Shear-Driven Transition to Isotropically Turbulent Solar Wind Outside the Alfv´en Critical Zone

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dc.contributor.authorRuffolo, D.
dc.contributor.authorMatthaeus, W. H.
dc.contributor.authorChhiber, R.
dc.contributor.authorUsmanov, A. V.
dc.contributor.authorYang, Y.
dc.contributor.authorBandyopadhyay, R.
dc.contributor.authorParashar, T. N.
dc.contributor.authorGoldstein, Melvyn
dc.contributor.authorDeForest, C. E.
dc.contributor.authorWan, M.
dc.contributor.authorChasapis, A.
dc.contributor.authorMaruca, B. A.
dc.contributor.authorVelli, M.
dc.contributor.authorKasper, J. C.
dc.date.accessioned2020-10-07T17:39:41Z
dc.date.available2020-10-07T17:39:41Z
dc.date.issued2020-09-15
dc.description.abstractMotivated by prior remote observations of a transition from striated solar coronal structures to more isotropic ``flocculated'' fluctuations, we propose that the dynamics of the inner solar wind just outside the Alfvén critical zone, and in the vicinity of the first β=1 surface, is powered by the relative velocities of adjacent coronal magnetic flux tubes. We suggest that large amplitude flow contrasts are magnetically constrained at lower altitude but shear-driven dynamics are triggered as such constraints are released above the Alfvén critical zone, as suggested by global magnetohydrodynamic (MHD) simulations that include self-consistent turbulence transport. We argue that this dynamical evolution accounts for features observed by {\it Parker Solar Probe} ({\it PSP}) near initial perihelia, including magnetic ``switchbacks'', and large transverse velocities that are partially corotational and saturate near the local Alfvén speed. Large-scale magnetic increments are more longitudinal than latitudinal, a state unlikely to originate in or below the lower corona. We attribute this to preferentially longitudinal velocity shear from varying degrees of corotation. Supporting evidence includes comparison with a high Mach number three-dimensional compressible MHD simulation of nonlinear shear-driven turbulence, reproducing several observed diagnostics, including characteristic distributions of fluctuations that are qualitatively similar to {\it PSP} observations near the first perihelion. The concurrence of evidence from remote sensing observations, {\it in situ} measurements, and both global and local simulations supports the idea that the dynamics just above the Alfvén critical zone boost low-frequency plasma turbulence to the level routinely observed throughout the explored solar system.en_US
dc.description.sponsorshipThe authors are grateful to Wiwithawin Charoenngam for plotting assistance. This work utilizes data produced collaboratively between AFRL/ADAPT and NSO/NISP. This research has been supported in part by grant RTA6280002 from Thailand Science Research and Innovation and the Parker Solar Probe mission under the ISOIS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165). M.L.G. acknowledges support from the Parker Solar Probe FIELDS MAG team. Y.Y. and M.W. acknowledge support from NSFC (Grants 11672123,11902138, and 91752201). Additional support is acknowledged from the NASA LWS program (NNX17AB79G) and the HSR program (80NSSC18K1210 & 80NSSC18K1648).en_US
dc.description.urihttps://iopscience.iop.org/article/10.3847/1538-4357/abb594en_US
dc.format.extent20 pagesen_US
dc.genrejournal articleen_US
dc.identifierdoi:10.13016/m2ewfl-mgwq
dc.identifier.citation“Shear-Driven Transition to Isotropically Turbulent Solar Wind Outside the Alfvén Critical Zone”, D. Ruffolo, W.H. Matthaeus, R. Chhiber, A.V. Usmanov, Yan Yang, R. Bandyopadhyay, T.N. Parashar, M.L. Goldstein, C.E. DeForest, Minping Wan, A. Chasapis, B.A. Maruca, M. Velli, J.C. Kasper, The Astrophys. J., https://doi.org/10.3847/1538-4357/abb594.en_US
dc.identifier.urihttp://hdl.handle.net/11603/19756
dc.identifier.urihttps://doi.org/10.3847/1538-4357/abb594
dc.language.isoen_USen_US
dc.publisherAAS
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Goddard Planetary Heliophysics Institute (GPHI)
dc.relation.ispartofUMBC Faculty Collection
dc.rightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
dc.titleShear-Driven Transition to Isotropically Turbulent Solar Wind Outside the Alfv´en Critical Zoneen_US
dc.typeTexten_US
dcterms.creatorhttps://orcid.org/0000-0002-5317-988X

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