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Photoionization in the atmosphere

Although the integrated energy in UV rays and X rays emitted from the Sun represents less than 10 percent of the total energy that the Sun sends in our direction, its interaction with the Earth’s atmosphere is considerable.

The Sun’s radiation causes photoionisation: 

Photoionization is a process in which a photon ejects one or more electrons from a neutral atmospheric particle (atom or molecule) turning it into a charged particle - an ion.

Photoionization plays a very important role in the chemistry of planetary atmospheres, including the atmospheric chemistry here on Earth.

The Sun, solar radiation and Earth seen from the International Space Station. Credits NASA.