An airglow is diffuse radiation, extending from the near infrared to the far ultraviolet, that is continuously emitted by a planetary atmosphere; also known as nightglow. It is caused by the collision of charged particles and X-rays from space, mainly from the Sun, with atoms and molecules high in the atmosphere.
Earth's airglow varies with the time of night or day, latitude, and season, goes from a minimum at the zenith to a maximum about 10° above the horizon, and arises mainly from discrete atomic and molecular transitions that give rise to a mostly emission-line and emission-band spectrum. Emission from oxygen at 5577 Å (green) predominates at night, while yellow sodium and red oxygen emission is prominent at twilight. Daytime airglow, though drowned by sunlight, is actually 1,000 times as intense as at night.
Related categories• ATMOSPHERIC PHENOMENA AND STRUCTURES
• OBSERVATIONAL ASTRONOMY
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