The Alpha-Proton Differential Flow in the Alfvénic Young Solar Wind: From Sub-Alfvénic to Super-Alfvénic
Fuente:
arXiv
Saved in:
| Main Authors: | , , , |
|---|---|
| Format: | Preprint |
| Published: |
2024
|
| Subjects: | |
| Online Access: | |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866914646042083328 |
|---|---|
| author | Ran, Hao Liu, Ying D. Chen, Chong Mostafavi, Parisa |
| author_facet | Ran, Hao Liu, Ying D. Chen, Chong Mostafavi, Parisa |
| contents | Data obtained from Parker Solar Probe (PSP) since 2021 April have shown the first in situ observation of the solar corona, where the solar wind is formed and accelerated. Here we investigate the alpha-proton differential flow and its characteristics across the critical Alfvén surface (CAS) using data from PSP during encounters 8-10 and 12-13. We first show the positive correlation between the alpha-proton differential velocity and the bulk solar wind speed at PSP encounter distances. Then we explore how the characteristics of the differential flow vary across the CAS and how they are affected by Alfvénic fluctuations including switchbacks. We find that the differential velocity below the CAS is generally smaller than that above the CAS, and the local Alfvén speed well limits the differential speed both above and below the CAS. The deviations from the alignment between the differential velocity and the local magnetic field vector are accompanied by large-amplitude Alfvénic fluctuations and decreases in the differential speed. Moreover, we observe that $V_{αp}$ increases from $M_A < 1$ to $M_A \simeq 2$ and then starts to decrease, which suggests that alphas may remain preferentially accelerated well above the CAS. Our results also reveal that in the sub-Alfvénic solar wind both protons and alphas show a strong correlation between their velocity fluctuations and magnetic field fluctuations, with a weaker correlation for alphas. In contrast, in the super-Alfvénic regime the correlation remains high for protons, but is reduced for alphas. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2401_10457 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The Alpha-Proton Differential Flow in the Alfvénic Young Solar Wind: From Sub-Alfvénic to Super-Alfvénic Ran, Hao Liu, Ying D. Chen, Chong Mostafavi, Parisa Solar and Stellar Astrophysics Plasma Physics Space Physics Data obtained from Parker Solar Probe (PSP) since 2021 April have shown the first in situ observation of the solar corona, where the solar wind is formed and accelerated. Here we investigate the alpha-proton differential flow and its characteristics across the critical Alfvén surface (CAS) using data from PSP during encounters 8-10 and 12-13. We first show the positive correlation between the alpha-proton differential velocity and the bulk solar wind speed at PSP encounter distances. Then we explore how the characteristics of the differential flow vary across the CAS and how they are affected by Alfvénic fluctuations including switchbacks. We find that the differential velocity below the CAS is generally smaller than that above the CAS, and the local Alfvén speed well limits the differential speed both above and below the CAS. The deviations from the alignment between the differential velocity and the local magnetic field vector are accompanied by large-amplitude Alfvénic fluctuations and decreases in the differential speed. Moreover, we observe that $V_{αp}$ increases from $M_A < 1$ to $M_A \simeq 2$ and then starts to decrease, which suggests that alphas may remain preferentially accelerated well above the CAS. Our results also reveal that in the sub-Alfvénic solar wind both protons and alphas show a strong correlation between their velocity fluctuations and magnetic field fluctuations, with a weaker correlation for alphas. In contrast, in the super-Alfvénic regime the correlation remains high for protons, but is reduced for alphas. |
| title | The Alpha-Proton Differential Flow in the Alfvénic Young Solar Wind: From Sub-Alfvénic to Super-Alfvénic |
| topic | Solar and Stellar Astrophysics Plasma Physics Space Physics |
| url | https://arxiv.org/abs/2401.10457 |