The Quest to Understand Supergranulation and Large-Scale Convection in the Sun

  title={The Quest to Understand Supergranulation and Large-Scale Convection in the Sun},
  author={Shravan M. Hanasoge and Katepalli R. Sreenivasan},
  journal={Solar Physics},
Surface granulation of the Sun is primarily a consequence of thermal transport in the outer 1 % of the radius. Its typical scale of about 1 – 2 Mm is set by the balance between convection, free-streaming radiation, and the strong density stratification in the surface layers. The physics of granulation is well understood, as demonstrated by the close agreement between numerical simulation, theory, and observation. Superimposed on the energetic granular structure comprising high-speed flows, are… 
The Sun’s supergranulation
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Supergranule aggregation for constant heat flux-driven turbulent convection
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Relation between trees of fragmenting granules and supergranulation evolution
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Plasma flows and sound-speed perturbations in the average supergranule
Supergranules create a peak in the spatial spectrum of photospheric velocity features. They have some properties of convection cells but their origin is still being debated in the literature. The
Stellar mixing length theory with entropy rain
The effects of a non-gradient flux term originating from the motion of convective elements with entropy perturbations of either sign are investigated and incorporated into a modified version of
On the Detectability of Large-Scale Flows by Asteroseismology
Large-scale convective motions are an integral part of stellar interior dynamics and might play a relevant role in stellar dynamo processes. However, they are difficult to detect or characterize.
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This paper provides an overview of the current understanding of how the corona is heated and how the solar wind is accelerated, and some key observational results from ultraviolet spectroscopy of the collisionless outer corona.
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Turbulent convection is thought to act as an effective viscosity in damping equilibrium tidal flows, driving spin and orbital evolution in close convective binary systems. Compared to mixing-length
Photospheric downflows observed with SDO/HMI, HINODE, and an MHD simulation
Downflows on the solar surface are suspected to play a major role in the dynamics of the convection zone, at least in its outer part. We investigate the existence of the long-lasting downflows whose
Turbulent Viscosity Acting on the Equilibrium Tidal Flow in Convective Stars
Convection is thought to act as a turbulent viscosity in damping tidal flows and in driving spin and orbital evolution in close convective binary systems. This turbulent viscosity should be reduced,


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Observations are reported showing that supergranulation undergoes oscillations and supports waves with periods of 6–9 days, which explains the apparent super-rotation of the pattern.
Structure and Evolution of Giant Cells in Global Models of Solar Convection
The global scales of solar convection are studied through three-dimensional simulations of compressible convection carried out in spherical shells of rotating fluid that extend from the base of the
On the Patterns of the Solar Granulation and Supergranulation
We study the cellular patterns of the white light granulation and of the chromospheric Ca II K supergranular network. We apply a gradient-based tessellation algorithm to define the cell outlines. The
The Scales of Granulation, Mesogranulation, and Supergranulation
  • M. Rast
  • Environmental Science, Physics
  • 2003
Solar granulation is described as an advection-fragmentation process in the upper layers of the convection zone. The fundamental hydrodynamic unit is the downflow plume, and from its structure the
Large-Scale Dynamics of the Convection Zone and Tachocline
The past few decades have seen dramatic progress in our understanding of solar interior dynamics, prompted by the relatively new science of helioseismology and increasingly sophisticated numerical
Giant Convection Cells Found on the Sun
Evidence is found for giant cellular flows that persist for months by tracking the motions of supergranules, suggesting the existence of much larger cells that have long been predicted by theory but not unambiguously detected.
On the power spectrum of solar surface flows
Context. The surface of the Sun provides us with a unique and very detailed view of turbulent stellar convection. Studying its dynamics can therefore help us make significant progress in stellar
We have measured the average radial (cell center to network boundary) profile of the continuum intensity contrast associated with supergranular flows using data from the Precision Solar Photometric
Anomalously weak solar convection
Advection is dominated by Coriolis forces for wavenumbers ℓ < 60, with Rossby numbers smaller than approximately 10-2 at r/R⊙ = 0.96, suggesting that the Sun may be a much faster rotator than previously thought, and that large-scale convection may be quasi-geostrophic.
Structure and Evolution of Supergranulation from Local Helioseismology
Supergranulation is visible at the solar surface as a cellular pattern of horizontal outflows. Although it does not show a distinct intensity pattern, it manifests itself indirectly in, for example,