Unusual Near-Horizon Cosmic-Ray-like Events Observed by ANITA-IV

• Published in: Physical Review Letters
• Main Authors: Gorham, P. W., Ludwig, A., Deaconu, C., Cao, P., Allison, P., Banerjee, O., Batten, L., Bhattacharya, D., Beatty, J. J., Belov, K., Binns, W. R., Bugaev, V., Chen, C. H., Chen, P., Chen, Y., Clem, J. M., Cremonesi, L., Dailey, B., Dowkontt, P. F., Fox, B. D., Gordon, J. W. H., Hast, C., Hill, B., Hsu, S. Y., Huang, J. J., Hughes, K., Hupe, R., Israel, M. H., Liu, T. C., Macchiarulo, L., Matsuno, S., McBride, K., Miki, C., Nam, J., Naudet, C. J., Nichol, R. J., Novikov, A., Oberla, E., Olmedo, M., Prechelt, R., Rauch, B. F., Roberts, J. M., Romero-Wolf, A., Rotter, B., Russell, J. W., Saltzberg, D., Seckel, D., Schoorlemmer, H., Shiao, J., Stafford, S., Stockham, J., Stockham, M., Strutt, B., Sutherland, M. S., Varner, G. S., Vieregg, A. G., Wang, S. H., Wissel, S. A.
• Language: unknown
• Published: 2023
• Subjects: 79 ASTRONOMY AND ASTROPHYSICS; Antarctic; The Antarctic; Antarc*
• Online Access: http://www.osti.gov/servlets/purl/1777246; https://www.osti.gov/biblio/1777246; https://doi.org/10.1103/physrevlett.126.071103

ANITA’s fourth long-duration balloon flight in 2016 detected 29 cosmic-ray (CR)-like events on a background of 0.37 - 0.17 + 0.27 anthropogenic events. CRs are mainly seen in reflection off the Antarctic ice sheets, creating a phase-inverted waveform polarity. However, four of the below-horizon CR-like events show anomalous noninverted polarity, a p = 5.3 × 10 - 4 chance if due to background. Furthermore, all anomalous events are from locations near the horizon; ANITA-IV observed no steeply upcoming anomalous events similar to the two such events seen in prior flights.