Abstract
The high temperatures and strong magnetic fields of the solar corona form streams of solar wind that expand through the Solar System into interstellar space. At 09:33 UT on 28 April 2021 Parker Solar Probe entered the magnetized atmosphere of the Sun 13 million km above the photosphere, crossing below the Alfvén critical surface for five hours into plasma in casual contact with the Sun with an Alfvén Mach number of 0.79 and magnetic pressure dominating both ion and electron pressure. The spectrum of turbulence below the Alfvén critical surface is reported. Magnetic mapping suggests the region was a steady flow emerging on rapidly expanding coronal magnetic field lines lying above a pseudostreamer. The sub-Alfvénic nature of the flow may be due to suppressed magnetic reconnection at the base of the pseudostreamer, as evidenced by unusually low densities in this region and the magnetic mapping.
- Received 31 October 2021
- Revised 9 November 2021
- Accepted 15 November 2021
- Corrected 15 December 2021
DOI:https://doi.org/10.1103/PhysRevLett.127.255101
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Corrections
15 December 2021
Correction: The first sentence of the caption to Fig. 2 contained an error and has been fixed.
Viewpoint
Momentous Crossing of a Solar Boundary
Published 14 December 2021
The Parker Solar Probe has entered, for the first time, the Sun’s magnetic atmosphere, where it started to gather data that could help researchers solve some of the greatest mysteries of solar physics.
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