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Астронет: Астрономическая картинка дня Окологоризонтальная дуга над Огайо http://variable-stars.ru/db/msg/1470462/eng |
Credit & Copyright: Todd Sladoje
Explanation:
Why would clouds appear to be different colors?
The reason here is that ice crystals in distant cirrus clouds are acting like little
floating
prisms.
Sometimes known as a fire rainbow for its flame-like appearance, a
circumhorizon arc lies
parallel to the horizon.
For a circumhorizontal arc
to be visible,
the Sun must be at least 58 degrees high in a sky where
cirrus clouds are present.
Furthermore, the numerous, flat,
hexagonal ice-crystals
that compose the
cirrus cloud must be
aligned horizontally
to properly
refract sunlight in a collectively
similar manner.
Therefore, circumhorizontal arcs are quite unusual to
see.
This circumhorizon display was photographed through a
polarized
lens above
Dublin,
Ohio in 2009.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.