Brocken Spectre [1]

Weather Online.co.uk - 3/14/13

The Brocken spectre (or Brocken bow) is an apparently greatly magnified shadow of an observer cast against mist or cloud below the level of a summit or ridge and surrounded by rainbow coloured fringes resulting from the diffraction of light. The effect is an illusion. Depth perception is altered by the mist [2], causing the shadow to appear more distant and to be interpreted as larger than normally expected.

Actually the Brocken Spectre is what meteorologists call a glory [3]. Most air travellers have already observed glories. They are most easily seen when one is riding on the shadow side of an aircraft above the clouds. 

For more detais click: Brocken Spectre [4]