Chhiber R.Pecora F.Usmanov A.V.Matthaeus W.H.Goldstein M.L.Roy S.Wang J.Thepthong P.Ruffolo D.Mahidol University2024-07-252024-07-252024-09-01Monthly Notices of the Royal Astronomical Society: Letters Vol.533 No.1 (2024) , L70-L75https://repository.li.mahidol.ac.th/handle/20.500.14594/99903The transition from subAlfvénic to superAlfvénic flow in the solar atmosphere is examined by means of Parker Solar Probe (PSP) measurements during solar encounters 8 to 14. Around 220 subAlfvénic periods with a duration ≥10 min are identified. The distribution of their durations, heliocentric distances, and Alfvén Mach number are analysed and compared with a global magnetohydrodynamic model of the solar corona and wind which includes turbulence effects. The results are consistent with a patchy and fragmented morphology, and suggestive of a turbulent Alfvén zone within which the transition from subAlfvénic to superAlfvénic flow occurs over an extended range of helioradii. These results inform and establish context for detailed analyses of subAlfvénic coronal plasma that are expected to emerge from PSP’s final mission phase, as well as for NASA’s planned PUNCH mission.Earth and Planetary SciencesPhysics and AstronomyArticleSCOPUS10.1093/mnrasl/slae0512-s2.0-8519892696217453933