When cosmic ray particles interact with nitrogen atoms in our atmosphere, they fluoresce, or emit ultraviolet (UV) light that can be detected by the fluorescence telescopes. The Auger telescopes view the air showers that occur above the tank array, seeing what looks like a dim UV light bulb descending through the atmosphere. The detectors track the cascade development by measuring the brightness of the emitted light as the particles travel down into the atmosphere.
When the particles reach ground level, they penetrate the detector tanks and interact with the highly purified water inside. Because they are traveling faster than particles normally would in water, they produce an electromagnetic shock wave known as the Cherenkov Effect. This shock wave interacts with the water molecules producing light that can be detected by the three large photomultiplier tubes (PMTs) located within the detector tanks. The data are recorded by special equipment in the tanks and is sent to a central observatory site by radio transmitters built into each tank. Since the tanks contain their own solar cells, batteries, and radio transmitters, no wires are needed to connect them to the central observatory site.