Half-sky auroras - 16.3.2023 at 00.55 - 16.3.2023 at 01.30 Joutsa Observation number 113481

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.

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.

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

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 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.

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. 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.