Characteristics of Four Upward-pointing Cosmic-ray-like Events Observed with ANITA

Understand

We report on four radio-detected cosmic-ray (CR) or CR-like events observed with the Antarctic Impulsive Transient Antenna (ANITA), a NASA-sponsored long-duration balloon payload.

• Two of the four were previously identified as stratospheric CR air showers during the ANITA-I flight.
• A third stratospheric CR was detected during the ANITA-II flight.
• Here we report on characteristics these three unusual CR events, which develop nearly horizontally, 20-30~km above the surface of the Earth.