New findings on sprite formation above thunderstorms

Florida Tech lightning research deepens understanding of sprite formation – link specific atmospheric conditions to exuberant, luminous displays above thunderstorms

From the FLORIDA INSTITUTE OF TECHNOLOGY

A sprite as captured in this pseudo-color, composite photo recorded from an aircraft by a high-speed, high-sensitivity camera. CREDIT Florida Institute of Technology

A sprite as captured in this pseudo-color, composite photo recorded from an aircraft by a high-speed, high-sensitivity camera. CREDIT Florida Institute of Technology

MELBOURNE, FLA. — A new study led by Florida Institute of Technology Professor Ningyu Liu has improved our understanding of a curious luminous phenomenon that happens 25 to 50 miles above thunderstorms.

These spectacular phenomena, called sprites, are fireworks-like electrical discharges, sometimes preceded by halos of light, in earth’s upper atmosphere. It has been long thought that atmospheric gravity waves play an important role in the initiation of sprites but no previous studies, until this team’s recent findings, provided convincing arguments to support that idea.

The research, published in the June 29 issue of Nature Communications, includes comprehensive computer-simulation results from a novel sprite initiation model and dramatic images of a sprite event, and provides a clearer understanding of the atmospheric mechanisms that lead to sprite formation.

Understanding the conditions of sprite formation is important, in part, because they can interfere with or disrupt long-range communication signals by changing the electrical properties of the lower ionosphere.

Predicted by Nobel laureate C. T. R. Wilson in 1924 but not discovered until 1989, sprites are triggered by intense cloud-to-ground lightning strokes. They typically last a few to tens of milliseconds; they are bright enough to be seen with dark-adapted naked eyes at night; and only the most powerful lightning strokes can cause them.

The study, conducted by Liu, a Florida Tech professor of physics and space sciences, and collaborators Joseph Dwyer, a former professor at Florida Tech now at University of New Hampshire, Hans Stenbaek-Nielsen from University of Alaska Fairbanks, and Matthew McHarg from the United States Air Force Academy, investigated how sprites are initiated.

According to Liu, the perturbations in the upper atmosphere created by atmospheric gravity waves can grow in the electric field produced by lightning and eventually lead to sprites.

“Perturbations with small size and large amplitude are best for initiating sprites,” Liu said. “If the size of the perturbation is too large, sprite initiation is impossible; if the magnitude of the perturbation is small, it requires a relatively long time for sprites to be initiated.”

To validate their model, the team analyzed a sprite event captured simultaneously by high-speed, high-sensitivity cameras on two aircraft during an observation mission sponsored by the Japanese broadcasting corporation NHK. The high-speed images show that a relatively long-lasting sprite halo preceded the fast initiation of sprite elements, exactly as predicted by the model.

Hamid Rassoul, an atmospheric physicist and the dean of Florida Tech’s College of Science, said the findings will be critical to future researchers.

“They will allow scientists to study not only sprites but also the mesospheric perturbations, which are difficult, if not impossible, to observe,” he said.

Liu added, “Our findings also suggest that small, dim glows in the upper atmosphere may be frequently caused by intense lightning but elude the detection. There may be many interesting phenomena waiting for discovery with more sensitive imaging systems.”

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More on the study can be found at the Nature Communications website http://www.nature.com/ncomms/2015/150629/ncomms8540/full/ncomms8540.html.

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63 thoughts on “New findings on sprite formation above thunderstorms

  1. A Watts says “Predicted by Nobel laureate C. T. R. Wilson in 1924 but not discovered until 1989”
    It took 61 years for this genius to have some of his work validated. I bet there was a chorus of old stick-in-the-mud monolith science practitioners who scoffed at him and his “unproven” ideas, none of whom we remember.
    Also, I like the common usage of the term “sprite” to refer to the lightning. Sprite is from the French word – espris, meaning spirit. Science often borrows words, when it has none to offer for new things. This one seems appropriate and charming.

    • Actually, ‘sprite’ comes from the Latin spirius.
      The word was adopted into Celtic, as many Latin words were since the 1st century, and it has been used for centuries in Celtic literature to describe faries and elves. And I imagine that the meteorological description came from the Celtic usage, rather than the Latin or French.
      Ralph

      • Silver ralph,
        You peeked my curiosity so I consulted my own OED (hardcopy volumes) and an online reference to the OED etymology.
        He is a close reference:
        http://www.etymonline.com/index.php?term=spirit
        “According to Barnhart and OED, [spirit] originally in English mainly from passages in Vulgate, where the Latin word translates Greek pneuma and Hebrew ruah. Distinction between “soul” and “spirit” (as “seat of emotions”) became current in Christian terminology (such as Greek psykhe vs. pneuma, Latin anima vs. spiritus) but “is without significance for earlier periods” [Buck]. Latin spiritus, usually in classical Latin “breath,” replaces animus in the sense “spirit” in the imperial period and appears in Christian writings as the usual equivalent of Greek pneuma. Spirit-rapping is from 1852.”
        I have not yet found the initial usage (sprite) in meteorological parlance…before 1989 though and after 1927.

      • RWTuner,
        Hmmm wikipedia is so notoriously unreliable. Even so, wiki is confined to use known reliable, documented sources if it uses any at all. The sole wiki source for “Sprite” is Katherine Briggs (1976). The OED source I used was the OED originally compiled in ~1844, and it cites the Vulgate written in 382 AD with the commissioned version in 1500’s.
        Spiritus existed in latin for +2000 years and was documented and in common use long before a similar word was recorded by the Celts et al. Possibly, the celts had a word, but the wiki article has no source from them rather a vague assertion from this Katherine Briggs, who wrote English folklore and fiction about fairies and the like in the 1970s.
        Quaint, but she was writing in the 1960s and 1970s. Spiritus was in use by scholars more than 2000 years ago. As you may know, they brought their language and writing to Britain in the 1st century. The Celts my have picked up a few things from the Romans.

      • And HOBGOBLIN – perchance.
        Puck in ‘A Mid-summer Night’s Dream’.
        Or Kipling’s ‘Puck of Pook’s Hill’;
        jolly similar to sprites, I suggest.
        Kudos to the Floridians, though!
        Auto

      • auto,
        There are a number of mythical creatures that are somewhat the same as “Sprite” with a whole host of attributes good and bad and all over the literature. But the actual use of the noun Sprite has a vague etymology wrt fairy-like creatures. Sprite, as a disembodied spirit or ghost or live breath or soul has a long, even ancient, etymology. As a fairy? Sprite is connected to a fiction written by Katherine Briggs in 1976 Encyclopedia of Fairies etc.
        If anyone can find an earlier reference to “Sprite” as a creature, Celt of otherwise, other than Briggs, I would like to know. Happy hunting!

      • Usage? Lsvaalgard is likely to be quite spritely (sprite-like); I’m getting that way myself.

      • The Spenser Encyclopaedia cites 16th century usage of the term ‘sprite’, as being cognate with ‘spirit’.
        The Spenser Encyclopedia
        By Albert Charles Hamilton

    • I remember seeing a plot (map) in a mid -1980’s issue of QST correlating large scale thunderstorm activity with sporadic E layer propagation at 50 MHz and above. The plot consisted of the paths of contacts made via sporadic E layer propagation overlaid on a weather map for the time the contacts were made. The QST article immediately came to mind when I first read about the sprites – the sprites being an obvious source of the intense ionization in the E layer.

  2. a WAG and computer game deepens our understanding of something….
    How do you design a computer game…..without understanding what it’s supposed to be based on?
    …and if that’s so, you don’t need the computer game in the first place

  3. …According to Liu, the perturbations in the upper atmosphere created by atmospheric gravity waves can grow in the electric field produced by lightning and eventually lead to sprites….
    Obligatory last paragraph of paper:
    “Of course, all this research is in full agreement with CAWG theory, and does not detract from it in any way.”
    Thank you. Can I have my grant cheque now?

    • DG – YEAH, you are perhaps completely correct. This is the kind of obligatory statement in papers that enabled one survey to conclude that X% or all papers agree with CAGW. If you take away the ones that have such statements in the last paragraph (and not anywhere in the papers), the numbers would come down significantly, IMHO.

  4. The gravity wave part of the conclusions seems strange to me. We build multi- billionare dollar long baseline laser interferometers to detect gravity waves coming from many millions of light years away, generated by revolvong pairs of neutron stars, and we yet to have any confirmed detection. Yet these sprite formations depend on a mechanism of terrestrial atmospheric gravity waves? What am I missing?

    • joelobryan,
      In fluid mechanics, a gravity wave is a wave for which the restoring force is gravity, such as the waves on the surface of a body of water. The relativistic gravity waves are a very different thing (waves in the space-time continuum?).

    • I don’t think you are missing anything. The gravity wave thesis is probably pulled from thin air. Sprites have also been hypothesized as being caused by Birkeland currents from the magnetosphere. Ultimately derived from plasma currents between the sun (solar wind) and the heliosphere. These currents interconnect all the planets. There is far more evidence for this kind of mechanism than gravity waves.
      His model may fit the data but that does not assure the hypothesis is correct. Nothing can do that. Hypotheses are matters of judgement which depend on experience. Experience with qualitative and quantitative data and hypotheses not immediately relevant to modeling are accessed, perhaps, unconsciously. Judgement suggests that gravity waves as an explanation is highly suspect.

      • So, gravity waves are simply waves on the top of the atmosphere? That seems like a totally bogus and imprecise and misleading phrase. Atmospheric ripples” if you ask me. I am glad to know exactly what this term means, but I disagree with even USING the term “gravity” in it.
        The term says NOTHING about the atmosphere, which is what it is about. OF COURSE such waves are associated with gravity, but so are water waves (apparently). And if water waves are included. . .
        Does it even say WHICH atmospheric layers it is associated with? Any and all layers? Or just the top? And if only the top, then ‘top’ as defined how?

      • JW – I am in agreement with you about about the gravity wave assertion being highly suspect. One, this is a model, and two, the connection seems strained and pre-concluded.
        I am always reminded of the Libyan Desert Glass, for which there are at least five different hypotheses (six, if memory serves). ALL of them are by reputable scientists, and if one is correct, then the other four or five must be mostly incorrect. I’ve seen people quote one of them or the other and they (and perhaps their readers, too) think they have the whole story. NONE of them covers all the bases. This one is one among many future hypotheses. My money is against it.

    • thanks to all. now I understand the semantics involved in the term used in this context.
      Seems logical to me that the troughs in the meso sphere allow for an easier pathway for ionization, and breakdown of an insulating barrier between the E layer and the charged cloud tops. like getting my damn flourescent tube light working (and not flickering) I need to replace an old ballast transformer. I suppose a sprite could really just be nature flourescent tube with cranky ballast.

    • Many billions of dollars? LIGO.. .. and I was wondering why the couldn’t have built it out in space somewhere, ( 3-d as well instead of a flat 2) and with longer distances with light being what it is (useful information in it) where it splits, they could measure the relative distances in the splits.

        • It can’t be that hard to figure out . Just need an idea or insight to gravity. Lightning is very interesting because it seems like a partial runaway fusion reaction. Strong enough to produce gamma rays. Finding out how to induce a local gravity wave will enable fusion reaction to become a reality.

    • Gamma rays are the newest phenomenon, as far as I know, to be conclusively linked to T-storms, Pointman.

      • I’m wondering if sprites are from cosmic rays, which had been thought to trigger lightning, it would seem reasonable that you’d get something like a sprite, and then there’s the x-rays and gamma rays from the lightning itself….

    • It is a homonym
      grav·i·ty wave nounPhysics
      noun: gravity wave; plural noun: gravity waves
      1. a hypothetical wave carrying gravitational energy, postulated by Einstein to be emitted when a massive body is accelerated.
      2. a wave propagated on a liquid surface or in a fluid through the effects of gravity.
      “If you wish to converse with me, define your terms.” Voltaire

      • If by ‘gravity wave’ one refers to a time-varying magnitude and/or direction of the gravitational ‘field’ (i.e. locally measured acceleration vector due to gravity), they have been known for millenia – under the name ‘tides’.

    • these are density waves in the neutral atmosphere – nothing to do with relativistic gravity waves

  5. “What else is out there?”
    ————
    Nothing for you to see. Science is settled.
    But we will let you know if there is anything else that requires your money.
    And oh, there will be – there will be…
    Thank you,
    the warmunists

  6. BREAKING: SCOTUS rules against EPA in mercury standards case (vs. coal-powered power stations).

  7. FIT, my old school. If anyone is around who may have attended in 1969-70 here’s a shout out to you. I was also the acting captain of the very first varsity soccer team, acting because I was a freshman who replaced the senior who suffered a nasty broken leg early in the season..

  8. In 1978 I was on a flight to El Salvador, my first jet flight, small TACA (take a chance airlines) we flew on. We were allowed to visit the cockpit and I got to see this happen and was shocked by it. The pilots explained they see this a lot. Mysteries can be beautiful and deadly. I respect them both.

  9. Here in Michigan, while I have not seen any sprites, I have taken many pictures of “rippled clouds”, ie atmospheric ‘gravity waves’, that occurred in almost all cases within hours of either solar flares or geomagnetic activity. Since in both instances the high atmosphere (ionosphere) is at a higher conductivity level due to either flare-induced photo-ionization and/or higher concentrations of charged particles (protons/electrons) via the solar wind, the high atmosphere becomes more ‘charged-up’ than usual and also potentially more capable of discharging to higher altitudes, beyond the reach of regular thunderstorm lightning.
    https://sp.yimg.com/ib/th?id=JN.IId37NwbDgWc8RmJB9IlQw&pid=15.1&P=0
    https://sp.yimg.com/ib/th?id=JN.mWTI3cS%2bvsXQorFfcQvSng&pid=15.1&P=0
    On the modern imaging of the filamentary nature of sprites, “Telescopic imaging of sprites” at http://vlf.stanford.edu/sites/default/files/publications/498.pdf, with more electrifying pictures of sprite filaments.

  10. been wondering if it was sprites I saw here last week, was a bad storm that blew over me fast (powerful one too) yet for 30 minutes the sky was blue/red and NO noise.
    none at all.
    this was with center of storm only 5 miles away too.

  11. I have been more engaged by theories that have kept the phenomena described as electrical discharge. Lightening discharging to the ground, sprites to the edge of the atmosphere and possibly to other planetary bodies such as the sun. Certainly an area of science where competing ideas are still fighting for dominance, though.

  12. “Understanding the conditions of sprite formation is important, in part, because they can interfere with or disrupt long-range communication signals by changing the electrical properties of the lower ionosphere.”
    No. They are interesting. Not important.

  13. What about the blue jets that also emerge from the tops of thunderstorms?
    Not a word about these?

    • The seemingly casual passing over of such newly recognized phenomena as sprites, blue jets and elves is puzzling. What mind-blowing chutzpah to think there’s nothing else to be discovered. Is puzzling over the origin of a word the very best that can be accomplished?

      • I am not sure If I was understood: I am wondering why there was no mention in this “study” of any of the other similar (in that they are energetic, shoot out of the top of thunderstorms towards space, are hard to spot, have always been there, can be seen and are now being seen from the ground, and were nonetheless just recently “discovered”) and possibly related phenomenon, the most well know of which are the blue jets.

      • They have to dismiss them because the world, the sun, the solar system and indeed the universe isn’t allowed to be electric in nature. Admitting this would hurt too many reputations, and funding models.

  14. The standard model of the universe is based on gravity, thus it was found most of the universe is missing.
    Rather than make up imaginary friends and gremlins to make it work, perhaps a re-think is needed.
    This study of sprites suffers the same gravity only illusion, time to think outside the self imposed box.

  15. “Sprite” as in 2D Computer Graphics.
    Then, there is Thomas Campian (1613) and his song…..the third -to-last word.

    • Fantastic! All the way back to AD 1613! Thanks TonyN. In the closing phrase “O come quickly, glorious Lord, and raise my sprite to thee!” , I don’t think Thomas Campion was referring to a fairy, fawn or goblin. In the previous lines they sing take my “soul” to rest. So in this case, Sprite is the disembodied ghost or spirit, as per the OED.
      Still I would like to know 1) the first meteorological use, and 2) when sprite was used before 1975 in reference to creatures of the forest?

  16. “…sprites are triggered by intense cloud-to-ground lightning strokes. They typically last a few to tens of milliseconds; they are bright enough to be seen with dark-adapted naked eyes at night; and only the most powerful lightning strokes can cause them.”
    Lightning is conventionally explained as the discharge of static electricity built up between raindrops.
    Alternatively, the sprites, jets and elves could indicate that the discharge involves a break down in a charged spherical capacitor between the ionosphere and the earth, where the ionosphere and earth are oppositely charged plates.
    Electric Field of Parallel Plates
    https://youtu.be/XSXKk_A3xUM?t=3m58s

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