solar constant

solar constant the average amount of radiant energy received by the earth's atmosphere from the sun; its value is about 2 calories per min incident on each square centimeter of the upper atmosphere. The actual value of the energy varies with several factors; the most important factor is the earth's distance from the sun, which changes because of the earth's elliptical orbit. For computing the value of the solar constant, the astronomical unit , or average earth-sun distance, is used.

solar constant The amount of solar energy, in all wavelengths, that falls on a given area at the top of the Earth's atmosphere. In fact, the solar ‘constant’ varies by 0.1% over the eleven‐year solar cycle, and perhaps by more over longer periods, so the term total solar irradiance is now preferred.

solar constant Steady rate at which energy from the Sun is received from just outside the Earth's atmosphere. Its value is c.1.353 kilowatts per square metre (perpendicular to the Sun's rays).