Radio Detection of Ultra-High Energy Cosmic Rays

The radio technique for the detection of cosmic particles has seen a major revival in recent years. New and planned experiments in the lab and the field, such as GLUE, Anita, LUNASKA, Codalema, LOPES as well as sophisticated Monte Carlo experiments have produced a wealth of new information and I review here briefly some of the main results with the main focus on air showers. Radio emission of ultra-high energy cosmic particles offers a number of interesting advantages. Since radio waves suffer no attenuation, radio measurements allow the detection of very distant or highly inclined showers, can be used day and night, and provide a bolometric measure of the leptonic shower component. The LOPES experiment has detected the radio emission from cosmic rays, confirmed the geosynchrotron effect for extensive air showers, and provided a good calibration fomula to convert the radio signal into primary particle energy. Moreover, Monte Carlo simulations suggest that also the shower maximum and the particle composition can be measured. Future steps will be the installation of radio antennas at the Auger experiment to measure the composition of ultra-high energy cosmic rays and the usage of the LOFAR radio telescope (and later the SKA) as a cosmic ray detector. Here an intriguing additional application is the search for low-frequency radio emission from neutrinos and cosmic rays interacting with the lunar regolith. This promises the best detection limits for particles above 10^21 eV and allows one to go significantly beyond current ground-based detectors.