The energies of cosmic rays, fully ionized charged nuclei, extend over a wide range up to 10 eV. A particularly interesting energy region spans from 10 to 10 eV, where the all-particle energy spectrum exhibits two interesting structures, the “knee” and the “second knee”. An explanation of these features is thought to be an important step in understanding the origin of the high-energy particles....

Developed as NASA Astrophysics Probe-class mission, the Probe Of Extreme Multi-Messenger (POEMMA) is designed to identify sources of ultra-high energy cosmic rays (UHECRs) and observe neutrinos. POEMMA consists two spacecraft flying in a loose formation at 525 km altitude, 28.5$^\circ$ inclination orbits. Each hosts Schmidt telescope with large collecting area wide Field-of-View (FoV). A novel ...

The southern part of the Pierre Auger Observatory (PAO) is nearing completion in the province of Mendoza, Argentina. Since 2004 the instrument is used to take air shower data at the highest energies [1]. The energy threshold of the 3000 km2 surface array of 1600 particle detectors for high quality air shower reconstruction is about 3 . 10 eV. The 24 Auger fluorescence telescopes (FD), located i...

The simulations of extensive air showers as well as the detectors involved in their detection play a fundamental role in the study of the high energy cosmic rays. At the highest energies the detailed simulation of air showers is very costly in processing time and disk space due to the large number of secondary particles generated in interactions with the atmosphere, e.g. ∼ 10 for 10 eV proton s...

The HEGRA system of Imaging Atmospheric Cherenkov Telescopes (IACTs) detects Cherenkov light produced by air showers. The concept of stereoscopic observation with the five HEGRA telescopes allows the reconstruction of various shower parameters, for example the shower direction, the location of the shower core and the energy of cosmic rays. One of the telescopes was modified so that measurements...

In air shower experiments information about the initial cosmic ray particle or about the shower development is obtained by exploiting the correlations between the quantities of interest and the directly measurable quantities. It is shown how these correlations are properly treated in order to obtain unbiased results. As an example, the measurement of the average penetration depth as a function ...

Analyzing measurements of the LOPES antenna array together with corresponding CoREAS simulations for more than 300 measured events with energy above 10 eV and zenith angles smaller than 45◦, we find that the radio wavefront of cosmic-ray air showers is of approximately hyperbolic shape. The simulations predict a slightly steeper wavefront towards East than towards West, but this asymmetry is ne...

The antenna field of LOPES uses inverted V-shaped dipole antennas to measure radio signals originating from extensive air showers (EAS). The LOPES antennas are measuring in coincidence with the air shower experiment KASCADE-Grande. For roughly one year data in the frequency range from 40–80 MHz were taken, having 30 linearly polarized antennas oriented to East-West. In this data set the East-We...

Cross sections for proton inelastic collision with different nuclei are described within the Glauber and multiple scattering approximations. A significant difference between approximate “Glauber” formula and exact calculations with a geometrical scaling assumption for very high-energy cross section is shown. Experimental values of proton–proton cross sections obtained using extensive air shower...

Monitoring of the atmospheric conditions is very important for fluorescence observations. Particularly, the presence of clouds can drastically distort the signal from the extensive air shower. Infra-red (IR) sensors, measuring sky temperature, can help to distinguish clouds, which are usually significantly warmer than clear skies. Array of such sensors, covering the detector’s field of view, wa...