First experimental characterization of microwave emission from cosmic ray air showers

Šmída, R.; Werner, F.; Engel, R.; Arteaga-Velázquez, J. C.; Bekk, K.; Bertaina, M.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Chiavassa, A.; Cossavella, F.; Di Pierro, F.; Doll, P.; Fuchs, B.; Fuhrmann, D.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Huber, D.; Huege, T.; Kampert, K. -H.; Kang, D.; Klages, H.; Kleifges, M.; Krömer, O.; Link, K.; Łuczak, P.; Ludwig, M.; Mathes, H. J.; Mathys, S.; Mayer, H. J.; Melissas, M.; Morello, C.; Neunteufel, P.; Oehlschläger, J.; Palmieri, N.; Pekala, J.; Pierog, T.; Rautenberg, J.; Rebel, H.; Riegel, M.; Roth, M.; Salamida, F.; Schieler, H.; Schoo, S.; Schröder, F. G.; Sima, O.; Stasielak, J.; Toma, G.; Trinchero, G. C.; Unger, M.; Weber, M.; Weindl, A.; Wilczyński, H.; Will, M.; Wochele, J.; Zabierowski, J.

doi:10.1103/PhysRevLett.113.221101

We report the first direct measurement of the overall characteristics of microwave radio emission from extensive air showers. Using a trigger provided by the KASCADE-Grande air shower array, the signals of the microwave antennas of the Cosmic-Ray Observation via Microwave Emission experiment have been read out and searched for signatures of radio emission by high-energy air showers in the GHz frequency range. Microwave signals have been detected for more than 30 showers with energies above 3×1016eV. The observations presented in this Letter are consistent with a mainly forward-directed and polarized emission process in the GHz frequency range. The measurements show that microwave radiation offers a new means of studying air showers at E≥1017eV.