Siberian Optics

Images by Brigitta Sipocz.

The aircraft thunders over the Great Siberian Plain criss-crossed by meandering rivers that eventually drain their fresh waters via mightier rivers into the Arctic Ocean.

The shadow of the craft's contrail adds a linear feature to the landscape of curves and bends. Sometimes contrail shadows are visible for hours.

At the shadow's head, the antisolar point directly opposite the sun and where the airplane's shadow would be if it was lower, the ground is slightly lighter and more yellow. This is the 'opposition glow' where shadows are hidden by the objects casting them making the area look relatively brighter. In this damp and no doubt midge and mosquito filled place the heiligenschein might also be adding its luminance.

When the sunlight is scattered by small water droplets in cloud the antisolar point shows another optic - the multi ringed glory.

Replace the droplets of low and medium level cloud with the ice crystals of higher ones to see sub-horizon halos.

At right a subsun shines - the direct reflection of sunlight from the upper and lower faces of hexagonal plate crystals, millions of them acting as mirrors.

At left a rarer sight, a subparhelion. Rays enter a plate crystal side face, make an odd number of internal reflections between its upper and lower horizontal faces and then leave through a side face inclined 60° to the first.

For nearly every sundog there is probably, somewhere, a subparhelion. They are only distinguished by whether there are are an odd or even number of internal reflections.

Images ©Brigetta Sipocz

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