changes in cloud cover, and have been demonstrated in studies to have no causal relationship to changes in global temperature. Possible mass extinction factor A handful of studies conclude that a nearby supernova or series of supernovas caused the Pliocene marine megafauna extinction event by substantially increasing radiation levels to hazardous amounts for large seafaring animals. Research and experiments There are a number of cosmic-ray research initiatives, listed below. Ground-based Akeno Giant Air Shower Array Chicago Air Shower Array CHICOS CLOUD CRIPT GAMMA GRAPES-3 HAWC HEGRA High Energy Stereoscopic System High Resolution Fly's Eye Cosmic Ray Detector IceCube KASCADE MAGIC MARIACHI Milagro NMDB Pierre Auger Observatory QuarkNet Spaceship Earth Telescope Array Project Tunka experiment VERITAS Washington Large Area Time Coincidence Array Satellite ACE (Advanced Composition Explorer) Alpha Magnetic Spectrometer Cassini–Huygens Fermi Gamma-ray Space Telescope HEAO 1, HEAO 2, HEAO 3 Interstellar Boundary Explorer Langton Ultimate Cosmic-Ray Intensity Detector PAMELA Solar and Heliospheric Observatory Voyager 1 and Voyager 2 Balloon-borne Advanced Thin Ionization Calorimeter BESS Cosmic Ray Energetics and Mass (CREAM) HEAT (High Energy Antimatter Telescope) PERDaix TIGER TRACER (cosmic ray detector) See also References Further references R.G. Harrison and D.B. Stephenson, Detection of a galactic cosmic ray influence on clouds, Geophysical Research Abstracts, Vol. 8, 07661, 2006 SRef-ID: 1607-7962/gra/EGU06-A-07661 R. Clay and B. Dawson, Cosmic Bullets, Allen & Unwin, 1997. T. K. Gaisser, Cosmic Rays and Particle Physics, Cambridge University Press, 1990. P. K. F. Grieder, Cosmic Rays at Earth: Researcher's Reference Manual and Data Book, Elsevier, 2001. A. M. Hillas, Cosmic Rays, Pergamon Press, Oxford, 1972 M. D. Ngobeni and M. S. Potgieter, Cosmic ray anisotropies in the outer heliosphere, Advances in Space Research, 2007. M. D. Ngobeni, Aspects of the modulation of cosmic rays in the outer heliosphere, MSc Dissertation, Northwest University (Potchefstroom campus) South Africa 2006. D. Perkins, Particle Astrophysics, Oxford University Press, 2003. C. E. Rolfs and S. R. William, Cauldrons in the Cosmos, The University of Chicago Press, 1988. B. B. Rossi, Cosmic Rays, McGraw-Hill, New York, 1964. Martin Walt, Introduction to Geomagnetically Trapped Radiation, 1994. TRACER Long Duration Balloon Project: the largest cosmic ray detector launched on balloons. External links Aspera European network portal BBC news, Cosmic rays find uranium, 2003. Introduction to Cosmic Ray Showers by Konrad Bernlöhr. Astroparticle physics Ionizing radiation Stellar phenomena Solar phenomena Concepts in astronomy