Properties of Steady Sub-Alfvénic Solar Wind in Comparison with Super-Alfvénic Wind from Parker Solar Probe Measurements
We identify more than 10 steady sub-Alfvénic solar wind intervals from the measurements of the Parker Solar Probe (PSP) from encounter 8 to encounter 14. An analysis of these sub-Alfvénic intervals reveals similar properties and similar origins. In situ measurements show that these intervals feature...
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| Format: | Article |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad0dfe |
| _version_ | 1827577016935776256 |
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| author | Yiming Jiao Ying D. Liu Hao Ran Wenshuai Cheng |
| author_facet | Yiming Jiao Ying D. Liu Hao Ran Wenshuai Cheng |
| author_sort | Yiming Jiao |
| collection | DOAJ |
| description | We identify more than 10 steady sub-Alfvénic solar wind intervals from the measurements of the Parker Solar Probe (PSP) from encounter 8 to encounter 14. An analysis of these sub-Alfvénic intervals reveals similar properties and similar origins. In situ measurements show that these intervals feature a decreased radial Alfvén Mach number resulting from a reduced density and a relatively low velocity, and that switchbacks are suppressed in these intervals. Magnetic source tracing indicates that these sub-Alfvénic streams generally originate from the boundaries inside coronal holes or narrow/small regions of open magnetic fields. Such properties and origins suggest that these streams are mostly low Mach-number boundary layers (LMBLs), which is a special component of the pristine solar wind proposed by Liu et al. We find that the LMBL wind, the fast wind from deep inside coronal holes, and the slow streamer wind constitute three typical components of the young solar wind near the Sun. In these sub-Alfvénic intervals, the Alfvén radius varies between 15 and 25 solar radii, in contrast with a typical 12 radii for the Alfvén radius of the super-Alfvénic wind. These results give a self-consistent picture interpreting the PSP measurements in the vicinity of the Sun. |
| first_indexed | 2024-03-08T21:20:41Z |
| format | Article |
| id | doaj.art-d88420ea3535447289c608d01496ac08 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-08T21:20:41Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-d88420ea3535447289c608d01496ac082023-12-21T10:57:32ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0196014210.3847/1538-4357/ad0dfeProperties of Steady Sub-Alfvénic Solar Wind in Comparison with Super-Alfvénic Wind from Parker Solar Probe MeasurementsYiming Jiao0https://orcid.org/0009-0004-4832-0895Ying D. Liu1https://orcid.org/0000-0002-3483-5909Hao Ran2https://orcid.org/0000-0002-8234-6480Wenshuai Cheng3https://orcid.org/0009-0005-3941-1514State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, People’s Republic of China ; liuxying@swl.ac.cn; University of Chinese Academy of Sciences , Beijing, People’s Republic of ChinaState Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, People’s Republic of China ; liuxying@swl.ac.cn; University of Chinese Academy of Sciences , Beijing, People’s Republic of ChinaState Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, People’s Republic of China ; liuxying@swl.ac.cn; University of Chinese Academy of Sciences , Beijing, People’s Republic of ChinaState Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, People’s Republic of China ; liuxying@swl.ac.cn; University of Chinese Academy of Sciences , Beijing, People’s Republic of ChinaWe identify more than 10 steady sub-Alfvénic solar wind intervals from the measurements of the Parker Solar Probe (PSP) from encounter 8 to encounter 14. An analysis of these sub-Alfvénic intervals reveals similar properties and similar origins. In situ measurements show that these intervals feature a decreased radial Alfvén Mach number resulting from a reduced density and a relatively low velocity, and that switchbacks are suppressed in these intervals. Magnetic source tracing indicates that these sub-Alfvénic streams generally originate from the boundaries inside coronal holes or narrow/small regions of open magnetic fields. Such properties and origins suggest that these streams are mostly low Mach-number boundary layers (LMBLs), which is a special component of the pristine solar wind proposed by Liu et al. We find that the LMBL wind, the fast wind from deep inside coronal holes, and the slow streamer wind constitute three typical components of the young solar wind near the Sun. In these sub-Alfvénic intervals, the Alfvén radius varies between 15 and 25 solar radii, in contrast with a typical 12 radii for the Alfvén radius of the super-Alfvénic wind. These results give a self-consistent picture interpreting the PSP measurements in the vicinity of the Sun.https://doi.org/10.3847/1538-4357/ad0dfeSolar windSolar coronal holesSolar coronaAlfven waves |
| spellingShingle | Yiming Jiao Ying D. Liu Hao Ran Wenshuai Cheng Properties of Steady Sub-Alfvénic Solar Wind in Comparison with Super-Alfvénic Wind from Parker Solar Probe Measurements The Astrophysical Journal Solar wind Solar coronal holes Solar corona Alfven waves |
| title | Properties of Steady Sub-Alfvénic Solar Wind in Comparison with Super-Alfvénic Wind from Parker Solar Probe Measurements |
| title_full | Properties of Steady Sub-Alfvénic Solar Wind in Comparison with Super-Alfvénic Wind from Parker Solar Probe Measurements |
| title_fullStr | Properties of Steady Sub-Alfvénic Solar Wind in Comparison with Super-Alfvénic Wind from Parker Solar Probe Measurements |
| title_full_unstemmed | Properties of Steady Sub-Alfvénic Solar Wind in Comparison with Super-Alfvénic Wind from Parker Solar Probe Measurements |
| title_short | Properties of Steady Sub-Alfvénic Solar Wind in Comparison with Super-Alfvénic Wind from Parker Solar Probe Measurements |
| title_sort | properties of steady sub alfvenic solar wind in comparison with super alfvenic wind from parker solar probe measurements |
| topic | Solar wind Solar coronal holes Solar corona Alfven waves |
| url | https://doi.org/10.3847/1538-4357/ad0dfe |
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