On the Energy Balance of Solar Active Regions

Steinegger, M.; Vázquez, M.; Bonet, J. A.; Brandt, Peter

doi:10.1086/177075

Cited by 52 publications

(21 citation statements)

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“…But still, the classical photometric starspot models are not applicable to the solar light curves for two reasons: 1) The brightening effect of faculae has not yet been included in the starspot models. However, the effect of faculae is known to be comparable and sometimes even larger than the darkening effect of sunspots (Chapman 1984;Chapman et al 1982Chapman et al , 1992Lawrence 1987;Foukal & Lean 1988;Steinegger et al 1996). 2) There is morphological evolution of sunspots.…”

Section: Sunspots and Starspotsmentioning

confidence: 99%

“…Thus, instead of the classical PSI, a new improved APSI (Area dependent Photometric Sunspot Index) was suggested by them. Steinegger et al (1996) used intensity histograms derived from a photometry of spots, so that not only accurately determined umbra/penumbra areas, but also variations of the spot contrast within the spot enter into the computation of the PSI. Using the empirical coefficients that partly reflect intensity variations among Ca plages by Vršnak et al (1991), Steinegger et al (1996) partly improved the PFI function too.…”

Section: Introductionmentioning

confidence: 99%

“…For the Sun, the effect of faculae is known to be comparable and sometimes even larger than the darkening effect of sunspots (Chapman 1984;Chapman et al 1982Chapman et al , 1992Lawrence 1987;Foukal & Lean 1988;Steinegger et al 1996). Faculae have zero or negligible contrast at or near the disk center.…”

Section: Introductionmentioning

confidence: 99%

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Deriving effective sunspot temperatures from SOHO/VIRGO irradiance measurements

Eker

Brandt²,

Hanslmeier

et al. 2003

A&A

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Abstract.A method is developed to obtain mean effective sunspot temperatures from satellite irradiance deficits. Using a formalism derived from a star spot modelling approach, this method only requires accurate positions and areas of sunspots -but not intensities. The method is applied to SOHO/VIRGO spectral solar irradiance (SSI) at 402, 500, and 862 nm as well as total solar irradiance (TSI) measured during the period 16 July to 17 August 1996, the disk passage of active region NOAA 7981. MDI full disk white-light images are used to extract sunspot positions and areas. First, using the spot pixels, which are identified on MDI images as I s < 0.92, we find the mean effective temperature of NOAA 7981 to be 300 K less than the local photospheric temperature. Because the area is dominated by penumbral pixels, the temperature is close to a value representing the penumbra. Second, separating umbral and penumbral pixels, we obtain a temperature difference of 850 K for the umbra and of 200 K for the penumbra. Finally, if a 5% binning of the spot intensities is applied, a temperature deficit of 1000 K is found for the darkest regions of the spot.

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Section: Sunspots and Starspotsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Deriving effective sunspot temperatures from SOHO/VIRGO irradiance measurements

Eker

Brandt²,

Hanslmeier

et al. 2003

A&A

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show abstract

“…During this process of decay the boundary of the spot remains well defined and its temperature deficit does not change too much (nor does its magnetic field strength vary by more than about 20%, cf. Collados et al, 1994;Steinegger et al, 1996). The extremely large individual variations among spots however did not make it possible to find quantitative regularities in the decay until the availability of sufficiently large and precise observational databases (GPR, Pulkovo, Mt.…”

Section: Introductionmentioning

confidence: 99%

Untitled

1997

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Abstract. In a statistical study of the decay of individual sunspots based on DPR data we find that the mean instantaneous area decay rate is related to the spot radius r and the maximal radius r0 as D = CD r/r0, CD = 32.0±0.26 MSH/day. This implies that sunspots on the mean follow a parabolic decay law; the traditional linear decay law is excluded by the data. The validity of the Gnevyshev-Waldmeier relationship between the maximal area A0 and lifetime T of a spot group, A0/T ≃ 10 MSH/day, is also demonstrated for individual sunspots. No evidence is found for a supposed supergranular "quantization" of sunspot areas. Our results strongly support the recent turbulent erosion model of sunspot decay while all other models are excluded.

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“…The ratio of the sunspot and facular areas is linked with the age of the active regions (young or old sunspot groups) (Pap 1985). The energy balance of individual active regions seems to depend mainly on the area ratio of the plage and the corresponding sunspot group (Steinegger et al 1996). During the solar minimum, when only a few active regions exist on the Sun, the main contribution to the irradiance variations arises from the active network, which is formed by Send offprint requests to: E. Bratsolis (ebrats@atlas.uoa.gr) the breakup and dispersion of the active regions (Fröhlich & Pap 1989).…”

Section: Introductionmentioning

confidence: 99%

Solar image segmentation by use of mean field fast annealing

Bratsolis

Sigelle

1998

Astron. Astrophys. Suppl. Ser.

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Abstract. We present a "continuous" analysis of a solar H α image in order to address the problem of image segmentation. Our approach is based on combinatorial optimization methods and in particular on Mean Field Fast Annealing (MFFA). Mean-field theory gives a deterministic nature to our algorithm while its efficiency is improved by a fast cooling schedule. We show how this method can be used to separate efficiently the regions of different solar activity giving a tool for a future automated recognition and classification of sunspots.

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On the Energy Balance of Solar Active Regions

Cited by 52 publications

References 0 publications

Deriving effective sunspot temperatures from SOHO/VIRGO irradiance measurements

Deriving effective sunspot temperatures from SOHO/VIRGO irradiance measurements

Untitled

Solar image segmentation by use of mean field fast annealing

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