Photospheric convection in strong magnetic fields

Weiss, N. O.; Brownjohn, D. P.; Matthews, P. C.; Proctor, M. R. E.

doi:10.1093/mnras/283.4.1153

Cited by 71 publications

(74 citation statements)

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“…Weiss et al 1990Weiss et al , 1996) the temperature was held xed at both the surface and base. In substituting the radiative boundary condition (7) at the surface, it is importanttodiscover how those results are changed.…”

Section: Thermal Boundary Conditionmentioning

confidence: 99%

“…The combined e ects of strati cation and compressibilitywere rst studied in a 2D model which showed that convection in a slot should indeed exhibit spatially modulated oscillations (Weiss et al 1990). Subsequently, three-dimensional (3D) computations revealed the changes that occur in both the scale and the pattern of convection as the overall eld strength is varied (Weiss et al 1996). Atany stage such calculations are limited by the computing power that is available in practice this means that turbulent motion cannot be faithfully represented, and that the normalized width of the computational box (its aspect ratio) is limited.…”

Section: Introductionmentioning

confidence: 99%

“…Atany stage such calculations are limited by the computing power that is available in practice this means that turbulent motion cannot be faithfully represented, and that the normalized width of the computational box (its aspect ratio) is limited. Experience shows that the pattern of convection may be drastically altered if the aspect ratio is too small (Weiss et al 1996).…”

Section: Introductionmentioning

confidence: 99%

“…2 THE MODEL PROBLEM Our basic con guration has already been used for both 2D (Hurlburt & Toomre 1988Weiss et al 1990) and 3D (Weiss et al 1996) investigations. Once again, weintroduce cartesian co-ordinates with the z-axis pointing downwards and two-dimensional elds suchthatthevelocity u and the magnetic eld B lie in the xz-plane and are independentofy.…”

Section: Introductionmentioning

confidence: 99%

“…Throughout this paper we shall takê R = 100 000 (cf. Weiss et al 1996). The strength of the imposed magnetic eld can be measured either by the ratio (z) of the gas pressure to the magnetic pressure in the static reference atmosphere or by the Chandrasekhar number…”

Section: Introductionmentioning

confidence: 99%

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Modelling photospheric magnetoconvection

Blanchflower

Rucklidge

Weiss

1998

Monthly Notices RAS

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The increasing power of computers makes it possible to model the nonlinear interaction between magnetic elds and convection at the surfaces of solar-type stars in ever greater detail. We present the results of idealized numerical experiments on twodimensional magnetoconvection in a fully compressible perfect gas. We rstvary the aspect ratio of the computational box and show that the system runs through a sequence of convective patterns, and that it is only for a su ciently wide box( 6) that the ow becomes insensitive to further increases in . Next, setting =6,we decrease the eld strength from a value strong enough to halt convection and nd transitions to small-scale steady convection, next to spatially modulated oscillations ( rst periodic, then chaotic) and then to a new regime of ux separation, with regions of strong eld (where convection is almost completely suppressed) separated by broad convective plumes. We also explore the e ects of altering the boundary conditions and show that this sequence of transitions is robust. Finally, we relate these model calculations to recent high-resolution observations of solar magnetoconvection, in plage regions as wellasinlight bridges and the umbrae of sunspots.

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Section: Thermal Boundary Conditionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Modelling photospheric magnetoconvection

Blanchflower

Rucklidge

Weiss

1998

Monthly Notices RAS

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Solar activity II: Sunspots and pores

Sobotka

2003

Astron Nachr

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Abstract. Sunspots and pores appear as a consequence of interactions between strong magnetic fields and moving plasma. A wide variety of small-scale features, presumably of convective origin, are observed in photospheric layers of sunspots and pores: Umbral dots, light bridges, penumbral filaments, and penumbral grains. Each type of features has specific morphological, photometric, spectral, and kinematic characteristics. Spots and pores modify velocity fields in adjacent photosphere and sub-photospheric layers. Recent high-resolution spectral, broad-band, and helioseismic observations of the structure, dynamics, and magnetic fields of sunspots and pores, together with theoretical interpretations, are discussed in this review.

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Coupling from the Photosphere to the Chromosphere and the Corona

Wedemeyer¹,

Lagg²,

Nordlund³

2008

Space Sciences Series of ISSI

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The atmosphere of the Sun is characterized by a complex interplay of competing physical processes: convection, radiation, conduction, and magnetic fields. The most obvious imprint of the solar convection and its overshooting in the low atmosphere is the granulation pattern. Beside this dominating scale there is a more or less smooth distribution of spatial scales, both towards smaller and larger scales, making the Sun essentially a multi-scale object. Convection and overshooting give the photosphere its face but also act as drivers for the layers above, namely the chromosphere and corona. The magnetic field configuration effectively couples the atmospheric layers on a multitude of spatial scales, for instance in the form of loops that are anchored in the convection zone and continue through the atmosphere up into the chromosphere and corona. The magnetic field is also an important structuring agent for the small, granulation-size scales, although (hydrodynamic) shock waves also play an important role -especially in the internetwork atmosphere where mostly weak fields prevail. Based on recent results from observations and numerical simulations, we attempt to present a comprehensive picture of the atmosphere of the quiet Sun as a highly intermittent and dynamic system.Observations of the solar atmosphere reveal a wealth of different phenomena, which occur over an extended range of different temporal and spatial scales. This is not surprising, considering the fact that already basic parameters such as gas density and temperature span many orders of magnitude, from the convection zone below the photosphere to the corona. At a first look, it may thus appear rather hopeless to construct an overall picture that can s c = c c = c A c = c network sp ic u le I B A Fig. 16Schematic, simplified structure of the lower quiet Sun atmosphere (dimensions not to scale): The solid lines represent magnetic field lines that form the magnetic network in the lower layers and a large-scale ("canopy") field above the internetwork regions, which "separates" the atmosphere in a canopy domain and a sub-canopy domain.The network is found in the lanes of the supergranulation, which is due to large-scale convective flows (large arrows at the bottom). Field lines with footpoints in the internetwork are plotted as thin dashed lines. The flows on smaller spatial scales (small arrows) produce the granulation at the bottom of the photosphere (z = 0 km) and, in connection with convective overshooting, the weak-field "small-scale canopies". Another result is the formation of the reversed granulation pattern in the middle photosphere (red areas). The mostly weak field in the internetwork can emerge as small magnetic loops, even within a granule (point B). It furthermore partially connects to the magnetic field of the upper layers in a complex manner. Upward propagating and interacting shock waves (arches), which are excited in the layers below the classical temperature minimum, build up the "fluctosphere" in the internetwork sub-canopy domain. The red...

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Photospheric convection in strong magnetic fields

Cited by 71 publications

References 0 publications

Modelling photospheric magnetoconvection

Modelling photospheric magnetoconvection

Solar activity II: Sunspots and pores

Coupling from the Photosphere to the Chromosphere and the Corona

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