Elongated Venus Corona ~ Pictured by Alexandra Farkas 24th November at Mogyoród, Hungary. ©Alexandra Farkas, shown with permission.
We see non circular coronae from oriented pollen grains and even pond algae. Both objects are non spherical and produce asymmetric coronae elongated perpendicular to the direction of their longer axes.
That Venus and Jupiter show them is a surprise. The phase of Venus does not produce the effect. It is likely that the coronae are produced by light diffracted by small ice crystals in clouds. Alexandra's corona or aureole is ~0.2° long. Crystals of size ~0.3mm would produce it. Column crystals of that size are large enough to be aerodynamically oriented with their long axis horizontal to give a vertically elongated Venus corona when reasonably low in the sky.
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