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Re: (meteorobs) Response to coloured meteors
At 02:23 AM 3/8/98 +1100, Adam wrote:
>
>Also to anyone on the list, what could be the cause of our potential
colour in a meteor train. I was guessing
>something in the atmosphere combined with something ablated in the meteor
process during its passage in the
>atmosphere. When the recombination effect takes place to produce the
train, if there was some chemical or
>molecule present could this explain it. Sorry, I'm just curious as this
is a gap in y knowledge and I can't
>find a reference to it anywhere. Plus as you've guessed my chemistry is
not so crash hot.
>
Hello Adam,
The below excerpt from the AMS FAQ on Meteors and Meteor Showers may help
to begin an answer to your enquiry. This was from my own research, and was
meant to answer the question on a rudimentary level. Someone like Ed
Majden can probably give us a more detailed explanation.
begin excerpt:
4. Where does a meteor's light and color come from? What is a meteor train?
The majority of light from a meteor radiates from a compact cloud of
gaseous atoms and molecules immediately surrounding the meteoroid or
closely trailing it. This cloud consists of a mixture of atoms and
molecules ablated from the meteoroid itself as well as from the surrounding
air. These excited particles will emit light at wavelengths characteristic
for each element/compound. The most common emission lines from meteors
originate from iron (Fe), oxygen (O), magnesium (Mg), sodium (Na), nitrogen
(N), and calcium (Ca). Less frequently seen are the emission lines of
hydrogen (H), Silicon (Si), Manganese (Mn), and Chromium (Cr).
While most meteors produce a wide blend of these emissions, giving the
meteor an overall white color, specifically colored meteors are often
reported by meteor observers. Usually, such colors are rather weak in
appearance; however, vivid colors are occasionally reported, especially
with fireballs. Reported colors range across the spectrum, from reds,
yellows, greens, and blues, to gold, orange, and (infrequently violet. The
velocity of the meteor also plays an important role, since a higher level
of kinetic energy will excite the atoms/molecules to a higher degree. Slow
meteors are often reported as red or orange, while fast meteors frequently
have a blue color. Due to the nearly identical composition and velocity of
meteors belonging to a particular shower, several showers are known for
their characteristically colored meteors.
Often, a brief glow will remain after the passage of the meteor. If this
glow persists for less than 0.5 seconds, it is called a wake. This residual
glow is caused by the same atoms which produced the original light from the
meteor, only at lower excitation energies.
If the glow from the meteor trail persists for a longer period, this is
called a meteor train. Trains are most often seen from fast, bright
meteors, in the altitude band from about 100 to 120 km (62 - 75 miles).
This type of train usually lasts about 1-2 seconds, and is primarily
generated by the green emissions of the neutral nitrogen atom. On very rare
occasions, a train may persist for several minutes, and will be observed to
change shape as the trail is blown by upper atmosphere winds. Such
persistent meteor trains provided scientists with their first data on winds
in this region.
end of excerpt.
The green color you reported matches with the neutral Nitrogen atom
emission mentioned above (although I don't know the exact wavelengths of
the most prominent line(s)).
Take care,
Jim
James Richardson
Graceville, Florida
richardson@digitalexp.com
Operations Manager / Radiometeor Project Coordinator
American Meteor Society (AMS)
http://www.serve.com/meteors/
References: