mode Detection The original particle arrives with high energy and hence a velocity near the speed of light, so the products of the collisions tend also to move generally in the same direction as the primary, while to some extent spreading sidewise. In addition, the secondary particles produce a widespread flash of light in forward direction due to the Cherenkov effect, as well as fluorescence light that is emitted isotropically from the excitation of nitrogen molecules. The particle cascade and the light produced in the atmosphere can be detected with surface detector arrays and optical telescopes. Surface detectors typically use Cherenkov detectors or Scintillation counters to detect the charged secondary particles at ground level. The telescopes used to measure the fluorescence and Cherenkov light use large mirrors to focus the light on PMT clusters. Finally, air showers emit radio waves due to the deflection of electrons and positrons by the geomagnetic field. As advantage over the optical techniques, radio detection is possible around the clock and not only during dark and clear nights. Thus, several modern experiments, e.g., TAIGA, LOFAR, or the Pierre Auger Observatory use radio antennas in addition to particle detectors and optical techniques. The longitudinal profile of the number of charged particles can be parameterized by the Gaisser–Hillas function. See also Cosmic-ray observatory References External links Extensive Air Showers. Buckland Park Air Shower Detector Haverah Park Detection System HiRes Detector System Pierre Auger Observatory HiSPARC (High School Project on Astrophysics Research with Cosmics) AIRES (AIRshower Extended Simulations) : Large and well documented Fortran package for simulating cosmic ray showers by Sergio Sciutto at the Department of Physics of the Universidad Nacional de La Plata, Argentina CORSIKA, CORSIKA: Another code for simulating cosmic ray air showers by Dieter Heck of the Forschungszentrum Karlsruhe, Germany COSMUS : Interactive animated 3d models of several different cosmic ray air showers, and instructions on how to make your own using AIRES simulations. From the COSMUS group at the University of Chicago. Milagro Animations : Movies and instructions for how to make them, showing how air showers interact with the Milagro detector. By Miguel Morales. CASSIM Animations : Animations of different cosmic ray air showers by Hajo Dreschler of New York University. SPASE2 Experiment : South-Pole Air Shower Experiment (SPASE). GAMMA Experiment : High mountain Air Shower Experiment. Atmosphere Earth phenomena Cosmic rays