Joseph McInerney

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.

Impact of increasing greenhouse gases on the ionosphere and thermosphere response to a May 2024-like geomagnetic superstorm

whawkins — Tue, 24 Jun 2025 18:38:29 +0000

Impact of increasing greenhouse gases on the ionosphere and thermosphere response to a May 2024-like geomagnetic superstorm whawkins Tue, 06/24/2025 - 12:38

Author:

whawkins

Jun 24, 2025

CESM(WACCM-X) (a) absolute global mean thermosphere neutral density, (b) storm-time change in global mean thermosphere neutral density, and (c) relative storm-time change in global mean thermosphere neutral density. (d) Geomagnetic Kp index used as forcing in CESM(WACCM-X). The CESM(WACCM-X) neutral density results are at an altitude of 350 km, and the storm-time changes are calculated relative to the average values on May 8-9 in each scenario. The storm is simulated in years 2016, 2040, 2061, and 2084, which have surface CO2 values of 403, 500, 652, and 918 ppmv.

Geophysical Research Letters: Geomagnetic storms lead to large changes in the Earth’s upper atmosphere (ionosphere and thermosphere) that can have adverse effects on technological systems, such as GPS positioning and orbits of satellites in low-Earth orbit (200-2000 km). It is now understood that increases in greenhouse gas concentrations result in a decrease in the thermosphere neutral density. This is primarily due to CO2 being a radiative cooler at high altitudes, leading to a reduction in temperatures in the mesosphere and thermosphere, and a contraction of the upper atmosphere. The ionosphere is also impacted by changes in CO2. The present study is focused on understanding how changes in the background state of the upper atmosphere due to increases in CO2 alter the response of the ionosphere and thermosphere to geomagnetic storms. Using a coupled Earth system model that includes an atmospheric component that extends to the ionosphere and thermosphere, the response of the upper atmosphere to a geomagnetic superstorm is simulated for different levels of CO2 concentrations. It is found that increasing levels of CO2 generally result in a weaker response of the ionosphere and thermosphere to geomagnetic storms in absolute terms, while their relative responses enhance at higher CO2 levels.

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.

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.

Investigation of the GOLD Observed Merged Nighttime EIA with WACCM-X Simulations during the Storm of November 3–4, 2021

whawkins — Tue, 27 Jun 2023 20:31:42 +0000

Investigation of the GOLD Observed Merged Nighttime EIA with WACCM-X Simulations during the Storm of November 3–4, 2021 whawkins Tue, 06/27/2023 - 14:31

Author:

whawkins

Jun 27, 2023

Geophysical Research Letters: During the storm on November 3 to 4, 2021, the Global-scale Observations of the Limb and Disk (GOLD) mission observed well separated EIA crests post sunset on Nov 3, but merged EIA on Nov 4. We used the Whole Atmosphere Community Climate Model (WACCM-X) to simulate the EIA structures during the two nights. The simulations show two separated post sunset EIA crests on November 3rd but merged post sunset EIA crests on November 4th, which are qualitatively consistent with the GOLD observations. Numerical simulations and Ionospheric Connection Explorer (ICON) neutral wind observations illustrate that the formation of merged EIA crests was due to several hours of downward E × B drifts before and after sunset. Further diagnostic analysis revealed that it was mainly driven by westward electric fields caused by the disturbance dynamo electric field during the recovery phase of the storm.

Nmax observed by GOLD and NmF2 simulated by WACCM-X at 20:10 UT on November 03-04, 2021. The red dotted lines represent the magnetic equator.

Climate responses under an extreme quiet sun scenario

whawkins — Tue, 14 Feb 2023 17:32:02 +0000

Climate responses under an extreme quiet sun scenario whawkins Tue, 02/14/2023 - 10:32

Author:

whawkins

Feb 14, 2023

Understanding how climate may change under different solar conditions is both interesting and important. However it is difficult to clearly identify solar signal from the very large climate variability on broad time scales. In this study, we tackle this problem by providing a lower bound of the solar minimum condition according to our current understanding of solar physics. By specifying this extremely low solar minimum condition in a climate model that takes into consideration of the effects of ocean and middle atmosphere, we are able to identify significant climate responses, which are very different between the northern and southern hemispheres. We gain an understanding of the processes driving these responses, including how the lower and upper atmospheric processes may enhance/offset each other. By comparing these climate responses to those under nominal solar minimum conditions, we expose climate patterns that are hidden under the large climate variability in the latter.

Differences of average zonal mean zonal wind (color contours) between 50--200 year of HD and Smax simulations for (a) DJF and (c) JJA. Line contours are average zonal mean zonal wind from Smax simulations (contour intervals: 15 m/s. (b) and (d): similar to (a) and (c) but for average zonal mean temperature differences (color contour and grey line contours for differences less than 1 K, with 0.25 K intervals). Line contours are average zonal mean temperature from Smax simulations (contour intervals: 10 K). (e) and (g): similar to (a) and (c) but for average vertical EP flux component differences. The EP flux (unit: Pa m) is normalized by p^0.75 (p: atmosphere pressure) to better visualize the change at all altitudes (color contour). Line contours are average normalized vertical EP flux component from Smax simulations (contour intervals: 10x10^2). (f) and (h): similar to (a) and (c) but for average EP flux divergence differences (color contour). Line contours are average EP flux divergence from Smax simulations (contour intervals: 1 m/s/d).}

Thermospheric Neutral Density Variation during the "SpaceX" Storm: Implications from Physics-based Whole Geospace Modeling

whawkins — Wed, 23 Nov 2022 18:32:53 +0000

Thermospheric Neutral Density Variation during the "SpaceX" Storm: Implications from Physics-based Whole Geospace Modeling whawkins Wed, 11/23/2022 - 11:32

Author:

whawkins

Nov 23, 2022

Space Weather—Dong Lin, Wenbin Wang, Katherine Garcia-Sage, Jia Yue, Viacheslav Merkin, Joseph McInerney, Kevin Pham, Kareem Sorathia

Neutral density variations along the Starlink orbit calculated by (a) MAGE, (b) TIEGCM, (c) DTM-2012, and (d) NRLMSIS 2.0. (e) Relative variations of neutral density based on the values on February 1 at the same UT and location. (f) Starlink altitude. (g) The Ap index used to drive NRLMSIS 2.0.

On February 3, 2022, 40 Starlink satellites were launched by the SpaceX Corporation when a moderate geomagnetic storm occurred, followed by another storm on February 4. The storm activities have been regarded as the culprit for the loss of the Starlink satellites afterwards. Although strong geomagnetic storms are well-known to be able to increase the neutral atmospheric mass density so as to satellite drag in the thermosphere where many space vehicles are orbiting around the Earth, a not-so-strong storm was not expected to bring such huge impacts based on engineering design evaluation using empirical atmospheric density models. This study compares the performance of a state-of-the-art physics-based, fully coupled whole geospace model and empirical models in predicting the neutral mass density variation in the thermosphere. It turns out that the physics-based model is more accurate in capturing the magnitude of storm enhancement of neutral density. It also resolves the gradual recovery process even though it is not reflected in some geomagnetic indices that are used to drive the empirical models. Using such first-principles whole geospace model is suggested as a necessary step in future space weather applications.

Investigation of the Post-Sunset Extra Electron Density Peak Poleward of the Equatorial Ionization Anomaly Southern Crest

whawkins — Tue, 18 Oct 2022 16:36:05 +0000

Investigation of the Post-Sunset Extra Electron Density Peak Poleward of the Equatorial Ionization Anomaly Southern Crest whawkins Tue, 10/18/2022 - 10:36

Author:

whawkins

Oct 18, 2022

JGR Space Physics—Xuguang Cai, Liying Qian, Wenbin Wang, Joseph M. McInerney, Han-Li Liu, and Richard W. Eastes

The Global-scale observation of limb and disk mission observed an extra electron density (Ne) peak after sunset at approximately 30°S near 40°W on 4 November 2019, which is poleward and immediately next to the southern equatorial ionization anomaly (EIA) crest. This Ne peak is different from previously reported mid-latitude peaks that occur at all local times. The Whole Atmosphere Community Climate Model-eXtended captures this phenomenon. Model diagnostic analysis reveals that the decrease of Ne and hmF2 between 15° and 25°S makes Ne near 30°S appear as an extra density peak relative to the southern EIA crest. Transport by poleward meridional wind decreases Ne between 15° and 25°S. Moreover, the upward E × B drifts due to pre-reversal enhancement lift the plasma between the dip equator and 15°S but do not affect Ne much between 15° and 25°S with a low drift speed. Comparison with days without the extra peak shows the importance of E × B drift latitudinal variations on the extra peak formation. This study provides new insights into the dynamic variability of the nighttime ionosphere.

Latitude-longitude distribution of OI 135.6 nm radiance observed by GOLD (top) and NmF2 simulated by WACCM-X (bottom) from 21:55 UT to 22:55 UT on DOY 308 in 2019.

Climate Changes in the Upper Atmosphere: Contributions by the Changing Greenhouse Gas Concentrations and Earth's Magnetic Field From the 1960s to 2010s

kolinski — Mon, 15 Nov 2021 21:52:05 +0000

Climate Changes in the Upper Atmosphere: Contributions by the Changing Greenhouse Gas Concentrations and Earth's Magnetic Field From the 1960s to 2010s kolinski Mon, 11/15/2021 - 14:52

Publication: JGR; HAO Author: Liying Qian; Authors as listed in article: Liying Qian, Joseph M. McInerney, Stan S. Solomon, Hanli Liu, and Alan G. Burns

Author:

kolinski

Nov 15, 2021

Previous studies have established the importance of the increasing greenhouse gas concentrations in causing trends in the thermosphere and ionosphere (T-I). Recent work indicates that the changing Earth’s magnetic field is also important. We conduct whole atmosphere model simulations to examine T-I trends driven by these two drivers and their relative importance.

Simulated thermosphere and ionosphere temperatures at 300 km in the 1960s, thermosphere mass density at 400 km in the 1960s, and their changes from the 1960s to 2010s, at 17UT, due to the change of greenhouse gas concentrations, and the change of the Earth’s magnetic field, respectively, under solar minimum and geomagnetically quiet conditions. (a), (a1), (a2): Neutral temperature and its changes; (b), (b1), (b2): ion temperature and its changes; (c), (c1, (c2): electron temperature and its changes; (d), (d1), d(2): mass density and its changes.

We found that, (1) trends in the T-I, driven by either of the two drivers, exhibited significant latitudinal and longitudinal variability; (2) in the thermosphere, trends were predominantly driven by the greenhouse gas driver except that the magnetic field driver played a small role in the neutral temperature trend (~ 25%) in some regions mainly in the longitude sector ~ 120oW – 20oE. The magnetic field driver played a more important role in the ionosphere in the longitude sector ~ 120oW – 20oE. In this longitude sector, the two drivers were comparable in driving the trends of hmF2, NmF2, and electron temperature; the relative importance of the two drivers to the ion temperature trend additionally depends on altitude, with the greenhouse gas driver being the dominant driver at lower altitudes (~ 200 km – 320 km), and the two drivers becoming comparable above; (3) although the magnetic field driver is important in the longitude sector ~ 120oW – 20oE, it drove both negative and positive trends in roughly equal amounts, consequently, its contributions to the global average trends in the T-I are negligible.

Joseph McInerney

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

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Impact of increasing greenhouse gases on the ionosphere and thermosphere response to a May 2024-like geomagnetic superstorm

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

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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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Investigation of the GOLD Observed Merged Nighttime EIA with WACCM-X Simulations during the Storm of November 3–4, 2021

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Climate responses under an extreme quiet sun scenario

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Thermospheric Neutral Density Variation during the "SpaceX" Storm: Implications from Physics-based Whole Geospace Modeling

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Investigation of the Post-Sunset Extra Electron Density Peak Poleward of the Equatorial Ionization Anomaly Southern Crest

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Climate Changes in the Upper Atmosphere: Contributions by the Changing Greenhouse Gas Concentrations and Earth's Magnetic Field From the 1960s to 2010s

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