Sunspot photometry and the total solar irradiance deficit measured in 1980 by ACRIM

Steinegger, M.; Brandt, Peter; Pap, J. M.; Schmidt, W.

doi:10.1007/bf00652658

Cited by 50 publications

(32 citation statements)

References 2 publications

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“…The umbral field strength perhaps also depends on the fraction of penumbral flux. Steinegger et al (1990) found that the ratio of the umbra to penumbra area is positively correlated with the spot size. The linearity of the relation of sunspot radius vs. flux (Fig.…”

Section: Magnetic Fluxmentioning

confidence: 94%

Properties of sunspot umbrae observed in cycle 24

Kiess

Rezaei

Schmidt

2014

A&A

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Aims. There is an ongoing debate whether the solar activity cycle is overlaid with a long-term decline that may lead to another grand minimum in the near future. We used the size, intensity, and magnetic field strength of sunspot umbrae to compare the present cycle 24 with the previous one. Methods. We used data of the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory and selected all sunspots between May 2010 and October 2012, using one image per day. We created two subsets of this dataset with a manual tracking algorithm, both without duplication. One contains each sunspot (910 umbrae within 488 spots) and was used to analyze the distribution of umbral areas, selected with an automated thresholding method. The other subset contains 205 fully evolved sunspots. We estimated their magnetic field and the total magnetic flux and discuss the relations between umbral size, minimum continuum intensity, maximum field strength, and total magnetic flux. Results. We find non-linear relations between umbral minimum intensity and size and between maximum magnetic field strength and size. The field strength scales linearly with the intensity and the umbral size scales roughly linearly with the total magnetic flux, while the size and field strength level off with stronger flux. When separated into hemispheres and averaged temporally, the southern umbrae show a temporal increase in size and the northern umbrae remain constant. We detected no temporal variation in the umbral mean intensity. The probability density function of the umbral area in the ascending phase of the current solar cycle is similar to that of the last solar cycle. Conclusions. From our investigation of umbral area, magnetic field, magnetic flux, and umbral intensity of the sunspots of the rising phase of cycle 24, we do not find a significant difference to the previous cycle, and hence no indication for a long-term decline of solar activity.

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Section: Magnetic Fluxmentioning

confidence: 94%

Properties of sunspot umbrae observed in cycle 24

Kiess

Rezaei

Schmidt

2014

A&A

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“…Later, various studies showed that the contrast of sunspots varies as a function of their area (e.g. Steinegger et al, 1990). In this study we have used contrast-area relationship between average sunspot contrast C a and the total sunspot area A s as defined by Wesolowski et al (2008), where C a = 0.049 * logA s + 0.017.…”

Section: Data Descriptionmentioning

confidence: 99%

Active region properties and irradiance variations

Baranyi

Pap

2012

Advances in Space Research

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Total solar irradiance (TSI) has been measured for more than three decades. These observations demonstrate that total irradiance changes on time scales ranging from minutes to years and decades. Considerable efforts have been made to understand the physical origin of irradiance variations and to model the observed changes using measures of sunspots and faculae. In this paper, we study the short-term variations in TSI during the declining portion and minimum of solar cycle 22 and the rising portion of cycle 23 (1993 -1998). This time interval of low solar activity allows us to study the effect of individual sunspot groups on TSI in detail. In this paper, we indicate that the effect of sunspot groups on total irradiance may depend on their type in the Zürich classification system and/or their evolution, and on their magnetic configuration. Some uncertainties in the data and other effects are also discussed.

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“…Lean & Foukal (1990) found a linear regression between their sunspot blocking, P", (identical to 2.1) and the Hoyt-Eddy relation with a correlation coefficient of 0.997 but where the P 3 values were systematically higher by about 20%. Also, the contrast of individual sunspots can be quite variable Steinegger et al 1990;Beck & Chapman 1993). It has been known for some time that individual sunspots vary and that umbrae can have darker or brighter parts.…”

Section: The Effect Of Sunspots On Solar Irradiancementioning

confidence: 99%

“…Several recent studies have shown that the average contrast of sunspots is not constant Steinegger et al 1990;Beck & Chapman 1993; (Lawrence &: Chapman 1988), the asterisks are from ELP observations (Chapman & Ziegler 1993), the open squares are from observations at the NSO (Foukal et al 1993), and the filled pyramids are based on S-series diode array observations (Lawrence & Chapman 1988). 1994b).…”

Section: Sunspotsmentioning

confidence: 99%

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Photometric Observations of the Sun

Chapman

1994

International Astronomical Union Colloquium

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Ground-based calorimetry and photometry of the Sun have been carried out for many years. Following the early years, ground-based photometry has largely replaced ground-based calorimetry, in part due to the advent of airborne and spaceborne detector systems for the broad-band measurement of the solar irradiance and the realization of the difficulty of correcting calorimetry measurements for the effects of the terrestrial atmosphere. Even from spacecraft, recent measurements of the total solar irradiance range from about 1367 to 1374 W/m 2 . Most of this difference can be ascribed to differences in instrumental scales, while a variation of about 1 to 2 W / m 2 appears to be due to solar variability. The quiet Sun may also change, globally, over longer time scales. Using disparate data to understand solar variability will require cooperation between a number of current groups, supported by various governments, covering several zones of longitude. I n t r o d u c t i o nStudying the Sun's output of energy (luminosity) has been a long-standing endeavor. Within the past decade or so, satellites have measured the solar output and have very clearly revealed variability. However, while the satellite measurements have agreed on the actual solar luminosity, agreeing for the most part on the short-and long-term temporal changes. Ground-based measurements, on the other hand, are hampered by the uncertainties in the opacity of the terrestrial atmosphere and its variations and cannot accurately determine the solar luminosity but might be able to measure relative changes in it. This review will attempt to place ground-based efforts into context with space-based experiments. An interesting, broad review of ground-based photometric measurements is that of LaBonte (1988). A general review of solar luminosity variability can be found in (Hudson 1988), Frohlich et al. (1991) and Frohlich (1992). We will not review nonimaged programs here. For a good review of these see White (1988) and Livingston (1992).One of the reasons for carrying out ground-based programs of relative photometry is to help understand the cause of the solar variations seen by satellites. Most of the satellite data have been obtained without any spatial resolution on the solar disk. By having photometric images obtained at selected wavelengths, the satellite measurements can be modeled using selected contrast features seen in ground-based images. We assume t h a t there is a non-changing quiet Sun output and that photometrically detectable features add to or subtract from this quiet Sun output. For relative ground-based photometry, the (assumed) quiet Sun is our photometric standard. If this assumption is not true, we can only find out by doing our very best in removing the effects of features on the solar output.It has been shown that most of the variations can be attributed to magnetic features Chapman et al. 1992). By modeling their effects on the solar output, we hope to gain a better understanding of the flow of energy in and around a solar active region and...

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Sunspot photometry and the total solar irradiance deficit measured in 1980 by ACRIM

Cited by 50 publications

References 2 publications

Properties of sunspot umbrae observed in cycle 24

Properties of sunspot umbrae observed in cycle 24

Active region properties and irradiance variations

Photometric Observations of the Sun

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