Evolution of Magnetohydrodynamic Turbulence in the Expanding Solar Wind: Residual Energy and Intermittency
We conduct 3D magnetohydrodynamic simulations of decaying turbulence in the context of the solar wind. To account for the spherical expansion of the solar wind, we implement the expanding box model. The initial turbulence comprises uncorrelated counterpropagating Alfvén waves and exhibits an isotrop...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ad9f38 |
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| author | Chen Shi Nikos Sioulas Zesen Huang Marco Velli Anna Tenerani Victor Réville |
| author_facet | Chen Shi Nikos Sioulas Zesen Huang Marco Velli Anna Tenerani Victor Réville |
| author_sort | Chen Shi |
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| description | We conduct 3D magnetohydrodynamic simulations of decaying turbulence in the context of the solar wind. To account for the spherical expansion of the solar wind, we implement the expanding box model. The initial turbulence comprises uncorrelated counterpropagating Alfvén waves and exhibits an isotropic power spectrum. Our findings reveal the consistent generation of negative residual energy whenever nonlinear interactions are present, independent of the normalized cross helicity σ _c and compressibility. The spherical expansion facilitates this process. The resulting residual energy is primarily distributed in the perpendicular direction, with S _2 ( b ) − S _2 ( u ) ∝ l _⊥ or equivalently $-{E}_{r}\propto {k}_{\perp }^{-2}$ . Here S _2 ( b ) and S _2 ( u ) are second-order structure functions of magnetic field and velocity respectively. In most runs, S _2 ( b ) develops a scaling relation ${S}_{2}({\boldsymbol{b}})\propto {l}_{\perp }^{1/2}$ ( ${E}_{b}\propto {k}_{\perp }^{-3/2}$ ). In contrast, S _2 ( u ) is consistently shallower than S _2 ( b ), which aligns with in situ observations of the solar wind. We observe that the higher-order statistics of the turbulence, which act as a proxy for intermittency, depend on the initial σ _c and are strongly affected by the expansion effect. Generally, the intermittency is more pronounced when the expansion effect is present. Finally, we find that in our simulations, although the negative residual energy and intermittency grow simultaneously as the turbulence evolves, the causal relation between them seems to be weak, possibly because they are generated on different scales. |
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| spelling | doaj-art-b1d688ad7127438d88f20db3b28487072025-01-23T08:13:17ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01979215210.3847/1538-4357/ad9f38Evolution of Magnetohydrodynamic Turbulence in the Expanding Solar Wind: Residual Energy and IntermittencyChen Shi0https://orcid.org/0000-0002-2582-7085Nikos Sioulas1https://orcid.org/0000-0002-1128-9685Zesen Huang2https://orcid.org/0000-0001-9570-5975Marco Velli3https://orcid.org/0000-0002-2381-3106Anna Tenerani4https://orcid.org/0000-0003-2880-6084Victor Réville5https://orcid.org/0000-0002-2916-3837Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles , Los Angeles, CA 90095, USA ; cshi1993@ucla.eduDepartment of Earth, Planetary, and Space Sciences, University of California, Los Angeles , Los Angeles, CA 90095, USA ; cshi1993@ucla.edu; Space Sciences Laboratory, University of California, Berkeley , Berkeley, CA 94720, USADepartment of Earth, Planetary, and Space Sciences, University of California, Los Angeles , Los Angeles, CA 90095, USA ; cshi1993@ucla.eduDepartment of Earth, Planetary, and Space Sciences, University of California, Los Angeles , Los Angeles, CA 90095, USA ; cshi1993@ucla.eduDepartment of Physics, The University of Texas at Austin , Austin, TX 78712, USAIRAP, Université Toulouse III–Paul Sabatier , CNRS, CNES, Toulouse, FranceWe conduct 3D magnetohydrodynamic simulations of decaying turbulence in the context of the solar wind. To account for the spherical expansion of the solar wind, we implement the expanding box model. The initial turbulence comprises uncorrelated counterpropagating Alfvén waves and exhibits an isotropic power spectrum. Our findings reveal the consistent generation of negative residual energy whenever nonlinear interactions are present, independent of the normalized cross helicity σ _c and compressibility. The spherical expansion facilitates this process. The resulting residual energy is primarily distributed in the perpendicular direction, with S _2 ( b ) − S _2 ( u ) ∝ l _⊥ or equivalently $-{E}_{r}\propto {k}_{\perp }^{-2}$ . Here S _2 ( b ) and S _2 ( u ) are second-order structure functions of magnetic field and velocity respectively. In most runs, S _2 ( b ) develops a scaling relation ${S}_{2}({\boldsymbol{b}})\propto {l}_{\perp }^{1/2}$ ( ${E}_{b}\propto {k}_{\perp }^{-3/2}$ ). In contrast, S _2 ( u ) is consistently shallower than S _2 ( b ), which aligns with in situ observations of the solar wind. We observe that the higher-order statistics of the turbulence, which act as a proxy for intermittency, depend on the initial σ _c and are strongly affected by the expansion effect. Generally, the intermittency is more pronounced when the expansion effect is present. Finally, we find that in our simulations, although the negative residual energy and intermittency grow simultaneously as the turbulence evolves, the causal relation between them seems to be weak, possibly because they are generated on different scales.https://doi.org/10.3847/1538-4357/ad9f38Interplanetary turbulenceMagnetohydrodynamicsMagnetohydrodynamical simulationsSolar wind |
| spellingShingle | Chen Shi Nikos Sioulas Zesen Huang Marco Velli Anna Tenerani Victor Réville Evolution of Magnetohydrodynamic Turbulence in the Expanding Solar Wind: Residual Energy and Intermittency The Astrophysical Journal Interplanetary turbulence Magnetohydrodynamics Magnetohydrodynamical simulations Solar wind |
| title | Evolution of Magnetohydrodynamic Turbulence in the Expanding Solar Wind: Residual Energy and Intermittency |
| title_full | Evolution of Magnetohydrodynamic Turbulence in the Expanding Solar Wind: Residual Energy and Intermittency |
| title_fullStr | Evolution of Magnetohydrodynamic Turbulence in the Expanding Solar Wind: Residual Energy and Intermittency |
| title_full_unstemmed | Evolution of Magnetohydrodynamic Turbulence in the Expanding Solar Wind: Residual Energy and Intermittency |
| title_short | Evolution of Magnetohydrodynamic Turbulence in the Expanding Solar Wind: Residual Energy and Intermittency |
| title_sort | evolution of magnetohydrodynamic turbulence in the expanding solar wind residual energy and intermittency |
| topic | Interplanetary turbulence Magnetohydrodynamics Magnetohydrodynamical simulations Solar wind |
| url | https://doi.org/10.3847/1538-4357/ad9f38 |
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