When I see meteors flash across the night sky, they always appear generally as streaks of white light. However, bright meteors leave a trail in the sky. It persists long enough that it's obviously not just an afterimage in the retina, it's a real, visible trail of plasma left in the wake of the meteor.

Whenever I see this phenomenon, the meteor trail looks greenish to me -- greenish with a slight yellowish tinge.

Does anyone know if that's the true color of the plasma, or is it a color trick played by the mind because of the retina's lack of color receptors at such a low light level? Or does it have more to do with the wavelengths of light scattered by the atmosphere -- maybe it's really a golden light, that gets scattered towards blue in its trip through the troposphere?

Anyone have any thoughts?

-the other Doug

I do not know the exact reply to your question, but plasma have not a black body emission. They emit rays at various frequencies which relative intensity (and thus its color) may change drastically with temperature, pressure, composition, trace elements, etc. So do not be asonished by these hues.

Also the phenomenon is usually so short, and it is a clear little thing into a black background, that it can easily trick the eye. But I do not know in what extent.

Green is good - it's the same green as you get in auroral discharges: it's the emission of photons from atomic oxygen, here plasmarised by the heat and friction of a passing meteor, and not by high speed charged particles as in aurorae.

Andy G

Years ago, on a cold maybe 20 degree night, I was crossing a footbridge across the creek on our property, watching my footing, when a very slow flashbulb went ....F....L...A...S...H... overhead, lighting up the ground and everything around me like a nearly full moon..

I looked up and within maybe 30 degrees of the zenity, I spotted a bright glowing meteor trail, which faded "zip" from one end to the outher end in about 1/2 second. A second later, all that was left was a glowing phosphorescent line, which slowly faded, drifted across the sky and turned into a curling rope over the next ?10? min or so.

I did NOT see the meteor itself. What I saw was a fast phosphorescence with a very short decay time, followed by a much longer lived fainter posphorescence. I've seen two bolides as well, but this in some ways was the most impressive meteor event I've seen so far.

Oh... One meteor I *DIDN'T* see.. in 1972, my body was some 60 or 70 kilometers from an asteroid. I was vacationing in Yellowstone when the great grazing fireball of '72 entered the atmosphere over NM, made sonic booms over Montana, and exited the atmosphere over Alberta or Saskatachawan. We were under spot showers and may not have been able to see it even if we'd been looking in the right direction at the right time. Grrrrrrr.

The physical size of meteor trail is a suprise. Assuming a width of 5 arc-minutes and a height of 70 miles, the width of a meteor trail is over 500 feet. Not a bad chunk of plasma.

--Bill

of course by friction you mean ram pressure

Oops...of course I do. :-)

...and especially for meteors that are part of the Arietides. ;-)

Andy G