a dim light from the upper atmosphere caused by emissions from atoms and molecules ionized by solar radiation: observed at night (nightglow), during the day (dayglow), and at twilight (twilight glow), with each having slightly different characteristics.
A faint photochemical luminescence in the upper atmosphere caused by the collision of x-rays and charged particles from the Sun with atoms and molecules, especially of oxygen, sodium, and the hydroxyl radical (OH). Airglow is strongest over low and middle latitudes.
