Bishops Ring, New Zealand
Stefan Krivan at Manawatu, New Zealand after the volcanic eruption in the Puyehue-Cordon Caulle chain in Chile June '11. ©Stefan Krivan, shown with permission
The ash and sulfate aerosol from the volcano quickly circulated the Southern Hemisphere's stratosphere.
Dust and aerosol scatter sunlight and here they created a 'Bishop's Ring', a large aureole or inner corona around the sun. The ring has characteristic straw to red hues at its rim.
The Bishops Ring is much larger than the normal corona produced by the scattering of water droplets in clouds. Coronae and aureoles are diffraction phenomena and their sizes depend inversely on the size of the scatterer, the smaller the particle the larger the aureole.
See the next OPOD for an unusual particle free sky.