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Abstract This paper reports the first possible evidence for the development of the Kelvin–Helmholtz (KH) instability at the border of coronal holes separating the associated fast wind from the slower wind originating from adjacent streamer regions. Based on a statistical data set of spectroscopic measurements of the UV corona acquired with the UltraViolet Coronagraph Spectrometer on board the SOlar and Heliospheric Observatory during the minimum activity of solar cycle 22, high temperature–velocity correlations are found along the fast/slow solar wind interface region and interpreted as manifestations of KH vortices formed by the roll-up of the shear flow, whose dissipation could lead to higher heating and, because of that, higher velocities. These observational results are supported by solving coupled solar wind and turbulence transport equations including a KH-driven source of turbulence along the tangential velocity discontinuity between faster and slower coronal flows: numerical analysis indicates that the correlation between the solar wind speed and temperature is large in the presence of the shear source of turbulence. These findings suggest that the KH instability may play an important role both in the plasma dynamics and in the energy deposition at the boundaries of coronal holes and equatorial streamers.
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First polar observations of the fast solar wind with the Metis – Solar Orbiter coronagraph: Role of 2D turbulence energy dissipation in the wind acceleration
Context. The fast solar wind is known to emanate from polar coronal holes. Aims. This Letter reports the first estimate of the expansion rate of polar coronal flows performed by the Metis coronagraph on board Solar Orbiter. Methods. By exploiting simultaneous measurements in polarized white light and ultraviolet intensity of the neutral hydrogen Lyman- α line, it was possible to extend observations of the outflow velocity of the main component of the solar wind from polar coronal holes out to 5.5 R ⊙ , the limit of diagnostic applicability and observational capabilities. Results. We complement the results obtained with analogous polar observations performed with the UltraViolet Coronagraph Spectrometer on board the SOlar and Heliospheric Observatory during the previous full solar activity cycle, and find them to be satisfactorily reproduced by a magnetohydrodynamic turbulence model. Conclusions. This suggests that the dissipation of 2D turbulence energy is a viable mechanism for coronal plasma heating and the subsequent acceleration of the fast solar wind.
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- Award ID(s):
- 2148653
- PAR ID:
- 10448667
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 670
- ISSN:
- 0004-6361
- Page Range / eLocation ID:
- L18
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1051/0004-6361/202245759
