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Skywarden,
Ursa Astronomical Association
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00130 Helsinki
taivaanvahti(at)ursa.fi

Ursa Astronomical Association

Quiet aurora band - 18.11.2022 at 21.25 - 18.11.2022 at 23.00 Taipalsaari Observation number 110848

Visibility II / V


On Friday evening, when the weather and space weather looked good, I went to the beach to see if I could see the northern lights. And you could see them. I was a little late at the start of the substorm, but nothing can be done.

While looking at the first pictures from the back screen of the camera, I wondered if RAGDA or several diffuse arcs were in the sky, it was hard to say because the clouds were moving at a furious speed, being torn by the strong wind from east to west over the arc. Looking at the pictures on the computer, I decided that they are probably arches and not so much RAGDA-related slopes, but we'll let the wiser decide. I'm also distinguishable above the auroras of the SAR arc, off the red top of the auroras.

Edit: I added one picture, where I also see green fog under the red. (Last picture)



More similar observations
Additional information
  • Aurora brightness
    • 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.

    • Band info

      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.

    • 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.

    • Stable Auroral Red (SAR) arc info

      The Stable Auroral Red arcs (SAR arcs)  are usually clearly distanced to the south from the aurora oval and is a very opaque and normally red ribbon. In most cases SAR arcs are only visible in the photo or on the liveview screen of the SLR camera. Using a camera with very high sensitivity is the best method for capturing these faint arcs. The arch usually settles between east and west.

      A stable red arc of aurora is a rare phenomenon. In some rare occasions, several SAR arcs may be simultaneously visible.

      The first SAR arcs of the Skywarden were observed on nights between November 3-4. and 4-5. days in 2015 in the latitudes of central Finland.   

      SAR
      SAR arc photographed by Lasse Nurminen 2018. Observation of the Skywarden 79113.

    • Red Arc with Green Diffuse Aurora (RAGDA) info

      Red Arc with Green Diffuse Aurora (RAGDA), is a two-component form of northern lights that occurs south of the oval.

      Both parts of the aurora are formed when positive particles from the magnetosphere hit the Earth's upper atmosphere. The phenomenon occurs before magnetic midnight during large aurora substorms and is best distinguished when it deteches southward from the bright rays of the substorm aurora.

      The phenomenon consists of a faint red arc, which looks a lot like a Stable Auroral Red (SAR)-arc. The common factor for these two red arcs is the reaction of the ring current with the substorm.

      Antero Ohranen, RAGDA
      A Red Arc with Green Diffuse Aurora
      Photo: Antero Ohranen

       

      Below the red arc are green diffuse patches or sausage-like shapes. RAGDA's green aurora is essentially featureless and without any rays. It may appear slightly more bluish in camera images compared to the green aurora of the oval.

      Lasse Nurminen, RAGDA
      RAGDA's green has slightly more bluish shade than the rest of the oval.
      Photo: Lasse Nurminen

       

      Sometimes the red arc and the green patches are clearly separated from the aurora oval and sometimes almost in contact with the southward edge of the oval.

      During an active substorm, the green northern lights can sometimes be seen with red tops. These usually have rays that RAGDA's green aurora lacks.

      An emissionless gap without any aurora light can be observed between the red arc and green diffuse aurora. The two features don't seem to be connected. Of the two aligned structures, the red one is located ~ 100 kilometers higher than the green aurora.

      Markku Ruonala, RAGDA
      There seems to be an empty area without any aurora light between the red and green aurora.
      Photo: Markku Ruonala

       

      The event is dynamic. It sometimes starts with green blobs, then a red arc appears. These two can also appear in the sky at the same time. The shapes move often from east to west. Then the Red Arc with Green Diffuse Aurora fades away and only the red arc remains visible in the sky. The red arc is recognized as the SAR arc.

      Observing this phenomenon is easier when the night sky is clear and dark before magnetic midnight. When looking for the red arc with green diffuse aurora, the best results can be achieved by pointing the camera towards south or southwest of the brightest part of the oval.

      A wide-angle lens is recommended for photographing the shape of the red arc going over the sky, but a regular lens can also be used. The red arc is quite dim, so the exposure times needed are typically longer than the ones for northern lights.

      Pirjo Koski, RAGDA
      Two RAGDA-arcs
      Photo: Pirjo Koski

       

      If the red arc cannot be distinguished in the images, the phenomenon identification 'Diffuse green auroras' should be used for isolated hazy green blobs/arc.

      Matias Takala, RAGDA
      Dunes in RAGDA's green aurora
      Photo: Matias Takala

       

  • Colors with unaided eye and other features
    • Green auroras info

      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.

    • Red coloration of the shapes top info

      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.

Comments: 5 pcs
Emma Bruus - 20.11.2022 at 19.08 Report this

Voi että miten hieno havis taas! Katselin kuvat läpi ja ajattelin "Mitä ikinä Terhi arvelee tässä oleva, niin sille löytyy perusteet" :) Eli alkukuvien perusteella tuossa on RAGDA-prosessia mukana ja olisin näkevinäni kolmoskuvassa pientä vihertävää utua tuossa mahdollisesti punaisen kaaren alla. Mutta aika diffuusia punaista on nämä viimeiset kuvat, joten SAR-tulkintakin (eli että jatkaa SAR-kaarena ionivirran kadottua) on yhtälailla perusteltu.

Terhi Törmälä - 20.11.2022 at 21.20 Report this

Kiitos Emma, melkein tuli täyspotti erikoisempien ilmiöiden osalta. Vielä se kunnollinen Steve puuttuu, mut kerkeehän tässä vielä. :D SAR tosiaan muodostui hiukan RAGDAn jälkeen. Kuvasin muutkin ilmansuunnat, niissä ei näkynyt muuta kuin pilviä ja tähtiä. 

Eero Karvinen - 22.11.2022 at 16.47 Report this

Hienoa settiä ollut!!

Terhi Törmälä - 22.11.2022 at 22.46 Report this

Kiitos Eero, niin kyllä oli. Ja kerrankin oli myös selkeää. 

Pirjo Koski - 28.11.2022 at 15.28 Report this

Onnittelut! 

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