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Sayram: A Positivity‐Preserving Open Source 3D Radiation Belt Modeling Code.

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Title: Sayram: A Positivity‐Preserving Open Source 3D Radiation Belt Modeling Code.
Authors: Peng, Peng1,2,3 (AUTHOR), Tao, Xin1,2,3 (AUTHOR) xtao@ustc.edu.cn, Albert, Jay M.4 (AUTHOR), Chan, Anthony A.5 (AUTHOR)
Source: Journal of Geophysical Research. Space Physics. Jul2025, Vol. 130 Issue 7, p1-17. 17p.
Subject Terms: Radiation belts, Open source software, Iterative methods (Mathematics), Particle interactions, C++, Computer simulation, Finite volume method, Space environment
Abstract: Radiation belt dynamics is typically modeled using a quasilinear diffusion equation. However, standard numerical methods often produce non‐physical negative or oscillatory solutions due to cross‐diffusion terms. Here, we present Sayram, an open‐source 3D radiation belt modeling code that employs a positivity‐preserving finite volume method to address this decades‐old numerical challenge. Sayram incorporates key physical processes of the radiation belts, including local wave–particle interactions, radial diffusion, and losses due to precipitation and magnetopause shadowing. We validate Sayram using 1D radial diffusion, 2D pitch‐angle and momentum diffusion, and a 3D model diffusion problem. Additionally, we apply it to a GEM challenge storm‐time radiation belt event, demonstrating consistency with previous results. Compared to other 3D radiation belt codes, Sayram employs an implicit time integration scheme, preserves positivity, and ensures conservation properties. The code is developed in C++ with a highly modular design, allowing for easy adaptation to similar tasks. By making Sayram open source, we aim to provide the radiation belt community with a robust tool to improve radiation belt modeling and forecasting. Key Points: Sayram is validated to be accurate, positivity‐preserving, and free from CFL condition constraints for stabilityNumerical tests using Sayram highlight the importance of staying positiveSayram successfully models a storm‐time radiation belt event, demonstrating its applicability to space weather studies [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Space Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: GreenFILE
An: 186955253
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PubTypeId: academicJournal
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  Data: Sayram: A Positivity‐Preserving Open Source 3D Radiation Belt Modeling Code.
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  Data: <searchLink fieldCode="AR" term="%22Peng%2C+Peng%22">Peng, Peng</searchLink><relatesTo>1,2,3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Tao%2C+Xin%22">Tao, Xin</searchLink><relatesTo>1,2,3</relatesTo> (AUTHOR)<i> xtao@ustc.edu.cn</i><br /><searchLink fieldCode="AR" term="%22Albert%2C+Jay+M%2E%22">Albert, Jay M.</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Chan%2C+Anthony+A%2E%22">Chan, Anthony A.</searchLink><relatesTo>5</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="DE" term="%22Radiation+belts%22">Radiation belts</searchLink><br /><searchLink fieldCode="DE" term="%22Open+source+software%22">Open source software</searchLink><br /><searchLink fieldCode="DE" term="%22Iterative+methods+%28Mathematics%29%22">Iterative methods (Mathematics)</searchLink><br /><searchLink fieldCode="DE" term="%22Particle+interactions%22">Particle interactions</searchLink><br /><searchLink fieldCode="DE" term="%22C%2B%2B%22">C++</searchLink><br /><searchLink fieldCode="DE" term="%22Computer+simulation%22">Computer simulation</searchLink><br /><searchLink fieldCode="DE" term="%22Finite+volume+method%22">Finite volume method</searchLink><br /><searchLink fieldCode="DE" term="%22Space+environment%22">Space environment</searchLink>
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  Data: Radiation belt dynamics is typically modeled using a quasilinear diffusion equation. However, standard numerical methods often produce non‐physical negative or oscillatory solutions due to cross‐diffusion terms. Here, we present Sayram, an open‐source 3D radiation belt modeling code that employs a positivity‐preserving finite volume method to address this decades‐old numerical challenge. Sayram incorporates key physical processes of the radiation belts, including local wave–particle interactions, radial diffusion, and losses due to precipitation and magnetopause shadowing. We validate Sayram using 1D radial diffusion, 2D pitch‐angle and momentum diffusion, and a 3D model diffusion problem. Additionally, we apply it to a GEM challenge storm‐time radiation belt event, demonstrating consistency with previous results. Compared to other 3D radiation belt codes, Sayram employs an implicit time integration scheme, preserves positivity, and ensures conservation properties. The code is developed in C++ with a highly modular design, allowing for easy adaptation to similar tasks. By making Sayram open source, we aim to provide the radiation belt community with a robust tool to improve radiation belt modeling and forecasting. Key Points: Sayram is validated to be accurate, positivity‐preserving, and free from CFL condition constraints for stabilityNumerical tests using Sayram highlight the importance of staying positiveSayram successfully models a storm‐time radiation belt event, demonstrating its applicability to space weather studies [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Geophysical Research. Space Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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      – Type: doi
        Value: 10.1029/2025JA033991
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 17
        StartPage: 1
    Subjects:
      – SubjectFull: Radiation belts
        Type: general
      – SubjectFull: Open source software
        Type: general
      – SubjectFull: Iterative methods (Mathematics)
        Type: general
      – SubjectFull: Particle interactions
        Type: general
      – SubjectFull: C++
        Type: general
      – SubjectFull: Computer simulation
        Type: general
      – SubjectFull: Finite volume method
        Type: general
      – SubjectFull: Space environment
        Type: general
    Titles:
      – TitleFull: Sayram: A Positivity‐Preserving Open Source 3D Radiation Belt Modeling Code.
        Type: main
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            NameFull: Peng, Peng
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            NameFull: Tao, Xin
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            NameFull: Albert, Jay M.
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            NameFull: Chan, Anthony A.
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            – D: 01
              M: 07
              Text: Jul2025
              Type: published
              Y: 2025
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              Value: 130
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            – TitleFull: Journal of Geophysical Research. Space Physics
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