Mie scattering
From The Glossary of Digital Photography
The scattering of light in the atmosphere caused by particles such as dust. Mie scattering generates the red hues of sunrise and sunset as well as the red hues seen after dust storms, volcanic eruptions, and forest fires. All of these activities release dust, smoke, soot, and ash particles into the air that cause low-angle scattering and produce the red, orange, and other colors associated with those events.
