1. TGF diffuse imaging and spectra as a function of altitude and location P.H.Connell University of Valencia

2. The University of Valencia is part of the phase-B study of a proposed imager and spectrometer instrument MXGS to be mounted on the Columbus module of ISS Nadir ↓ Earth horizon The Columbus model on Node-2 of the ISS

3. Proposed MXGS coded-mask X-ray imager/spectrometer instrument How effective is it for TGF angular and spatial location estimates? What is the effect if a TGF has a significant diffuse structure?

4. Images of X-ray sources may be created by the method of photon back projection N photons must come through N mask holes How many photons are required to make an image of just one X-ray source?

5. TGF photon beam simulator software Generates TGF photon energy, altitude, radius, azimuth, angular distribution Simulates TGF beam azimuth, zenith and photon transport through atmosphere Uses photoelectric, Klein-Nishina and NPP-EPP scattering statistics Returns images and spectra observed at any location in or above atmosphere Does not simulate any coexistent electron accelerator or runaway breakdown

6. What is the mechanism to generate Terrestrial Gamma-Ray flashes? Relativistic runaway electrons above thunderstorms PhD Thesis - Nikolai G. Lehtinen – U.S.Inan.et.al Dept. Physics - Stanford University - March 2000 Creating a high energy electron avalanche? Model components and geometry of a Gamma-Ray flash? Gamma-ray flashes are assumed to originate in the Bremsstrahlung radiation from a stream high velocity electrons – coming from where?

7. TGF photon transport simulation through atmosphere 2x2 km Gaussian ball at 20 km altitude Vertical beam - zero angular width Photon escape locations – low concentrations enhanced

8. TGF photon transport simulation through atmosphere 2x10 km Gaussian ellipsoid - 20 km altitude Vertical beam - zero angular width Photon locations before escaping

9. TGF photon transport simulation through atmosphere 2x10 km Gaussian ellipsoid - 20 km altitude Vertical beam - 30° angular width Photon locations before escaping

10. TGF photon transport simulation through atmosphere 2x10 km Gaussian ellipsoid - 20 km altitude Vertical beam - 60° angular width Photon locations before escaping

11. TGF photon transport simulation through atmosphere 2x10 km Gaussian ellipsoid - 20 km altitude 30° beam tilt – zero angular width Photon locations before escaping

12. TGF photon transport simulation through atmosphere 2x10 km Gaussian ellipsoid - 20 km altitude 45° beam tilt – zero angular width Photon locations before escaping

13. What does a TGF and its spectrum look like ? A vertical 2x10 km Gaussian ellipsoid beam At 350 km altitude in orbit From various off-axis observation angles

14. On-axis view of 2x10 km ellipsoid TGF at 350 km altitude <500 keV <20000 keV

15. 10° off-axis view at 350 km altitude of 2x10 km ellipsoid TGF <500 keV <20000 keV Vertical asymmetry probably due to HE photons exiting after 1-2 scatters off beam -axis

16. 20° off-axis view at 350 km altitude of 2x10 km ellipsoid TGF <500 keV <20000 keV

17. 30° off-axis view at 350 km altitude of 2x10 km ellipsoid TGF <500 keV <20000 keV Most photons contained within ~4° circleMost photons contained within ~2° circle

18. 40° off-axis view at 350 km altitude of 2x10 km ellipsoid TGF <500 keV <20000 keV

19. 50° off-axis view at 350 km altitude of 2x10 km ellipsoid TGF <500 keV <20000 keV Note beam centre shift of ~1° from TGF centrepoint – corresponds to ~13 km altitude

20. 60° off-axis view at 350 km altitude of 2x10 km ellipsoid TGF <500 keV <20000 keV Beam starting to flatten out

21. 70° off-axis view at 350 km altitude of 2x10 km ellipsoid TGF <500 keV <20000 keV

22. 80° off-axis view at 350 km altitude of 2x10 km ellipsoid TGF <500 keV <20000 keV

23. Spectra of TGFs observed over 0,10,20,….80° off-axis at 350 km altitude Calibrated to an estimate of RHESSI mean photon spectrum

24. Fitting of mean TGF spectrum over 10-50° off-axis to an estimate of a B-spline deconvolved RHESSI mean photon spectrum. (D.Smith, N.Ostergaard, et.al.) Beware of f(E) = 1/E TGF spectrum, RHESSI altitude correction and LE efficiency!

25. What is observed at low altitude? At 20 km altitude At 15, 20 km radius from the TGF beam axis

26. TGF transport simulation in atmosphere 2x10 km Gaussian ellipse at 20 km altitude Vertical beam – zero angular width Photon locations at absorption – low concentrations enhanced

27. TGF simulation imaging within lower atmosphere Observation point at 20 km altitude 15 and 20 km radius from 2x10 km beam axis Observation direction toward beam axis Will an insect-eye imager detect the beam axis?

29. TGFs could have significant diffuse structure Could impact on coded-mask location imaging High counts at high flight altitudes – the place to be? Too diffuse at low-altitudes to see beam tilt angle? Software needs electron accelerator and Bremstrahlung photon generator Conclusions