South Pole Corona

        Image Index 

A solar corona shines over the wastes of the South Pole. Imaged by Marko Riikonen (site) on 1st February 1999. Marko says "The temperature earlier on that day was -31.5 C on the ground. But at the corona cloud level it's warmer. and well above the temperature for homogeneous nucleation." So the corona was probably produced by supercooled water droplets. Image ©1999 Marko Riikonen, reproduced with permission.