Magnetic Field Turbulence in the Solar Wind at Sub‐ion Scales: In Situ Observations and Numerical Simulations
We investigate the transition of the solar wind turbulent cascade from MHD to sub‐ion range by means of a detailed comparison between in situ observations and hybrid numerical simulations. In particular, we focus on the properties of the magnetic field and its component anisotropy in Cluster measure...
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Frontiers Media S.A.
2020-12-01
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| Series: | Frontiers in Astronomy and Space Sciences |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fspas.2020.563075/full |
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| author | L. Matteini L. Matteini L. Matteini L. Franci L. Franci O. Alexandrova C. Lacombe S. Landi S. Landi P. Hellinger E. Papini E. Papini A. Verdini A. Verdini |
| author_facet | L. Matteini L. Matteini L. Matteini L. Franci L. Franci O. Alexandrova C. Lacombe S. Landi S. Landi P. Hellinger E. Papini E. Papini A. Verdini A. Verdini |
| author_sort | L. Matteini |
| collection | DOAJ |
| description | We investigate the transition of the solar wind turbulent cascade from MHD to sub‐ion range by means of a detailed comparison between in situ observations and hybrid numerical simulations. In particular, we focus on the properties of the magnetic field and its component anisotropy in Cluster measurements and hybrid 2D simulations. First, we address the angular distribution of wave vector in the kinetic range between ion and electron scales by studying the variance anisotropy of the magnetic field components. When taking into account a single-direction sampling, like that performed by spacecraft in the solar wind, the main properties of the fluctuations observed in situ are also recovered in our numerical description. This result confirms that solar wind turbulence in the sub‐ion range is characterized by a quasi-2D gyrotropic distribution of k-vectors around the mean field. We then consider the magnetic compressibility associated with the turbulent cascade and its evolution from large-MHD to sub‐ion scales. The ratio of field aligned to perpendicular fluctuations, typically low in the MHD inertial range, increases significantly when crossing ion scales and its value in the sub‐ion range is a function of the total plasma beta only, as expected from theoretical predictions, with higher magnetic compressibility for higher beta. Moreover, we observe that this increase has a gradual trend from low to high beta values in the in situ data; this behavior is well captured by the numerical simulations. The level of magnetic field compressibility that is observed in situ and in the simulations is in fairly good agreement with theoretical predictions, especially at high beta, suggesting that, in the kinetic range explored, the turbulence is supported by low-frequency and highly oblique fluctuations in pressure balance, like kinetic Alfvén waves or other slowly evolving coherent structures. The resulting scaling properties as a function of the plasma beta and the main differences between numerical and theoretical expectations and in situ observations are also discussed. |
| first_indexed | 2024-12-21T14:23:24Z |
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| id | doaj.art-b30633fdef174126b6209164d78f2cff |
| institution | Directory Open Access Journal |
| issn | 2296-987X |
| language | English |
| last_indexed | 2024-12-21T14:23:24Z |
| publishDate | 2020-12-01 |
| publisher | Frontiers Media S.A. |
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| series | Frontiers in Astronomy and Space Sciences |
| spelling | doaj.art-b30633fdef174126b6209164d78f2cff2022-12-21T19:00:43ZengFrontiers Media S.A.Frontiers in Astronomy and Space Sciences2296-987X2020-12-01710.3389/fspas.2020.563075563075Magnetic Field Turbulence in the Solar Wind at Sub‐ion Scales: In Situ Observations and Numerical SimulationsL. Matteini0L. Matteini1L. Matteini2L. Franci3L. Franci4O. Alexandrova5C. Lacombe6S. Landi7S. Landi8P. Hellinger9E. Papini10E. Papini11A. Verdini12A. Verdini13Department of Physics, Imperial College London, London, United KingdomLESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, Paris, FranceINAF, Osservatorio Astrofisico di Arcetri, Firenze, ItalySchool of Physics and Astronomy, Queen Mary University of London, London, United KingdomINAF, Osservatorio Astrofisico di Arcetri, Firenze, ItalyLESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, Paris, FranceLESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, Paris, FranceDipartimento di Fisica e Astronomia, Universitá di Firenze, Florence, ItalyINAF, Osservatorio Astrofisico di Arcetri, Firenze, ItalyAstronomical Institute, CAS, Prague, Czech RepublicDipartimento di Fisica e Astronomia, Universitá di Firenze, Florence, ItalyINAF, Osservatorio Astrofisico di Arcetri, Firenze, ItalyDipartimento di Fisica e Astronomia, Universitá di Firenze, Florence, ItalyINAF, Osservatorio Astrofisico di Arcetri, Firenze, ItalyWe investigate the transition of the solar wind turbulent cascade from MHD to sub‐ion range by means of a detailed comparison between in situ observations and hybrid numerical simulations. In particular, we focus on the properties of the magnetic field and its component anisotropy in Cluster measurements and hybrid 2D simulations. First, we address the angular distribution of wave vector in the kinetic range between ion and electron scales by studying the variance anisotropy of the magnetic field components. When taking into account a single-direction sampling, like that performed by spacecraft in the solar wind, the main properties of the fluctuations observed in situ are also recovered in our numerical description. This result confirms that solar wind turbulence in the sub‐ion range is characterized by a quasi-2D gyrotropic distribution of k-vectors around the mean field. We then consider the magnetic compressibility associated with the turbulent cascade and its evolution from large-MHD to sub‐ion scales. The ratio of field aligned to perpendicular fluctuations, typically low in the MHD inertial range, increases significantly when crossing ion scales and its value in the sub‐ion range is a function of the total plasma beta only, as expected from theoretical predictions, with higher magnetic compressibility for higher beta. Moreover, we observe that this increase has a gradual trend from low to high beta values in the in situ data; this behavior is well captured by the numerical simulations. The level of magnetic field compressibility that is observed in situ and in the simulations is in fairly good agreement with theoretical predictions, especially at high beta, suggesting that, in the kinetic range explored, the turbulence is supported by low-frequency and highly oblique fluctuations in pressure balance, like kinetic Alfvén waves or other slowly evolving coherent structures. The resulting scaling properties as a function of the plasma beta and the main differences between numerical and theoretical expectations and in situ observations are also discussed.https://www.frontiersin.org/articles/10.3389/fspas.2020.563075/fullsolar windplasma turbulencekinetic physicsnumerical simulationsin situ observation |
| spellingShingle | L. Matteini L. Matteini L. Matteini L. Franci L. Franci O. Alexandrova C. Lacombe S. Landi S. Landi P. Hellinger E. Papini E. Papini A. Verdini A. Verdini Magnetic Field Turbulence in the Solar Wind at Sub‐ion Scales: In Situ Observations and Numerical Simulations Frontiers in Astronomy and Space Sciences solar wind plasma turbulence kinetic physics numerical simulations in situ observation |
| title | Magnetic Field Turbulence in the Solar Wind at Sub‐ion Scales: In Situ Observations and Numerical Simulations |
| title_full | Magnetic Field Turbulence in the Solar Wind at Sub‐ion Scales: In Situ Observations and Numerical Simulations |
| title_fullStr | Magnetic Field Turbulence in the Solar Wind at Sub‐ion Scales: In Situ Observations and Numerical Simulations |
| title_full_unstemmed | Magnetic Field Turbulence in the Solar Wind at Sub‐ion Scales: In Situ Observations and Numerical Simulations |
| title_short | Magnetic Field Turbulence in the Solar Wind at Sub‐ion Scales: In Situ Observations and Numerical Simulations |
| title_sort | magnetic field turbulence in the solar wind at sub ion scales in situ observations and numerical simulations |
| topic | solar wind plasma turbulence kinetic physics numerical simulations in situ observation |
| url | https://www.frontiersin.org/articles/10.3389/fspas.2020.563075/full |
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