Motions in the Sun at the Photospheric Level: VI. Large-Scale Motions in the Equatorial Region

Hart, Abraham

doi:10.1093/mnras/116.1.38

Cited by 70 publications

(30 citation statements)

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“…Actually, it is most probable that this "noise"was already detected as early as 1915 by Plaskett (1916). Two years after her first detailed report, Hart (1956) confirmed the discovery and was able to give the first estimate 1 of 26 Mm for the typical horizontal length scale of these "velocity fluctuations" (sic). Supergranulation was further recognised as a characteristic feature of the whole surface of the quiet Sun (the regions of weak magnetic fields, which represent the most important part of the solar surface) after the seminal work of Leighton et al (1962), who published the first Doppler images of the Sun (and also the first detection of the five minutes oscillations).…”

Section: Introductionmentioning

confidence: 78%

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The Sun’s Supergranulation

Rincon

Rieutord

2010

Living Rev. Solar Phys.

165

132

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The Sun's supergranulation refers to a physical pattern covering the surface of the quiet Sun with a typical horizontal scale of approximately 30,000 km and a lifetime of around 1.8 d. Its most noticeable observable signature is as a fluctuating velocity field of 360 m s -1 rms whose components are mostly horizontal. Supergranulation was discovered more than fifty years ago, however explaining why and how it originates still represents one of the main challenges of modern solar physics.A lot of work has been devoted to the subject over the years, but observational constraints, conceptual difficulties and numerical limitations have all concurred to prevent a detailed understanding of the supergranulation phenomenon so far. With the advent of 21st century supercomputing resources and the availability of unprecedented high-resolution observations of the Sun, a stage at which key progress can be made has now been reached. A unifying strategy between observations and modelling is more than ever required for this to be possible.The primary aim of this review is therefore to provide readers with a detailed interdisciplinary description of past and current research on the problem, from the most elaborate observational strategies to recent theoretical and numerical modelling efforts that have all taken up the challenge of uncovering the origins of supergranulation. Throughout the text, we attempt to pick up the most robust findings so far, but we also outline the difficulties, limitations and open questions that the community has been confronted with over the years.In the light of the current understanding of the multiscale dynamics of the quiet photosphere, we finally suggest a tentative picture of supergranulation as a dynamical feature of turbulent magnetohydrodynamic convection in an extended spatial domain, with the aim of stimulating future research and discussions.

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Section: Introductionmentioning

confidence: 78%

“…Using correlation of the signal, Hart (1956) found a typical length of 26 Mm. Since this pioneering work, this value has oscillated around 30 Mm.…”

Section: Length Scalesmentioning

confidence: 99%

The Sun’s Supergranulation

Rincon

Rieutord

2010

Living Rev. Solar Phys.

165

132

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“…The divergent flow within each cell tends to sweep its interior clear of magnetic elements, thereby clustering the field at the cell boundaries and forming a magnetic network (e.g., Simon & Leighton 1964). The flows associated with supergranulation were first detected in the 1950s (Hart 1956), but recognition that the cellular pattern covered the entire solar surface awaited the publication of the first Dopplergram images of the Sun (Leighton et al 1962). Figure 1 provides a modern Dopplergram generated by the Helioseismic and Magnetic Imager (HMI; Scherrer et al 2012;Schou et al 2012) aboard the Solar Dynamics Observatory (SDO).…”

Section: Introductionmentioning

confidence: 99%

Helioseismic Imaging of Supergranulation Throughout the Sun’s Near-Surface Shear Layer

Greer

Hindman

Toomre

2016

ApJ

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We present measurements of the Sun's sub-surface convective flows and provide evidence that the pattern of supergranulation is driven at the surface. The pattern subsequently descends slowly throughout the near-surface shear layer in a manner that is inconsistent with a 3D cellular structure. The flow measurements are obtained through the application of a new helioseismic technique based on traditional ring analysis. We measure the flow field over the course of eleven days and perform a correlation analysis between all possible pairs of depths and temporal separations. In congruence with previous studies, we find that the supergranulation pattern remains coherent at the surface for slightly less than two days and the instantaneous surface pattern is imprinted to a depth of 7 Mm. However, these correlation times and depths are deceptive. When we admit a potential time lag in the correlation, we find that peak correlation in the convective flows descends at a rate of 10-40 m s −1 (or equivalently 1-3 Mm per day). Furthermore, the correlation extends throughout all depths of the near-surface shear layer. This pattern-propagation rate is well matched by estimates of the speed of downflows obtained through the anelastic approximation. Direct integration of the measured speed indicates that the supergranulation pattern that first appears at the surface eventually reaches the bottom of the near-surface shear layer a month later. Thus, the downflows have a Rossby radius of deformation equal to the depth of the shear layer and we suggest that this equality may not be coincidental.

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“…Os grânulos são gerados pelo topo das células de convecção de gás quente proveniente do interior do Sol. Os Super Grânulos são um padrão de fluxo celular muito maior comparado com os grânulos com ∼30 Mm e tempo de vida de ∼1 dia (Figura 4) [31,32].…”

Section: O Solunclassified

A irradiância solar: conceitos básicos

Gómez‬

Carlesso

Vieira

et al. 2018

Rev. Bras. Ensino Fís.

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A radiação solar ou irradiância constitui um importante fator que influencia os processos químicos, físicos e biológicos na Terra. Essa radiação emitida por diferentes camadas da atmosfera solar afeta a atmosfera superior e também o clima da Terra. Neste artigo serão descritos os conceitos físicos sobre a irradiância total e irradiância espectral. Essas medidas são fundamentais para a modelagem do clima da Terra. Também alguns modelos utilizados são descritos. A relação entre a irradiância solar e o clima da Terra será discutido. Palavras-chave: Sol, Irradiância, Radiação eletromagnética, Fenômenos solares, Clima da Terra.The solar radiation or irradiance influences chemical, physical and biological processes on the Earth. This radiation emitted from the solar atmosphere through different layers can affect the Earth's upper atmosphere and climate. An overview about the Sun were presented. The physical description of Total Solar Irradiance (TSI) and Solar Spectral Irradiance (SSI) are explained. Some models of irradiance are briefly described. The relationship between the solar irradiance and the Earth's climate were discussed. Keywords: Sun, Irradiance, Electromagnetic radiation, Solar features, Earth's climate. IntroduçãoA energia solar esta diretamente relacionada com os processos químicos, físicos e biológicos, ou seja, esta associada com a vida na Terra. As variações dessa energia têm impacto na atmosfera e no clima da Terra em largas escalas de tempo [1]. Além disso, a química da atmosfera superior, da ionosfera e da estratosfera também são influenciadas [2,3].A radiação solar é o fluxo de energia emitida pelo Sol e transmitida sob a forma de radiação eletromagnética. Durante muitos anos foi considerada uma constante em torno de 1. A obtenção de valores da irradiância solar com alta precisão são importantes nos modelos climáticos e atmosféricos [5]. Apesar da radiação solar ser a principal fonte de energia da Terra o clima também é influenciado pelo efeito estufa, emissões de vulcões [6,7], raios cósmi-* Endereço de correspondência: jemfisi@gmail.com.cos [8] e energia radiante da supernova [9]. Além disso, mudanças de longo prazo na órbita da Terra modulam a irradiância solar que atinge o topo da atmosfera. As variações nas inclinações orbitais também podem causar pequenas diferenças na TSI [10].O principal motivo para abordar o estudo da irradiân-cia solar é conhecer qual é a verdadeira influência dela, nas variações do clima da Terra já que elas afetam nossa vida diária. Assim, como determinar qual é a influência dos processos humanos (efeito estufa e emissões de CO 2 , por exemplo) no clima e sua variabilidade. Esse trabalho fornece uma visão geral desde os conceitos básicos da radiação solar, a estrutura do Sol, a geração de campo magnético do Sol, a descrição física da irradiância solar, modelos de reconstrução da irradiância e a relação da irradiância solar e o clima da Terra. Conceitos básicos da radiação solarA radiação eletromagnética está relacionada com cargas elétricas aceleradas que irradiam en...

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Motions in the Sun at the Photospheric Level: VI. Large-Scale Motions in the Equatorial Region

Cited by 70 publications

References 0 publications

The Sun’s Supergranulation

The Sun’s Supergranulation

Helioseismic Imaging of Supergranulation Throughout the Sun’s Near-Surface Shear Layer

A irradiância solar: conceitos básicos

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