South Pole Halos

Halos at the South Pole ~ A series of images by Joseph Phillips (flickr) of the diamond dust display of 2nd January '14 when the near midsummer sun circled the sky at a constant 23° high. All images ©Joseph Phillips

A HaloSim ray tracing simulation

There were plenty of randomly oriented hexagonal prism forms to make the bright 22° halo and its rather fainter 46° counterpart.   46° halos are relatively rare because their rays pass between a prism side face and a hexagonal end (basal) face.    The end faces often have indentations and other defects which block the rays.

Plenty also of horizontal column crystals to form a strong upper tangent arc and the supralateral and infralateral arcs.   The arcs are not as sharp as they might be and the simulation used crystals with a 1° standard deviation tilt.    Fuzzy arcs can result from less than perfect aerodynamic alignment but also from crystals with bubble inclusions or other flaws.

Just a few crystals (3%) were enough to generate the Parry arc.   The top image perhaps show a hint of the once very rare Parry supralateral arcs.    We see them more often nowadays on ski slopes where snow blowers generate perfect crystals. But for fully natural ones Antarctica is the place.

Halos and 2 South Poles

"Down here are 2 pole markers. The geographic pole (at left) is the actual bottom of the world. It's surveyed every year because the ice sheet we sit on moves [the poles also drift slightly relative to Earth's crust]. It moved about 15 feet from last year. This marker is redesigned every year by the previous winter crew (i.e. since I'm wintering this season, I'll be part of the design for the 2015 pole marker) and unveiled during a ceremony on Jan 1.

The striped barber shop looking pole with the orb on top (below) is the ceremonial pole and is surrounded by flags of the original signers of the Antarctic Treaty. Its an arbitrary marker that's great for pictures and public relations."