Half-sky auroras - 7.10.2015 at 21.29 - 7.10.2015 at 21.32 Lieto Observation number 87870

Visibility IV / V

Sakari Ekko, Turun Ursa

I also dug up old northern lights, and from this and the other two pictures I found a dune-like formation on the left side. The formation moved a few minutes further south, away from the field of view. It is no longer visible in the image taken at 21.33. I have processed the image quite heavily to make the dunes I assume more visible.

My diary includes e.g. an indication of the final stage of the northern lights, after the corona at about 11.30 pm: "Finally, fast streaks and spots flashed in the sky, which I could not picture, for the changes took place even in tenths of a second. I have not just seen such a thing."

This description has been automatically translated from Finnish. Click here to see the original text.

10 9

Additional information

Aurora brightness
- Bright auroras
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

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Half-sky auroras - 7.10.2015 at 21.29 - 7.10.2015 at 21.32 Lieto Observation number 87870

Dunes