[neilep (OP)]

This is question good for Paul...He's a cloud master !!


..But please do chip in if  ewe also know the answers !



See these clouds ?

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Nice eh ?....being delivered Tuesday !


But what makes these clouds so special that they should shine so bright at night !!.....?..these pictures (I believe) are not the crack of dawn or dusk...they are bona fide night time piccys !!

So, what's going on ?

Thanks


neil
A Cloud With Legs

[LeeE]

They're noctilucent clouds.

http://en.wikipedia.org/wiki/Noctilucent_cloud

[paul.fr]

Lee is correct, they are noctilucent clouds. The second image is pretty much the standard one you will find in books and on websites.

One of the fascinating things about these clouds is that they are not totally understood, two of the hypotheses of how they come about are that they are seeded from meteorite debris or from the constituent elements of the space shuttels exhaust fumes!

Another interesting fact is that clouds on mars have been found to be very similar to noctilucents here on earth...ooooh

[neilep (OP)]

They're noctilucent clouds.

http://en.wikipedia.org/wiki/Noctilucent_cloud

Thank Ewe LeeE !

Noctilucent !!....not the kind of name that rolls off the tongue so easily !!

85 km up !!!..Oh My !!

Thank ewe for the link !!

[neilep (OP)]

Lee is correct, they are noctilucent clouds. The second image is pretty much the standard one you will find in books and on websites.

One of the fascinating things about these clouds is that they are not totally understood, two of the hypotheses of how they come about are that they are seeded from meteorite debris or from the constituent elements of the space shuttels exhaust fumes!

Another interesting fact is that clouds on mars have been found to be very similar to noctilucents here on earth...ooooh

Thank Ewe Paul.......those are wonderful hypotheses.....crikey !!..I had no idea that the shuttle also orbits Mars  []

Thank ewe for the fascinating information.

[chris]

I think air traffic in general, rather than just space ships, can contribute to this phenomenon.

Chris

[LeeE]

Civilian air traffic rarely exceeds 40,000ft - just over 12000 m - so there's about another 70+ km in altitude to account for.  Very high-flying aircraft such as the SR-71 could get up to around 25-30 km though, and could exceed that by a fair margin in a (totally impractical) 'zoom-climb'.

[RD]

NASA video on noctilucent clouds ...
http://uk.youtube.com/watch?v=-xF2vSKINK0
love that acappella  []

[Alandriel]

I've never heard of this before. Thanks guys - this is WONDERFUL stuff !

 []

[Karen W.]

ALANDRIEL!!!!!!! YAYYYYYYYYYYYYYYYY! How are you and what have you been doing?
Welcome back.. it is a cool subject.. I also had not heard of them until Neils Post!

[Alandriel]

ALANDRIEL!!!!!!! YAYYYYYYYYYYYYYYYY! How are you and what have you been doing?
Welcome back.. it is a cool subject.. I also had not heard of them until Neils Post!

Hello Karen, nice that you still remember me…..

I’m ok. Took a long sabbatical from a lot of things but it seems that this place
still holds way too many nice people for me to totally stay away. What got me back here

hmmm, but no! Let’s take this some place else and not disrupt this lovely cloud thread with unrelated trivia.



Instead..... some more pretty noctilucent clouds

[Karen W.]

This last picture is particularly beauiful!

Are noctilucent clouds more common in certain areas of the world or are they likely to be found anywhere? Whoops never mind  Lee answerd that with the wiki link......I forgot.... [:I] [:I]

[paul.fr]

There is, of course, a second class of night shining clouds..Nacreous clouds.
http://www.atoptics.co.uk/highsky/nacr1.htm

[Alandriel]

There is, of course, a second class of night shining clouds..Nacreous clouds.
http://www.atoptics.co.uk/highsky/nacr1.htm

and quote from that link Paul posted: <<Nacreous clouds, sometimes called mother-of-pearl clouds, are rare but once seen are never forgotten>>

They are  g o r g e o u s !!!!  Unbelievably beautiful. What would I give to actually see those in real life.....

Thanks for sharing Paul  []

[Karen W.]

There is, of course, a second class of night shining clouds..Nacreous clouds.
http://www.atoptics.co.uk/highsky/nacr1.htm

Shes right Paul.. they are quite beautiful... what a treat!

[paul.fr]

Alandriel (nice to see you back) and Karen, all clouds are beautiful my favourite are these;

Kelvin-Helmholtz wave clouds

[SkepticSam]

Update on 23 September: The dust released in the CARE experiment scattered sunlight, creating a bright cloud that could be seen at visible wavelengths for several minutes before it dispersed. The cloud's effects on the ionosphere lingered longer, however, and were detected by radar for about four hours after the dust's release. Researchers are still analysing the data and expect to know more about the results in the coming weeks. Watch a video of the cloud

See a gallery of noctilucent clouds

The study of Earth's mysterious noctilucent clouds got a boost on Saturday, when a rocket was launched to create an artificial cloud at the edge of space.

"Noctilucent", or night-shining, clouds float dozens of kilometres higher than other clouds, at an altitude of about 80 kilometres. Because of their height, they can be seen glowing before sunrise or after sunset as the sun illuminates them from below the horizon.

The clouds were first observed above polar regions in 1885 – suggesting they may have been caused by the eruption of Krakatoa two years before. But in recent years they have spread to latitudes as low as 40°, while also growing in number and getting brighter – a change that some attribute to global warming.

The ice-covered particles in these clouds are commonly thought to get their start as tiny dust particles that had been sloughed off comets and meteoroids. See a gallery of noctilucent clouds

These particles build up a charge as they are bombarded by fast-moving electrons and ions. Since charged particles reflect radio waves, they are good candidates for radar studies, which could help measure the dust at an early stage in the clouds' formation. But the radar data is hard to interpret.

To get a better sense of how high-flying dust reflects radio waves, researchers launched the Charged Aerosol Release Experiment (CARE) at 2346 GMT on Saturday from NASA's Wallops Flight Facility in Virginia. The experiment, which blasted off on a Black Brant XII suborbital sounding rocket, spewed more than 100 kilograms of aluminium oxide into the atmosphere at an altitude of about 280 km.

Radar scatter
A combination of ground- and space-based instruments will watch this cloud for days and perhaps months as its particles become charged, sink, and disperse. Laser pulses will be used to measure the density of the particles in the cloud. These will be compared with radar measurements of the plume.

"Our primary science goal is to understand [how] radar [scatters] from a dusty plasma," says CARE's principal investigator, Paul Bernhardt of the Naval Research Laboratory in Washington, DC. "We want to understand what kind of information you get back when you send out radar pulses."

Radar has been used to examine icy dust that hovers some 90 km above the Earth and can grow to become the ice particles inside noctilucent clouds, says Scott Bailey of Virginia Tech in Blacksburg. He is a lead scientist for NASA's Aeronomy of Ice in the Mesosphere spacecraft, which launched in 2007 to study noctilucent clouds.

Controlled experiment
But at the moment, interpreting radar measurements of these proto-cloud particles is difficult. Although they reflect radar brightly, it is difficult to say how large the particles are or how many there might be, Bailey says.

Studying an artificial cloud created in a controlled manner could help resolve these uncertainties. "If the radar could be used to say exactly what the population of particles is up there that the ice is forming around, that would be a major step forward," Bailey told New Scientist.

The CARE experiment could also pave the way for future launches that would use the uppermost part of Earth's atmosphere as a large physics laboratory for studying charged dust, Bernhardt says. Dusty plasmas, like those that will be created in the CARE experiment, are seen in a range of environments, from Saturn's rings and comet tails to the dust hovering above the lunar surface.

http://www.newscientist.com/article/dn17822-artificial-cloud-created-at-the-edge-of-space.html