EUV Irradiance Inputs to Thermospheric Density Models: Open Issues and Path Forward

Vourlidas, A.; Bruinsma, Sean

doi:10.1002/2017sw001725

Cited by 18 publications

(19 citation statements)

References 65 publications

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“…The F30 radio flux DTM2013 and DTM2020_Res are driven by F30 because the observed densities can be reconstructed with higher fidelity than with F10.7, most likely because of the much higher contribution of thermal Bremsstrahlung (Dudok de Wit et al, 2014). Similar to F10.7, it is a ground-based radio measurement, and therefore more robust and more accurately calibrated than satellite measurements of solar emissions (Vourlidas & Bruinsma, 2018). Still, the absolute calibration also of ground-based radio instruments remains a challenging issue.…”

Section: 8mentioning

confidence: 99%

The operational and research DTM-2020 thermosphere models

Bruinsma

Boniface

2021

J. Space Weather Space Clim.

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Aims - The semi-empirical Drag Temperature Models (DTM) predict temperature, density and composition of the Earth's thermosphere, especially for orbit computation purposes. Twonew models were developed in the framework of the H2020 Space Weather Atmosphere Models and Indices project (SWAMI). The operational model is driven by the trusted and established F10.7 and Kp indices for solar and geomagnetic activity, respectively. The so-called research model is more accurate, but it uses the indices F30 and the hourly Hpo, which are not yet accredited operationally. Methods - The backbone of the DTM2020 models is made up of GOCE, CHAMP and Swarm A densities, processed by TU Delft, and Stella processed in-house. They constitute the standards for absolute densities, and they are 20-30% smaller than the datasets used in the fit of DTM2013. Also, the global daily mean TLE densities at 250 km, spanning four solar cycles, were now used in the fit to improve solar cycle variations. The operational model, which employs the same algorithm as DTM2013, was obtained through fitting to all data in our database from 1967-2019. Because of the Hpo index, which is not available before 1995, the coefficients linked to geomagnetic activity of the research model are fitted to data from 2000-2019. The algorithm was updated to take advantage of the higher cadence of Hpo. Both models are assessed with independent data and compared with the COSPAR International Reference Atmosphere models NRLMSISE-00, JB2008, and DTM2013. The bias and precision of the models are assessed through comparison with observations according to published metrics on several time scales. Secondly, binning of the density ratios is used in order to detect specific model errors. Results –The DTM2020 densities are on average 20-30% smaller than those of DTM2013, NRLMSISE-00 and JB2008. The assessment shows that the research DTM2020 is the least biased and most precise model compared to assimilated data. It is a significant improvement over DTM2013 under all conditions and at all altitudes. This is confirmed by the comparison with independent SET HASDM density data. The operational DTM2020 is always less accurate than the research model except at 800 km altitude. It has comparable or slightly higher precision than DTM2013, despite using F10.7 instead of F30 as solar activity driver. DTM, and semi-empirical models in general, can still be significantly improved on the condition of setting up a more complete and consistent total density, composition and temperature database than available at this time by means of a well-conceived observing system.

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Section: 8mentioning

confidence: 99%

The operational and research DTM-2020 thermosphere models

Bruinsma

Boniface

2021

J. Space Weather Space Clim.

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“…Vourlidas and Bruinsma () reviewed the status and issues of EUV measurements and proxies. The EUV and far ultraviolet radiation accounts for ~80% of the energy input into the thermosphere.…”

Section: Contributionsmentioning

confidence: 99%

Introduction to NASA Living With a Star Institute Special Section on Low Earth Orbit Satellite Drag: Science and Operational Impact

2018

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This paper provides a brief description of the NASA Living With a Star (LWS) Institute special section on low Earth orbit (LEO) satellite drag: Science and operational impact. The goals of the LWS institute are to (a) review the current status of atmospheric drag research and operational concerns for LEO satellites, (b) identify and understand the major issues in atmospheric drag estimation, and (c) provide recommendations for future improvement in our ability to provide nowcasts of satellite drag. This special section presents the progress made by the 17 institute members of the 11 participating institutes from four countries as well as additional contributions from scientists who were not part of the original NASA LWS LEO drag team. Contributions cover topics in measurement and modeling of solar extreme ultraviolet inputs, thermospheric neutral density profiles, changes in composition and total density, and satellite conjunction and orbit prediction. Errors in the thermosphere density specification are the dominant source in uncertainty of LEO drag estimation and satellite conjunction. The consensus opinion is that significant funded future effort needs to address and improve measurements and modeling of the thermospheric neutral density and composition under different solar and geomagnetic conditions.

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“…Without accurate expressions of instrument errors, decadal climate change signals cannot be confidently assessed (Ohring et al, 2005;Fox et al, 2011;Wielicki et al, 2013;Kopp, 2014). Solar physicists need to understand long-term solar variability to properly constrain past solar variations (Coddington et al, 2016), while satellite operators need an accurate UV flux to estimate satellite drag (Vourlidas & Bruinsma, 2018). Of particular interest for all these users is the spectrally-resolved solar irradiance, or solar spectral irradiance (SSI), because different wavelengths impact the Earth's environment in distinct ways.…”

Section: Introductionmentioning

confidence: 99%

Detecting undocumented trends in solar irradiance observations

Wit

2022

J. Space Weather Space Clim.

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Quantifying the long-term stability of solar irradiance observations is crucial for determining how the Sun varies in time and for detecting decadal climate change signals. The stability of irradiance observations is challenged by the degradation of instrumental sensitivity in space and by the corrections that are needed to mitigate this degradation. We propose a new framework for detecting instrumental trends, based on the existing idea of comparing the solar irradiance at pairs of dates for which a proxy quantity reaches the same level. Using a parametric model we then reconstruct the trend and its confidence interval at all times. While this method cannot formally prove the instrumental origin of the trends, the \modif{observation} of similar trends with different proxies provides strong evidence for a non-solar origin. We illustrate the method with spectral irradiance observations from the Solar Radiation and Climate Experiment (SORCE) mission, using various solar proxies such as sunspot number, MgII index, F10.7 index. The results support the existence of non-solar trends that exceed the level of solar cycle variability. After correcting the spectral irradiance for these trends, we find the difference between the levels observed at solar maximum and at solar minimum to be in better agreement with irradiance models.

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EUV Irradiance Inputs to Thermospheric Density Models: Open Issues and Path Forward

Cited by 18 publications

References 65 publications

The operational and research DTM-2020 thermosphere models

The operational and research DTM-2020 thermosphere models

Introduction to NASA Living With a Star Institute Special Section on Low Earth Orbit Satellite Drag: Science and Operational Impact

Detecting undocumented trends in solar irradiance observations

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