|Prairie Rainbow seen by Alan Clark south of Calgary, Alberta, Canada. ŠAlan Clark.|
|"We were driving alongside a large and developing
thunderstorm in the early evening when sections of a rainbow
appeared and disappeared as both the storm and ourselves moved to place
different portions of the rain clouds in the correct position for rainbows
Local sections of the cloud produced rays within this region to produce these interesting patterns. The changing appearance of this spectacular cartwheel pattern was reminiscent of auroral changes, though less rapid and ephemeral and of course, much brighter and with different colour bands. Of particular interest is the extent of the brighter regions, though these are the "normal" appearance, with the dark regions being the intruders on the normal rainbow."
The 'rays' are regions where bright sunlight is illuminating part of the rainbow cone. They are actually parallel beams but perspective makes them appear to converge towards the antisolar point.
They behave like anti-crepuscular rays. They mark the path where raindrops are refracting and reflecting light towards the eye.