All-sky aurora - 7.10.2019 at 21.53 - 7.10.2019 at 21.57 Grovfjord, Norja Observation number 88116

• Aurora brightness
• • Very bright auroras
• Colors with unaided eye and other features
• • Green auroras

    Green, seen with the naked eye, is one the most common colors of the aurora. The green color is derived from atomic oxygen.

    Green auroras. Lea Rahtu-Korpela.

    Green auroras. Photo by Juha Ojanperä.

• Observed aurora forms
• • Dunes

    Dunes

    The dunes are a dim and very rare shape that has so far been associated with the aurora visible in early evening.

    Aurora dunes can be most easily confused to ribbons on lower clouds. In order to fill in the description of the phenomenon, a striped pattern formed by parallel lines must also appear in the aurora. The stripes are most easily recognizable right at the front edge of the aurora but they may also occur among the rest of the aurora.

    The dune auroras are visible as a parallel striped float. Photo by Tapio Terenius

    Raidallisen dyynilautan reunassa voi toisinaan olla voimakastakin aaltoilua.

    There can sometimes be strong ripples at the edge of a striped dune float. The rippling of the edge of the dune float can vary from minor to large (pictured). Photo by Pirjo Koski

  • Band

    Bands are usually narrower, more twisty at the bottom, brighter, and more active than arches. Bands usually develop from arches.

    Bands can form J and U shapes, sometimes even full spirals. The corona can also arise from bands. Bands are a fairly common form of aurora.

    Aurora band. Photo by Merja Ruotsalainen.

    Aurora band. Photo by Matias Takala.

    Aurora band. Photo by Lea Rahtu-Korpela.

    Aurora bands. Photo by Lauri Koivuluoma.

    Aurora band. Photo by Matias Takala.

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