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Monte Carlo Simulations of the temporal behavior
of Terrestrial Gamma ray Flashes, and analysis of
the BATSE measurements

T. Gjesteland1
N. Ostgaard1, J. Stadsnes1 , P. H. Connell2
1) Department of Physics and Technology,
University of Bergen, Norway 2) Institute of
Mechanical Science, University of Valencia, Spain
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Outline

• Monte Carlo simulations
• Time delay
• BATSE
• Calculate the deadtime losses
• Compare MC time delay with BATSE measurements,
  which has low deadtime losses

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Monte Carlo simulation

• MC start with a 1/E energy spectrum
• Compton scattering changes the energy spectrum

60 km altitude
20 km altitude
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Monte Carlo simulations

• Compton scattering reduces the energy and
  increases the path length.
• Assumption
• -High energy photons arrives at a satellite
  detector before low energy photons

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• Hard Egt300 keV
• Soft Elt300 keV

Time delay
25 km altitude
hard
soft
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BATSE measurements shows larger time delays
Average 81 µs time delay

• Time delay in previous studies
• Hard Egt110 keV
• Soft Elt110 keV
• Nemiroff et al 1997
• 100-200 µs time delay
• Feng et al 2002
• 100 µs time delay

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A paralyzable detector
Counts per time

• The deadtime, t, is found from the peak

m
n
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Highest count rate in a single LAD 5 cnt/10µs
Deadtime 0,725 µs
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(No Transcript)
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How many photons hits one BATSE LAD?

• R2 effect 1,78
• Effective area BATSE LADs
• Total 2000 cm2
• 502 cm2 (Grefenstette et al 2008)
• Effective area RHESSI
• Total 250 cm2
• 239 cm2 (Grefenstette et al 2008)

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• Max RHESSI count rate (Grefenstette et al 2008)
• -0.056 cnt/(50 µs effective area) 13 cnt/ 50
  µs
• Mean RHESSI TGF contains 26 photons (mean
  duration 1 ms)
• -Assume 26 photons during 0.26 ms
• -RHESSI average 1 photon per 10 µs

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How many photons hits one BATSE LAD?lt 15
photons / 10 µs
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BATSE time profiles

• 3 types of TGF
• Long duration bursts- excluded
• Multi peak TGF are separated into single peaks

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All 8 LADs count rate 3 cnt / 10µs
Calculate the Time delay for each peak
Egt300keV
Elt300keV
Milli sec
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Average 55 µs time delay
Average deadtime loss
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Conclusions

• MC-simulations 40 µs time delay for TGF
  produced below 25 km altitude.
• MC-simulations gives no time delay above 25 km
• The smal BATSE peaks
• 55 µs time delay on average
• The time delay indicates that TGF are produced
  below 25 km altitude

• Deadtime 1 µs
• BATSE is most likely not total paralyzed
• Smal TGF lt15 losses due to deadtime.