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The Polarity Asymmetry of Sprite Producing Lightning: A Paradox Earle R. Williams MIT IAMAS Beijing, China August 2005.

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Presentation on theme: "The Polarity Asymmetry of Sprite Producing Lightning: A Paradox Earle R. Williams MIT IAMAS Beijing, China August 2005."— Presentation transcript:

1 The Polarity Asymmetry of Sprite Producing Lightning: A Paradox Earle R. Williams MIT IAMAS Beijing, China August 2005

2 IAMAS 2 ERW Aug 05 Outline 3-way linkage: positive CG—sprite—Q-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

3 IAMAS 3 ERW Aug 05 HR163-5 Sprite HR163-5 Lightning 3-Way Connection Positive Cloud-to-Ground Lightning (“Spider” Lightning) Sprites and Elves in the Mesosphere Transient Excitation of the Earth-Ionosphere Waveguide (Schumann Resonances) 410880_P_1Y.ppt S A

4 IAMAS 4 ERW Aug 05 Theory Used for Global Mapping

5 IAMAS 5 ERW Aug 05 Sprite Initiation Following C.T.R. Wilson (1925)

6 IAMAS 6 ERW Aug 05 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 < 0.1% of sprites caused by ground flashes with negative polarity

7 IAMAS 7 ERW Aug 05 Map Comparison for Positive and Negative Flashes

8 IAMAS 8 ERW Aug 05 Global Map of Large Lightning Events from Rhode Island Station

9 IAMAS 9 ERW Aug 05 Bipolar Distribution of Large Charge Moments

10 IAMAS 10 ERW Aug 05 Percentage of All Lightning with Positive Polarity (Above Sprite Threshold)

11 IAMAS 11 ERW Aug 05 Daytime Sprites Where on the globe are the sprites caused by supercritical negative charge moments? Hypothesis: In the daytime, when sprites cannot be seen

12 IAMAS 12 ERW Aug 05 How Many of the Supercritical Events in the Daytime? (When Sprites Would Not Be Seen)

13 IAMAS 13 ERW Aug 05 Oceanic Sprites Where are the sprites on the globe caused by supercritical negative charge moments? Hypothesis: Over the oceans where we lack observational coverage

14 IAMAS 14 ERW Aug 05 World Color Map

15 IAMAS 15 ERW Aug 05 Sprite-Capable Negative Lightning for Oceans

16 IAMAS 16 ERW Aug 05 Sprite Halos What are the events caused by supercritical negative charge moments? Hypothesis: Halos caused by more-impulsive- than-usual negative ground flashes

17 IAMAS 17 ERW Aug 05 Current Moment Spectra (I(f)dS) in Lower ELF Region Lightning current duration << light time around the Earth  ‘white’ current moment spectrum; ‘impulsive’ Lightning current duration <= light time around the Earth  ‘red’ current moment spectrum

18 IAMAS 18 ERW Aug 05 Current Moment Spectra – Slope Comparison Negative Flashes Positive Flashes

19 IAMAS 19 ERW Aug 05 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

20 IAMAS 20 ERW Aug 05 Global Map of Terrestrial Gamma Flashes Courtesy of Space Sciences Laboratory University of California, Berkeley (2005)

21 IAMAS 21 ERW Aug 05 What Lightning Configurations are Favorable for Upward Gamma Rays

22 IAMAS 22 ERW Aug 05 Gamma Ray Attenuation in Air

23 IAMAS 23 ERW Aug 05 Effect of Gamma Ray Source Height on Flux at Satellite Altitude

24 IAMAS 24 ERW Aug 05 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)

25 IAMAS 25 ERW Aug 05 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)

26 IAMAS 26 ERW Aug 05 Global Map of Large Lightning Events from Rhode Island Station

27 IAMAS 27 ERW Aug 05 Global Map of Large Lightning Events from Rhode Island Station

28 IAMAS 28 ERW Aug 05 Global Map of Large Lightning Events from Rhode Island Station

29 IAMAS 29 ERW Aug 05 Global Map of Large Lightning Events from Rhode Island Station

30 IAMAS 30 ERW Aug 05 Global Map of Large Lightning Events from Rhode Island Station

31 IAMAS 31 ERW Aug 05 Global Map of Large Lightning Events from Rhode Island Station

32 IAMAS 32 ERW Aug 05 Global Map of Large Lightning Events from Rhode Island Station

33 IAMAS 33 ERW Aug 05 Map Comparison for Positive and Negative Flashes

34 IAMAS 34 ERW Aug 05 Map Comparison for Positive and Negative Flashes

35 IAMAS 35 ERW Aug 05 Map Comparison for Positive and Negative Flashes

36 IAMAS 36 ERW Aug 05 Final Query Why are almost all Sprites caused by lightning with positive polarity?

37 IAMAS 37 ERW Aug 05 Distribution of Charge Moment Change (all data)

38 IAMAS 38 ERW Aug 05 Intense Oceanic Lightning M. Füllekrug et al

39 IAMAS 39 ERW Aug 05 Sprite Initiation Following C.T.R. Wilson

40 IAMAS 40 ERW Aug 05 SCL Neg Land Water

41 IAMAS 41 ERW Aug 05 Percent Neg Land Water

42 IAMAS 42 ERW Aug 05 Percent Neg Oceans


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