Our Sun in the Light of the Hydrogen Alpha Spectral Line

With the usual focus on satellite-based solar imagery, one often forgets about the important contributions of ground-based observatories. Here we present a movie of imagery collected at Big Bear Solar Observatory (BBSO) site as part of GONG (Global Oscillations Network Group) of the National Solar Observatory (NSO). The light from the Sun is passed through a filter that admits light from the hydrogen alpha spectral line (6562.8 angstroms or 656.28 nanometers) in the red region of the spectrum. This reveals many details which cannot be seen in our usual broad-spectrum view of the Sun, particularly filaments across the solar disk and limb.

Ground-based observatories are subjected to a number of challenges different from their space-based counterparts, including gaps in the visibility of their target (i.e. nighttime), clouds (some slightly visible in this movie) and atmospheric turbulence (also some visible here).

The spectral line for hydrogen alpha is a deep red and rather dark for regular digital displays. For this visualization, we have used a brighter 'blackbody' color table to improve visibility.