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IUGG 2007

IUGG 2007. Runaway Relativistic Electron Avalanche Seeding Brant Carlson Nikolai Lehtinen, Umran Inan Space, Telecommunications and Radioscience Laboratory Electrical Engineering Department Stanford University, Stanford, California 94305 http://www-star.stanford.edu/~vlf/. Outline.

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IUGG 2007

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  1. IUGG 2007 Runaway Relativistic Electron Avalanche Seeding Brant Carlson Nikolai Lehtinen, Umran Inan Space, Telecommunications and Radioscience Laboratory Electrical Engineering Department Stanford University, Stanford, California 94305 http://www-star.stanford.edu/~vlf/

  2. Outline • Runaway Relativistic Electron Avalanche (RREA) • Context, physics. • RREA seeding • Seed sources • Seed efficiency • Results / Conclusions

  3. Context Runaway Relativistic Electron Avalanche (RREA): • Large-scale E-field-driven avalanche, low threshold electric field. • Energetic e-, e+, . Important for • Terrestrial Gamma-ray Flashes? • Sprites? • Lightning Initiation?

  4. Dynamic friction on e- in air data from ICRU (1984)

  5. Electric field in air, with seed E RREA electrons photons seed e-

  6. Seeding Issues Seed sources: Cosmic rays, cosmic ray air showers. Concerns: • Relative direction? • Energy effects? • Particle type? downstream upstream low energy high energy

  7. Main Questions • What are available seeds? • How do they behave? • What does this tell us about RREA in the atmosphere?

  8. What are available seeds? air showers Cosmic rays W.-M. Yao et al., J. Phys. G 33, 1 (2006)

  9. CR secondary distributions • Air shower simulations (AIRES) • Range of Epri, pri. • Secondary distributions • histogram over z in x, y, E,  for e-, e+,, . What particles are caught by a sphere of radius R in a time t at alt. z? library energetic particle distrib.

  10. Energetic particle distributions

  11. Energetic particle distributions What about fluctuations? (100 sets)

  12. Seed behavior, efficiency GEANT simulations (various type, direction, etc.) • propagate seed for 100 ns. • track secondaries for 20 ns. • count secondary (avalanche) electrons. • repeat, average. E low energy high energy

  13. Seed behavior, efficiency Energy, particle species effects

  14. Seed behavior, efficiency Direction, energy, particle species effects

  15. Combined results, fluctuations

  16. Combined results, fluctuations

  17. Summary CR primary distrib. + Air shower sims.  energetic particle distributions. With seeding efficiency calculations,  effective seeding as function of alt. Effective seeding is large (thousands), Fluctuations are small (< 3x), unless A t is small (< 10 km2s).

  18. Preliminary conclusions If A dt > 10 km2 s (many seeds, small fluctuations) • Continuous seeding. • RREA presence tracks E-field presence. • TGF emission should track E-field presence. (QES, EMP mechanisms fall in this regime) If A dt < 10 km2 s, • Fluctuations relevant (single high-energy CRs) • Average flux still relevant. …further research is ongoing.

  19. References Handbook of Geophysics and the Space Environment, A. S. Jursa, Ed., Air Force Systems Command, U.S. Air Force ; Springfield, VA, 1985. W.-M. Yao et al., J. Phys. G 33, 1 (2006) GEANT4 website: http://geant4.web.cern.ch/geant4/ AIRES website: http://www.fisica.unlp.edu.ar/auger/aires International Commission on Radiation Units and Measurement, Stopping powers for electrons and positrons, ICRU Rep. 37.

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