Forecasting global and multi-level thermospheric neutral density and ionospheric electron content by tuning models against satellite-based accelerometer measurements

Ehsan Forootan; Mona Kosary; Saeed Farzaneh; Timothy Kodikara; Kristin Vielberg; Isabel Fernandez-Gomez; Claudia Borries; Maike Schumacher

doi:10.1038/s41598-022-05952-y

Forecasting global and multi-level thermospheric neutral density and ionospheric electron content by tuning models against satellite-based accelerometer measurements

Sci Rep. 2022 Feb 8;12(1):2095. doi: 10.1038/s41598-022-05952-y.

Authors

Ehsan Forootan¹, Mona Kosary², Saeed Farzaneh², Timothy Kodikara³, Kristin Vielberg⁴, Isabel Fernandez-Gomez³, Claudia Borries³, Maike Schumacher⁵

Affiliations

¹ Geodesy Group, Department of Planning, Aalborg University, Rendburggade 14, 9000, Aalborg, Denmark. efo@plan.aau.dk.
² School of Surveying and Geospatial Engineering, College of Engineering, University of Tehran, P.O. Box 113654563, Tehran, Iran.
³ Institute of Solar-Terrestrial Physics, German Aerospace Center (DLR), Kalkhorstweg 53, 17235, Neustrelitz, Germany.
⁴ Institute of Geodesy and Geoinformation, University of Bonn, Nussallee 17, 53115, Bonn, Germany.
⁵ Geodesy Group, Department of Planning, Aalborg University, Rendburggade 14, 9000, Aalborg, Denmark.

Abstract

Global estimation of thermospheric neutral density (TND) on various altitudes is important for geodetic and space weather applications. This is typically provided by models, however, the quality of these models is limited due to their imperfect structure and the sensitivity of their parameters to the calibration period. Here, we present an ensemble Kalman filter (EnKF)-based calibration and data assimilation (C/DA) technique that updates the model's states and simultaneously calibrates its key parameters. Its application is demonstrated using the TND estimates from on-board accelerometer measurements, e.g., those of the Gravity Recovery and Climate Experiment (GRACE) mission (at [Formula: see text] km altitude), as observation, and the frequently used empirical model NRLMSISE-00. The C/DA is applied here to re-calibrate the model parameters including those controlling the influence of solar radiation and geomagnetic activity as well as those related to the calculation of exospheric temperature. The resulting model, called here 'C/DA-NRLMSISE-00', is then used to now-cast TNDs and individual neutral mass compositions for 3 h, where the model with calibrated parameters is run again during the assimilation period. C/DA-NRLMSISE-00 is also used to forecast the next 21 h, where no new observations are introduced. These forecasts are unique because they are available globally and on various altitudes (300-600 km). To introduce the impact of the thermosphere on estimating ionospheric parameters, the coupled physics-based model TIE-GCM is run by replacing the O2, O1, He and neutral temperature estimates of the C/DA-NRLMSISE-00. Then, the non-assimilated outputs of electron density (Ne) and total electron content (TEC) are validated against independent measurements. Assessing the forecasts of TNDs with those along the Swarm-A ([Formula: see text] km), -B ([Formula: see text] km), and -C ([Formula: see text] km) orbits shows that the root-mean-square error (RMSE) is considerably reduced by 51, 57 and 54%, respectively. We find improvement of 30.92% for forecasting Ne and 26.48% for TEC compared to the radio occulation and global ionosphere maps (GIM), respectively. The presented C/DA approach is recommended for the short-term global multi-level thermosphere and enhanced ionosphere forecasting applications.

Abstract

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