Solar luminosity fluctuations and active region photometry

Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.; Shelton, J. C.

doi:10.1086/184315

Cited by 16 publications

(8 citation statements)

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“…We note that Ap/N is marginally correlated with As/N (p = 5)'0). The (anti) correlation between Ap/A s and AJN and the lack of correlation between Ap/A s and Ap/N were also reported in an earlier study by Lawrence (1986) which used similar data from the years 1971-1982. No correlation with the ll-yr cycle was found, however. This may be related to the fact that the earlier data set was divided between solar cycles 20 and 21, while the present data set is more nearly confined to cycle 21.…”

Section: Resultssupporting

confidence: 79%

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Sunspot cycle variations of ensemble-averaged active regions

Lawrence

1987

Sol Phys

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We examine published sunspot and calcium plage areas for 1620 solar active regions between 1974 and 1985. With these data we study the properties of ensemble-averaged active regions. The average sunspot area per region, the average plage to sunspot area ratio, and the average plage intensity of regions all vary significantly with the sunspot cycle and in correlation with one another. The average plage area per region varies significantly but is uncorrelated with the sunspot cycle and with the other quantities. While the plage and sunspot areas and the plage intensities of individual active regions observed over a two-year period are strongly correlated, the relationship among these quantities appears to change over an 11-yr period. These results suggest the existence of some energetic connection between active region sunspot areas and plage intensities. Further, if energy balance between sunspot luminosity deficits and facular luminosity excesses holds, then standard models relating these quantities to sunspot and plage areas will have to be modified. Overall energy balance can neither be established nor ruled out.

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Section: Resultssupporting

confidence: 79%

“…The work by Chapman et al (1986) and by Chapman and Meyer (1986) indicates that energy balance requires Ap/A s = 11 + 2.…”

Section: Introductionmentioning

confidence: 99%

Sunspot cycle variations of ensemble-averaged active regions

Lawrence

1987

Sol Phys

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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%

“…The photometric facular index (PFI) later was included in irradiance models by Chapman et al (1982), Chapman (1984), and Chapman & Meyer (1986). Those early models use constant contrasts for the spots and the faculae.…”

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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3.1.2.1 Active regions

Durrant¹

Instruments, Methods, Solar System

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Solar luminosity fluctuations and active region photometry

Cited by 16 publications

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Sunspot cycle variations of ensemble-averaged active regions

Sunspot cycle variations of ensemble-averaged active regions

Deriving effective sunspot temperatures from SOHO/VIRGO irradiance measurements

3.1.2.1 Active regions

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