Observation of Ultra-high-energy Cosmic Rays with the ANITA Balloon-borne Radio Interferometer

Understand

We report the observation of sixteen cosmic ray events of mean energy of 1.5 x 10^{19} eV, 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 the first ultra-wideband, far-field measurements of the radio spectral density of geosynchrotron emission in the range from 300-1000 MHz.
• The emission is 100% linearly polarized in the plane perpendicular to the projected geomagnetic field.
• Fourteen of our observed 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.