|Lowitz Arc at Yosemite
Matthew Walker of New Zealand captured this magnificent rare halo display over the High Sierra near May Lake at Yosemite, California - November 4, 2010. A sharp and clear upper Lowitz arc curves upwards from the 22° halo, crosses a tangent arc and touches an upper suncave Parry arc. ©Matthew Walker, shown with permission.
Lowitz arcs were first recorded at St Petersburg, Russia in 1790. From then on their very existence was argued about because they were rarely observed with any clarity and they were not finally photographed until about two decades ago.
Another possibility is that the upper arc was produced by column crystals rocking back and forth about a Lowitz axis from a horizontal Parry orientation position.