The Polarity Asymmetry of Sprite Producing Lightning: A Paradox

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The Polarity Asymmetry of Sprite Producing
Lightning A Paradox

• Earle R. WilliamsMIT
• Multi-Scale Nature of Spark Precursors and High
  Altitude Lightning University of Leiden May
  9-13, 2005

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Outline

• 3-way linkage positive CGspriteQ-burst
• Global location of lightning
• C.T.R. Wilson idea for sprite initiation
• Polarity of ground flashes causal to sprites
• Why the overwhelming tendency for positive
  sprites?
• Global maps of energetic flashes
• Bimodal distributions of vertical charge moments
• Possible role of the duration of the moment
  change, and halos
• Asymmetry in slopes of current moment spectra
• Lightning responsible for gamma rays
• Conclusions

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3-Way Connection
HR163-5 Lightning
Positive Cloud-to-GroundLightning(Spider
Lightning)
Transient Excitation of theEarth-Ionosphere
Waveguide(Schumann Resonances)
Sprites and Elvesin the Mesosphere
S
HR163-5 Sprite
A
410880_P_1Y.ppt
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Theory Used for Global Mapping
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Sprite Initiation Following C.T.R. Wilson (1925)
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General Results on the Polarity of Parent
Lightning for Sprites

• Thousands of sprites caused by positive ground
  flashes
• Two well documented sprites caused by negative
  ground flashes (Barrington-Leigh et al, 1999)
• Estimate lt 0.1 of sprites caused by ground
  flashes with negative polarity

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Global Map of Large Lightning Events from Rhode
Island Station
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Map Comparison for Positive and Negative Flashes
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Bipolar Distribution of Large Charge Moments
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Percentage of All Lightning with Positive
Polarity (Above Sprite Threshold)
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Daytime Sprites

• Where on the globe are the sprites caused by
  supercritical negative charge moments?
• Hypothesis In the daytime, when sprites cannot
  be seen

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How Many of the Supercritical Events in the
Daytime? (When Sprites Would Not Be Seen)
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Oceanic Sprites

• Where are the sprites on the globe caused by
  supercritical negative charge moments?
• Hypothesis Over the oceans where we lack
  observational coverage

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World Color Map
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Sprite-Capable Negative Lightning for Oceans
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Sprite Halos

• What are the events caused by supercritical
  negative charge moments?
• Hypothesis Halos caused by more-impulsive-than-u
  sual negative ground flashes

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Current Moment Spectra (I(f)dS) in Lower ELF
Region

• Lightning current duration ltlt light time around
  the Earth
• white current moment spectrum impulsive
• Lightning current duration lt light time around
  the Earth
• red current moment spectrum

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Current Moment Spectra Slope Comparison
Negative Flashes Positive Flashes
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Electron-Runaway Hypothesis

• Sprite events are Gamma Producers
• Positive CG lightning required to accelerate
  electrons upward to cause bremmstrahlung and
  launch gamma rays upward
• Current evidence failure of this hypothesis
• No help for sprite polarity paradox

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Global Map of Terrestrial Gamma Flashes
Courtesy of Space Sciences Laboratory University
of California, Berkeley (2005)
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What Lightning Configurations are Favorable for
Upward Gamma Rays
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Behavior Over Oceans is Different

• Negative sprites over water?
  (Barrington-Leigh et al, 1999)
• Negative elves over water?(Barrington-Leigh
  and Inan, 1999)(Recent ROCSAT results (Cummer,
  pers. comm.)
• Negative charge moments over water(Fullekrug et
  al, 2002)
• Peculiar behavior near Haiti (V. Pasko,
  unpublished)
• Giant cloud-to-ionosphere discharges(V. Pasko,
  M. Stanley and others)
• Anomalous peak currents over water(W. Lyons
  (NLDN), A. Jacobson (Met Office VLF obs)

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Conclusions

• Substantially greater negative charge moments
  above the sprite initiation threshold than there
  are observed negative sprites (the paradox)
• Energetic negative ground flashes transfer their
  charge in a shorter time than positive flashes.
  Perhaps the stress period is shorter for
  negative events, and difficult-to-detect halos
  are the result (possible resolution to the
  paradox)