photo #5441693

Sean Norman (Member 62,390) spotted this halo while on a helicopter tour from Whitehorse, Yukon, Canada. Sean explains, ‘I’ve lived in northern Canada for almost 10 years, and see these optical effects often, but this was by far the most spectacular I've witnessed.’ Essential for the formation of these light displays is for the air to contain tiny hexagonal plate- and column-shaped crystals clear enough to act as microscopic prisms that refract and reflect the sunlight shining through. The tumbling ice crystals would have sparkled in the air, and, if you look carefully, you can just see some appearing as tiny streaks across the photo due to Sean’s movement through the sky.Visible here is a 22-degree halo, the delicately tinted partial ring framing the Sun – so named because the angle between the direction of the Sun and that of any point on the halo is always 22 degrees. Three points of brightening appear on this 22-degree halo. On either side are parhelia, also known as sun dogs or mock suns, while at the bottom is a lower tangent arc. All these were formed by light shining through the geometric ice crystals, but the vertical column of light extending down from the Sun, known as a lower sun pillar, was caused by reflections off the top surfaces of plate-shaped crystals. The tumbling ice crystals contributed to the light effects, each with just a fleeting glint of light in Sean’s direction as they passed momentarily at the right angle through the right parts of his field of vision. Together, the countless glints combined to form a steady display of light effects hovering in the crisp air of the Yukon sunrise.