On a frozen, foggy morning in October 2013, Pauli Hänninen stepped outside in Sirkka, the village at the foot of Levi in Finnish Lapland, and found the sky full of rings, arcs and false suns. His photographs of the display, with family and friends standing on the snowy road beneath it, travelled around the world as one of the finest ice-halo shows ever caught on camera.
The halo display over Sirkka, Lapland
Sirkka is in the municipality of Kittilä, well north of the Arctic Circle, and serves as the village for the Levi ski resort. Speaking to the Finnish broadcaster Yle, Hänninen described the conditions: “It was cold and very foggy, the temperature was around −10 degrees Celsius.” Then the fog began to thin. “When the clouds began to break, there were rainbow colours in the sky and a halo spanning 360 degrees!”
That combination of freezing fog and low sun is ideal for halos. Fog at −10 °C is made largely of tiny ice crystals floating close to the ground, known as diamond dust, and every one of them acts as a small prism or mirror for sunlight.
How ice crystals bend sunlight into halos
Ice crystallises as hexagonal prisms: flat plates or longer columns. When sunlight passes through one side face and out another, it is bent by about 22 degrees. Crystals tumbling in every direction send that light toward you from all points 22 degrees from the Sun, forming a ring. Light reflected off crystal faces, or passing through crystals that hold a steady orientation, produces the other shapes.
- 22° halo: the most common halo, a white ring with a reddish inner edge around the Sun. The sky inside it looks darker.
- Sun dogs (parhelia): bright, often coloured spots on either side of the Sun, just outside the 22° ring. They come from plate crystals drifting with their faces nearly horizontal.
- Parhelic circle: a white band running horizontally through the Sun at the same height above the horizon, sometimes all the way around the sky.
- Upper arcs: bright, curved arcs touching the top of the 22° halo, and colourful arcs higher up near the zenith.
Reading the photographs
Hänninen’s pictures show several of these features together. The circular halo surrounds the low Sun, with bright patches beside it. A broad white horizontal arc runs above the frosted forest, and in the vertical frame coloured arcs stack above the ring. A complete display like this needs huge numbers of crystals in different shapes and orientations at once, which is why such shows are rare even in Lapland.
The people on the road add scale. A 22° halo is large: hold your hand at arm’s length with the fingers spread, cover the Sun with your thumb, and the ring sits near the tip of your little finger.
Where and when to see sun halos
Halos are far more common than most people realise. Away from the Arctic they usually form in thin, high cirrus or cirrostratus cloud 5 to 10 kilometres up, so look for a pale veil over the Sun. Because cirrostratus often runs ahead of a weather front, a halo can be a sign of rain or snow within a day. Diamond-dust displays at ground level need serious cold and are a speciality of still winter mornings in places such as northern Finland, Alaska and Canada. Shield the Sun behind a lamp post or roof edge to see the arcs clearly and protect your eyes.
Learn more about recognised cloud terminology and why ice can look blue.
Related reading
- Finnish Lapland in Winter: Forests, Light and Snow-Covered Landscapes
- Light Pillars over Winter Towns: Reflections in the Night Sky
- Snow Swimming in Finland: A Winter Comedy Clip
- Kakslauttanen’s Glass Igloos: A Room with a Sky View
- Snowboarding and Freestyle in Finnish Lapland
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