Constants

Solar constants and their properties

The solar constant (GSC) measures the amount of energy received by a given area one astronomical unit away from the Sun. . Changes in the solar constant from 1600 to 2000. The blue region is from a model that is based on observations of stars such as the Sun, and the purple region is based on the effect of the solar magnetic flux on bright regions called faculae. It is measured on a surface perpendicular to the. . Scientists quantify it using something called the solar constant — a foundational value that defines how much sunlight our planet receives at the boundary of space and the Earth's atmosphere. Only a small part of it reaches the Earth. [PDF Version]