Half-sky auroras - 18.9.2023 at 21.10 - 19.9.2023 at 01.00 Laitila Observation number 118825

Visibility IV / V

Pirjo Koski, Porin Karhunvartijat

It was night. Repos could be seen already after nine in the evening, but they were difficult to photograph, there was so much light. A possible diffuse proton arc became visible already at the beginning of the evening. It remained in the sky for a commendable long time (perhaps as much as one hour?) until after the northern lights corona it was no longer visible.

An exciting night, sometimes the shapes and colors were so bright that you could actually screw the opening, you wanted to burn it. At the beginning of the set, a couple of really tall pillars appeared in the sky. They traveled across the entire sky to the west. At one point, instead of the corona, at the very zenith you could see many aurora belts next to each other. There was also a lot of red as the basic color, which appeared as a kind of reddish hue to the eye. It was getting late, lots of shapes and events, but there were enough clouds and finally at one point the sky was blocked so badly that we had to give up.

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

3 6

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.
- Corona
  
  CoronaA corona is a hand fan shaped structure, it usually forms south of the observer's zenith, most commonly consisting of rays or bands. The corona is usually the most beautiful part of the aurora show. It is bright and active, but on the other hand also short-lived.
  
  Aurora corona. Photo by Anna-Liisa Sarajärvi.
  
  Aurora corona. Photo by Merja Ruotsalainen.
  
  Corona formed from bands. Photo by Markku Ruonala.
  
  Aurora corona. Photo by Tapio Koski.
- 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.
- Rays
  
  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
  
  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.
- Pulsating patches
  
  Pulsating patches or -aurora typically have more or less regular shape and size. They typically appear in the later part of an aurora display. They are almost always pulsating in variable periods.
- Form not identifiable
  
  Form not identifiable
  Sometimes auroras have to be observed in such poor conditions that it is not possible to reliably identify the shape even if for example the structure and conditions could be recognized. Such a situation could be the outcome of for example alight background sky, cloud cover or a covered horizon.

Colors with unaided eye and other features
- White auroras
  
  Paljain silmin valkoinen väri näkyy useimmiten himmeissä näytelmissä, kun silmä ei kykene erottamaan mitään varsinaista väriä. Harvoin kirkkaissa näytelmissä valkoinen väri voi myös syntyä sopivista vihreän, punaisen ja sinisen yhdistelmistä.
- 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.
- 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.
- 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.
- Fully red auroras
  
  Completely dark red aurora is a very rare and strikingly handsome revelation. This phenomenon is also due to the discharge of an excitation state of an atomic oxygen.
  
  Throughout red aurora. Photo by Tobias Billings.
- Blue auroras
  
  Clearly blue auroras can be seen only during the best aurora displays close to the maximum phase or soon after it. Sometimes blue auroras can be seen shortly after the sunset at the top part of the auroral shapes, specially rays. It is created by the mission of the ionized nitrogen molecules created by the suns radiation.
  
  Strongly colored blue auroras. Photo by Jorma Mäntylä.
  
  Blue top parts of the aurora. Image by Tom Eklund.
  
  Blue top parts of the aurora. Image by Jaakko Hatanpää.
  
  Partly blue corona. Photo by Tapio Koski.
  
  Faintly blue top parts of an aurora veil. Photo by Jaakko Hatanpää.
- Pulsating auroras
  
  Pulsating aurora. The brightness of the pulsating aurora usually varies rhythmically over a period that can be only a fraction of a second at its fastest, but can also be several minutes. Pulsing usually only occurs in(strong auroral conditions) higher quality shows , especially towards the end of them. However, the pulsation may be followed by yet another eruption. Sometimes the variation in brightness is at the same stage in the whole form, whereby the whole form "turns on and off" at the same time. Pulsation is also found in arches and bands, but above all in spots..
- Flaming auroras
  
  Flaming. This rare subclass of aurora does not mean so much a single shape, but a large area in the sky. In the flaming aurora, bright waves that are sweeping upward towards the magnetic zenith emerge in the sky. Very rarely waves can wipe downwards. Bands are usually reported during flaming, less often spots.
- Flickering auroras
  
  Flickering. This rare subclass refers to a situation where irregular variations in brightness occur in aurora, such as in fluttering flames.
- Streaming auroras
  
  Streaming. In streaming aurora fast irregular variations in brightness occur along the horizontal dimension of homogeneous shapes.
- Violet auroras
  
  Usually in Lapland or even in the south you can see purple auroras in stronger aurora shows. The most common color in auroras along with green and red.

Technical information

Canon EOS 6D, Irix Blackstone 15mm and wholesale various settings ISOt 800-6400 f2.8-4, 2-15s

Send a comment

Comments are checked and moderated before publication If you want to contact the observer directly about possibilities to use these images, use the Media -form.

Newest observations

Contact information

Half-sky auroras - 18.9.2023 at 21.10 - 19.9.2023 at 01.00 Laitila Observation number 118825