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Terrestrial Gamma-Ray Flashes (TGFs) Observed with Fermi-GBM

Terrestrial Gamma-Ray Flashes (TGFs) Observed with Fermi-GBM G. J. Fishman 1 , M. S. Briggs 2 , and V. Connaughton 2 for the GBM TGF Team 1 NASA-Marshall Space Flight Center Huntsville, AL USA 2 Univ. Alabama in Huntsville Huntsville, AL USA

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Terrestrial Gamma-Ray Flashes (TGFs) Observed with Fermi-GBM

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  1. Terrestrial Gamma-Ray Flashes (TGFs) • Observed with Fermi-GBM • G. J. Fishman1, M. S. Briggs2, and V. Connaughton2 • for the GBM TGF Team • 1NASA-Marshall Space Flight Center • Huntsville, AL USA • 2Univ. Alabama in Huntsville • Huntsville, AL USA • Thunderstorms and Elementary Particle Acceleration • (TEPA 2010) • Nor Amberd, Armenia • 6-11 September 2010 • ( -for TEPA Web site posting)

  2. TGFs - Overview & • Some New Results • History; Spacecraft observations • Observations from Fermi-GBM • Future Space Missions

  3. Observations of TGFs • with • Four Spacecraft: • BATSE /Compton Observatory:1991-2000 • Solar Spectroscopic Imager • AGILE Gamma-ray Telescope • Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope (this talk)

  4. Burst and Transient Source Experiment (BATSE) - Compton Observatory (CGRO) 1991-2000

  5. BATSE TGFs: • Determined rough spectral properties (extremely energetic) • Associated with thunderstorms • Observed 78 in 9 years

  6. TGFs from BATSE (showing saturation at ~300,000 cps)

  7. II. RHESSI(Ramaty High-Energy Solar Spectroscopic Imager) - Solar Observatory - Launched 2002; currently operational

  8. RHESSI Observations of TGFs: • Doesn’t require trigger; all data are transmitted • Detected many more TGFs than BATSE, but they were much weaker • Determined very hard spectra (> 20 MeV) Time Profiles of some RHESSI TGFs:

  9. Hi Bkgnd - Low Sensitivity Region SAA Region High Background, Low Sensitivity Region Map of RHESSI TGFs (820 events)

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

  11. III. AGILE - Italian Gamma-ray Astronomy Satellite - 100kg Experiment - Launched: April 2007 Large CsI Scintillator Can Detect TGFs

  12. IV. GBM (Gamma-ray Burst Monitor) Launched June 11, 2008 NASA Kennedy Space Center Fermi Gamma-Ray Space Telescope

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

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

  15. Gamma-Ray Burst Monitor (GBM) Sodium Iodide (NaI) Detectors (12) 1.27 cm thick 12.7 cm dia. 8 keV to 1 MeV

  16. GBM Bismuth Germinate (BGO) Detectors (2) 12.7 cm thick 12.7 cm dia. 150 keV to 45 MeV

  17. NaI Detectors (all 12 combined) TGF “Overflow” Chan. (127) Gamma-ray Energy Chan. (~1 MeV max.) milliseconds (rel. to trigger time)

  18. 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

  19. 6 of the fastest TGFs Risetimes & Falltimes ~7 μs to 15 μs (4 μs per bin) (400 μs , total span}

  20. Two Well-separated, Double-Pulse TGFs seen with GBM (all detectors summed) Narrowest Pulse seen with GBM, ~ 50 μs

  21. Fermi – GBM Locations of 85 TGFs

  22. TGF & Lightning are usually Simultaneous

  23. How simultaneous? Distribution of GBM TGF peaks - WWLLN sferic peaks.

  24. 2 Exceptions: TGF Lightning sferic TGF Lightning sferic Of 15 associated sferics (5 ms, 300 km), 2 are not consistent with being simultaneous with the TGF pulse Difference: ~few ms.

  25. TGF & Lightning - Summary • Simultaneous, no preferred order • GBM detects gamma-ray TGFs within 300 km of sub-spacecraft. • We need other VLF data to explore shape, size of sferics (Duke, Stanford, LASA groups).

  26. Triggered TGF Rate in GBM: ~1/mo., prior to 11 Nov. 2010 ~8/mo., after “ “

  27. Pulse Durations of First 50 GBM TGFs Median TGF Pulse Duration = 0.11ms - Does not include 5 longer “electron” TGFs - Solid column – includes 10 possible un-resolved pulses

  28. Electron TGFs: No Storm in Region Below Spacecraft Geomagnetic Conjugate Region Below Spacecraft

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

  30. Long “Electron” TGF 31

  31. August 2010 – Implemented “un-triggered” TGF capability Over selected “America’s Region”: • RHESSI TGFs • RHESSI TGFs, May-November est.: ~several TGFs per day in this Reion

  32. First look at a GBM an Un-triggered TGF Binned Data 20μs/bin TGFFull-Width: ~0.25ms Total cts above bkgnd: ~35 cts Peak ct. rate: ~20kcps (Spectrum appears similar to strong TGFs)

  33. TGFs – • Major Observational Questions: • Altitude of origin? • Extent & volume of the emitting region? • Beaming properties of the emission? • What is the intensity distribution of TGFs ? • Are TGFs related to Gigantic Blue Jets ?

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

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

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

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

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

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

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

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

  42. Fermi – GBM Locations of 85 TGFs

  43. 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., in press, 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 Complete list of Huntsville Gamma-Ray Team Publications: http://gammaray.nsstc.nasa.gov/publications/tgf_journal.html

  44. 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)

  45. Future Spacecraft to Study TGFs: • Firefly – NSF cubesat; GSFC; Siena College • ASIM – on ISS; ESA, led by Danish • TIRANIS – French & others • CHIBIS-M – Russian (IKI) & others

  46. End

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