It stops solar radiation not fully .. but, most of it. The atmosphere acts as a filter, absorbing and reflecting portions of the electromagnetic spectrum, such as the ultraviolet region, that are harmful to humans and other life forms.
The atmosphere provides a natural "greenhouse effect," maintaining the temperatures and climates in which life forms on Earth have evolved to survive. The atmosphere controls the amount of solar radiation reaching the surface of the earth, and regulates the amount of radiation from the Earth escaping into space.