Radio signals of cosmic-ray-induced air showers at the Pierre Auger Observatory

PhD ceremony: Mr. S. Harmsma, 13.15 uur, Doopsgezinde kerk, Oude Boteringestraat 33, Groningen

Dissertation: Radio signals of cosmic-ray-induced air showers at the Pierre Auger Observatory

Promotor(s): prof. A.M. van den Berg, prof. F.L. Linde

Faculty: Mathematics and Natural Sciences

This PhD thesis reports on the measurement of radio signals from cosmic-ray-induced air showers. These measurements were performed with a first-generation radio setup, located at the site of the Pierre Auger Observatory.

The Pierre Auger Observatory has been built in Argentina to study cosmic rays at the highest energies (1018 eV and above). With 3,000 km2the Pierre Auger Observatory is world's largest cosmic-ray observatory; it was built by an international collaboration of more than 450 scientists from 18 countries.

The ultra-high-energy cosmic rays that are studied at the observatory are part of an interesting scientific puzzle. Although we know that these cosmic rays have an energy that is extremely high, we do not know how they have obtained this energy. An attempt to solve this puzzle is made at the observatory by measuring the properties of these cosmic rays. What are they and where do they come from?

When ultra-high-energy cosmic rays hit the Earth's atmosphere, an avalanche of billions of particles is created. This avalanche is called an air shower, and cosmic rays are studied through the measurement of these air showers. To improve these measurements, we have worked on a relatively new detection technique. This technique uses radio antennas to detect radiation that is emitted by the charged particles within an air shower.

This thesis reports on the first results of the radio measurements on cosmic rays at the site of the Auger observatory. Although the amount of data is limited, clear radio signals from cosmic rays have been observed with the first-generation radio setup. The properties of cosmic rays with a clear radio signal are discussed, and reasons are given why some cosmic rays give a clear radio signal while others do not.