Contributions to the 30th International Cosmic Ray Conference, Merida, Mexico, 2007 by Forschungszentrum Karlsruhe Institut für Kernphysik, Institut für Prozessdatenverarbeitung und Elektronik and Universitàt Karlsruhe Institut für Experimentelle Kernphysik

Abstract

The bi-annual International Cosmic Ray Conferences have become the most central meetings for discussing new results and recent progress in the field of cosmic ray research. The contributions to these conferences cover a wide range of subjects extending from the physics of the sun and heliosphere, over gamma-ray observations to direct and indirect cosmic ray measurements and their interpretation. Many new results are announced for the first time at these meetings. The present volume is a compilation of the contributions of Institutes of Forschungszentrum Karlsruhe and University Karlsruhe to the 30 th International Cosmic Ray Conference (ICRC), held in Merida, Mexico from July 3 to 11, 2007. The collection of contributions provides an up-to-date review of the current activities and research projects related to cosmic rays that are pursued in Karlsruhe. The articles also demonstrate the enormous progress that has been made during the last years, in particular in the field of ultra-high energy cosmic rays. Most of these contributions are the result of close and fruitful collaboration of many different groups worldwide, first of all within international collaborations such as the Pierre Auger, LOPES and KASCADE-Grande Collaborations, but also within smaller groups. The articles compiled in this report are sorted according to the main research foci of the Karlsruhe groups. These include the physics of the knee in the cosmic ray spectrum, the transition between galactic and extra-galactic cosmic rays, and extragalactic cosmic rays of the highest energies. Cosmic rays in the energy range from just below the knee in the cosmic ray spectrum (10 14.5 eV) to the energy of the conjectured transition between galactic and extra-galactic cosmic rays are studied with the KASCADE-Grande detector at the site of Forschungszentrum Karlsruhe. KASCADE-Grande is a multi-detector air shower array, which combines the electron and muon detectors of the KASCADE (KArlsruhe Shower Core and Array Detector) array with a 0.5 km 2 array of scintillators. Based on a data set from about 3 years of operation, first shower size spectra have been derived and limits on the anisotropy of the cosmic ray flux were presented at the conference. An alternative method of air shower detection is the measurement of radio signals produced by the particles showers in the atmosphere. The physics potential of this detection technique is investigated with the LOPES (LOFAR PrototypE Station) array of dipole antennas at the site of the KASCADE-Grande installation. Measuring the electric field strength in the frequency range from 40 to 80 MHz, a very good correlation between the shower energy reconstructed with KASCADE-Grande and the radio signal was found. Important contributions presented at the conference include the investigation of the influence of thunderstorms on the measured field strength and the measurement of showers with large zenith angles as well as significant progress in the modelling of the emission processes of the radio signals during the shower development. The study of cosmic rays at the highest energies and the transition between galactic and extra-galactic cosmic rays is the aim of the Pierre Auger Project. The Pierre Auger Observatory is the largest cosmic ray detector with one installation in the northern and southern hemisphere to ensure full sky coverage. The southern detector is currently under construction in the Province of Mendoza, Argentina.