The flash of the top image is well above the horizon and largely above a still visible sun sliced into ever changing layers. This is a �mock-mirage� green flash.
Contrast with the lower image. A brilliant green flash blazes forth as the last sliver of sun slips beneath the waves. This is the much sought classical (Jules Verne) flash � an �inferior-mirage� flash.
Opposite temperature gradients produce the two mirages. The mock-mirage results from one or more temperature inversions where cooler air is trapped beneath warmer. Inferior-mirages are produced when abnormally warm air is beneath cooler.
Both flashes need mirage conditions to vertically magnify the otherwise small separation of colours produced by differential refraction.
Mock-mirage flashes are hard to see visually and they are more easily photographed. An inferior mirage flash is unforgettable.
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