Unusual RHESSI TGFs: Electron Beams and Others
Abstract
We will summarize observations and conclusions about two unusual Terrestrial Gamma-ray Flashes (TGFs) observed by the RHESSI satellite. Both events are unusually bright and occur in the Northern hemisphere during the winter -- unusual in itself, since TGFs are overall a phenomenon associated with summer storms. The first event, on January 17, 2004, can be modeled as the signature of the satellite passing through an electron beam ejected from the atmosphere at the magnetic conjugate point. The mechanism behind this process is now understood, and will be presented here and, in more depth, in the accompanying paper by Dwyer, Grefenstette, and Smith in this session. The second event occurred in the Mediterranean -- the only TGF ever reported in that region -- on November 7, 2004. This event seems to be associated with a nearby thunderstorm, not a conjugate one, but is still extremely unusual. We will examine the question of whether its unusual location and brightness is due to its being another electron beam event (caught on the way out instead of the way back in), or whether the storm itself was unique. Finally, we will briefly show the other RHESSI TGFs with the most extreme behavior in duration, average energy per photon, and geographical location.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFMAE31A0051S
- Keywords:
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- 2716 Energetic particles: precipitating;
- 2736 Magnetosphere/ionosphere interactions (2431);
- 3304 Atmospheric electricity;
- 3324 Lightning