Active aurora band - 27.9.2019 at 22.00 - 28.9.2019 at 02.00 Pori Observation number 85829

Visibility III / V

Jarkko Suominen, Porin Karhunvartijat

In the evening we took the dogs out with the family and noticed a small movement of the active northern lights belt. After a short time there, we decided to take the dogs home quickly and return to the scene with my son and take the camera with him. Eventually, we found ourselves in the yyteri describing. The sky showed an active northern lights belt, northern lights gauze, and a calm northern lights belt from the northwest sky all the way to the east sky. At times, you could notice a little red among the northern lights.

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10 15

Additional information

Aurora brightness
- Dim auroras
Colors with unaided eye and other features
- Red coloration of the shapes top
  
  Auroras which have red top part that can be seen with naked eye are most often observed in the bands and long rays. In this case the lower parts are usually green. If the upper parts are in sunlight, red may be stronger than green. This shade of red is due to the discharge of the excitation state of the atomic oxygen.
  
  Aurora that shift to reddish towards the top. Photo by Karri Pasanen.
  
  Red top in a aurora band. Photo by Simo Aikioniemi.
  
  Red at the top of the aurora. Picture of Tom Eklund.
- 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.

Observed aurora forms
- Veil
  
  Veil
  Veil is the most bland and very common form of aurora. It usually covers its homogeneous dim glow over a wide area of the sky at once. Most often, the veil is seen in the calmer and quiet phase of the night after the aurora maximum as a background for other forms. The veil can also occur alone and in that case it will be quite difficult to reliably identify as an aurora, especially at a observation site which has a lot of light pollution.
  
  A similar glow of light can also be caused by airborne moisture, smoke, or a very thin layer of clouds that reflects the light that hits them. However, clouds can also be used to identify veil, especially if the middle or upper cloud appears dark against a lighter background, then it is very likely to be aurora veil if the brightness of the background sky is not due to the rising or falling Moon or Sun. When photographing, very long exposure times usually reveal the green colour of the veil auroras.
  
  Veil and rays. Photo by Esa Palmi.
  
  Red aurora veil. Photo by Marko Mikkilä.
  
  Veil. Photo by Milla Myllymaa.
  
  Aurora veil that changes color from green at the lower edge through purple to blue at the top. Photo by Jaakko Hatanpää.
  
  Dim green veil. Photo by Jarmo Leskinen.
  
  Radial aurora band surrounded by veil. Photo by Jussi Alanenpää.
- 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.

Technical information

Canon Eos 1000Da, ISO 800, 15 sec, f 3.5

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Active aurora band - 27.9.2019 at 22.00 - 28.9.2019 at 02.00 Pori Observation number 85829