Colors of lightning

Discussion in 'Earth Science' started by curioucity, Dec 10, 2004.

  1. curioucity Unbelievable and odd Registered Senior Member

    Hi all

    I think you can guess what I'll ask judging from the title. Okay. I just saw a show of lightnings when it was raining a few hours ago, and I remembered something. What causes lightning to have different colors? I myself have seen bluish white, purplish and yellow lightnings, so I wonder...

    Thanks for answers ^_^
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  3. Ophiolite Valued Senior Member

    This response is straight off the top of my head, so may well be rubbish.
    The colour of any radiating body, including a lightning bolt, is determined by its temperature. We know that lightning bolts are extremely hot - hotter than the surface of the sun, as the documentary writers like to tell us. I think the bluish-white light you see is the 'native' colour of lightning.
    The purplish and yellow lightnings I think could be caused by one, or both, of two other factors, one internal, one external.
    External: if the lightning is seen partly through cloud or rain we would expect the colour to be altered.
    Internal: the sudden bright flash will leave after images on the retina, that will likely have a different colour from the triggering flash.
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  5. Shenzhou Shameless Reductionist Registered Senior Member

    The colour is determined by the moisture content of the atmosphere, I seem to remember reading once. I think it's purple/pink when it occurs in a heavily water-laden environment. I'm buggered if I know why though. Sorry.
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  7. Shenzhou Shameless Reductionist Registered Senior Member

    Here we are. This is from NewScientist's 'Last Word' section:

    "A lightning plasma is quite dense, because the degree of ionisation in the air near the lightning is high. It therefore gives off a lot of infrared, visible light and ultraviolet. A lightning flash consists mainly of light emitted at all wavelengths, plus line and band emissions at characteristic wavelengths from the atoms and molecules present in the surrounding air * mostly argon, oxygen, nitrogen and water. The lightning we see contains contributions from all these sources and the colour depends on the kind of atoms in the air.

    "A discharge in dry air looks white because there are few strong visible lines those which exist are mainly blue and violet * and the bulk of the visible light is emitted in a continuous spectrum. If water vapour is present, then the hydrogen atoms in the water create a very strong red line (known as the Balmer alpha line) that can dominate the visible line emission. If this line is superimposed on the white background created by the other atoms in the plasma, it would explain the reddish appearance of some lightning flashes. The reddish colour will be easier to see at night. The variability in the amount of red in a series of lightning flashes is explained by variations in the amount of water in the air. In addition, water vapour or tiny water droplets are more easily ionised and their hydrogen atoms more easily excited than the hydrogen in large water droplets * the latter must first evaporate, which takes longer than the duration of a single flash. It is possible that large droplets were broken up during the long series of localised flashes reported by your correspondent, thereby creating an exceptional redness."
  8. curioucity Unbelievable and odd Registered Senior Member

    Thank you.
    Oddly enough, I myself have never really seen red lightnings, which I should be wondering about since I've often seen lightnings during heavy rains, but then again, I must remember that distance matters... it may be raining where I am, but who knows whether it's also wet where the bolts occur.....
    I also forgot to mention that I very very rarely see yellow lightnings, in fact, I've seen it only once in my life, even that was years ago... So, would you please help me find whether scientists have ever made any data gathering on lightning colors?

    Once again, thanks.
  9. slotty Colostomy-its not my bag Registered Senior Member

    I posted a thread about mega- lightning, it seems to be neon red and blue, they seem to think its the similar action to the northern lights

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