Half-sky auroras - 2.3.2017 at 20.20 Muonio, Särkitunturi Observation number 61648

• Aurora brightness
• • Bright auroras
• Colors with unaided eye and other features
• • Streaming auroras

    Streaming. In streaming aurora fast irregular variations in brightness occur along the horizontal dimension of homogeneous shapes.

  • Flaming auroras

    Flaming. This rare subclass of aurora does not mean so much a single shape, but a large area in the sky. In the flaming aurora, bright waves that are sweeping upward towards the magnetic zenith emerge in the sky. Very rarely waves can wipe downwards. Bands are usually reported during flaming, less often spots.

  • Red coloration of the shapes lower edge

    Red lower edge visible with the naked eye. The bands which are starting to level up their activity and are green colored have quite often a narrow red lower edge. This is the most common form of red color which is derived from molecular nitrogen.

    Aurora band with purple lower edge. Photo by Ilmo Kemppainen.

    The low hanging brightest aurora band is colored red at the lower edge. Photo by Tero Ohranen.

    Narrow purple reddish tones at the lower part of this aurora band. Photo by Merja Ruotsalainen.

    Purple band at the bottom. Photo by Panu Lahtinen.

  • 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.

  • Violet auroras

    Usually in Lapland or even in the south you can see purple auroras in stronger aurora shows. The most common color in auroras along with green and red.

• Observed aurora forms
• • 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.

  • Arc

    ARC The arcs are wider than the bands and do not fold as strongly. The arcs are normally neither very bright nor active.

    The arc is probably the most common form of aurora. When aurora show is a calm arc in the low northern sky it often doesn’t evolve to anything more during night. In more active shows the arc is often the first form to appear and the last to disappear.

    The lower edge of the arc is usually sharp but the upper edge can gradually blend into the background sky. As activity increases rays and folds normally develop, and the arcs turn gradually into bands.

    An aurora arc runs across the picture. Vertical shapes are rays. Photo by Atacan Ergin.

    Aurora Arc. Photo by Mauri Korpi.

    Aurora Arc. Photo by Anna-Liisa Sarajärvi.

    Aurora Arc. Photo by Matti Asumalahti.

Canon eos 6d, Samyang 14 mm, f2.8, iso 3200, time 5-15 s.

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