Terrestrial Gamma-Ray Flashes (TGFs)
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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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Terrestrial gamma ray flashes tgfs observed with fermi gbm

  • 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)


Terrestrial gamma ray flashes tgfs observed with fermi gbm

  • TGFs - Overview &

  • Some New Results

  • History; Spacecraft observations

  • Observations from Fermi-GBM

  • Future Space Missions


Terrestrial gamma ray flashes tgfs observed with fermi gbm

  • 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)


Terrestrial gamma ray flashes tgfs observed with fermi gbm

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


Terrestrial gamma ray flashes tgfs observed with fermi gbm

  • BATSE TGFs:

    • Determined rough spectral properties (extremely energetic)

    • Associated with thunderstorms

    • Observed 78 in 9 years


Terrestrial gamma ray flashes tgfs observed with fermi gbm

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


Terrestrial gamma ray flashes tgfs observed with fermi gbm

II. RHESSI(Ramaty High-Energy Solar Spectroscopic Imager)

- Solar Observatory

- Launched 2002; currently operational


Terrestrial gamma ray flashes tgfs observed with fermi gbm

  • 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:


Terrestrial gamma ray flashes tgfs observed with fermi gbm

Hi Bkgnd - Low Sensitivity Region

SAA Region

High Background, Low Sensitivity Region

Map of RHESSI TGFs (820 events)


Terrestrial gamma ray flashes tgfs observed with fermi gbm

GLOBAL FLASH RATE – ANNUAL (from LIS-TRMM data)

H. Christian et al.


Terrestrial gamma ray flashes tgfs observed with fermi gbm

III. AGILE

- Italian Gamma-ray Astronomy Satellite

- 100kg Experiment

- Launched: April 2007

Large CsI Scintillator

Can Detect TGFs


Terrestrial gamma ray flashes tgfs observed with fermi gbm

IV. GBM

(Gamma-ray Burst Monitor)

Launched June 11, 2008

NASA Kennedy Space Center

Fermi

Gamma-Ray Space Telescope


Terrestrial gamma ray flashes tgfs observed with fermi gbm

BGO Det.

(1 of 2)

NaI Det.

(3 of 12)

GBM

Detector Locations on the

Fermi Spacecraft – Launched June 2008


Terrestrial gamma ray flashes tgfs observed with fermi gbm

GBM(Gamma-ray Burst Monitor)

on theFermiObservatory

- Launched June 11, 2008

- Primary Objective: GRBs

Fermi

Gamma-Ray

Space Telescope


Gamma ray burst monitor gbm sodium iodide nai detectors 12

Gamma-Ray Burst Monitor (GBM) Sodium Iodide (NaI) Detectors (12)

1.27 cm thick

12.7 cm dia.

8 keV to 1 MeV


Gbm bismuth germinate bgo detectors 2

GBM Bismuth Germinate (BGO) Detectors (2)

12.7 cm thick

12.7 cm dia.

150 keV to 45 MeV


Terrestrial gamma ray flashes tgfs observed with fermi gbm

NaI Detectors (all 12 combined)

TGF

“Overflow” Chan. (127)

Gamma-ray Energy Chan.

(~1 MeV max.)

milliseconds (rel. to trigger time)


Terrestrial gamma ray flashes tgfs observed with fermi gbm

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


Terrestrial gamma ray flashes tgfs observed with fermi gbm

6 of the fastest TGFs

Risetimes & Falltimes

~7 μs to 15 μs

(4 μs per bin)

(400 μs , total span}


Terrestrial gamma ray flashes tgfs observed with fermi gbm

Two Well-separated, Double-Pulse TGFs

seen with GBM (all detectors summed)

Narrowest Pulse

seen with GBM, ~ 50 μs


Terrestrial gamma ray flashes tgfs observed with fermi gbm

Fermi – GBM

Locations of 85 TGFs


Tgf lightning are usually simultaneous

TGF & Lightning are usually Simultaneous


How simultaneous

How simultaneous?

Distribution of GBM TGF peaks - WWLLN sferic peaks.


2 exceptions

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.


Tgf lightning summary

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).


Terrestrial gamma ray flashes tgfs observed with fermi gbm

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

~8/mo., after “ “


Terrestrial gamma ray flashes tgfs observed with fermi gbm

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


Electron tgfs no storm in region below spacecraft

Electron TGFs: No Storm in Region Below Spacecraft

Geomagnetic Conjugate Region

Below Spacecraft


Terrestrial gamma ray flashes tgfs observed with fermi gbm

Five “Electron” TGFs (in the first 50)

  • Characteristics:

    • Longer than usual

    • Fast rise, then decaying

    • Some are not over thunderstorms


Terrestrial gamma ray flashes tgfs observed with fermi gbm

Long “Electron” TGF

31


Terrestrial gamma ray flashes tgfs observed with fermi gbm

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


Terrestrial gamma ray flashes tgfs observed with fermi gbm

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)


Terrestrial gamma ray flashes tgfs observed with fermi gbm

  • 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 ?


Terrestrial gamma ray flashes tgfs observed with fermi gbm

TGF #5 , Individual Detectors, 0.1ms bins

NaI (12) BGO (2)

Plot by M. Briggs


Terrestrial gamma ray flashes tgfs observed with fermi gbm

TGF #1 , Individual Detectors, 0.1ms bins

NaI (12) BGO (2)


Terrestrial gamma ray flashes tgfs observed with fermi gbm

Properties of 10 Short TGF Pulses

Energies of Single Counts -

BGO Detectors Only

Time Profiles –

All Detectors Combined


Terrestrial gamma ray flashes tgfs observed with fermi gbm

Four Longer TGF Pulses (~1-3 ms)

Time Profiles –

All Detectors Combined

Energies of Single Counts -

BGO Detectors Only


Terrestrial gamma ray flashes tgfs observed with fermi gbm

Overlapping Double Pulses

- 3 in the first 50 TGFs

(~7 others are less obvious)


Terrestrial gamma ray flashes tgfs observed with fermi gbm

Overlapping Double Pulses

- 3 in the first 50 TGFs

(~7 others are less obvious)


Terrestrial gamma ray flashes tgfs observed with fermi gbm

TGF #1 , Individual Detectors, 0.1ms bins

NaI (12) BGO (2)


Terrestrial gamma ray flashes tgfs observed with fermi gbm

TGF #5 , Individual Detectors, 0.1ms bins

NaI (12) BGO (2)

Plot by M. Briggs


Terrestrial gamma ray flashes tgfs observed with fermi gbm

Fermi – GBM

Locations of 85 TGFs


Gbm tgf papers 2010

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


Terrestrial gamma ray flashes tgfs observed with fermi gbm

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)


Terrestrial gamma ray flashes tgfs observed with fermi gbm

  • 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


Terrestrial gamma ray flashes tgfs observed with fermi gbm

End


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