Alfvénic velocity spikes and rotational flows in the near-Sun solar wind

Kasper, J. C.; Bale, S. D.; Belcher, J. W.; Berthomier, M.; Case, A. W.; Chandran, B. D. G.; Curtis, D. W.; Gallagher, D.; Gary, S. P.; Golub, L.; Halekas, J. S.; Ho, G. C.; Horbury, T. S.; Hu, Q.; Huang, J.; Klein, K. G.; Korreck, K. E.; Larson, D. E.; Livi, R.; Maruca, B.; Lavraud, B.; Louarn, P.; Maksimovic, M.; Martinovic, M.; McGinnis, D.; Pogorelov, N. V.; Richardson, J. D.; Skoug, R. M.; Steinberg, J. T.; Stevens, M. L.; Szabo, A.; Velli, M.; Whittlesey, P. L.; Wright, K. H.; Zank, G. P.; MacDowall, R. J.; McComas, D. J.; McNutt, R. L.; Pulupa, M.; Raouafi, N. E.; Schwadron, N. A.

Alfvénic velocity spikes and rotational flows in the near-Sun solar wind

J. C. Kasper (), S. D. Bale, J. W. Belcher, M. Berthomier, A. W. Case, B. D. G. Chandran, D. W. Curtis, D. Gallagher, S. P. Gary, L. Golub, J. S. Halekas, G. C. Ho, T. S. Horbury, Q. Hu, J. Huang, K. G. Klein, K. E. Korreck, D. E. Larson, R. Livi, B. Maruca, B. Lavraud, P. Louarn, M. Maksimovic, M. Martinovic, D. McGinnis, N. V. Pogorelov, J. D. Richardson, R. M. Skoug, J. T. Steinberg, M. L. Stevens, A. Szabo, M. Velli, P. L. Whittlesey, K. H. Wright, G. P. Zank, R. J. MacDowall, D. J. McComas, R. L. McNutt, M. Pulupa, N. E. Raouafi and N. A. Schwadron
Additional contact information
J. C. Kasper: University of Michigan
S. D. Bale: University of California
J. W. Belcher: Massachusetts Institute of Technology
M. Berthomier: Sorbonne Université, Ecole Polytechnique, Observatoire de Paris, Université Paris-Saclay
A. W. Case: Smithsonian Astrophysical Observatory
B. D. G. Chandran: University of New Hampshire
D. W. Curtis: University of California
D. Gallagher: Heliophysics and Planetary Science Branch ST13, Marshall Space Flight Center
S. P. Gary: Los Alamos National Laboratory
L. Golub: Smithsonian Astrophysical Observatory
J. S. Halekas: Department of Physics and Astronomy
G. C. Ho: Johns Hopkins University Applied Physics Laboratory
T. S. Horbury: Imperial College London
Q. Hu: University of Alabama in Huntsville
J. Huang: University of Michigan
K. G. Klein: University of Arizona
K. E. Korreck: Smithsonian Astrophysical Observatory
D. E. Larson: University of California
R. Livi: University of California
B. Maruca: University of Delaware
B. Lavraud: Université de Toulouse
P. Louarn: Université de Toulouse
M. Maksimovic: LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris
M. Martinovic: University of Arizona
D. McGinnis: Department of Physics and Astronomy
N. V. Pogorelov: University of Alabama in Huntsville
J. D. Richardson: Massachusetts Institute of Technology
R. M. Skoug: Los Alamos National Laboratory
J. T. Steinberg: Los Alamos National Laboratory
M. L. Stevens: Smithsonian Astrophysical Observatory
A. Szabo: NASA/Goddard Space Flight Center
M. Velli: University of California
P. L. Whittlesey: University of California
K. H. Wright: Universities Space Research Association, Science and Technology Institute
G. P. Zank: University of Alabama in Huntsville
R. J. MacDowall: NASA/Goddard Space Flight Center
D. J. McComas: Princeton University
R. L. McNutt: Johns Hopkins University Applied Physics Laboratory
M. Pulupa: University of California
N. E. Raouafi: Johns Hopkins University Applied Physics Laboratory
N. A. Schwadron: University of New Hampshire

Nature, 2019, vol. 576, issue 7786, 228-231

Abstract: Abstract The 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.

Date: 2019
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DOI: 10.1038/s41586-019-1813-z

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