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Anomalously Weak Solar ConvectionConvection in the solar interior is thought to comprise structures on a spectrum of scales. This conclusion emerges from phenomenological studies and numerical simulations, though neither covers the proper range of dynamical parameters of solar convection. Here, we analyze observations of the wavefield in the solar photosphere using techniques of time-distance helioseismology to image flows in the solar interior. We downsample and synthesize 900 billion wavefield observations to produce 3 billion cross-correlations, which we average and fit, measuring 5 million wave travel times. Using these travel times, we deduce the underlying flow systems and study their statistics to bound convective velocity magnitudes in the solar interior, as a function of depth and spherical- harmonic degree l..Within the wavenumber band l < 60, convective velocities are 20-100 times weaker than current theoretical estimates. This constraint suggests the prevalence of a different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? Advection is dominated by Coriolis forces for wavenumbers l < 60, with Rossby numbers smaller than approximately 10(exp −2) at r∕R-solar = 0.96, suggesting that the Sun may be a much faster rotator than previously thought, and that large-scale convection may be quasi-geostrophic. The fact that isorotation contours in the Sun are not coaligned with the axis of rotation suggests the presence of a latitudinal entropy gradient.
Document ID
20140007404
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1073/pnas.1206570109
Authors
Hanasoge, Shravan M. (Princeton Univ. Princeton, NJ, United States)
Duvall, Thomas L. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Sreenivasan, Katepalli R. (New York Univ. New York, NY, United States)
Date Acquired
June 13, 2014
Publication Date
July 24, 2012
Publication Information
Publication: Proceedings of the National Academy of Sciences (PNAS)
Publisher: PNAS
Volume: 109
Issue: 30
ISSN: 0027-8424
Subject Category
Solar Physics
Report/Patent Number
GSFC-E-DAA-TN9941
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
Sun
Convection
Helioseismology

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