Active aurora band - 19.12.2021 at 21.59 - 19.12.2021 at 22.12 Jyväskylä Observation number 103241

Visibility III / V

Harri Kiiskinen, Jyväskylän Sirius

A fast northern arc of about 10 min happened just right at the time the clouds were gone. Pictures from Nyrölä's allsky camera.

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Additional information

Aurora brightness
- Bright auroras
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.

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.

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Active aurora band - 19.12.2021 at 21.59 - 19.12.2021 at 22.12 Jyväskylä Observation number 103241