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taivaanvahti(at)ursa.fi

Ursa Astronomical Association

Quiet aurora arc - 21.1.2023 at 18.21 - 21.1.2023 at 19.30 Kokkola Observation number 111513

Visibility II / V

Sami Mutka

Finally, we were promised a cloudless winter vacation and got to work on bonga. After arriving at the bongause place, a test picture of the sky and a nice-looking arc was there in the sky. I set the camera on the shore to take pictures and went a little way to the fire place, to build a fire from the nice embers someone left. After some time, I went to check the camera and already saw on the camera screen that there were special stripes above the northern lights arc. I interpreted them on the spot as air glow.

I went to change places on the beach, the purpose was to try to get some kind of picture of the comet, if the northern lights don't get excited. Well, that's what happened traditionally. After five minutes of walking, the sky was suddenly completely overcast. After a couple of minutes, an unimaginably dense fog arrived. Once again. In five minutes, you can go from a pleasant sky to completely gray.

Based on a tip from a photographer colleague (Thanks to Tommy Lågland, who always has enough interest and stamina to analyze the events in the sky better than myself), I started looking for possible dunes in the picture. This resulted in an interesting timelapse, which the camera shot from 18:21 to 19:04. What I interpreted as an airglow on the spot was indeed dim in the sky the whole time, but in the final stage of the timelapse it would seem as if the aurora borealis passed through this glow, brightening it.



More similar observations
Additional information
  • Aurora brightness
    • Very dim auroras
  • Observed aurora forms
    • Arc info

      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.

    • Rays info

      The raysare parallel to the lines of force of the magnetic field, i.e. quite vertical, usually less than one degree thick light streaks. The rays can occur alone or in connection with other shapes, mainly with arcs and bands. Short rays are usually brightest at the bottom but dim quickly. The longest rays, even extending almost from the horizon to the zenith, are usually uniformly bright and quite calm, and unlike the shorter rays, most often occur in groups of a few rays or alone. Rays, like bands, are a very typical form of aurora.

      Artificial light pillars, which are a halo phenomenon visible in ice mist, can sometimes be very similar to the rays of aurora. Confusion is possible especially when the lamps that cause the artificial light pillars are far away and not visible behind buildings or the forest. The nature of the phenomenon is clear at least from the photographs.

      Rays. Picture of Tom Eklund.

      Rays. Photo by Mika Puurula.

      Two beams rise from the aurora veil. Photo by Anssi Mäntylä.

      Two radial bands. Show Jani Lauanne.

      Radial band and veil. Photo by Jussi Alanenpää.

      Two rays. Photo by Aki Taavitsainen.

      It may be possible to confuse such rays with artificial light columns. Compare the image below. Picture of Tom Eklund.

      There is no aurora in this image, but all the light poles - including the wide and diffuse bar seen at the top left - are artificial light pillars born of ice mist. Photo by Sami Jumppanen.

      Aurora and artificial light pillars. All the radial shapes in the picture above are probably artificial light pillars that coincide appropriately with the aurora band. In the image below, the aurora band has shifted and does not overlap with the pillars produced by the orange bulbs. There is no orange in auroras. Photo by Katariina Roiha

    • Veil info

      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.

Comments: 2 pcs
Eero Karvinen - 22.1.2023 at 18.15 Report this

Ilmahehkun luoma aaltoilu erottuu tässä havainnossa hyvin. Ilmahehku muodostuu päivällä auringon voimakkaan säteilyn muodostamista epävakaista kemiallisista yhdisteistä. Pimeän tullen reaktiot kulkevat takaisinpäin ja ylimääräinen energia vapautuu samoina väreinä, kuin revontulissa. Ilmakehä aaltoilee ja muodostaa kemiallisesti erilaisia kerroksia tällä korkeudella toisinaan voimakkaasti ja siten ilmahehku saa aaltomaisia muotoja. Samat gravitaatioaallot aiheuttavat dyynimuodostelmat revontuliovaalin kohdalla joutuessaan elektroni/ionisateen alle. Rajanveto näiden kahden välillä on toisinaan hankalaa ja ilmahehku voi esiintyä aaltomaisena samaan aikaan dyynien kanssa.

Sami Mutka - 22.1.2023 at 19.40 Report this

Kiitos loistavasta selityksestä, Eero! Paljon on opittavaa näissä taivaan ilmiössä.

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