Observation of ultrahigh-energy cosmic rays with the ANITA balloon-borne radio interferometer

S. Hoover, J. Nam, P. W. Gorham, E. Grashorn, P. Allison, S. W. Barwick, J. J. Beatty, K. Belov, D. Z. Besson, W. R. Binns, C. Chen, P. Chen, J. M. Clem, A. Connolly, P. F. Dowkontt, M. A. Duvernois, R. C. Field, D. Goldstein, A. G. Vieregg, C. HastM. H. Israel, A. Javaid, J. Kowalski, J. G. Learned, K. M. Liewer, J. T. Link, E. Lusczek, S. Matsuno, B. C. Mercurio, C. Miki, P. Miočinović, C. J. Naudet, J. Ng, R. J. Nichol, K. Palladino, K. Reil, A. Romero-Wolf, M. Rosen, L. Ruckman, D. Saltzberg, D. Seckel, G. S. Varner, D. Walz, F. Wu

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We report the observation of 16 cosmic ray events with a mean energy of 1.5×1019eV via radio pulses originating from the interaction of the cosmic ray air shower with the Antarctic geomagnetic field, a process known as geosynchrotron emission. We present measurements in the 300-900 MHz range, which are the first self-triggered, first ultrawide band, first far-field, and the highest energy sample of cosmic ray events collected with the radio technique. Their properties are inconsistent with current ground-based geosynchrotron models. The emission is 100% polarized in the plane perpendicular to the projected geomagnetic field. Fourteen events are seen to have a phase inversion due to reflection of the radio beam off the ice surface, and two additional events are seen directly from above the horizon. Based on a likelihood analysis, we estimate angular pointing precision of order 2° for the event arrival directions.

Original languageEnglish (US)
Article number151101
JournalPhysical review letters
Issue number15
StatePublished - Oct 5 2010


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