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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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Journal ArticleDOI
TL;DR: In this article, the authors investigated the kinematic effect on the open solar flux estimates of large-scale longitudinal structure in the solar wind flow, with particular emphasis on correcting estimates made using data from near-Earth satellites.
Abstract: [1] We investigate the “flux excess” effect, whereby open solar flux estimates from spacecraft increase with increasing heliocentric distance. We analyze the kinematic effect on these open solar flux estimates of large-scale longitudinal structure in the solar wind flow, with particular emphasis on correcting estimates made using data from near-Earth satellites. We show that scatter, but no net bias, is introduced by the kinematic “bunching effect” on sampling and that this is true for both compression and rarefaction regions. The observed flux excesses, as a function of heliocentric distance, are shown to be consistent with open solar flux estimates from solar magnetograms made using the potential field source surface method and are well explained by the kinematic effect of solar wind speed variations on the frozen-in heliospheric field. Applying this kinematic correction to the Omni-2 interplanetary data set shows that the open solar flux at solar minimum fell from an annual mean of 3.82 × 1016 Wb in 1987 to close to half that value (1.98 × 1016 Wb) in 2007, making the fall in the minimum value over the last two solar cycles considerably faster than the rise inferred from geomagnetic activity observations over four solar cycles in the first half of the 20th century.

64 citations

Journal ArticleDOI
22 Jun 1979-Science
TL;DR: Variations of the solar radius between 1850 and 1937 are limited to about 0.25 arc second; modeling of the sun indicates that the solar constant did not vary by more than 0.3 percent during that time.
Abstract: Climatically significant variation of the solar constant (the energy output of the sun) implies measurable change in the solar radius. The available data limit variations of the solar radius between 1850 and 1937 to about 0.25 arc second; modeling of the sun indicates that the solar constant did not vary by more than 0.3 percent during that time.

63 citations

Journal ArticleDOI
27 Jan 1977-Nature
TL;DR: In this article, an alternative hypothesis which still retains McCrea's association with the passage of the solar system through a spiral arm, but which relates the initiation of an ice epoch, plus biological catastrophes, to an encounter of the Solar System with a nearby supernova outburst rather than a super-dense interstellar cloud is presented.
Abstract: MCCREA1,2 has proposed that the encounter of the Solar System with a dense cloud of interstellar material during its passage through a spiral arm of the Galaxy may produce such climatic catastrophes on Earth as the ice epochs. His thesis, an extension of several earlier investigations3,4,5, is based on the expected effect on the solar constant of an increased accretion rate. Unfortunately, the cloud density necessary to produce the required variation is 105 to 107 cm−3, and although clouds with such extreme densities are thought to exist6, Begelman and Rees7 point out that they are so compact and unusual as to reduce the likelihood of the Sun ever encountering one. (Dennison and Mansfield's suggestion8 that there is no evidence for the existence of a nearby super-dense cloud which could have caused the most recent ice epoch has been answered by McCrea9.) Begelman and Rees7 in fact showed that a much more modest cloud density (≃102 to 103 cm−3) would prevent the solar wind from reaching the Earth, with resulting modification of the near-Earth environment; however, the climate consequences of such a modification are not well understood. We present here an alternative hypothesis which still retains McCrea's association with the passage of the Solar System through a spiral arm, but which relates the initiation of an ice epoch, plus biological catastrophes, to an encounter of the Solar System with a nearby supernova outburst rather than a super-dense interstellar cloud.

63 citations

Journal ArticleDOI
TL;DR: Frohlich as discussed by the authors reviewed the solar luminosity variability due to magnetic activity and found that the variations so far seen have been as large as approximately 0.4% over a time scale of a week.
Abstract: Variations in the Sun's luminosity have become, almost overnight, an active and productive field of astrophysics. There is now a nearly unbroken time series of precise data, from two separate satellites, beginning in late 1978 and running to the time of this writing. The study of these solar variations has jumped to a level of activity that might be expected in any field suddenly presented with a three-decade improvement in data quality. This improvement has been created largely by Willson's (90-93) Active Cavity Irradiance Monitor (ACRIM) on the Solar Maximum Mission (SMM). This was the first satellite to have been repaired in space by a manned mission; the repair was tremendously important for the study of solar variability. The variations so far seen have been as large as approximately 0.4% over a time scale of a week. The irradiance has also exhibited a steady decline since 1980 of the order of 0.02% per year. A review of temporal variations is given by Frohlich (3 1 a). In this review, we concentrate on solar luminosity variability due to magnetic activity. The precision of the ACRIM while operating in its normal mode approached 1 0 ppm of the mean solar irradiance, when averaged over a day. At this level of precision, the Sun's output is almost always changing. Another experiment, the Earth Radiation Budget (ERB) on the Nimbus-7 satellite, has produced an even longer record of solar variability measurements, though with less precision (35). The data from the two spacecraft have revolutionized the field within the past six or seven years.

62 citations

Journal ArticleDOI
TL;DR: In this article, the NCAR CCM0 model is applied to an all-land planet with no topography (Terra Blanda), and the decay of natural anomalies in the large-scale temperature field in each model is examined.
Abstract: This paper considers the climate response to step function changes in the solar constant in two versions of a general circulation model with simplified geography. The NCAR CCM0 model is applied to an all-land planet with no topography (Terra Blanda). In one version there is moisture in the air (as well as self-generated clouds) as evaporated from an ideal surface at a fixed 80% of saturation. In the other version there is no moisture in the atmosphere. We examine the decay of natural anomalies in the large-scale temperature field in each model and compare the time dependence of the ensemble average with the average temporal behavior of the response to step function changes in the solar constant. The fluctuation-dissipation theorem of statistical mechanics makes specific predictions about the relationship between the two curves. We conduct the experiments for both versions of the model since the sensitivity is quite different for each. The theorem is found to hold reasonably well in each case.

61 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20238
202215
20219
20202
201911
201810