Three Sun Mirage
~ Renowned atmospheric optics photographer Pekka Parviainen (Polar Image) assembled this composite to show the progression of a solar mirage. All images ©Pekka Parviainen, shown with permission.
|The sun is setting through a temperature inversion layer where unusually warmer air overlays cooler. Inversions are a ripe source of ‘mock-mirage’ type sunsets and ‘photographer’s’ green flashes. A single inversion can produce three solar images. The sun breaks up into multiple slices when several inversions are stacked.
At left in the top image, half of the solar disk has sunk below the inversion’s upper boundary. The upmost partial disc is from rays that have grazed the inversion’s temperature gradients and are strongly refracted to curve downwards - thus raising the solar disk in the sky. Rays passing deeper and across the inversion are refracted upwards relative to Earth’s curvature and create a second sun below the first. In images from left to right there are not one but two solar slices within the inversion layer. This is the norm, one is inverted and rises while the other descends.
These mirages are visible when the eye/camera is above the inversion. What is then seen varies much with height. Inversion layers can be very close to the sea surface and the best effects are seen when the eye is not much higher.
The uppermost sun can show multiple green or even blue flashes. Mock-mirage flashes are more easily photographed than observed visually (care!) compared to the more classical intense final flash of an Etruscan vase or omega sunset.