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Ultra-High Energy Cosmic Particles Produce Unusual Radio Flash
Munich, Germany (SPX) May 19, 2005 Using the LOPES experiment, a prototype of the new high-tech radio telescope LOFAR to detect ultra-high energy cosmic ray particles, a group of astrophysicists, in collaboration with Max-Planck-Gesellschaft and Helmholtz-Gemeinschaft, has recorded the brightest and fastest radio blasts ever seen on the sky. The blasts, whose detection are reported in this week's issue of the journal Nature, are dramatic flashes of radio light that appear more than 1000 times brighter than the sun and almost a million times faster than normal lightning. For a very short moment these flashes - which had gone largely unnoticed so far - become the brightest light on the sky with a diameter twice the size of the moon. The experiment showed that the radio flashes are produced in the Earth atmosphere, caused by the impact of the most energetic particles produced in the cosmos. These particles are called ultra-high energy cosmic rays and their origin is an ongoing puzzle. The astrophysicists now hope that their finding will shed new light on the mystery of these particles. The scientists used an array of radio antennas and the large array of particle detectors of the KASCADE-Grande experiment at Forschungszentrum Karlsruhe. They showed that whenever a very energetic cosmic particle hit the Earth atmosphere a corresponding radio pulse was recorded from the direction of the incoming particle. Using imaging techniques from radio astronomy the group even produced digital film sequences of these events, yielding the fastest movies ever produced in radio astronomy. The particle detectors provided them with basic information about the incoming cosmic rays. The researchers were able to show that the strength of the emitted radio signal was a direct measure of the cosmic ray energy. "It is amazing that with simple FM radio antennas we can measure the energy of particles coming from the cosmos" says Prof. Heino Falcke from the Netherlands Foundation for Research in Astronomy (ASTRON) who is the spokesperson of the LOPES collaboration. "If we had sensitive radio eyes, we would see the sky sparkle with radio flashes", he adds. The scientists used pairs of antennas similar to those used in ordinary FM radio receivers. "The main difference to normal radios is the digital electronics and the broad-band receivers, which allow us to listen to many frequencies at once", explains Dipl. Phys. Andreas Horneffer, a graduate student of the University of Bonn and the International Max-Planck Research School (IMPRS), who installed the antennas as part of his PhD project. In principle some of the detected radio flashes are in fact strong enough to wipe out conventional radio or TV reception for a short time. To demonstrate this effect the group has converted their radio reception of a cosmic ray event into a sound track. However, since the flashes only last for some 20-30 nanoseconds and bright signals happen only once a day, they would be hardly recognisable in everyday life.
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