Liying Qian

The Long-term Trend of Thermospheric Compositions from Whole Atmospheric Simulation and Satellite Observation

whawkins — Tue, 11 Nov 2025 20:32:51 +0000

The Long-term Trend of Thermospheric Compositions from Whole Atmospheric Simulation and Satellite Observation whawkins Tue, 11/11/2025 - 13:32

Author:

whawkins

Nov 11, 2025

JGR space physics: This study examines the long-term trend of column-integrated atomic oxygen to molecular nitrogen ratio, O/N2, in the upper atmosphere and investigates the cause of this long-term trend in O/N2. We first validate the feasibility of using a physics-based model for a long-term climate reanalysis by applying a model-data comparison between 2002 and 2018. O/N2 simulated by NSF NCAR's Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) and measured by Global Ultraviolet Imager (GUVI) aboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission is used to determine the long-term trend of O/N2 from 2002 to 2018 and validate the model result. The model and data show good agreement after removing the impact of solar irradiance and geomagnetic activity using a least-squares fitting method, revealing a decreasing trend of O/N2 of about -0.54% per decade relative to the O/N2 in 2018 in the model and about -0.45% per decade in data along the satellite orbit during the period between 2002 and 2018. A decreasing trend of global O/N2 of about -0.70% per decade is found in the model between 1960 and 2018. After that, four WACCM-X long-term simulations are performed from 1960 to 2018 to identify the cause of the decreasing trend of O/N2. The results show that this decreasing trend is mainly caused by the increase in greenhouse gas concentrations.

O/N2 measured by TIMED/GUVI and simulated by WACCM-X Case4 and their linear trends. (a) Black and grey lines are the O/N2 data derived from TIMED/GUVI and simulated by WACCM-X, respectively. (b) Dark and light green lines are the fitting curves of the black and grey lines in (a) using the least-squares fitting method with an equation that includes the annual, semi-annual, F10.7 index, and Ap index variations. (c) The blue line is the residual term of TIMED/GUVI O/N2 by subtracting the dark green line from the black line, while the cyan line is the residual term of WACCM-X O/N2 by subtracting the light green line from the grey line. (d) Red and magenta lines are the fitting results of blue and cyan lines using the least-squares fitting method with a linear equation, respectively.

Penetrating electric field with/without disturbed electric fields During the 7-8 July 2022 geomagnetic storm simulated by MAGE and observed by ICON MIGHTI

whawkins — Wed, 09 Apr 2025 21:17:49 +0000

Penetrating electric field with/without disturbed electric fields During the 7-8 July 2022 geomagnetic storm simulated by MAGE and observed by ICON MIGHTI whawkins Wed, 04/09/2025 - 15:17

Author:

whawkins

Apr 9, 2025

7 July, MAGE simulation and ICON observation of zonal thermospheric winds and ion drifts. ICON MIGHTI observed zonal wind and MAGE simulations along the MIGHTI sampling points (right) are plotted. Data from each orbit are plotted according to the longitude. The starting time for each orbit is provided. The midnight is marked by blue triangles. MIGHTI data gaps are due to SAA (South Atlantic Anomaly) or day-night transitions (see Englert et al., 2023). The IMF Bz southward turning occurred after 12 UT, which is highlighted by a dashed oval. The nightside zonal wind start to see reaction in the next orbit. Not much change is seen on the dayside. The ExB meridional ion drifts (vertical upward at the magnetic equator) for each orbit are plotted on the right.

JGR Space Physics: Using a numerical model where the coupled physical processes of the magnetosphere, ionosphere, and thermosphere are represented, we simulated the nighttime ionospheric disturbances caused by electric fields that enter this system from the magnetosphere and electric fields generated internally by changes in the thermospheric winds. The former is quick to reach the low latitudes, and the latter is delayed by the slower response of the neutral winds. The coupled model and NASA satellite observation showed good agreement. The results show good capability and lend themselves to the future effort to forecasting space weather at low latitudes.

Evaluating F10.7 and F30 radio fluxes as long-term solar proxies of energy deposition in the thermosphere

whawkins — Tue, 25 Feb 2025 16:24:07 +0000

Evaluating F10.7 and F30 radio fluxes as long-term solar proxies of energy deposition in the thermosphere whawkins Tue, 02/25/2025 - 09:24

Author:

whawkins

Feb 25, 2025

Annale Geophsicae: We use model simulations and observations to examine how well the F10.7 and F30 solar radio fluxes have represented solar forcing in the thermosphere during the last 60 years of weakening solar activity. We found that increased saturation of radio fluxes during the last two extended solar minima leads to an overestimation of solar energy deposition, which manifests as a change in the linear relation between thermospheric parameters and F10.7. On the other hand, the linear relation between thermospheric parameters and F30 remains nearly the same throughout the whole studied period because of a recently found relative increase of F30 with respect to F10.7. This explains the earlier finding that F30 correlates better with several ionospheric and thermospheric parameters than F10.7 during recent decades. We note that continued evaluation is needed to see how well F10.7 and F30 will serve as solar proxies in the future when solar activity may start increasing toward the next grand maximum.

Averaged mass density at 400 km. Black: mass density derived from satellite drag data; blue: simulated mass density using F10.7 as a solar EUV proxy; red: simulated mass density using F30 as a solar EUV proxy. (b) Solid black: mass density ratio of the simulated density using F10.7 as a solar EUV proxy to the density derived from satellite drag; dotted red line: linear fit to the mass density ratio from 1967–1996; dotted black line: linear fit to the mass density ratio from 1967–2019; blue: daily F10.7 for reference. (c) Same as panel (b) but for the case with the simulated mass density using F30 as a solar EUV proxy.

The Formation Mechanism of Merged EIA During a Storm on 4 November 2021

whawkins — Wed, 05 Feb 2025 16:29:40 +0000

The Formation Mechanism of Merged EIA During a Storm on 4 November 2021 whawkins Wed, 02/05/2025 - 09:29

Author:

whawkins

Feb 5, 2025

Nmax observed by GOLD (a, b) and NmF2 simulated by WACCM-X (c, d) at 20:10 UT on November 03-04, 2021. The red dotted lines represent the magnetic equator. The black dotted lines represent the 0° longitude. The temporal variations of NmF2 at the 0° longitude (40°S - 40°N latitude) from 9:00 UT and 24:00 UT, simulated by WACCM-X, for November 3rd (e) and 4th (f); The corresponding temporal variations of the peak distance of the South and North EIA crests in (e) and (f), for November 3rd (g) and 4th (h).

JGR-Space Physics: In this study, we conduct an in-depth analysis of Whole Atmosphere Community Climate Model-eXtended (WACCM-X) simulations to examine physical mechanisms of the formation and evolution of an equatorial ionization anomaly (EIA) merging phenomenon during a storm on November 4th, 2021. A quantitative analysis reveals that the rapid decay of the EIA crests at their poleward sides at altitudes of ~200-250 km plays a crucial role in the EIA merging during that day. This rapid decay is due to the fast recombination at low altitudes (~200-250 km) as the plasma are transported downward by the westward disturbance dynamo electric field (DDEF) and poleward neutral winds during the storm. The results suggested EIA-merging is not merely northern and southern EIA crests moving together, but it involves a crucial rapid decay of the EIA crests at their poleward sides that descended to low altitudes (rapid recombination, ~200-250 km), driven by regional electric fields and neutral winds. This study plays a crucial role in our understanding of the evolution and formation of the merged EIA on November 4th, 2021 during the storm.

Impact of Upward Propagating Migrating Diurnal and Semidiurnal Tides on the Ionosphere-Thermosphere Seasonal Variation

whawkins — Tue, 17 Dec 2024 23:19:49 +0000

Impact of Upward Propagating Migrating Diurnal and Semidiurnal Tides on the Ionosphere-Thermosphere Seasonal Variation whawkins Tue, 12/17/2024 - 16:19

Author:

whawkins

Dec 17, 2024

Seasonal variation of the global mean (a) O/N2, (b) TEC, and (c) neutral density at 350 km in WACCM-X. The results are shown for the control simulation with all tides (black), simulation without the migrating diurnal tide (noDW1, blue), and simulation without the migrating semidiurnal tide (noDW2, red). The results illustrate the impact of the diurnal and semidiurnal tides on the seasonal variation of the thermosphere composition and neutral density as well as the ionosphere electron density.

JGR Space Physics: The Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) is used to investigate the impact of the upward propagating migrating diurnal (DW1) and semidiurnal (SW2) tides on the seasonal variability in the ionosphere and thermosphere. In the lower thermosphere, the tides induce a westward acceleration that obtains maximum values of 10-20 m/s around solstice. The tidal dissipation also changes the meridional circulation and leads to a ~5K cooling of the lower thermosphere. These changes result in a decrease in atomic oxygen in the lower thermosphere that maximizes during local winter. In the lower thermosphere, the DW1 has a greater impact around December solstice, while the SW2 has a greater impact around June solstice. The DW1 and SW2 induced changes in the lower thermosphere composition lead to changes in the thermosphere column integrated atomic oxygen to molecular nitrogen ratio (O/N2). This leads to a reduction in the thermosphere annual variation at middle to high latitudes. The DW1 and SW2 also reduce the thermosphere neutral mass density. In the ionosphere, the DW1 and SW2 decrease the zonal and diurnal mean total electron content by ~20% globally, which is primarily attributed to the reduction in thermosphere O/N2. The SW2 is found to have a greater influence on the low latitude ionosphere compared to the DW1 due to the SW2 having a greater impact on the equatorial electrodynamics. The results demonstrate that the upward propagating DW1 and SW2 both have significant effects on the ionosphere and thermosphere, including influencing the seasonal variability.

Interactions between MSTIDs and Ionospheric Irregularities in the Equatorial Region Observed on May 13-14, 2013

whawkins — Fri, 28 Jun 2024 18:19:03 +0000

Interactions between MSTIDs and Ionospheric Irregularities in the Equatorial Region Observed on May 13-14, 2013 whawkins Fri, 06/28/2024 - 12:19

Author:

whawkins

Jun 28, 2024

Airglow images from the all-sky imager (630 nm filter) located at Fuke station between 22:14 and 03:00 LT on 13-14 May, 2013. All images were mapped into the geographic coordinates by assuming that the emission layer was at an altitude of 250 km. The red circle represents the field of view of the digisonde at an altitude of 250 km. The yellow dashed lines represent the MSTID structures, and the red dashed lines represent EPB structures. The top of each image is the north and the right of each image is east.

Remote Sensing: We investigate the interactions between medium-scale traveling ionospheric disturbances (MSTIDs) and the equatorial ionization anomaly (EIA), and between MSTIDs and equatorial plasma bubbles (EPBs) on the night of May 13-14, 2013, based on observations from multiple instruments (all-sky imager, digisonde, and global positioning system (GPS)). Two dark bands (the low plasma density region) of MSTIDs were observed moving towards each other, encountered, and interacted with the EIA, and subsequently interacted again with the EIA before eventually dissipated. Then, a new dark band of MSTIDs moved in the southwest direction, drifted into the all-sky imager’s field of view (FOV), and interacted with the EIA. Following this interaction, a new dark band split off from the original dark band, slowly moved in the northeast direction and eventually faded away in a short time. Subsequently, the original southwestward-propagating dark band of the MSTIDs encountered eastward-moving EPBs, leading to an interaction between the MSTIDs and the EPBs. Then, the dark band of the MSTIDs faded away, while the EPBs grew larger with a pronounced westward tilt. Results from various observational instruments indicate the pivotal role played by the high-density region of the EIA in the occurrence of various interaction processes. In addition, this study also revealed that MSTIDs propagating into the equatorial region can significantly impact the morphology and evolution characteristics of EPBs.

HIWIND Balloon and Antarctica Jang Bogo FPI High Latitude Conjugate Thermospheric Wind Observations and Simulations

whawkins — Fri, 21 Jun 2024 18:59:58 +0000

HIWIND Balloon and Antarctica Jang Bogo FPI High Latitude Conjugate Thermospheric Wind Observations and Simulations whawkins Fri, 06/21/2024 - 12:59

Author:

whawkins

Jun 21, 2024

JGR Space Physics: Using balloon instrument in the northern hemisphere and ground based instrument in the southern hemisphere, we study the conjugacy of the thermospheric winds of high latitudes. We found that the more summer hemispheric heating alters the thermospheric winds and resulted in a double-hump feature on the dayside meridional winds. We also used model with cusp heating to simulate the winds and were able to reproduce the double-hump feature.

Thermospheric wind observations from HIWIND (northern summer) and JBS (southern winter) along with the TIEGCM simulations at the respective locations. The JBS data were shifted by 7 hours so that the local time of the JBS is approximately equal to that of HIWIND. The meridional winds from JBS were reversed so that the poleward meridional winds from JBS is positive for easy comparison with HIWIND data. The prominent double hump feature in northern hemisphere meridional winds (HIWIND, upper penal) is a result of the high energy input in the summer hemisphere.
Which working group is this paper relevant to?

MAGE Model Simulation of the Pre-reversal Enhancement and Comparison with ICON and Jicamarca ISR Observations

whawkins — Fri, 21 Jun 2024 18:52:03 +0000

MAGE Model Simulation of the Pre-reversal Enhancement and Comparison with ICON and Jicamarca ISR Observations whawkins Fri, 06/21/2024 - 12:52

Author:

whawkins

Jun 21, 2024

JGR Space Physics: Using the latest coupled geospace model MAGE (Multiscale Atmosphere-Geospace Environment) and observations from Jicamarca ISR and ICON IVM instrument, we examine the pre-reversal enhancement during geomagnetic quiet time period. The MAGE shows comparable PRE to both the Jicamarca ISR and ICON observations. There appears to be a discrepancy between the Jicamarca ISR and ICON IVM with the later showed PRE about two times larger (~ 40 m/s). This is the first time that MAGE is used to simulate the PRE. The results show that the MAGE can simulate the PRE well and are mostly consistent with observations.

MAGE simulations of the equatorial vertical ion drifts (black vectors along the magnetic equator) at 23:49 UT. The MAGE simulated ExB meridional ion drift (IVM definition) sampled along the ICON satellite track (black line above the satellite track shown as the dashed line) and the IVM observed ExB meridional drift (lime or magenta vector) from 23:15 to 23:55 UT. The magenta vectors are values near 2349 UT. The PRE is visible in the simulated equatorial vertical ion drift and in both the MAGE simulated and ICON observed ExB meridional ion drifts along the satellite tracks . The background shows the nmf2 from the MAGE simulation.

Climate Change in the Thermosphere and Ionosphere From the Early Twentieth Century to Early Twenty‐First Century Simulated by the Whole Atmosphere Community Climate Model—eXtended

whawkins — Fri, 02 Feb 2024 22:11:17 +0000

Climate Change in the Thermosphere and Ionosphere From the Early Twentieth Century to Early Twenty‐First Century Simulated by the Whole Atmosphere Community Climate Model—eXtended whawkins Fri, 02/02/2024 - 15:11

Author:

whawkins

Feb 2, 2024

Five-year zonal mean decadal value differences relative to the 1920s at March equinox (top) and June solstice (bottom) for neutral temperature on the 2.84×10-8 hPa pressure surface a) at ~295 km and e) at ~285 km, neutral density b) at ~377 km and f) at ~395 km, electron density c) at ~377 km and g) at ~395 km, and d) and h) electron column density.

Journal of Geophysical Research, Atmospheres: From seeing lower atmosphere computer climate models run for the past century, we decided to do the same for the upper atmosphere using the Whole Atmosphere Community Climate Model-eXtended (WACCM-X) for the decades from the 1920s to 2010s. In this higher region, the atmosphere is affected strongly by the Sun and removing the Sun’s effect is tricky in previous observation and model studies. We make the Sun’s effect small to see only effects from the Earth’s magnetic field and greenhouse gases. Earlier studies focused on recent decades show effects of greenhouse gas increases on the upper atmosphere but not for the early decades of the past century with greenhouse gas changes from less than 5% increase prior to the space age and the transition to the over 25% increase in the latter half of the 20th century. We cover this entire period and get results like those in studies before, with especially the temperature change matching very well with the greenhouse gas carbon dioxide change. Because WACCM-X performs well over the past century, it will be useful to predict what will happen in the century ahead as greenhouse gases increase and humans make efforts to reverse the increase.

Investigation of the physical mechanism of the formation and evolution of equatorial plasma bubbles during a moderate storm on September 17, 2021

whawkins — Wed, 06 Dec 2023 16:34:59 +0000

Investigation of the physical mechanism of the formation and evolution of equatorial plasma bubbles during a moderate storm on September 17, 2021 whawkins Wed, 12/06/2023 - 09:34

Author:

whawkins

Dec 6, 2023

GOLD Namx on September 16-17, 2021. Left panels show the observations on the night of September 16th, while right panels show the observations on the night of September 17th. The red dotted lines represent the magnetic dip equator.

Space Weather: We investigate in detail the occurrence and evolution of ionospheric equatorial plasma bubbles (EPBs) during a moderate storm on September 17th, 2021, using Global-scale Observation of the Limb and Disk (GOLD) observations and Whole Atmosphere Community Climate Model-eXtended (WACCM-X) simulations. GOLD observations show that there were no EPBs on September 16th before the storm but EPBs occurred after the storm commencement on September 17th. The EPBs extended to ~ 30° magnetic latitude. A diagnostic analysis of WACCM-X simulations reveals that the rapid enhancement of prompt penetration electric fields (PPEFs) after the sudden storm commencement is the main reason that triggered the occurrence of the EPBs. Further quantitative analysis shows that vertical plasma drifts, which are enhanced by the PPEF, played a dominant role in strengthening the Rayleigh-Taylor instability, leading to the occurrence of the EPBs and the large latitudinal extension of the EPBs to ~ 30° magnetic latitude during the night of September 17th.

Liying Qian

The Long-term Trend of Thermospheric Compositions from Whole Atmospheric Simulation and Satellite Observation

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Penetrating electric field with/without disturbed electric fields During the 7-8 July 2022 geomagnetic storm simulated by MAGE and observed by ICON MIGHTI

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Evaluating F10.7 and F30 radio fluxes as long-term solar proxies of energy deposition in the thermosphere

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The Formation Mechanism of Merged EIA During a Storm on 4 November 2021

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Impact of Upward Propagating Migrating Diurnal and Semidiurnal Tides on the Ionosphere-Thermosphere Seasonal Variation

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Interactions between MSTIDs and Ionospheric Irregularities in the Equatorial Region Observed on May 13-14, 2013

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HIWIND Balloon and Antarctica Jang Bogo FPI High Latitude Conjugate Thermospheric Wind Observations and Simulations

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MAGE Model Simulation of the Pre-reversal Enhancement and Comparison with ICON and Jicamarca ISR Observations

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Climate Change in the Thermosphere and Ionosphere From the Early Twentieth Century to Early Twenty‐First Century Simulated by the Whole Atmosphere Community Climate Model—eXtended

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Investigation of the physical mechanism of the formation and evolution of equatorial plasma bubbles during a moderate storm on September 17, 2021

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