Meridional flow in the Sun’s convection zone is a single cell in each hemisphere

Gizon, Laurent; Cameron, R. H.; Pourabdian, Majid; Liang, Zhangqian; Fournier, Damien; Birch, A. C.; Hanson, Chris

doi:10.1126/science.aaz7119

Cited by 106 publications

(174 citation statements)

References 37 publications

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“…Global torsional oscillations in the longitudinal direction (Howe et al 2018) and a large scale meridional flow have also been observed. The meridional flow involves motions in both the latitudinal and radial directions and takes the form of a single cell in each hemisphere of the Sun (Gizon et al 2020). Numerical simulations of this meridional flow show that, like differential rotation, it is established by angular momentum transport resulting from the convective Reynolds stress in the presence of rotation (e.g., Featherstone & Miesch 2015;Hotta, Rempel, & Yokoyama 2015).…”

Section: Discussionmentioning

confidence: 99%

On a new formulation for energy transfer between convection and fast tides with application to giant planets and solar type stars

Terquem

2021

Monthly Notices of the Royal Astronomical Society

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All the studies of the interaction between tides and a convective flow assume that the large scale tides can be described as a mean shear flow which is damped by small scale fluctuating convective eddies. The convective Reynolds stress is calculated using mixing length theory, accounting for a sharp suppression of dissipation when the turnover timescale is larger than the tidal period. This yields tidal dissipation rates several orders of magnitude too small to account for the circularization periods of late–type binaries or the tidal dissipation factor of giant planets. Here, we argue that the above description is inconsistent, because fluctuations and mean flow should be identified based on the timescale, not on the spatial scale, on which they vary. Therefore, the standard picture should be reversed, with the fluctuations being the tidal oscillations and the mean shear flow provided by the largest convective eddies. We assume that energy is locally transferred from the tides to the convective flow. Using this assumption, we obtain values for the tidal Q factor of Jupiter and Saturn and for the circularization periods of PMS binaries in good agreement with observations. The timescales obtained with the equilibrium tide approximation are however still 40 times too large to account for the circularization periods of late–type binaries. For these systems, shear in the tachocline or at the base of the convective zone may be the main cause of tidal dissipation.

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Section: Discussionmentioning

confidence: 99%

On a new formulation for energy transfer between convection and fast tides with application to giant planets and solar type stars

Terquem

2021

Monthly Notices of the Royal Astronomical Society

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“…The Sun's surface and subsurface flow fields at low and middle heliolatitudes have been mapped very successfully thanks to the large amount of high-quality data from the SOHO/MDI (Scherrer et al 1995) and SDO/HMI (Scherrer et al 2012) instruments. These data have provided accurate knowledge of differential rotation (Schou et al 1998), and have allowed us to determine the low-latitude part of the meridional flows (Gizon et al 2020), near-surface torsional oscillations (Howe et al 2006), and the three-dimensional structure of the shallow velocity field beneath the solar surface (Gizon & Birch 2005;Gizon et al 2010). However, as described above the near-polar flow fields and the differential rotation at high lati-tudes (Beck 2000;Thompson et al 2003) cannot be mapped well from locations near the ecliptic plane.…”

Section: How Is Magnetic Flux Transported To and Reprocessed At High mentioning

confidence: 99%

The Solar Orbiter mission

Müller

Cyr

Zouganelis

et al. 2020

A&A

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Aims. Solar Orbiter, the first mission of ESA’s Cosmic Vision 2015–2025 programme and a mission of international collaboration between ESA and NASA, will explore the Sun and heliosphere from close up and out of the ecliptic plane. It was launched on 10 February 2020 04:03 UTC from Cape Canaveral and aims to address key questions of solar and heliospheric physics pertaining to how the Sun creates and controls the Heliosphere, and why solar activity changes with time. To answer these, the mission carries six remote-sensing instruments to observe the Sun and the solar corona, and four in-situ instruments to measure the solar wind, energetic particles, and electromagnetic fields. In this paper, we describe the science objectives of the mission, and how these will be addressed by the joint observations of the instruments onboard. Methods. The paper first summarises the mission-level science objectives, followed by an overview of the spacecraft and payload. We report the observables and performance figures of each instrument, as well as the trajectory design. This is followed by a summary of the science operations concept. The paper concludes with a more detailed description of the science objectives. Results. Solar Orbiter will combine in-situ measurements in the heliosphere with high-resolution remote-sensing observations of the Sun to address fundamental questions of solar and heliospheric physics. The performance of the Solar Orbiter payload meets the requirements derived from the mission’s science objectives. Its science return will be augmented further by coordinated observations with other space missions and ground-based observatories.

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“…One may note that it is necessary in the quasi-three-dimensional approach to have some variation in the z-direction otherwise the semianalytical handling of the Fourier discretization would mean we would not trigger the three-dimensionality of the problem. To identify the flow saturation states, we observe the time evolution of the kinetic energy of each of the Fourier modes defined as E m (t) = 1 2 ∫ Ω ||û m || 2 dx whereû m is the complex Fourier coefficient of the velocity field as defined in Equation (21). The evolution of kinetic energy of the leading Fourier components (N m = 0, 1, 2, 3) is shown in Figure 7.…”

Section: Ta B L E 3 Flow Quantities For Channel Flowmentioning

confidence: 99%

A spectral/hp element method for thermal convection

Hossain

Cantwell

Sherwin

2021

Numerical Methods in Fluids

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We report on a high-fidelity, spectral/hp element algorithm developed for the direct numerical simulation of thermal convection problems. We consider the incompressible Navier-Stokes (NS) and advection-diffusion equations coupled through a thermal body-forcing term. The flow is driven by a prescribed flowrate forcing with explicit treatment of the nonlinear advection terms. The explicit treatment of the body-force term also decouples both the NS and the advection-diffusion equations. The problem is then temporally discretized using an implicit-explicit scheme in conjunction with a velocity-correction splitting scheme to decouple the velocity and pressure fields in the momentum equation. Although not unique, this type of discretization has not been widely applied to thermal convection problems and we therefore provide a comprehensive overview of the algorithm and implementation which is available through the open-source package Nektar++. After verifying the algorithm on a number of illustrative problems we then apply the code to investigate flow in a channel with uniform or streamwise sinusoidal lower wall, in addition to a patterned sinusoidal heating. We verify the solver against previously published two-dimensional results. Finally, for the first time we consider a three-dimensional problem with a streamwise sinusoidal lower wall and sinusoidal heating which, for the chosen parameter, leads to the unusual dynamics of an initially unsteady two-dimensional instability leading to a steady three-dimensional nonlinear saturated state. K E Y W O R D Sincompressible Navier-Stokes, spectral/hp element method, thermal convection INTRODUCTIONThermal convection intuitively plays an important role in many engineering processes and natural phenomena such as atmospheric circulation, daily weather events, and the generation of the Sun's magnetic field. 1 Techniques used for the thermal management of power plants, engines, turbo-machinery, and even computer design (that we use to simulate fluid flow problems) often employ the principle of thermal convection. Despite a plethora of applications, simulations of thermal convection flow problems using the spectral/hp element method are rather limited. This method combines the geometric flexibility of classical h-type (mesh-size h) finite element or finite volume methods with theThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Meridional flow in the Sun’s convection zone is a single cell in each hemisphere

Cited by 106 publications

References 37 publications

On a new formulation for energy transfer between convection and fast tides with application to giant planets and solar type stars

On a new formulation for energy transfer between convection and fast tides with application to giant planets and solar type stars

The Solar Orbiter mission

A spectral/hp element method for thermal convection

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