Friday, February 25, 2011

My shadow, my fog bow, my aura

My shadow, my fog bow, my aura, originally uploaded by ystenes.

While walking in the Sykkylven mountains with a beautiful autumn sun behind, a cloud raised up in front of me, and I saw the shadow of my head within a halo.

I have seen such haloes several times surrounding the shadow of an aeroplane, but I had never seen anything like this before. I was puzzeled and experimented with the situation. Here I have found a place where I could create a shadow of my whole body. I have spread my legs, and you can se a slight shadow of my lifted right arm.

There is partly sunlit grass in the foreground, in the background another hill and the fjord further behind.

I always regarded this as a rainbow phenomenon, but learned today that it is a different phenomenon based on Mie scattering and not refraction and reflection. I found this explanation on internet ( ).

"How about fog bows? Yes, fog bows, also known as fog dogs, cloud bows or white rainbows, can be observed on occasion. But even when one has formed, it may go unnoticed, since fog dogs are generally bereft of color. Whereas rain drops may be 0.5 mm in diameter, fog droplets are typically less than 1/10 this diameter. If you happen to see such a bow, you may notice that it's broader than a rainbow (rainbows cover about 2 degrees of the sky or about 4 times the width of the Sun or Moon), and there may be an orange tint on the outer portion of the bow. Actually, fog bows are caused by a diffraction of light rather than refraction and reflection. Because the fog droplets are so tiny, the wavelengths of visible light, which are obvious in the larger drops producing the rainbow, interfere with each other. The result is color bands that overlap. As the droplets get smaller, the interference is even greater, and the light that emerges is completely colorless. As with rainbows, in order to see a fog bow, you need to look in the opposite direction of the Sun."

Vassfjellet, Sykkylven, Sunnmøre, Norge/Norway.

Enhanced contrast in Picnik.

A larger view, unmodified, is seen here:

January 2010 this photo was in second place of d90 photos on flickr.

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