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Analysis of Magnetohydrodynamic Perturbations in the Radial-field Solar Wind from Parker Solar Probe Observations
| Author | Zhao, S.~Q.; Yan, Huirong; Liu, Terry; Liu, Mingzhe; Shi, Mijie; |
| Keywords | Parker Data Used; 1534; 830; 1964; 1544; 1636; Astrophysics - Solar and Stellar Astrophysics; Physics - Plasma Physics; Physics - Space Physics |
| Abstract | We report analysis of sub-Alfv\ enic magnetohydrodynamic (MHD) perturbations in the low-\ensuremath\beta radial-field solar wind employing the Parker Solar Probe spacecraft data from 2018 October 31 to November 12. We calculate wavevectors using the singular value decomposition method and separate MHD perturbations into three eigenmodes (Alfv\ en, fast, and slow modes) to explore the properties of sub-Alfv\ enic perturbations and the role of compressible perturbations in solar wind heating. The MHD perturbations show a high degree of Alfv\ enicity in the radial-field solar wind, with the energy fraction of Alfv\ en modes dominating (\raisebox-0.5ex\textasciitilde45\%-83\%) over those of fast modes (\raisebox-0.5ex\textasciitilde16\%-43\%) and slow modes (\raisebox-0.5ex\textasciitilde1\%-19\%). We present a detailed analysis of a representative event on 2018 November 10. Observations show that fast modes dominate magnetic compressibility, whereas slow modes dominate density compressibility. The energy damping rate of compressible modes is comparable to the heating rate, suggesting the collisionless damping of compressible modes could be significant for solar wind heating. These results are valuable for further studies of the imbalanced turbulence near the Sun and possible heating effects of compressible modes at MHD scales in low-\ensuremath\beta plasma. |
| Year of Publication | 2021 |
| Journal | \apj |
| Volume | 923 |
| Number of Pages | 253 |
| Section | |
| Date Published | dec |
| ISBN | |
| URL | |
| DOI | 10.3847/1538-4357/ac2ffe |
