Definitions for "H-alpha"
The strongest spectral line in the solar spectrum. The wavelength is 656.3 nm. H-alpha radiation is formed in the chromosphere and its intensity increases during solar flares. It is the spectral line used for world wide surveillance of solar flares.
Light emitted at a wavelength of 656.3 nanometers from an atomic transition in hydrogen. This wavelength is in the red portion of the visible spectrum and is emitted by plasma at about 10,000 K, mainly in the solar chromosphere.
This absorption line of neutral hydrogen falls in the red part of the visible spectrum and is convenient for solar observations. The H-alpha line is universally used for observations of solar flares.