Modelling Umbrae

Severino, G.; Gomez, M. T.; Caccin, B.

doi:10.1007/978-94-011-1188-1_15

Cited by 20 publications

(33 citation statements)

References 9 publications

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“…The temperature minimum in the sunspot umbra models generally lies deeper than in the FAL − C model. Furthermore the temperature in the temperature minimum region drops to below 3000 K in the models of Severino et al (1994) (iii) and of Socas-Navarro (2007) (iv). However, the model of Severino et al (1994) (iii) possesses an extended temperature minimum, i.e.…”

Section: Model Simulationsmentioning

confidence: 95%

“…Furthermore the temperature in the temperature minimum region drops to below 3000 K in the models of Severino et al (1994) (iii) and of Socas-Navarro (2007) (iv). However, the model of Severino et al (1994) (iii) possesses an extended temperature minimum, i.e. the temperature minimum reaches to much greater heights in the atmosphere than do those of the other models.…”

Section: Model Simulationsmentioning

confidence: 95%

“…The models we analyzed are the sunspot model of Avrett (1981), model M of Maltby et al (1986), the sunspot model of Severino et al (1994), models A (dark umbra) and B (bright umbra) of Socas-Navarro (2007), and model S of Fontenla et al (2009). The first two models are classical semiempirical sunspot models covering the umbral photosphere, chromosphere and transition region.…”

Section: Model Simulationsmentioning

confidence: 99%

“…The first two models are classical semiempirical sunspot models covering the umbral photosphere, chromosphere and transition region. The model of Severino et al (1994) the model of Caccin et al (1993) which is in its turn a modified version of one of the Maltby et al (1986) models with a steeper temperature gradient in the photosphere. The model of Socas-Navarro (2007) was derived from non-LTE inversions of high-resolution spectropolarimetric observations of four Ca ii and Fe i lines.…”

Section: Model Simulationsmentioning

confidence: 99%

“…The sunspot umbra appears darker than the quiet Sun at these wavelengths and umbral contrast decreases towards longer wavelengths. It is more interesting, however, to use millimeter wavelength radio data, which can constrain the temperature in the chromosphere and address the controversy regarding the umbral temperature in these layers (see, e.g., Maltby et al 1986;Severino et al 1994;Fontenla et al 2009, and Sect. 3).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

The chromosphere above sunspots at millimeter wavelengths

Loukitcheva

Solanki

White

2014

A&A

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Aims. The aim of this paper is to demonstrate that millimeter wave data can be used to distinguish between various atmospheric models of sunspots, whose temperature structure in the upper photosphere and chromosphere has been the source of some controversy. Methods. We use observations of the temperature contrast (relative to the quiet Sun) above a sunspot umbra at 3.5 mm obtained with the Berkeley-Illinois-Maryland Array (BIMA), complemented by submm observations from Lindsey & Kopp (1995) and 2 cm observations with the Very Large Array. These are compared with the umbral contrast calculated from various atmospheric models of sunspots. Results. Current mm and submm observational data suggest that the brightness observed at these wavelengths is low compared to the most widely used sunspot models. These data impose strong constraints on the temperature and density stratifications of the sunspot umbral atmosphere, in particular on the location and depth of the temperature minimum and the location of the transition region. Conclusions. A successful model that is in agreement with millimeter umbral brightness should have an extended and deep temperature minimum (below 3000 K). Better spatial resolution as well as better wavelength coverage are needed for a more complete determination of the chromospheric temperature stratification above sunspot umbrae.

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Section: Model Simulationsmentioning

confidence: 95%

Section: Model Simulationsmentioning

confidence: 95%

Section: Model Simulationsmentioning

confidence: 99%

Section: Model Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The chromosphere above sunspots at millimeter wavelengths

Loukitcheva

Solanki

White

2014

A&A

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Properties of flux tubes and the relation with solar irradiance variability

Fligge

Solanki

2000

J Astrophys Astron

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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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Modelling Umbrae

Cited by 20 publications

References 9 publications

The chromosphere above sunspots at millimeter wavelengths

The chromosphere above sunspots at millimeter wavelengths

Properties of flux tubes and the relation with solar irradiance variability

Modeling the Subsurface Structure of Sunspots

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