Earth's upper atmosphere

Equinoctial Asymmetry in the Upper Ionosphere: Comparison of Satellite Observations and Models

whawkins — Wed, 05 Oct 2022 17:16:46 +0000

Equinoctial Asymmetry in the Upper Ionosphere: Comparison of Satellite Observations and Models whawkins Wed, 10/05/2022 - 11:16

Author:

whawkins

Oct 5, 2022

JGR Space Phyics—L. Lomidze, D. J. Knudsen, M. Shepherd, J. D. Huba, and A. Maute

SAMI3 simulation results for electron density near noon using TIE-GCM neutral atmosphere as a model input, the bottom panel is the corresponding relative (in %) change for Ne. The wind effect on electron density is shown by the black dashed line and the neutral density by the turquoise line.

The terrestrial ionosphere displays significant equinoctial asymmetry despite the upper atmosphere receiving similar levels of solar ionization energy at a given location and local time in spring and fall during similar solar activity conditions. This intriguing feature is not well understood or modelled, particularly in the upper ionosphere, and causes of the asymmetry are not fully established and quantified. Yet, their study is important to provide better insights into the atmosphere-ionosphere coupling processes. Analysis of Langmuir probe data from ESA’s Swarm satellite at ~525 km altitude reveals that the daytime electron density is larger for all latitudes during March than during September, while the electron temperature shows inverted asymmetry except at low latitudes. Simultaneously obtained neutral density data from Swarm GPS accelerations indicate that the thermosphere is denser during the spring. The asymmetry seen by Swarm electron density observations is also present in electron densities obtained using GPS radio occultation measurements from the COSMIC satellites. Simulations were performed using physics-based ionosphere models (SAMI3, WACCM-X, and TIE-GCM) to determine their ability to produce the observed asymmetry, understand the generation mechanism(s), and establish the relative role of physical drivers. Modeling of the asymmetry by SAMI3 driven with the TIE-GCM neutral atmosphere shows that both neutral density and winds play a critical role, but the density has a greater effect.

The effects of IMF By on the middle thermosphere during a geomagnetically “quiet” period at solar minimum

kolinski — Mon, 11 Jul 2022 21:02:35 +0000

The effects of IMF By on the middle thermosphere during a geomagnetically “quiet” period at solar minimum kolinski Mon, 07/11/2022 - 15:02

Publication: JR Space Physics; Authors: Xuguang Cai, Wenbin Wang, Alan Burns, Liying Qian, Richard W. Eastes

Author:

kolinski

Jul 11, 2022

The polar view of the percentage difference of simulated ∑O/N2 and GOLD observed ∑O/N2 between DOY 111 and 110 at 15:10 UT in 2019. The perimeter latitude is 30°N

Numerical simulations using the National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM) are performed to elucidate the effects of the interplanetary magnetic field (IMF) on the middle thermosphere composition during a “geomagnetically quiet” period from the day of year (DOY) 110-111 in 2019 (when the Auroral electrojet (AE) index never exceeded 300 nT and the Kp never exceeded 2). In particular, this paper aims to examine how the Global-scale Observations of the Limb and Disk (GOLD) mission observed daytime thermospheric O and N2 column density ratio (∑O/N2) depletion at mid-latitudes originated under such a “geomagnetically quiet” condition. A comparison of electric potential, Joule heating rate per unit mass, ion velocity, neutral temperature and winds in the middle thermosphere (∼160 km) between real IMF and without the IMF east-west component (By) indicates that a By dominant condition can enhance their strengths under this “geomagnetically quiet” condition. Consequently, ∑O/N2 depletion with a stronger magnitude (30% compared with ∼8% without By) and larger disturbed area was introduced in the post-midnight sector at high-latitudes due to strong and localized upwelling associated with the enhanced Joule heating rate per unit mass. The ∑O/N2 depletion was transported equatorward and corotated from local post-midnight to early morning, and was observed by GOLD at middle latitudes during daytime.

The Molecular Oxygen Density Structure of the Lower Thermosphere as Seen by GOLD and Models

kolinski — Mon, 11 Jul 2022 20:39:20 +0000

The Molecular Oxygen Density Structure of the Lower Thermosphere as Seen by GOLD and Models kolinski Mon, 07/11/2022 - 14:39

Publication: Geophysics Research Letters; Author's: K. R. Greer, F. Laskar, R. Eastes, J. Lumpe, H.-L. Liu, and N. Pedatella

Author:

kolinski

Jul 11, 2022

Comparisons of local time structure of molecular oxygen at 21°N, 170 km altitude. Red dots are for the longitude of 33°E, while blue dots are for the longitude of 128°W. Panel (a) shows molecular oxygen densities as observed by the GOLD instrument for one star, HD74280, between January 2019 and July 2021. Panel (b) are results from the MSISE-00 empirical model sampled for the same locations and conditions as the GOLD observations. Panel (c) is as panel (b) but for the MSIS2.0 empirical model. Panel (d) shows the SD-WACCM-X model sampled for the GOLD observations. The observations show a distinctly diurnal structure in local time, while all the model results indicate a semidiurnal structure.

This paper compares new observations from the Global-scale Observations of Limb and Disk (GOLD) mission of molecular oxygen (O2) in the lower thermosphere (130 - 200 km in altitude) to widely used models in the aeronomy community. The main finding is that the local time structure of the observed molecular oxygen has a minimum at 6 hours local time and a peak near 18 hours local time while the models all show a structure that has peaks at both 6 and 18 hours local time. This significant difference not only influences the total neutral thermospheric density results from the models, but may ultimately impact the calculated ionospheric plasma density and its temporal variability. Understanding ionospheric plasma densities is vital for the proper modeling of the propagation of communications and navigational signals.

Impacts of Different Causes on the Inter–Hemispheric Asymmetry of Ionosphere–Thermosphere System at Mid– and High–Latitudes: GITM Simulations

kolinski — Mon, 04 Apr 2022 18:49:10 +0000

Impacts of Different Causes on the Inter–Hemispheric Asymmetry of Ionosphere–Thermosphere System at Mid– and High–Latitudes: GITM Simulations kolinski Mon, 04/04/2022 - 12:49

Publication: Space Weather; Authors: Yu Hong, Yue Deng, Qingyu Zhu, Astrid Maute, Cheng Sheng, Daniel Welling, Ramon Lopez

Author:

kolinski

Apr 4, 2022

Interhemispheric differences poleward of 40deg geog. latitude of E-region electron density (a), F-region neutral density (b) and neutral wind (c), and height integrated Joule heating (d) with symmetric magnetic field (aligned dipole- top) and realistic Earth's magnetic field (IGRF- bottom).

There are significant differences between the Earth’s two hemispheres such as the Earth's magnetic field and the intensity of solar radiation due to Earth's tilt of the rotation axis with respect to the Sun. Understanding the impact and therefore the importance of these asymmetries on the mid- and high-latitude upper atmosphere is a challenge in the geospace community. The main contributions to these asymmetries include among others: (1) the displacement between Earth’s magnetic poles and geographic poles, (2) the seasonal solar EUV irradiation, and (3) the magnetospheric forcing, including the electric field and the auroral particle precipitation. However, it is still unclear to what extent the ionosphere-thermosphere (I-T) quantities such as the electron density can be affected by these asymmetric causes. In this study, the asymmetric contributions of the above causes on I-T quantities have been estimated through comparisons of numerical experiments using the Global Ionosphere and Thermosphere Model (GITM). It is found that season plays a dominant role in causing hemispheric asymmetries in all the examined quantities; our results also suggest that the contributions of the asymmetric magnetospheric forcing could be even more important during intense storms than the other causes shown in this work.

Impact of Thermospheric Wind Data Assimilation on Ionospheric Electrodynamics using a Coupled Whole Atmosphere Data Assimilation System

kolinski — Thu, 03 Mar 2022 21:39:21 +0000

Impact of Thermospheric Wind Data Assimilation on Ionospheric Electrodynamics using a Coupled Whole Atmosphere Data Assimilation System kolinski Thu, 03/03/2022 - 14:39

Publication: Journal of Geophysical Research, Space Physics; Authors: Chih-Ting Hsu, Nick Pedatella, Jeff Anderson

Author:

kolinski

Mar 3, 2022

Three Observing System Simulation Experiments (OSSEs) are carried out in this study. Thermospheric wind and temperature states are updated using synthetic data sampled from a Nature Run (NR) in this experiment. The updated thermospheric states will further change the plasma drift and electron density in the ionosphere. This figure shows the longitude-latitude maps of NmF2 from the NR (first column) and the difference of NmF2 between OSSEs and NR (second to fourth columns) at six different times. From top to bottom rows are maps at 1200 UT on 05, 10, 15, 20, 25, and 30 December 2009. From the second to fourth columns are the difference of NmF2 between OSSE-MIGHTI-ELF, OSSE-MIGHTI-GC, and OSSE-GC and NR.

The upward plasma drift and equatorial ionization anomaly (EIA) in the Earth's ionosphere are strongly influenced by the zonal electric field, which is generated by the wind dynamo. Specification and forecasting of thermospheric winds thus plays an important role in ionospheric weather prediction. In this study, we assess the impact of assimilating thermospheric wind observations from the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument on NASA's Ionospheric CONnection (ICON) explorer satellite on the ionospheric electrodynamics. Empirical Localization Functions (ELFs) of ICON/MIGHTI zonal and meridional winds are also computed and applied to our data assimilation experiments, enabling improved assimilation of the ICON/MIGHTI wind observations. A set of Observing System Simulation Experiments (OSSEs) are performed using the National Center for Atmospheric Research (NCAR) Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCMX) with data assimilation provided by the Data Assimilation Research Testbed (DART) ensemble adjustment Kalman filter. The results show that assimilating the ICON/MIGHTI wind observations with the ELF improves the zonal and meridional wind root mean square error (RMSE) by 16-18% and 7-10%, respectively. The improved wind specification further improves the low-latitude ExB vertical drift RMSE by about 18%. The response of electron densities is slower, and the overall impact is smaller. The improvement of the ionosphere F-region maximum electron density (NmF2) between -45 to 45 degree is about 8% after 18 days of data assimilation.

HAO affiliate scientist, Dr. Joe Huba, published in a popular-science journal

kolinski — Tue, 23 Nov 2021 18:40:25 +0000

HAO affiliate scientist, Dr. Joe Huba, published in a popular-science journal kolinski Tue, 11/23/2021 - 11:40

Space Storms in the Upper Atmosphere and Ionosphere

kolinski — Mon, 22 Nov 2021 18:42:26 +0000

Space Storms in the Upper Atmosphere and Ionosphere kolinski Mon, 11/22/2021 - 11:42

HIWIND Prepares for a New Zealand Flight in 2022

kolinski — Thu, 18 Nov 2021 21:06:13 +0000

HIWIND Prepares for a New Zealand Flight in 2022 kolinski Thu, 11/18/2021 - 14:06

Interhemispheric Coupling Mechanisms in the Middle Atmosphere of WACCM6

kolinski — Thu, 18 Nov 2021 19:30:34 +0000

Interhemispheric Coupling Mechanisms in the Middle Atmosphere of WACCM6 kolinski Thu, 11/18/2021 - 12:30

Publication Name: Journal of Atmospheric Sciences; First HAO Author's Name: Nick Pedatella

Author:

kolinski

Nov 18, 2021

Simulations with the Community Earth System Model 2 using the Whole Atmosphere Community Climate Model configuration, known as CESM2(WACCM6), show evidence of dynamical coupling from the high latitudes of the winter middle atmosphere to the tropics and the middle and high latitudes of the summer hemisphere.

Differences in the monthly mean temperature from the long-term average over three WACCM realizations. The months are sorted by the perturbation temperature in the high latitude winter stratosphere, specifically the region poleward of 60° and between 10 and 1 hPa (warmer than average in the left column; cooler in the middle column). The right column gives the differences of the two panels to the left. The top row is for NH winter in January and the bottom row is for SH winter in September. The contour interval is 2 K; the zero contour is not shown; and contours for 1 K and -1 K are shown as dashed lines. The numbers in parentheses show the number of months contributing to the average.

Analysis of monthly and daily output covering 195 simulation years indicates that the response in the summer middle and high latitudes has a weak overall magnitude of a few Kelvin or less in temperature but has a repeatable pattern whose structure and phase agree with observational studies. Lag correlation indicates that perturbations in wave activity in the winter stratosphere, as quantified by EP flux divergence, are accompanied by perturbations in the transformed Eulerian mean meridional wind extending into the summer hemisphere. There is not an appreciable correlation with momentum forcing in the summer hemisphere by either resolved waves or parameterized gravity waves. The rapid circulation response and the lack of a wave response in the summer hemisphere suggest that the interhemispheric coupling that is simulated in WACCM6 in both the stratosphere and mesosphere owes its existence to a circulation that develops to restore balance to the zonally averaged state of the atmosphere. This is an alternative explanation for the coupling from the winter stratosphere to the summer mesosphere; previous studies have assumed a necessary role for wave activity in the summer hemisphere.

Upper atmosphere radiance data assimilation: A feasibility study for GOLD far ultraviolet observations

kolinski — Thu, 18 Nov 2021 19:25:07 +0000

Upper atmosphere radiance data assimilation: A feasibility study for GOLD far ultraviolet observations kolinski Thu, 11/18/2021 - 12:25

Publication Name: Journal of Geophysical Research Space Physics; First HAO Author's Name: Stanley C. Solomon

Author:

kolinski

Nov 18, 2021

Availability of far ultraviolet observations of Earth’s dayglow by the NASA Global-scale Observations of the Limb and Disk (GOLD) mission presents an unparalleled opportunity for upper atmosphere radiance data assimilation.

Assimilation of the observed dayglow emissions can be formulated in a similar fashion to lower atmosphere radiance data assimilation approaches using the sensitivity of the Lyman-Birge-Hopfield (LBH) band emission to thermospheric temperature. To demonstrate such an approach, this paper presents a proof-of-concept implementation of an ensemble filter measurement update step using ensemble simulation of the thermosphere and LBH emission by the NOAA's Whole Atmosphere Model (WAM) and NCAR’s Global Airglow model.

Accuracy of temperature estimates in the measurement update step for four different assimilated observations.

Testing the approach with observing system simulation experiments has yielded the following findings: (1) Assimilation of GOLD LBH disk emission data can reduce the error in model temperature specification from forecast to analysis by 97% under geomagnetically quiet conditions and 87% under disturbed conditions, (2) The reduction in model uncertainty from forecast to analysis as a result of GOLD assimilation is ~20% in the lower thermosphere and ~25% in the upper thermosphere, and (3) Ingestion of three prominent LBH features, in comparison to the entire LBH spectrum, into the WAM leads to more accurate assimilation analyses. With the help of a radiance data assimilation approach, the utility of GOLD observations can be extended to reveal global, time-dependent, altitude-resolved thermospheric structure, offering the key to addressing a number of outstanding questions such as those relating to the properties of travelling atmospheric disturbances.

Link to paper: Upper atmosphere radiance data assimilation: A feasibility study for GOLD far ultraviolet observations

Earth's upper atmosphere

Equinoctial Asymmetry in the Upper Ionosphere: Comparison of Satellite Observations and Models

Recent News

The effects of IMF By on the middle thermosphere during a geomagnetically “quiet” period at solar minimum

Recent News

The Molecular Oxygen Density Structure of the Lower Thermosphere as Seen by GOLD and Models

Recent News

Impacts of Different Causes on the Inter–Hemispheric Asymmetry of Ionosphere–Thermosphere System at Mid– and High–Latitudes: GITM Simulations

Recent News

Impact of Thermospheric Wind Data Assimilation on Ionospheric Electrodynamics using a Coupled Whole Atmosphere Data Assimilation System

Recent News

HAO affiliate scientist, Dr. Joe Huba, published in a popular-science journal

Recent News

Space Storms in the Upper Atmosphere and Ionosphere

Recent News

HIWIND Prepares for a New Zealand Flight in 2022

Recent News

Interhemispheric Coupling Mechanisms in the Middle Atmosphere of WACCM6

Recent News

Upper atmosphere radiance data assimilation: A feasibility study for GOLD far ultraviolet observations

Recent News