It is important to measure the spectral composition of ultraviolet radiation emitted by the sun to improve our understanding of the roles played by different wavelengths of radiation in both the formation and destruction of atmospheric ozone and other atmospheric gases.
Solar ultraviolet (UV) light is primarily responsible for both creation and destruction of ozone in the EarthΓÇÖs stratosphere. Ozone is the molecular form of oxygen, made up of three 3 atoms, that shields the EarthΓÇÖs surface from solar UV radiation by absorbing much of this radiation. The same process also causes the temperature in the stratosphere to be higher than in the upper troposphere.
Stratospheric ozone densities are known to vary with the 11-year solar cycle. Solar variability over the solar cycle causes expansion and contraction of the outward extension of the EarthΓÇÖs atmosphere into space. Scientists use UV spectral observation of solar irradiance along with measurements of atmospheric gases and winds to better model the processes occurring in the EarthΓÇÖs upper atmosphere, particularly involving the creation and destruction of ozone.
The chart above provides data from the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM). Irradiance is measured in Watts per meter cubed, and wavelength, which is the distance between corresponding points on a wave along the direction of propagation measured in nanometers. An AU is an astronomical unit, or the mean distance of the Earth from the Sun, which is approximately 93 million miles.
