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Skywarden,
Ursa Astronomical Association
Kopernikuksentie 1
00130 Helsinki
taivaanvahti(at)ursa.fi

Ursa Astronomical Association

Active aurora band - 30.9.2016 at 20.40 - 30.9.2016 at 21.25 Uurainen Observation number 57406

Visibility III / V


An aurora borealis began to stand out in the northern sky as soon as the evening began to darken. So the camera on the stand and at the edge of the field to watch how the situation develops. It didn't take long for the arc to come to life and soon the entire northern sky was full of colorful arcs and rays. The best phase lasted only a few minutes, but the most interesting was the red-green plant that appeared in the western sky in the last three pictures, which expanded across the sky and slowly faded into the invisible.

#sargs



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Additional information
  • Aurora brightness
    • Bright auroras
  • Observed aurora forms
    • 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

       

Comments: 7 pcs
Heidi Rikala - 30.9.2016 at 23.45 Report this

Tuo pläntti oli kyllä mielenkiintoinen. Ikaalisissa se näkyi vihreänä. Eikä reposet olleet ihan noin kirkkaat, pilvisyys hieman haittasi.

Mikko Peussa - 1.10.2016 at 00.24 Report this

Kauniita kuvia jälleen kerran Erkiltä!

Roope Luukkainen - 1.10.2016 at 04.07 Report this

Upeita ja hyvälaatuisia kuvia.

Erkki Rauhala - 1.10.2016 at 09.43 Report this

Kiitos !!!

Marianne Laapio - 1.10.2016 at 18.42 Report this

Se punainen väri oli poikkeuksellisen voimakasta, koska silmäkin sen hyvin erotti. Hienot kuvat! 

Paljon ihana  upeita revontulia

Emma Bruus - 25.1.2023 at 12.06 Report this

Nyt on timanttista kamaa! Olisiko siulla vielä lisäkuvia tuosta lopun vihreästä läiskäsetistä, jossa on tuo violetti?

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