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| Titel |
Constraints on the Emission Cone of Terrestrial Gamma-ray Flashes by Spectral Analysis of Geolocated Events. |
| VerfasserIn |
Thomas Gjesteland, Nikolai Østgaard, Andrew Collier |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250051585
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| Zusammenfassung |
| The source lightning discharges associated with TGFs detected by the RHESSI satellite are
determined from WWLLN data. 36 events occurring before 2006 are used in this analysis.
Later events are not included because of radiation damage to the RHESSI instrument, which
changed the energy response. The energy spectra are binned according to observation angle,
i.e. the angle between the RHESSI nadir and the straight line to the source lightning. The
result is a significant softening of the energy spectrum for TGFs detected at large
(> 40°) observation angles. The softening is due to Compton scattering which
reduces the photon energies. It is also found that the highest photon energies in the
distant TGFs are in order of  10 MeV indicating that they can not be scattered
more than ~ 15°. Based on these results TGFs seems to be produced in a nearly
vertical electrical field which is consistent with the ambient field in thunder clouds
and not around streamer/leader tips which imply highly divergent electrical fields. |
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