14 August 2015

Spectrums of light.

Whilst out on the fells in all conditions we are sometimes privileged with great spectacles in the sky. Often accompanying the various atmospheric cloud formations are halos.

Golden rings have appeared in the sky on a couple of occasions in the form of sun halos. Without being blinded we took pictures and researched what it was all about.

The golden ring.

A mix of chemistry, physics and geometry are the main components for sun halos. At high enough altitudes in the sky, the water vapour condenses and then freezes into ice crystals. The ice crystals responsible for halos are typically suspended in cirrus or cirrostratus clouds. As sunlight passes through the ice crystals, the geometry of the crystals cause the light to refract, similar to what happens when light passes through a prism.

This geometric size and shape causes light to undergo two refractions, or bends, as the light passes through the ice crystal. Once the second bend is made, the light appears as a halo in the sky. Light from the moon can also form halos.

Rings galore.

On another occasion whilst working on the fells, the team witnessed an even rarer phenomenon. Usually the halos are formed by one, simple uncomplicated ring. However a variety of halos can appear, caused by a corresponding variety of ice crystals. In the photo above you can see an additional ring starting to form.

Diagram of weather halo elements.

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