The Surface Temperature of the Sun and Changes in the Solar Constant

Kuhn, J. R.; Libbrecht, K. G.; Dicke, R. H.

doi:10.1126/science.242.4880.908

Cited by 160 publications

(80 citation statements)

References 16 publications

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“…In the synoptic map mentioned above, there is no trace of magnetic activity visible in the active belts in 2009; moreover, our results show that the granulation is not perturbed in these latitudes. Consequently, if at this phase of minimum of activity some strong magnetic field is embedded deep in the convection zone, the structure of the atmosphere close to the surface is not perturbed, which is in disagreement with the predictions of several theoretical works (Parker 1987(Parker , 1995Kuhn 1988Kuhn , 1993Kuhn et al 1988;Goode & Kuhn 1990). Therefore, the magnetic field (neither the quiet Sun magnetic field nor the strong magnetic field in active regions) is probably not the cause of the latitude variation of the solar granulation in the period of minimum of activity reported in this paper.…”

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Latitude dependence of the solar granulation during the minimum of activity in 2009

Müller

Hanslmeier

Utz

2017

A&A

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Context. Knowledge of the latitude variation of the solar granulation properties (contrast and scale) is useful to better understand interactions between magnetic field, convection, differential rotation, and meridional circulation in the solar atmosphere. Aims. We investigated the latitude dependence of the contrast and scale of the solar granulation, with the help of HINODE/SOT blue continuum images taken in the frame of the HOP 79 program, along the central meridian and along the equator on a monthly basis in 2009 during the last solar minimum of activity. Methods. We selected the sharpest images in latitude and longitude intervals. The selected images in all the N-S and E-W scans taken in 2009 were combined to get statistically reliable results. Results. The contrast of the solar granulation decreases towards the poles and the scale increases, but not regularly since a perturbation occurs at around 60 • where both quantities return close to their values at the disk center. Conclusions. Such a latitude variation in a period of minimum of activity (2009), is probably not due to magnetic field, neither the quiet magnetic field at the surface, nor the strong magnetic flux tubes associated with active regions, which could be embedded more or less deeply in the convection zone before they reach the surface. The decrease in contrast and increase in scale towards the pole seem to be related to the differential rotation and the perturbation around 60 • to the meridional circulation.

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“…Previously, Kuhn et al (1988) also suggested that a latitudinal temperature distribution characterized by large-scale quadrupolar variations could be related to the solar differential rotation. Then the question arises about the cause of the perturbation which occurs around 60 • .…”

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confidence: 96%

Latitude dependence of the solar granulation during the minimum of activity in 2009

Müller

Hanslmeier

Utz

2017

A&A

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“…Summary of total solar irradiance measurements total irradiance, which is not explained by the effect of sunspots, faculae, and the magnetic network, is a difficult problem since global effects may also produce variations in total irradiance. It has been shown that changes in the differential rotation in the interior of the Sun, the solar dynamo magnetic field near the base of the convective zone (Kuhn 1996, photospheric temperature changes (Kuhn et al 1988), large scale missing flows or large scale convective cells (Ribes et al 1985;Fox & Sofia 1994) and/or radius changes (Delache et al 1985;Ulrich & Bertello 1995;Kuhn et al 1985Kuhn et al , 1988Godier & Rozelot 2000) may also contribute to irradiance variations. Therefore, simultaneous studies of total irradiance and solar global parameters are essential to better understand the underlying physical mechanism of irradiance changes and to predict solar-induced climate changes.…”

Section: Description Of the Total Irradiance Measurementsmentioning

confidence: 99%

On the relation between total irradiance and radius variations

Pap

Rozelot²,

Godier³

et al. 2001

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Abstract. We use Singular Spectrum Analysis (SSA) to analyze total solar irradiance variations and CERGA radius measurements. Total solar irradiance has been monitored from space for more than two decades, whilst ground-based radius measurements are available as a coherent time series from 1975. We compare these indicators to try to understand the origin of energy production inside the Sun. One of the main objectives was to assess the reality of the observed variations of the Sun's radius by distinguishing the signal from the noise. Two approaches were used: one using SSA on ground-based data averaged over 90 days, in order to smooth the signal (especially over periods when no data were obtained, mainly in winter time); the second repeats the analysis on individual measurements corrected by reporting data to the zenith. As expected, the level of noise is higher in the first case and the reconstructed noise level, which is large, indicates the difficulty in ascertaining the solar origin in the apparent variability of the solar radius. It is shown from the reconstructed components that the main variation in amplitude (over 930 days) is pronounced during the first part of the measurements and seems to disappear after 1988. There is also a variation with a periodicity of 1380 days, of lower amplitude than that of the shorter component. In both cases, these variations disappear during the rising portion of cycle 23. The first reconstructed component shows that total irradiance varies in parallel with the solar cycle, being higher during maximum activity conditions. The reconstructed radius trend indicates that the solar radius was higher during the minimum of solar cycle 21, but its decrease with the rising activity of cycle 23 is less obvious. The observed value of the solar radius increased by about 0.11 arcsec from the maximum of cycle 21 to the minimum between cycles 21 and 22. Most importantly, we report a long-term radius variation which increased from the maximum of cycle 21 to minimum by about 0.015%, while a smaller decrease (around 0.01%) is seen from the minimum of cycle 21 to the maximum of cycle 22. This study indicates need for measurements of the degree of the radius changes taken from space, together with total irradiance measurements to establish the phase relation between these two quantities.

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“…Kroll et al (1990) and Kroll & Hill (1991) used the Santa Catalina Laboratory for Experimental Relativity by Astrometry (SCLERA) telescope to fit changes in limb darkening, associated with solar activity, to variations in the solar irradiance. and Kuhn et al (1988) have fit measurements of latitudinal fluctuations in photospheric temperature near the solar limb, obtained from the Princeton Distortion Telescope (PDT), to variations in the ACRIM I total irradiance. Kuhn et al (1988) have been able to obtain fits to total irradiance measurements from satellites with high correlations.…”

Section: Def = '£^-mentioning

confidence: 99%

“…and Kuhn et al (1988) have fit measurements of latitudinal fluctuations in photospheric temperature near the solar limb, obtained from the Princeton Distortion Telescope (PDT), to variations in the ACRIM I total irradiance. Kuhn et al (1988) have been able to obtain fits to total irradiance measurements from satellites with high correlations. Kroll et al (1990), on the other hand, have found evidence for a change in the limb darkening that is not like the solar cycle.…”

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confidence: 99%

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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The Surface Temperature of the Sun and Changes in the Solar Constant

Cited by 160 publications

References 16 publications

Latitude dependence of the solar granulation during the minimum of activity in 2009

Latitude dependence of the solar granulation during the minimum of activity in 2009

On the relation between total irradiance and radius variations

Photometric Observations of the Sun

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