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    Rights: University of Waikato
    Published 29 April 2014 Referencing Hub media


    Craig Rodger

    We used to think we understood lightning, and to some extent, we do understand lightning, but relatively recently, we’ve started to realise that there are a whole lot of things going on in the lightning discharge process that we don’t know about, and one example is anti-matter production in lightning.

    But another example is that we think of lightning as being something that happens in the thunderstorm and goes down to the ground or possibly is a flash inside the thunderstorm itself. We’ve started to realise that there’s also upward lightning – lightning that’s occurring at very high altitudes – and there’s a whole lot of different variants of this upward lightning, and they have nice exotic names.

    The first one that we discovered was called a red sprite. You could call it upward-going lightning, but when we first discovered red sprites, these pulses – big flashes of pink in the sky high above thunderstorms – they weren’t sure what they were. And rather than calling them upward lightning, which says you understand what they are immediately, the suggestion was made by a researcher from Alaska that we should give it a sort of meaningless name while we went away and tried to work out what they actually were.

    And he had just recently watched a Shakespearean play where there were sprites as characters, and he thought this was a lovely name. And the sprites are sort of pinkish-reddish colour, and so we call them red sprites.

    And they now have – let’s call them friends – there’s other varieties of upward lightning like jets, elves. Somebody has put forward the idea of a troll, but that name hasn’t taken off yet. Essentially, they’re varieties of high-altitude lightning. They tend to be bigger than the low-altitude lightning that we’re used to, but that’s really just a consequence of the fact that the density of the atmosphere up there is much lower.

    There is essentially a one-to-one relationship between lightning and red sprites. A powerful lightning discharge can produce a red sprite.

    And as far as we can tell, you always need lightning to produce a red sprite.

    Associate Professor Craig Rodger, University of Otago, Department of Physics
    NASA Goddard Space Flight Center
    Night-time thunderstorm footage courtesy Nathan Boor, Aimed Research, Creative Commons 3.0 license
    Lightning over rainy streets courtesy of Sterling Coffey Creative Commons 3.0 license
    A Midsummer Night’s Dreampaintings by Arthur Rackham (1867–1939)
    Diagram of blue jets and ELVE, courtesy of Abestrobi Creative Commons 3.0 license