More sprites, as well as blue jets and elves

This lovely four-minute video was posted by NASA just today, and was found by reader Vera. It shows not only the red sprites described in the previous post, but also “blue jets” and “elves’. These “transient luminous events”, or TLEs, appear to be a mystery. They’re defined by weather.com as given below; they’re clearly very short electromagnetic events that are hard to study since they’re so quick:

Red sprites appear high in the atmosphere, usually 25 to 55 miles above thunderstorms, with tendril-like structures that extend downward as far as 25 miles. They usually are associated with positively charged cloud-to-ground lightning strikes.

Atmospheric researchers have discovered that sprites are common above the decaying portion of large mesoscale convective systems but are rare above supercell thunderstorms.

Sprites are thought to occur due to ionization of the upper atmosphere above terrestrial lightning strikes. When a positively charged lightning bolt strikes the ground, it leaves the top of the thunderstorm negatively charged. When enough electric potential builds up, a discharge results in the form of a red sprite.

It is possible to see red sprites with the naked eye, but special video and photography equipment, coupled with elevated observation stations, increase the likelihood of observing the beautiful scarlet flashes.

Blue jets are a visual phenomenon that propel upward from active thunderstorms. They can extend up to 12 miles from the top of the thundercloud, though they are not necessarily associated with a specific cloud-to-ground lightning strike. Atmospheric research indicates that blue jets only last one-tenth of a second, making them difficult to see with the naked eye. Scientists are still unsure as to what causes blue jets and how they form.

Elves are electromagnetic pulses generated by lightning strikes. Elves is an acronym for Emission of Light and Very Low Frequency Perturbations Due to Electromagnetic Pulse Sources. They look like doughnut-shaped flashes that spread laterally up to 186 miles. Atmospheric research indicates the brightness of elves is closely related to the peak current in a return lightning stroke (the movement of charges from the ground to the cloud), and that elves may be the most dominant type of TLEs in the atmosphere.

Clearly there are a number of mysteries about what’s going on, even in our own atmosphere, but what fun would science be if we understood everything?

17 Comments

  1. Posted October 10, 2017 at 5:42 pm | Permalink

    Fascinating!

  2. ThyroidPlanet
    Posted October 10, 2017 at 5:45 pm | Permalink

    I still don’t understand why they’re red – is it the gas composition up there? Evidently they’re not really comparable to lightning either .. so comparing the white/blue flash might be apples to oranges …

    • GBJames
      Posted October 10, 2017 at 5:52 pm | Permalink

      Yeah. Nitrogen, according to the previous post.

      • ThyroidPlanet
        Posted October 10, 2017 at 6:02 pm | Permalink

        What’s the % N2 up higher compared to where lightning appears?

        • gravelinspector-Aidan
          Posted October 10, 2017 at 6:17 pm | Permalink

          What’s the % N2 up high

          Close to the surface composition.

          I don’t know why the colour changes – I’m not sure if anyone does know. But it’s not gross atmospheric composition, TTBOMK.

          • David Harper
            Posted October 11, 2017 at 6:58 am | Permalink

            The colour change may be due to the change in density. Different electron energy level transitions are favoured at different densities, hence different wavelengths.

            • ThyroidPlanet
              Posted October 11, 2017 at 7:12 am | Permalink

              Huh! I did not know that!

            • gravelinspector-Aidan
              Posted October 12, 2017 at 4:54 pm | Permalink

              Plausible. I don’t know with any high degree of confidence.

    • gravelinspector-Aidan
      Posted October 10, 2017 at 6:14 pm | Permalink

      The atmosphere is pretty well mixed – same composition at sea level as well up into the upper stratosphere. There are minor variations like the few ppt (parts per thousand) of water vapour, which drops out as it freezes out, and the up to 50 ppm (parts per million) of ozone which is thermodynamically stable at low pressures, but destroyed by physical impacts at higher pressures.
      I routinely challenge gas analyst technicians who quote me (sea level) gas readings of 0.01ppm of methane in air as being important to show me their methane chromatograph peaks for sea level air at 1.8ppm. That’s an unfair question on my behalf because the 1.8ppm is a figure from Mauna Loa (and it changes through the year, and from year to year – like the CO2 figure) and you wouldn’t expect the same reading at sea level. Maybe 1.6ppm instead. But if someone is waving their machine’s output at you and claiming 0.1ppm as a significant value, you do have to take the wind out of their sails somehow. (Mea culpa – I once cranked up the settings on my chromatograph and thought I could see 0.5ppm sporadically, and reported it with photocopies of the chromatograms. It was probably the atmospheric methane. This was before I had internet access, and researching it involved waiting to my week off, a 600 mile drive home, and a walk down to the university library building to realise my error.)
      At the other end of the analytical scale, before doing tank entry (any tank), we equip each worker with personal CO and O2 monitors which high-alarm on CO at 0.1% and low-alarm on O2 at 18%, and get an annual calibration while I’d calibrate my GC daily.
      If that gives you a better idea on the fairly low levels of natural variation in atmosphere composition.

      • ThyroidPlanet
        Posted October 10, 2017 at 7:13 pm | Permalink

        Ice then plays a role

        Some frozen water up there, with dust maybe – the storms..

        • gravelinspector-Aidan
          Posted October 10, 2017 at 7:34 pm | Permalink

          There’s definitely water up there. One of the complexities of the depletion of stratospheric ozone is that it required not only ozone (obviously) and chlorofluorocarbons, but also ice crystal surfaces. Dust too is definitely up there, but only a very minor component.

      • Diane G.
        Posted October 12, 2017 at 1:14 am | Permalink

        (Mea culpa – I once cranked up the settings on my chromatograph and thought I could see 0.5ppm sporadically, and reported it with photocopies of the chromatograms. It was probably the atmospheric methane. This was before I had internet access, and researching it involved waiting to my week off, a 600 mile drive home, and a walk down to the university library building to realise my error.)

        Your secret is safe with me.

        • gravelinspector-Aidan
          Posted October 12, 2017 at 4:57 pm | Permalink

          Just because I’m not a research scientist, doesn’t mean that we didn’t have to work to the limits of our equipment.

          • Diane G.
            Posted October 13, 2017 at 2:13 am | Permalink

            Dunno, some of your posts about your doings sound awfully much like scientific research.

            At any rate, my comment was meant to be a slight joke at my expense, since most of the time you’re talking about doings that are so far beyond me I couldn’t begin to convey them to anyone else if my life depended on it. 😉

  3. Posted October 11, 2017 at 6:37 am | Permalink

    Well we now know that shipping lanes increase lightning strikes…
    http://onlinelibrary.wiley.com/doi/10.1002/2017GL074982/abstract

    • Diane G.
      Posted October 12, 2017 at 1:18 am | Permalink

      Wow, fascinating! And I love that there’s a “plain talk summary.” 😀

  4. Posted October 11, 2017 at 8:31 am | Permalink

    Very cool stuff, and I hope to see at least one of these phenomena during my lifetime

    One nit with the weather.com website: They make a common mistake by implying a level of precision when talking about how far elves spread out. They report that the doughnut-shaped flashes “…spread laterally up to 186 miles.” To see such a number reported to three significant digits is odd, unless you realize it was converted from 300km.


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