solar constant

solar constant
the average rate at which radiant energy is received from the sun by the earth, equal to 1.94 small calories per minute per square centimeter of area perpendicular to the sun's rays, measured at a point outside the earth's atmosphere when the earth is at its mean distance from the sun.
[1865-70]

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 the total radiation energy received from the Sun per unit of time per unit of area on a theoretical surface perpendicular to the Sun's rays and at Earth's (Earth) mean distance from the Sun. It is most accurately measured from satellites (satellite) where atmospheric effects are absent. The value of the constant is approximately 1.4 kilowatts per square metre. The “constant” is fairly constant, increasing by only 0.2 percent at the peak of each 11-year solar cycle. Sunspots (sunspot) block out the light and reduce the emission by a few tenths of a percent, but bright spots, called plages, that are associated with solar activity are more extensive and longer lived, so their brightness compensates for the darkness of the sunspots. Moreover, as the Sun burns up its hydrogen, the solar constant increases by about 10 percent every billion years.

Harold Zirin
 

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Universalium. 2010.

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Look at other dictionaries:

  • Solar constant — Constant Con stant, n. 1. That which is not subject to change; that which is invariable. [1913 Webster] 2. (Math.) A quantity that does not change its value; used in countradistinction to {variable}. [1913 Webster] 3. (Astron.) A number whose… …   The Collaborative International Dictionary of English

  • solar constant — n. the average amount of solar radiation received normally by a unit area just outside the earth s atmosphere, equal to c. 1.37 x 106 ergs per cm2 per second …   English World dictionary

  • solar constant — The solar constant (as defined for the planet Earth) is the power collected at the top of the atmosphere by a unit area perpendicular to the light path. In practice, the unit area is 1 m squared (m2). Its value is about 1.98 calories per minute… …   Aviation dictionary

  • solar constant —   The strength of sunlight; 1353 watts per square meter in space and about 1000 watts per square meter at sea level at the equator at solar noon.   Solar Electric Glossary …   Energy terms

  • solar constant — noun Date: 1869 the quantity of radiant solar energy received at the outer layer of the earth s atmosphere that has a mean value of 1370 watts per square meter …   New Collegiate Dictionary

  • solar constant — noun The amount of incoming solar radiation per unit area, measured on the outer surface of Earths atmosphere, in a plane perpendicular to the rays …   Wiktionary

  • Solar Constant —   The average amount of solar radiation that reaches the earth s upper atmosphere on a surface perpendicular to the sun s rays; equal to 1353 Watts per square meter or 492 Btu per square foot …   Energy terms

  • Solar constant —   The average amount of solar radiation that reaches the earth s upper atmosphere on a surface perpendicular to the sun s rays; equal to 1353 Watts per square meter or 492 Btu per square foot.   U.S. Dept. of Energy, Energy Information… …   Energy terms

  • solar constant — so′lar con′stant n. astron. the average rate at which solar radiant energy is received by the earth: 1.94 small calories per minute per sq. cm …   From formal English to slang

  • solar constant — noun the rate at which radiant solar energy is received at the outer layer of the earth s atmosphere • Hypernyms: ↑rate …   Useful english dictionary

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