Turbulence in the Sun is suppressed on large scales and confined to equatorial regions

Convection in the Sun’s outer envelope generates turbulence and drives differential rotation, meridional circulation, and the global magnetic cycle. We develop a greater understanding of these processes by contrasting observations with simulations of global convection. These comparisons also enhance our comprehension of the physics of distant Sun-like stars. Here, we infer toroidal flow power as a function of wave number, frequency, and depth in the solar interior through helioseismic analyses of space-based observations. The inferred flows grow with spatial wave number and temporal frequency and are confined to low latitudes, supporting the argument that rotation induces systematic differences between the poles and equator. In contrast, the simulations used here show the opposite trends—power diminishing with increasing wave number and frequency while flow amplitudes become weakest at low latitudes. These differences highlight gaps in our understanding of solar convection and point to challenges ahead.

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Rotation of the solar convection zone from helioseismology

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307000816 ◽

2006 ◽

Vol 2 (S239) ◽

pp. 393-404 ◽

Cited By ~ 1

Author(s):

Jørgen Christensen-Dalsgaard

Keyword(s):

Solar Cycle ◽

Convection Zone ◽

Periodic Variation ◽

Solar Interior ◽

Slow Rotation ◽

Magnetic Cycle ◽

Solar Convection Zone ◽

Zonal Flows ◽

Solar Convection ◽

Solar Magnetic Cycle

AbstractHelioseismology has provided very detailed inferences about rotation of the solar interior. Within the convection zone the rotation rate roughly shares the latitudinal variation seen in the surface differential rotation. The transition to the nearly uniformly rotating radiative interior takes place in a narrow tachocline, which is likely important to the operation of the solar magnetic cycle. The convection-zone rotation displays zonal flows, regions of slightly more rapid and slow rotation, extending over much of the depth of the convection zone and converging towards the equator as the solar cycle progresses. In addition, there is some evidence for a quasi-periodic variation in rotation, with a period of around 1.3 yr, at the equator near the bottom of the convection zone.

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Turbulence functions useful for probes (space–time correlation) and for scattering (wave-number–frequency spectrum) analysis

Canadian Journal of Physics ◽

10.1139/p68-636 ◽

1968 ◽

Vol 46 (23) ◽

pp. 2683-2702 ◽

Cited By ~ 11

Author(s):

I. P. Shkarofsky

Keyword(s):

Characteristic Size ◽

Time Correlation ◽

Exponential Model ◽

Time Correlation Function ◽

Maximum Energy ◽

Confluent Hypergeometric Function ◽

Space Time ◽

Wave Number ◽

Taylor’S Hypothesis ◽

Number Frequency

The wave-number–frequency dependent spectral function, S(k, ω), and the space–time correlation function, C(r, t), are considered in a turbulent flowing plasma. The decay mechanisms are associated with either velocity fluctuations about the mean convection velocity or diffusion effects or attachment, or combinations of these, including the Brownian motion model. The ψ(k, ω) function, which is the ratio of S(k, ω) to its frequency-integrated value, depends on the mechanism and exhibits a profile which can be Gaussian, Lorentzian, a Z function, a Hermite polynomial modification of the Gaussian, or a confluent hypergeometric function. Anisotropic forms are also considered.The function C(r, t), obtained by convolving ψ (r, t) with C(r), the space autocorrelation function, is next considered. Adopting a Gaussian or an exponential model (which may be anisotropic) for C(r), we illustrate C(r, t) forms, which can readily be manipulated. Furthermore, letting r = 0, we derive two conditions for the applicability of Taylor's hypothesis. The assumption of frozen flow is not necessary, only that the root-mean-square Lagrangian displacement in a given time, associated with the decay, be much smaller than both the flow distance and the characteristic size of blobs having maximum energy.

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