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Terrestrial Gamma-Ray Flashes ( TGFs) – Part II G. J. (Jerry) Fishman

Terrestrial Gamma-Ray Flashes ( TGFs) – Part II G. J. (Jerry) Fishman NASA-Marshall Space Flight Center Huntsville, AL USA for Michael S. Briggs University of Alabama in Huntsville Huntsville, AL USA Thunderstorms and Elementary Particle Acceleration (TEPA 2010)

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Terrestrial Gamma-Ray Flashes ( TGFs) – Part II G. J. (Jerry) Fishman

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  1. Terrestrial Gamma-Ray Flashes (TGFs) – Part II G. J. (Jerry) Fishman NASA-Marshall Space Flight Center Huntsville, AL USA for Michael S. Briggs University of Alabama in Huntsville Huntsville, AL USA Thunderstorms and Elementary Particle Acceleration (TEPA 2010) Nor Amberd, Armenia 6-11 September 2010

  2. Four Orbiting Spacecraft Have Observed TGFs: • BATSE on the Compton Gamma-ray Observatory • Discovered TGFs (Science,1994) • Operational 1991-2000 • RHESSI - Solar Spectroscopy Spacecraft • Comprehensive TGF Observations • On-line Catalog Available; still in-orbit • AGILE • Italian Gamma-ray Astronomy Mission • Detects TGFs in calorimeter, still operational • The Gamma-ray Burst Monitor, “GBM” on the Fermi Gamma-ray Space Telescope • This talk

  3. GBM(Gamma-ray Burst Monitor) on theFermiObservatory - Launched June 11, 2008 - Primary Objective: GRBs Fermi Gamma-Ray Space Telescope

  4. BGO Det. (1 of 2) NaI Det. (3 of 12) GBM Detector Locations on the Fermi Spacecraft – Launched June 2008

  5. Secondary electron beams MUST occur:

  6. TGF Simulation - Courtesy J. Dwyer, Florida Tech.Gamma-rays (red); Electrons (blue) 200 150 100 50 20 Altitude (km) -200 -100 0 100 200 Horizontal Distance (km)

  7. J. Dwyer, D. Smith, B. Grefenstette & B. Carlson ~2006: Some BATSE events and one RHESSI event are clearly electron beams: BATSE RHESSI

  8. Five “Electron” TGFs (in the first 50) • Characteristics: • Longer than usual • Fast rise, then decaying • Some are not over thunderstorms

  9. Long “Electron” TGF 9

  10. Positrons ! Spectrum of TGF 511 keV gamma line line from positrons 10

  11. 6 of the fastest TGFs Risetimes & Falltimes ~7 μs to 15 μs (4 μs per bin) (400 μs , total span}

  12. MeV Spectral Differences TGF #1: Low energies dominate TGF #7: High energies dominate 45 40 20 7 5.5 4.2 2.0 1.3 0.3 1 MeV 45 40 20 7 5.5 4.2 2.0 1.3 0.3 7

  13. Overlapping Double Pulses - 3 in the first 50 TGFs (~7 others are less obvious)

  14. TGF #1 , Individual Detectors, 0.1ms bins NaI (12) BGO (2)

  15. TGF #5 , Individual Detectors, 0.1ms bins NaI (12) BGO (2) Plot by M. Briggs

  16. Properties of 10 Short TGF Pulses Energies of Single Counts - BGO Detectors Only Time Profiles – All Detectors Combined

  17. Four Longer TGF Pulses (~1-3 ms) Time Profiles – All Detectors Combined Energies of Single Counts - BGO Detectors Only

  18. Fermi – GBM Locations of 85 TGFs

  19. RHESSI TGFs: Seasonal dependence follows lightning

  20. GLOBAL FLASH RATE – ANNUAL (from LIS-TRMM data) H. Christian et al.

  21. GBM TGF Papers - 2010 • “First Results on Terrestrial Gamma-ray Flashes from the Fermi Gamma-ray Burst Monitor”, M. S. Briggs, et al., JGR • “Associations between Fermi GBM Terrestrial Gamma-ray Flashes and sferics from the WWLLN”, V. Connaughton, et al, to appear in JGR • “Temporal Properties of Terrestrial Gamma-ray Flashes from the Gamma-ray Burst Monitor on the Fermi Observatory”, G. J. Fishman, submitted to JGR • “Positrons observed from Terrestrial Lightning with Fermi GBM”, M. S. Briggs, et al., in preparation

  22. New! GBM-Fermi: August 2010 – Implemented “un-triggered” TGF capability Over selected “America’s Region”: - All RHESSI TGFs - RHESSI TGFs, May-November, in Americas GBM expects ~1 TGF per day in this Region (~30x initial rate!) (- may be able to expand region)

  23. First look at a GBM Un-triggered TGF Binned Data 20μs/bin Un-triggered (weak) TGFFull-Width: ~0.2 ms Total cts above bkgnd: ~35 cts Peak ct. rate: ~20 kcps (~ zero deadtime!) (Spectrum appears similar to strong TGFs)

  24. End

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