Speaker
Description
At the Pierre Auger Observatory, designed primarily to study ultra-high-energy cosmic rays, phenomena related to atmospheric electricity are also observed. Particularly peculiar events have been detected with the Surface Detector (SD), characterized by long-lasting signals (tens of microseconds) and event footprints much larger (up to 200 km$^2$) than those produced by the highest energy cosmic rays. Moreover, some of them appear to be accompanied by smaller events occurring in the same area within about 1 ms and probably produced by the same phenomenon. A previously reported correlation with the World Wide Lightning Location Network, as well as the observation of very low-altitude clouds confirm that such events are related to thunderstorms. An ad-hoc reconstruction points to high-energy particles being produced very close to the ground, suggesting that they originate from electrons accelerated to relativistic energies in strong electric fields inside low clouds, as is the case for Terrestrial Gamma-ray Flashes above thunderstorms.
A definitive explanation of the observed phenomenon is hindered by two facts.
One is that the rate of such events, serendipitously detected, is very small (less than 2 events/year) and decreased even further after an optimization of the SD trigger for low-energy shower-events. The second is that most events show a puzzling lack of signals in the central part of the footprint.
We have studied in detail both effects and will present such studies here.
We developed a strategy for a dedicated trigger to enhance the detection efficiency for such atmospheric-electricity events.
Keywords
atmospheric electricity; TGF; lightning
| Subcategory | Experimental Results |
|---|---|
| Collaboration | Auger |
