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The NASA sponsored balloon-borne ANITA (Antarctic Impulsive Transient Antenna) detector in Antarctica is designed to detect ultra-high energy cosmic neutrinos with energies exceeding 1 EeV (10 18 eV). ANITA also detects the ultra-high energy cosmic rays (UHECR) by collecting the radio pulses generated through the interaction of the primary particles with Earth’s atmosphere. The radio pulse is detected after reflection from the Antarctic ice surface. For calibration and measurement of surface reflectivity, the balloon borne HiCal radio-frequency (RF) transmitter is used. Here we are interested in determining the mean value of reflection coefficient over the range of frequencies which are of interest in HiCal observations. Our main objective is interpretation of radio wave signals produced by cosmic ray interactions with Earth's atmosphere which are observed by the ANITA detector. We developed a general formalism to treat reflection of spherical electromagnetic waves from a spherical surface. The incident wave is decomposed into plane waves and each plane wave is reflected off the surface using the standard Fresnel formalism. For each plane wave the reflected wave is assumed to be locally a plane wave. The surface roughness effects are also included by using realistic surface roughness models. In this talk, I will explain our formalism and the effect of various surface roughness models on the pulse shape to provide an explanation for the observed ANITA mystery events.
Ioana Maris and Steven Lowette