

The Physics of a Fighter Jet Rainbow - eduardoflores
http://scienceblogs.com/startswithabang/2010/09/the_physics_of_a_fighter_jet_r.php

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yread
Nice picture and explanation, but probably wrong. I'm with the commenter
Steffen here:

 _The shot is probably taken from the ground and during a (relatively) slow
maneuver where the aircraft pulls hard up, causing the flow of air to become
almost perpendicular to the alignment of the wings, which will cause said
large pocket of low pressure which rapidly is equalized causing condensation
of the water vapor in the air._

You can see a similar (very) low speed condensation effect here

[http://www.airliners.net/photo/Air-
France/Boeing-777-228-ER/...](http://www.airliners.net/photo/Air-
France/Boeing-777-228-ER/0981791/&sid=306820fc2c6a8a3183a42afae56afb8f)

here with a fighter jet but also low speed and high angle of attack

[http://www.airliners.net/photo/USA---Air/McDonnell-
Douglas-F...](http://www.airliners.net/photo/USA---Air/McDonnell-
Douglas-F-15E/1130381/&sid=306820fc2c6a8a3183a42afae56afb8f)

and this is rather extreme example of the same thing

[http://www.airliners.net/photo/Russia---Air/Sukhoi-
Su-30.../...](http://www.airliners.net/photo/Russia---Air/Sukhoi-
Su-30.../1631566/)

and here is a similar rainbow effect, but behind an A340 which surely isn't
supersonic.

[http://www.airliners.net/photo/Virgin-Atlantic-
Airways/Airbu...](http://www.airliners.net/photo/Virgin-Atlantic-
Airways/Airbus-A340-642/1088680/&sid=306820fc2c6a8a3183a42afae56afb8f)

Another factor which makes super sonic flight unlikely is that the
photographer had to wait for the moment when the sun is behind the aircraft
which would be very difficult to do if it was flying that fast.

edit: oh and apparently it is called
<http://en.wikipedia.org/wiki/Prandtl–Glauert_singularity>

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demallien
Hmmmm, you raise some interesting points. That said, I agree with Ethan that
the rainbow in question is a Fire Rainbow. I had never seen one in real life
until just recently, but I have seen several in the sky over Paris this
summer, and they have the same distinctive colour distribution. Having had the
opportunity to see a few, I can tell you that although it is true that the sun
needs to be behind the aircraft, the definition of behind is very loose indeed
- typically the fire rainbows that I have seen are about a quarter of the sky
away from the sun itself (I'm starting to wonder if it's actually 46° away,
having read Ethan's explanation), so there is a large expanse of sky where
this effect could be seen.

I agree that this is a low-speed manoeuvre though, and not an example of a
transonic cloud - have a look at this photo from RAAF Amberley earlier this
year:
[http://www.defence.gov.au/media/download/2010/Jun/20100607/2...](http://www.defence.gov.au/media/download/2010/Jun/20100607/20100603raaf8490713_0040.jpg)
\- it has the same cloud structure as the F22 photo.

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ursablanco
That it's being viewed through a polarized filter is key. If you were to view
this unaided, you wouldn't perceive the colours.

My guess is that this caused by internal reflections in a slew of similarly
sized water droplets. Much like a rainbow, except that this is backlit.

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pencil
ok people ..can someone tell me what is that circular "thing" that surrounds
the aircraft as the plane crosses the sound barrier? is that moisture or
something? if yes how does it occur? an explanation on this would would really
fulfill my curiosity.

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heresy
Here we go: <http://en.wikipedia.org/wiki/Prandtl-Glauert_Singularity>

