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Ursa Astronomical Association
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taivaanvahti(at)ursa.fi

Ursa Astronomical Association

Quiet aurora arc - 17.10.2021 at 20.30 Mäntyharju Observation number 101828

Visibility II / V

Markku Siljama, Ursa (Etelä-Suomi)

A calm arc of northern lights in the north at an altitude of about 10 degrees.

The magnetic field of the solar wind was good but the speed unhappy. The result was a dim arc.



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.

Comments: 1 pcs
Eero Karvinen - 18.10.2021 at 00.56 Report this

Näyttää siltä, että alimyrsky ei vielä ole syttynyt täyteen loistoonsa. Diffuusin kaaren vaiheessa kannattaa odottaa ja vertailla kuvien kesken, miten kaari käyttäytyy.

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