Topic
Solar constant
About: Solar constant is a research topic. Over the lifetime, 967 publications have been published within this topic receiving 29647 citations.
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TL;DR: Stellar observations from the Lowell and Mount Wilson observatories show that older stars similar to the sun tend to become brighter as their magnetic activity level increases, just as the sun does during its 11-year activity cycle.
Abstract: Radiometric measurements during the past decade from the Solar Maximum Mission and Nimbus 7 satellites have shown that the total solar irradiance varies in step with the sun's 11-year magnetic activity cycle. Stellar observations from the Lowell and Mount Wilson observatories now confirm and elaborate this discovery. These measurements show that older stars similar to the sun tend to become brighter as their magnetic activity level increases, just as the sun does during its 11-year activity cycle. Younger stars, however, tend to become fainter as their magnetic activity level increases. This contrasting behavior suggests that the balance between the competing phenomena that influence solar brightness variability has shifted during the sun's lifetime.
78 citations
TL;DR: In this article, the problem of attempting to measure the solar spectral irradiance with hereto-fore unachieved levels of accuracy and precision via spectroradiometer measurements made at high-altitude ground stations is addressed.
Abstract: Ground-based solar radiometer measurements have long been used to investigate various properties of both the Earth's atmosphere and the sun. This paper addresses the problem of attempting to measure the solar spectral irradiance with heretofore unachieved levels of accuracy and precision (~0.5 and ~0.1 percent, respectively) via spectroradiometer measurements made at high-altitude ground stations. Instrumentation and calibration approaches are discussed, but attention is primarily directed toward assessing limitations imposed by the atmosphere. Assessments of factors such as diffuse light contributions, uncertainty in airmass determination, variability in atmospheric optical depth, spectroradiometer bandwidth, and data analysis methods are included in the paper.
77 citations
TL;DR: In this paper, the record of determinations of the total and spectral solar irradiance of the last 15 years is analyzed, and it is concluded that the solar constant has not changed during the last fifteen years.
Abstract: In order to assess the variability of the solar radiation, the record of determinations of the total and spectral solar irradiance of the last 15 years is analysed. Although the datapoints for the period before 1969 suggest a slight decrease, the uncertainties of these determinations are too large to render this statement significant. Together with the results of the following period (1969–1980) which show that within the uncertainty no change is detectable, it can be concluded, that the solar constant has not changed during the last 15 years. The same result is found from the spectral distribution record, though not as conclusive as for the solar constant, due to the much larger uncertainties of the spectral data.
76 citations
TL;DR: In this paper, correlations of the solar radiation for the Athens area are provided, based on hourly measurements over the period 1955-1980, and correlations are of two kinds: the first, which provides the average total radiation incident on a horizontal surface in terms of hour, day, and month of the typical year, is suitable for solar energy collection applications, and the second kind provides the maximum radiation and are suitable for use in the design of airconditioning installations or other applications requiring knowledge of maximum values.
75 citations
TL;DR: For more than 90 years, solar extreme ultraviolet (EUV) irradiance modeling has progressed from empirical blackbody radiation formulations, through fudge factors, to typically measured irradiances and reference spectra was well as time-dependent empirical models representing continua and line emissions.
Abstract: For more than 90 years, solar extreme ultraviolet (EUV) irradiance modeling has progressed from empirical blackbody radiation formulations, through fudge factors, to typically measured irradiances and reference spectra was well as time-dependent empirical models representing continua and line emissions. A summary of recent EUV measurements by five rockets and three satellites during the 1980s is presented along with the major modeling efforts. The most significant reference spectra are reviewed and threee independently derived empirical models are described. These include Hinteregger's 1981 SERF1, Nusinov's 1984 two-component, and Tobiska's 1990/1991/SERF2/EUV91 flux models. They each provide daily full-disk broad spectrum flux values from 2 to 105 nm at 1 AU. All the models depend to one degree or another on the long time series of the Atmosphere Explorer E (AE-E) EUV database. Each model uses ground- and/or space-based proxies to create emissions from solar atmospheric regions. Future challenges in EUV modeling are summarized including the basic requirements of models, the task of incorporating new observations and theory into the models, the task of comparing models with solar-terrestrial data sets, and long-term goals and modeling objectives. By the late 1990s, empirical models will potentially be improved through the use of proposed solar EUV irradiance measurements and images at selected wavelengths that will greatly enhance modeling and predictive capabilities.
74 citations