Alfvénic velocity spikes and rotational flows in the near-Sun solar wind
AuthorKasper, J C
Bale, S D
Belcher, J W
Case, A W
Chandran, B D G
Curtis, D W
Gary, S P
Halekas, J S
Ho, G C
Horbury, T S
Klein, K G
Korreck, K E
Larson, D E
Pogorelov, N V
Richardson, J D
Skoug, R M
Steinberg, J T
Stevens, M L
Whittlesey, P L
Wright, K H
Zank, G P
MacDowall, R J
McComas, D J
McNutt, R L
Raouafi, N E
Schwadron, N A
AffiliationUniv Arizona, Lunar & Planetary Lab
Univ Arizona, Dept Planetary Sci
MetadataShow full item record
PublisherNATURE PUBLISHING GROUP
CitationKasper, J.C., Bale, S.D., Belcher, J.W. et al. Alfvénic velocity spikes and rotational flows in the near-Sun solar wind. Nature 576, 228–231 (2019) doi:10.1038/s41586-019-1813-z
Rights© The Author(s), under exclusive licence to Springer Nature Limited 2019
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
AbstractThe prediction of a supersonic solar wind1 was first confirmed by spacecraft near Earth2,3 and later by spacecraft at heliocentric distances as small as 62 solar radii4. These missions showed that plasma accelerates as it emerges from the corona, aided by unidentified processes that transport energy outwards from the Sun before depositing it in the wind. Alfvénic fluctuations are a promising candidate for such a process because they are seen in the corona and solar wind and contain considerable energy5-7. Magnetic tension forces the corona to co-rotate with the Sun, but any residual rotation far from the Sun reported until now has been much smaller than the amplitude of waves and deflections from interacting wind streams8. Here we report observations of solar-wind plasma at heliocentric distances of about 35 solar radii9-11, well within the distance at which stream interactions become important. We find that Alfvén waves organize into structured velocity spikes with duration of up to minutes, which are associated with propagating S-like bends in the magnetic-field lines. We detect an increasing rotational component to the flow velocity of the solar wind around the Sun, peaking at 35 to 50 kilometres per second-considerably above the amplitude of the waves. These flows exceed classical velocity predictions of a few kilometres per second, challenging models of circulation in the corona and calling into question our understanding of how stars lose angular momentum and spin down as they age12-14.
Note6 month embargo; published online: 4 December 2019
VersionFinal accepted manuscript
SponsorsPSP mission under NASA [NNN06AA01C]; 2019 Summer School at the Center for Computational Astrophysics, Flatiron Institute; Simons Foundation; Leverhulme Trust Visiting Professorship programmeLeverhulme Trust; UK STFCScience & Technology Facilities Council (STFC) [ST/S0003641/1]
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