Solar constant

About: Solar constant is a research topic. Over the lifetime, 967 publications have been published within this topic receiving 29647 citations.

Irradiance Variability of the Sun

Abstract: Direct measurements of the solar constant--the total irradiance at mean Sun-Earth distance--during the last ten years from satellites show variations over time scales from minutes to years and decades. At high frequencies the spectral power is determined by granulation, super- and mesogranulation. In the 5-minute range, moreover, it is dominated by power from the solar p-mode oscillations. Their power and frequencies change with time, yielding information about changes in the convection zone. During periods of several hours, the power is steadily increasing and may be partly due to solar gravity modes. The most important variance is in the range from days to several months and is related to the photospheric features of solar activity, decrease of the irradiance during the appearance of sunspots, and increasing by faculae and the magnetic network. Long-term modulation by the 11-year activity cycle are observed conclusively with the irradiance being higher during solar maximum. All these variations can be explained--at least qualitatively--by their manifestation on the photosphere. For the long-term changes, the simultaneous changes of the frequencies of solar p-mode oscillations suggest a more global origin of the variations. Indeed, it seems that the observed irradiance modulation is a true luminosity change with the magnetic cycle of the Sun.

Intensity of Prolonged Solar Luminosity Cycles and Their Influence Over Past Climates and Geomagnetic Field

Abstract: Calcite speleothems luminescence depends exponentially upon soil temperatures that are determined primarily by solar visible and infrared radiation. So microzonality of luminescence of speleothems was used as an indirect Solar Insolation (SI) proxy index. For Cold Water cave, Iowa, US we obtained high correlation coefficient of 0.9 between a luminescence record and the experimentally observed Solar Luminosity Sunspot index. We measured a luminescent speleothem record from Jewel Cave, South Dakota, US. It is still the first available experimental solar insolation proxy record with sufficiently long duration to reproduce the orbital variations. This record covers 89300- 138600 yrs B.P. with high resolution. It reveals determination of millennial and century cycles in the record. This solar insolation proxy record contains not only orbital variations, but also solar luminosity self variations, producing many cycles with duration from several centuries to 11500 years. The most powerful non- orbital cycle is 11500 years cycle (as powerful as the 23000 a. orbital cycle in our record). It was found previously to be the most intensive cycle in the delta C-14 calibration record and was interpreted to be of geomagnetic origin. Our recent studies suggest, that this is a solar cycle modulating the geomagnetic field. We found also cycles with duration of 6000, 4400, 3300, 2500, 2300, 1900 and 1460, years (in order of decreasing intensity) with amplitude ranging respectively from 3 to 0.7 % of the Solar Constant. Latest results suggest that these millennial solar luminosity cycles can produce climatic variations with intensity comparable to that of the orbital variations. Known decadal and even century solar cycles have negligible intensity (100 times less intensive) relatively to this cycles. Solar luminosity (SL) and orbital variations both cause variations of solar insolation affecting the climate by the same mechanism. In spite their influence over the geomagnetic field involve fundamentally different mechanisms, determined by the properties of the solar wind.

Review of ground-based measurements

Abstract: Early measurements of the solar constant are described and discussed with particular emphasis on the Smithsonian program A brief description is given of the monitoring program currently operating at San Diego State

Method for measuring solar constant

Abstract: A method for measuring solar constant from earth or satellite features that an absolute radiometer is such installed that it faces against sun. In the measuring procedure, the included angle between the optical axis of absolute radiometer and light vector of sun varies, that is, the measurement of solar constant is conducted in variation procedure. Its advantages are no need of two-axle rotating platform, sun tracker and its drive mechanism, simple structure, light weight, low power consumption, high reliability and simplified measurement.