The Evershed effect in sunspots as a siphon flow along a magnetic flux tube

Montesinos, B.; Thomas, John H.

doi:10.1038/37307

Cited by 109 publications

(117 citation statements)

References 21 publications

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“…Two models have been proposed to explain a number of observational properties: the "siphon-flow" model as proposed by Montesinos and Thomas (1997), and the "movingtube" model by Schlichenmaier, Jahn, and Schmidt (1998). Montesinos and Thomas (1997) elaborated on the idea of Meyer and Schmidt (1968) that the flow is driven by a gas-pressure difference between the footpoints of a thin magnetic-flux tube in magnetohydrostatic (MHS) equilibrium.…”

Section: Evershed Flowmentioning

confidence: 99%

“…Montesinos and Thomas (1997) elaborated on the idea of Meyer and Schmidt (1968) that the flow is driven by a gas-pressure difference between the footpoints of a thin magnetic-flux tube in magnetohydrostatic (MHS) equilibrium. On the other hand, Schlichenmaier, Jahn, and Schmidt (1998) developed a dynamical 2D model of a thin magnetic-flux tube that acts as a convective element in a superadiabatic and magnetized penumbral atmosphere.…”

Section: Evershed Flowmentioning

confidence: 99%

“…• Moon, Yun, and Park (1998): Included a description of the energy balance and the observed horizontal variation of the Wilson depression when determining the shape function from the observed radial dependence of the magnetic field.…”

Section: Self-similar Fieldsmentioning

confidence: 99%

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Modeling the Subsurface Structure of Sunspots

et al. 2010

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While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do not yet allow helioseismology to probe the internal structure with sufficient confidence to distinguish between the monolith and cluster models, the development of physically realistic sunspot models are a priority for helioseismologists. This is because they are not only important indicators of the variety of physical effects that may influence helioseismic inferences in active regions, but they also enable detailed assessments of the validity of helioseismic interpretations through numerical forward modeling. In this article, we provide a critical review of the existing sunspot models and an overview of numerical methods employed to model wave propagation through model sunspots. We then carry out a helioseismic analysis of the sunspot in Active Region 9787 and address the serious inconsistencies uncovered by Gizon et al. (2009aGizon et al. ( , 2009b. We find that this sunspot is most probably associated with a shallow, positive wave-speed perturbation (unlike the traditional two-layer model) and that travel-time measurements are consistent with a horizontal outflow in the surrounding moat.

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Section: Evershed Flowmentioning

confidence: 99%

Section: Evershed Flowmentioning

confidence: 99%

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Modeling the Subsurface Structure of Sunspots

et al. 2010

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“…With recent advances in techniques of sunspot observations, a coherent picture of magnetic fields and velocity fields in sunspots is drawn step by step (Plaza et al, 1997;Montesinos and Thomas, 1997;Schlichenmaier et al, 1998, Lites et al, 1998.…”

Section: Medium-scale Solar Activitymentioning

confidence: 99%

Commission 10: Solar Activity: (Activite Solaire)

Ai¹,

Benz²,

Dere³

et al. 2000

Trans. Int. Astron. Union

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The Sun’s activity has been evolving in the ascending phase of Solar Cycle 23 since 1996. Similarly, the research on solar activity is also in the ascending phase of a new active period. Numerous new results have been obtained from a large amount of space and ground observations covering a wide spectral range. In particular, observations with YOHKOH, SOHO, and TRACE have revealed a multitude of phenomena and processes in the solar atmosphere which provide us a new picture of the Sun.

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“…Numerical investigations, which began during the late 1980s, led to the modeling of these flows over the next decade (e.g., Thomas 1988;Degenhardt 1989;Montesinos & Thomas 1989;Thomas & Montesinos 1990, 1991Degenhardt & Kneer 1992;Degenhardt et al 1993;Montesinos & Thomas 1997). The standard picture for siphon flows in an isolated magnetic flux tube, using the thin-flux tube approximation, depends on the critical speed in the tube, v C , given by…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Observations of Siphon Flows in a Solar Magnetic Pore

Guglielmino

Zuccarello

2011

ApJ

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We investigate signatures of siphon flows in a region around a solar magnetic pore, observed in the photosphere at μ = 0.6, during its decay phase. We analyze high-resolution Stokes spectra acquired by Hinode/Solar Optical Telescope along the Fe i pair at 630.2 nm. We determine the vector magnetic field and the line-of-sight velocity by an inversion of the full Stokes vector using the SIR code. We also analyze photospheric G-band filtergrams. We find evidence of a transient siphon (counter)flow at the edge of the pore. An arch-shaped structure is found to have upflow motions of 4 km s −1 in the footpoint with a stronger magnetic field and positive polarity, and downflows of the same order of magnitude in the footpoint with opposite polarity and a weaker magnetic field. The event is different from those reported in previous observations of the Sun's atmosphere and may represent a physical constraint for numerical models.

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The Evershed effect in sunspots as a siphon flow along a magnetic flux tube

Cited by 109 publications

References 21 publications

Modeling the Subsurface Structure of Sunspots

Modeling the Subsurface Structure of Sunspots

Commission 10: Solar Activity: (Activite Solaire)

High-Resolution Observations of Siphon Flows in a Solar Magnetic Pore

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