There is no simple definition of a plasma. An attempt is that a plasma is a gas in which the molecules have been ionized; where ionized means that the molecules have one or more electrons stripped from them. A plasma would then be a collection of charged molecules and electrons. However plasmas are never that simple, they have fields, many neutral molecules, and always changing. Most of the universe is in a plasma state. Examples of plasmas include the sun, the ionosphere (outer atmosphere), fluorescent lights, gas lasers, and lightning. Plasmas are used in many industrial applications such as silicon chip manufacture, cutting, coating (such as diamond), lighting, and lasers.
Atmospheric Optics are phenomena involving light in the atmosphere. It includes rainbows, blue skies, white clouds, red sunsets, halos, and glories.