What Does the Solar Constant Mean?

What Does the Solar Constant Mean?

The solar constant is the amount of energy coming in contact with the top of Earth's atmosphere in watts per meter-squared. This includes the energy deposited from the entire spectrum of solar radiation: radio, infrared, visible light, ultraviolet and X-rays. The approximate value of the constant is 1.361 W/m squared.

NASA explains that the term "solar constant" is actually an oxymoron. With the deployment of more advanced satellite-based measuring techniques, it has been observed that the value of the solar constant rises and falls with the sunspot cycle by a significant amount. When the solar irradiance is at a maximum, it is about 0.1 percent brighter than it is at the minimum.