Hydrogen-alpha

Hydrogen-alpha is the red spectral line of hydrogen at about 656.3 nanometers, emitted when an electron falls from the third energy level to the second.

Balmer series: A series of hydrogen spectral lines produced when electrons transition to the second energy level. Hydrogen-alpha is the longest-wavelength prominent line in this series.
Solar prominence: A large, relatively cool structure of dense plasma extending from the Sun’s visible surface into its corona. Hydrogen-alpha images show prominences brightly against the dark solar disk.
Anders Jonas Ångström: A Swedish physicist who measured solar and atmospheric spectra in the nineteenth century. His detailed solar spectral maps helped establish the study of identifiable spectral lines.
Hydrogen-beta: A visible hydrogen Balmer line near 486.1 nanometers, emitted in a transition to the second energy level. It shares the same final energy level but comes from a higher initial level and appears blue-green.
Hydrogen atom: The simplest atom, with one proton and one electron. Its electron’s transition from level three to level two produces this line.
Solar flare: A sudden release of magnetic energy in the Sun’s atmosphere, producing enhanced radiation and energetic particles. Hydrogen-alpha observations trace flare ribbons and chromospheric changes.
Johann Balmer: A Swiss mathematician who found a formula describing visible spectral lines of hydrogen. His formula organized the series that includes hydrogen-alpha.
Lyman-alpha: A hydrogen spectral line near 121.6 nanometers produced by a transition from the second energy level to the first. Its ultraviolet wavelength comes from a transition to the ground state rather than level two.
Rydberg formula: A mathematical formula that predicts the wavelengths of spectral lines in hydrogen and hydrogen-like atoms. It calculates the wavelength associated with the transition that emits this line.
Solar chromosphere: The layer of the Sun’s atmosphere between the photosphere and corona. Its hydrogen emission makes this wavelength a standard way to observe the layer.

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