University of Oulu

Reid, B., Themens, D. R., McCaffrey, A., Jayachandran, P. T., Johnsen, M. G., & Ulich, T. (2023). A-CHAIM: Near-real-time data assimilation of the high latitude ionosphere with a particle filter. Space Weather, 21, e2022SW003185.

A-CHAIM : Near-Real-Time data assimilation of the high latitude ionosphere with a particle filter

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Author: Reid, Ben1; Themens, David R.1,2; McCaffrey, Anthony1;
Organizations: 1Department of Physics, University of New Brunswick, Fredericton, NB, Canada
2School of Engineering, University of Birmingham, Birmingham, UK
3Tromsø Geophysical Observatory, UiT the Arctic University of Norway, Tromsø, Norway
4Sodankylä Geophysical Observatory, Sodankylä, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.6 MB)
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Language: English
Published: American Geophysical Union, 2023
Publish Date: 2023-08-24


The Assimilative Canadian High Arctic Ionospheric Model (A-CHAIM) is an operational ionospheric data assimilation model that provides a 3D representation of the high latitude ionosphere in Near-Real-Time (NRT). A-CHAIM uses low-latency observations of slant Total Electron Content (sTEC) from ground-based Global Navigation Satellite System (GNSS) receivers, ionosondes, and vertical TEC from the JASON-3 altimeter satellite to produce an updated electron density model above 45° geomagnetic latitude. A-CHAIM is the first operational use of a particle filter data assimilation for space environment modeling, to account for the nonlinear nature of sTEC observations. The large number (>10⁴) of simultaneous observations creates significant problems with particle weight degeneracy, which is addressed by combining measurements to form new composite observables. The performance of A-CHAIM is assessed by comparing the model outputs to unassimilated ionosonde observations, as well as to in-situ electron density observations from the SWARM and DMSP satellites. During moderately disturbed conditions from 21 September 2021 through 29 September 2021, A-CHAIM demonstrates a 40%–50% reduction in error relative to the background model in the F2-layer critical frequency (foF2) at midlatitude and auroral reference stations, and little change at higher latitudes. The height of the F2-layer (hmF2) shows a small 5%–15% improvement at all latitudes. In the topside, A-CHAIM demonstrates a 15%–20% reduction in error for the Swarm satellites, and a 23%–28% reduction in error for the DMSP satellites. The reduction in error is distributed evenly over the assimilation region, including in data-sparse regions.

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Series: Space weather
ISSN: 1542-7390
ISSN-E: 1542-7390
ISSN-L: 1542-7390
Volume: 21
Issue: 3
Article number: e2022SW003185
DOI: 10.1029/2022SW003185
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: A-CHAIM development has been supported by Defense Research and Development Canada contract W7714-186507/001/SS and by Canadian Space Agency Grant 21SUSTCHAI. Infrastructure funding for CHAIN was provided by the Canadian Foundation for Innovation and the New Brunswick Innovation Foundation. CHAIN operations are conducted in collaboration with the Canadian Space Agency. This research was undertaken with the financial support of the Canadian Space Agency FAST program and the Natural Sciences and Engineering Research Council of Canada. The Svalbard ionosonde is partly funded by the Svalbard Integrated Observing System (SIOS) InfraNOR program.
Copyright information: © 2023 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.