Several
atmospheric effects are formed by backward-scattering
refraction of
light while looking directly away from the sun. The particular optics that form these effects ensure that they are always centered around the head of the observer's cast shadow.
They are the heiligenschein, the dewbow, the glory, and the opposition effect.
A glory is a series of continuous spectral rings that spread outward a few degrees from the head of the observer's shadow.
To see a glory you must be facing the antisolar point, and have your shadow cast against a water vapor wall such as fog, mist, or clouds. Your shadow forms a spectre of the Brocken, and around the head of your shadow you may see a glory. From a plane, where glories are commonly seen, the spectre may disappear altogether as the umbra converges to nothing.
As with a rainbow and aureole, blues are towards the inside of the glory and continue in the rainbow spectrum order outwards. As fog is rarely still and flat, the glory will seem to move, grow, and shrink of its own accord, even if you are standing still. Because the fog is a volume, the refractions appear quite deep and rich.
The radius of the effect is inversely proportional to water droplet size. The largest droplet size that can support a glory is around .025 m, which produces a radius of about 5°. Droplets of .0096 m form three complete concentrentric spectral rings with a maximum radius of 20°.
Interestingly, though most of the atmospheric effects can be accurately explained and modeled with ray path formulas and scattering theories, no such formula accurately predicts and explains the appearance of glories.
Sources
- http://amsglossary.allenpress.com/glossary/search?p=1&query=glory
- http://www.meteoros.de/glorie/gloriee.htm
- http://www.sundog.clara.co.uk/droplets/glofeat.htm
- http://www.du.edu/~jcalvert/astro/glory.htm