Colorful Arcs over Buenos Aires
Explanation:
What are those colorful arcs in the sky?
Like
rainbows that are caused by rain, arcs of sunlight
broken up into
component colors
can also result when ice crystals floating in
Earth's atmosphere
act together as a gigantic
prism.
The top color arc is more typical as it is part of the
22 degree halo surrounding the Sun when
hexagonal ice crystals
refract sunlight between two of the six sides.
More unusual, though, is the bottom color arc.
Sometimes called a fire rainbow, this
circumhorizon arc
is also created by ice, not fire nor even rain.
Here, a series of horizontal, thin,
flat ice crystals in
high cirrus clouds
refract sunlight between the top and bottom faces toward the
observer.
These
arcs only occur when the Sun is
higher than 58 degrees above the horizon.
The featured sky occurred to the northwest in the early afternoon last month over
a street Diagonal of
La Plata City,
Buenos Aires,
Argentina.
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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.
