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The solar constant includes radiation over the entire electromagnetic spectrum. It is measured by satellite as being 1.361 kilo watts per square meter (kW/m 2) at solar minimum (the time in the 11-year solar cycle when the number of sunspots is minimal) and approximately 0.1% greater (roughly 1.362 kW/m 2) at solar maximum. [1]
This represents the power per unit area of solar irradiance across the spherical surface surrounding the Sun with a radius equal to the distance to the Earth (1 AU). This means that the approximately circular disc of the Earth, as viewed from the Sun, receives a roughly stable 1361 W/m 2 at all times.
The F10.7 index is a measure of the solar radio flux per unit frequency at a wavelength of 10.7 cm, near the peak of the observed solar radio emission. F10.7 is often expressed in SFU or solar flux units (1 SFU = 10 −22 W m −2 Hz −1). It represents a measure of diffuse, nonradiative coronal plasma heating.
4-1 10-1 Solar cycle 16: 1923 – Aug 9.3 1928 – Apr 130 68 4-8 10-1 Solar cycle 17: 1933 – Sep 5.8 1937 – Apr 199 96 3-7 10-5 Solar cycle 18: 1944 – Feb 12.9 1947 – May 219 109 3-3 10-2 Solar cycle 19: 1954 – Apr 5.1 1958 – Mar 285 129 3-11 10-6 Solar cycle 20: 1964 – Oct 14.3 1968 – Nov 157 86 4-1 11-5 Solar cycle 21: 1976 ...
Solar radiation pressure on objects near the Earth may be calculated using the Sun's irradiance at 1 AU, known as the solar constant, or G SC, whose value is set at 1361 W/m 2 as of 2011. [17] All stars have a spectral energy distribution that depends on their surface temperature. The distribution is approximately that of black-body radiation.
The updated figure (right) shows the variations and contrasts solar cycles 14 and 24, a century apart, that are quite similar in all solar activity measures (in fact cycle 24 is slightly less active than cycle 14 on average), yet the global mean air surface temperature is more than 1 degree Celsius higher for cycle 24 than cycle 14, showing the ...
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In active regions the energy flux is about 10 7 erg cm −2 sec −1, in the quiet Sun it is roughly 8 10 5 – 10 6 erg cm −2 sec −1, and in coronal holes 5 10 5 - 8 10 5 erg cm −2 sec −1, including the losses due to the solar wind. [1] The required power is a small fraction of the total flux irradiated from the Sun, but this energy is ...