Characterization of the Trans-Alfvénic Region Using Observations from Parker Solar Probe
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| Main Authors: | , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| author | Adhikari, Subash Bandyopadhyay, Riddhi Goodwill, Joshua Matthaeus, William H. Ruffolo, David Thepthong, Panisara Pongkitiwanichakul, Peera Roy, Sohom Pecora, Francesco Chhiber, Rohit Pradata, Rayta Usmanov, Arcadi Stevens, Michael Badman, Samuel Romeo, Orlando Wang, Jiaming Goldstein, Melvyn L. |
| author_facet | Adhikari, Subash Bandyopadhyay, Riddhi Goodwill, Joshua Matthaeus, William H. Ruffolo, David Thepthong, Panisara Pongkitiwanichakul, Peera Roy, Sohom Pecora, Francesco Chhiber, Rohit Pradata, Rayta Usmanov, Arcadi Stevens, Michael Badman, Samuel Romeo, Orlando Wang, Jiaming Goldstein, Melvyn L. |
| contents | Close to Earth the solar wind is usually super-Alfvénic, i.e. the speed of the solar wind is much larger than the Alfvén speed. However, in the lower coronal regions, the solar wind is mostly sub-Alfvénic. With the Parker Solar Probe (PSP) crossing the boundary between the sub- and super-Alfvénic flow, Bandyopadhyay et al. (2022) performed a turbulence characterization of the sub-Alfvénic solar wind with initial data from encounters 8 and 9. In this study, we re-examine the turbulence properties such as turbulence amplitude, anisotropy of the magnetic field variance, intermittency and switchback strength extending with PSP data for encounters 8-19. The later orbits probe lower altitudes and experience sub-Alfvénic conditions more frequently providing a greater statistical coverage to contrast sub- and super-Alfvénic solar wind. Also, by isolating the intervals where the solar wind speed is approximately equal to the Alfvén speed, we explore the transition in more detail. We show that the amplitude of the normalized magnetic field fluctuation is smaller for the sub-Alfvénic samples. While solar wind turbulence in general is shown to be anisotropic, the sub-Alfvénic samples are more anisotropic than the super-Alfvénic samples, in general. Further, we show that the sub- and super-Alfvénic samples do not show much distinction in terms of intermittency strength. Finally, consistent with prior results, we find no evidence for polarity reversing > 90 degrees switchbacks in the sub-Alfvénic solar wind |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_07472 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Characterization of the Trans-Alfvénic Region Using Observations from Parker Solar Probe Adhikari, Subash Bandyopadhyay, Riddhi Goodwill, Joshua Matthaeus, William H. Ruffolo, David Thepthong, Panisara Pongkitiwanichakul, Peera Roy, Sohom Pecora, Francesco Chhiber, Rohit Pradata, Rayta Usmanov, Arcadi Stevens, Michael Badman, Samuel Romeo, Orlando Wang, Jiaming Goldstein, Melvyn L. Solar and Stellar Astrophysics Space Physics Close to Earth the solar wind is usually super-Alfvénic, i.e. the speed of the solar wind is much larger than the Alfvén speed. However, in the lower coronal regions, the solar wind is mostly sub-Alfvénic. With the Parker Solar Probe (PSP) crossing the boundary between the sub- and super-Alfvénic flow, Bandyopadhyay et al. (2022) performed a turbulence characterization of the sub-Alfvénic solar wind with initial data from encounters 8 and 9. In this study, we re-examine the turbulence properties such as turbulence amplitude, anisotropy of the magnetic field variance, intermittency and switchback strength extending with PSP data for encounters 8-19. The later orbits probe lower altitudes and experience sub-Alfvénic conditions more frequently providing a greater statistical coverage to contrast sub- and super-Alfvénic solar wind. Also, by isolating the intervals where the solar wind speed is approximately equal to the Alfvén speed, we explore the transition in more detail. We show that the amplitude of the normalized magnetic field fluctuation is smaller for the sub-Alfvénic samples. While solar wind turbulence in general is shown to be anisotropic, the sub-Alfvénic samples are more anisotropic than the super-Alfvénic samples, in general. Further, we show that the sub- and super-Alfvénic samples do not show much distinction in terms of intermittency strength. Finally, consistent with prior results, we find no evidence for polarity reversing > 90 degrees switchbacks in the sub-Alfvénic solar wind |
| title | Characterization of the Trans-Alfvénic Region Using Observations from Parker Solar Probe |
| topic | Solar and Stellar Astrophysics Space Physics |
| url | https://arxiv.org/abs/2510.07472 |