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2016

YEAR: 2016     DOI: 10.1002/2015JA022169

Equatorial ionization anomaly; interhemispheric circulation; ionosphere winter anomaly; plasma-neutral collisional heating; thermosphere composition; vertical advection

Is There a Compositional Signature That Could Explain Middle Latitude Ionospheric Signatures during Sudden Stratospheric Warmings?

Burns, Alan; Qian, Liying; Wang, Wenbin; Goncharenko, Larisa; Solomon, Stanley;

Published by:       Published on:

YEAR: 2016     DOI:

Effects of the equatorial ionosphere anomaly on the interhemispheric circulation in the thermosphere

Qian, Liying; Burns, Alan; Wang, Wenbin; Solomon, Stanley; Zhang, Yongliang; , Hsu;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2016     DOI:

Explaining solar cycle effects on composition as it relates to the winter anomaly

The solar cycle variation of\ F₂\ region winter anomaly is related to solar cycle changes in the latitudinal winter-to-summer difference of O/N₂. Here we use the National Center for Atmospheric Research\textendashGlobal Mean Model to develop a concept of why the latitudinal winter-to-summer difference of O/N₂\ varies with solar cycle. The main driver for these seasonal changes in composition is vertical advection, which is expressed most simply in pressure coordinates. Meridional winds do not change over the solar cycle, so the vertical winds should also not change. The other component of vertical advection is the vertical gradient of composition. Is there any reason that this should change? At solar maximum vertical temperature gradients between 100 and 200 km altitude are strong, whereas they are weak at solar minimum. To maintain the same pressure, the weak vertical temperature gradients at solar minimum must be balanced by weak density gradients and the strong temperature gradients at solar maximum must be balanced by strong density gradients to obtain the same pressure profile. Changes in the vertical density gradients are species dependent: heavy species change more and light species change less than the average density change. Hence, vertical winds act on stronger O/N₂\ gradients at solar maximum than they do at solar minimum, and a stronger winter-to-summer difference of O/N₂\ occurs at solar maximum compared with solar minimum.

Burns, A.; Solomon, S.; Wang, W.; Qian, L.; Zhang, Y.; Paxton, L.; Yue, X.; Thayer, J.; Liu, H.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 07/2015

YEAR: 2015     DOI: 10.1002/2015JA021220

composition; solar cycle; upper atmosphere

Latitudinal and Solar Cycle Variability of Thermosphere Composition at the Solstices

Qian, Liying; Burns, Alan; Wang, Wenbin; Solomon, Stanley; Zhang, Yongliang;

Published by:       Published on:

YEAR: 2015     DOI:

On the solar cycle variation of the winter anomaly

Constellation Observing System for Meteorology, Ionosphere and Climate, Ionosonde, and Global Ultraviolet Imager data have been used to investigate the solar cycle changes in the winter anomaly (the winter anomaly is defined as the enhancement of the F₂ peak electron density in the winter hemisphere over that in the summer hemisphere) in the last solar cycle. There is no winter anomaly in solar minimum, and an enhancement of about 50\% in winter over summer ones on the same day of the year at solar maximum. This solar cycle variation in the winter anomaly is primarily due to greater winter to summer differences of [O]/[N₂] in solar maximum than in solar minimum, with a secondary contribution from the effects of temperature on the recombination coefficient between O⁺ and the molecular neutral gas. The greater winter increases in electron density in the Northern Hemisphere than in the Southern Hemisphere appear to be related to the greater annual variation of [O]/[N₂] in the north than in the south.

Burns, A.; Wang, W.; Qian, L.; Solomon, S.; Zhang, Y.; Paxton, L.; Yue, X.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 06/2014

YEAR: 2014     DOI: 10.1002/jgra.v119.610.1002/2013JA019552

Anomaly; Cycle; Ionosphere

Composition and the Winter Anomaly

Burns, Alan; Wang, Wenbin; Qian, Liying; Solomon, Stanley; Zhang, Yongliang; Paxton, Larry; Thayer, Jeffrey;

Published by:       Published on:

YEAR: 2014     DOI:

Ensemble Assimilation Using Three First-Principles Thermospheric Models as a Tool for 72-hour Density and Satellite Drag Forecasts

Hunton, Don; Pilinski, Marcin; Crowley, Geoff; Azeem, I; Fuller-Rowell, Timothy; Matsuo, Tomoko; Fedrizzi, Mariangel; Solomon, Stanley; Qian, Liying; Thayer, Jeffrey; , others;

Published by:       Published on:

YEAR: 2014     DOI:

Energetics and Composition in the Thermosphere

Burns, AG; Wang, W; Solomon, SC; Qian, L;

Published by: Modeling the Ionosphere-Thermosphere System      Published on:

YEAR: 2014     DOI:

The NCAR TIE-GCM: A community model of the coupled thermosphere/ionosphere system

Qian, Liying; Burns, Alan; Emery, Barbara; Foster, Benjamin; Lu, Gang; Maute, Astrid; Richmond, Arthur; Roble, Raymond; Solomon, Stanley; Wang, Wenbin;

Published by: Modeling the Ionosphere-Thermosphere System      Published on:

YEAR: 2014     DOI:

The anomalous ionosphere between solar cycles 23 and 24

The solar minimum period during 2008\textendash2009 was characterized by lower thermospheric density than the previous solar minimum and lower than any previously measured. Recent work used the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model to show that the primary cause of density changes from 1996 to 2008 was a small reduction in solar extreme ultraviolet (EUV) irradiance, causing a decrease in thermospheric temperature and hence a contracted thermosphere. There are similar effects in the ionosphere, with most measurements showing an F region ionosphere that is unusually low in density, and in peak altitude. This paper addresses the question of whether model simulations previously conducted, and their solar, geomagnetic, and anthropogenic inputs, produce ionospheric changes commensurate with observations. We conducted a 15 year model run and obtained good agreement with observations of the global mean thermospheric density at 400 km throughout the solar cycle, with a reduction of ~30\% from the 1996 solar minimum to 2008\textendash2009. We then compared ionosonde measurements of the midday peak density of the ionospheric F region (N_mF₂) to the model simulations at various locations. Reasonable agreement was obtained between measurements and the model, supporting the validity of the neutral density comparisons. The global average N_mF₂ was estimated to have declined between the two solar minima by ~15\%. In these simulations, a 10\% reduction of solar EUV plays the largest role in causing the ionospheric change, with a minor contribution from lower geomagnetic activity and a very small additional effect from anthropogenic increase in CO₂.

Solomon, Stanley; Qian, Liying; Burns, Alan;

Published by: Journal of Geophysical Research: Space Physics      Published on: 10/2013

YEAR: 2013     DOI: 10.1002/jgra.v118.1010.1002/jgra.50561

climate; Ionosphere; irradiance; solar; thermosphere; ultraviolet

Annual/semiannual variation of the ionosphere

We investigated the relationship between the systematic annual and semiannual variations in the ionosphere and thermosphere using a combination of data analysis and model simulation. A climatology of daytime peak density and height of the ionospheric F₂ layer was obtained from GPS radio occultation measurements by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) during 2007\textendash2010. These measurements were compared to simulations by the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). Model reproduction of the ionospheric annual and semiannual variations was significantly improved by imposing seasonal variation of eddy diffusion at the lower boundary, which also improves agreement with thermospheric density measurements. Since changes in turbulent mixing affect both the thermosphere and ionosphere by altering the proportion of atomic and molecular gases, these results support the proposition that composition change drives the annual/semiannual variation in both the neutral and ionized components of the coupled system.

Qian, Liying; Burns, Alan; Solomon, Stanley; Wang, Wenbin;

Published by: Geophysical Research Letters      Published on: 05/2014

YEAR: 2013     DOI: 10.1002/grl.50448

annual/semiannual variations; climatology; eddy diffusion; gravity waves; neutral density and composition; NmF2

Determination of the Ionospheric Electron Density Profile from FUV Remote Sensing Measurements

A limb viewing model is established in this paper based on GUVI measurements of OI 135.6 nm nightglow and a method with Chapman function describing the distribution of ionospheric electron density is presented to obtain the ionospheric electron density profile. We apply the regularization and Newton iteration method to calculate ionospheric peak electron density and peak height with GUVI measurements, eliminating the ill condition of the weighted matrix. The ionospheric electron density profile is obtained using the calculated peak electron density and peak height as inputs. To evaluate the fidelity of the proposed algorithm in this paper, the retrieved electron density profiles are compared with those from ground-based observations. The results show that the retrieved electron density profiles agree well with those from ISR. Afterwards, the effects of magnetic storms on EDP are studied with the retrieved EDPs of the period between Sep 29 and Oct 3, 2002.

Jing, Wang; Yi, TANG; Zhi-Ge, ZHANG; Xu-Li, ZHENG; Guo-Qiang, NI;

Published by: Chinese Journal of Geophysics      Published on: 03/2013

YEAR: 2013     DOI: 10.1002/cjg2.20011

Electron density profile; Far ultraviolet spectrum remote sensing; GUVI; Ionosphere

The effects of Corotating interaction region/High speed stream storms on the thermosphere and ionosphere during the last solar minimum

Burns, A.G.; Solomon, S.C.; Qian, L.; Wang, W.; Emery, B.A.; Wiltberger, M.; Weimer, D.R.;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: Jan-07-2012

YEAR: 2012     DOI: 10.1016/j.jastp.2012.02.006

Anomalously low geomagnetic energy inputs during 2008 solar minimum

Deng, Yue; Huang, Yanshi; Solomon, Stan; Qian, Liying; Knipp, Delores; Weimer, Daniel; Wang, Jing-Song;

Published by: Journal of Geophysical Research      Published on: Jan-01-2012

YEAR: 2012     DOI: 10.1029/2012JA018039

Daytime climatology of ionospheric N _m F ₂ and h _m F ₂ from COSMIC data

Burns, A.; Solomon, S.; Wang, W.; Qian, L.; Zhang, Y.; Paxton, L.;

Published by: Journal of Geophysical Research      Published on: Jan-01-2012

YEAR: 2012     DOI: 10.1029/2012JA017529

Modeling studies of the impact of high-speed streams and co-rotating interaction regions on the thermosphere-ionosphere

Solomon, Stanley; Burns, Alan; Emery, Barbara; Mlynczak, Martin; Qian, Liying; Wang, Wenbin; Weimer, Daniel; Wiltberger, Michael;

Published by: Journal of Geophysical Research      Published on: Jan-01-2012

YEAR: 2012     DOI: 10.1029/2011JA017417

The seasonal changes in the relationship between neutral composition and NmF2 from 2002 to 2007

Burns, AG; Solomon, SC; Wang, W; Qian, L; Zhang, Y; Paxton, LJ;

Published by:       Published on:

YEAR: 2012     DOI:

Progress in observations and simulations of global change in the upper atmosphere

Qian, Liying; La\vstovi\vcka, Jan; Roble, Raymond; Solomon, Stanley;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2011     DOI:

Model simulation of thermospheric response to recurrent geomagnetic forcing

Qian, Liying; Solomon, Stanley; Mlynczak, Martin;

Published by: Journal of Geophysical Research      Published on: Jan-01-2010

YEAR: 2010     DOI: 10.1029/2010JA015309

LWS FST: Determine and Quantify the Responses of Atmospheric/Ionospheric Composition and Temperature to Solar XUV Spectral Variability and Energetic Particles

Talaat, Elsayed; Fuller-Rowell, Tim; Qian, Liying; Richards, Phil; Ridley, Aaron; Burns, Alan; Bernstein, Dennis; Chamberlin, Phillip; Fedrizzi, Mariangel; Hsieh, Syau-Yun; , others;

Published by: 38th COSPAR Scientific Assembly      Published on:

YEAR: 2010     DOI:

Seasonal variation of thermospheric density and composition

Thermospheric neutral density and composition exhibit a strong seasonal variation, with maxima near the equinoxes, a primary minimum during northern hemisphere summer, and a secondary minimum during southern hemisphere summer. This pattern of variation is described by thermospheric empirical models. However, the mechanisms are not well understood. The annual insolation variation due to the Sun-Earth distance can cause an annual variation, large-scale interhemispheric circulation can cause a global semiannual variation, and geomagnetic activity can also have a small contribution to the semiannual amplitude. However, simulations by the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) indicates that these seasonal effects do not fully account for the observed annual/semiannual amplitude, primarily because of the lack of a minimum during northern hemisphere summer. A candidate for causing this variation is a change in composition, driven by eddy mixing in the mesopause region. Other observations and model studies suggest that eddy diffusion in the mesopause region has a strong seasonal variation, with eddy diffusion larger during solstices than equinoxes, and stronger turbulence in summer than in winter. A seasonal variation of eddy diffusion compatible with this description is obtained. Simulations show that when this function is imposed at the lower boundary of the TIE-GCM, neutral density variation consistent with satellite drag data and O/N₂ consistent with measurements by TIMED/GUVI, are obtained. These model-data comparisons and analyses indicate that turbulent mixing originated from the lower atmosphere may contribute to seasonal variation in the thermosphere, particularly the asymmetry between solstices that cannot be explained by other mechanisms.

Qian, Liying; Solomon, Stanley; Kane, Timothy;

Published by: Journal of Geophysical Research      Published on: 01/2009

YEAR: 2009     DOI: 10.1029/2008JA013643

eddy diffusion; thermospheric annual/semiannual variation; thermospheric density and composition

XUV Photometer System (XPS): Improved Solar Irradiance Algorithm Using CHIANTI Spectral Models

Woods, Thomas; Chamberlin, Phillip; Peterson, W.; Meier, R.; Richards, Phil; Strickland, Douglas; Lu, Gang; Qian, Liying; Solomon, Stanley; Iijima, B.; Mannucci, A.; Tsurutani, B.;

Published by: Solar Physics      Published on: Jan-08-2008

YEAR: 2008     DOI: 10.1007/s11207-008-9196-6

Impact of Eddy Diffusivity on Seasonal Variations of the Thermosphere

Qian, Liying; Solomon, Stanley; Kane, Timothy;

Published by:       Published on:

YEAR: 2008     DOI:

Solar Cycle and Seasonal Variation of Thermospheric Density and Composition

Qian, L; Solomon, SC;

Published by:       Published on:

YEAR: 2007     DOI:

Thermospheric Response to Solar EUV during Quiet and Flare Conditions

Solomon, SC; Qian, L; Gladstone, GR; Bailey, SM; Rodgers, EM;

Published by:       Published on:

YEAR: 2005     DOI: