Quiet aurora arc - 13.9.2018 at 02.56 - 13.9.2018 at 03.01 Helsinki Observation number 77562

Visibility II / V

Georg Kieninger

As the clouds ranged from closed cover to full clarity, a very dim echo of northern lights was visible for a few minutes. Note: The image is a combination of six images. Location Hietalahti.

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12 9

Additional information

Aurora brightness
- Can only be seen in photos
Observed aurora forms
- 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.

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Quiet aurora arc - 13.9.2018 at 02.56 - 13.9.2018 at 03.01 Helsinki Observation number 77562