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

P. W. Gorham, A. Ludwig, C. Deaconu, P. Cao, P. Allison, O. Banerjee, L. Batten, D. Bhattacharya, J. J. Beatty, K. Belov, W. R. Binns, V. Bugaev, C. H. Chen, P. Chen, Y. Chen, J. M. Clem, L. Cremonesi, B. Dailey, P. F. Dowkontt, B. D. FoxJ. W.H. Gordon, C. Hast, B. Hill, S. Y. Hsu, J. J. Huang, K. Hughes, R. Hupe, M. H. Israel, T. C. Liu, L. Macchiarulo, S. Matsuno, K. McBride, C. Miki, J. Nam, C. J. Naudet, R. J. Nichol, A. Novikov, E. Oberla, M. Olmedo, R. Prechelt, B. F. Rauch, J. M. Roberts, A. Romero-Wolf, B. Rotter, J. W. Russell, D. Saltzberg, D. Seckel, H. Schoorlemmer, J. Shiao, S. Stafford, J. Stockham, M. Stockham, B. Strutt, M. S. Sutherland, G. S. Varner, A. G. Vieregg, S. H. Wang, S. A. Wissel

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


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. 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.

Original languageEnglish (US)
Article number071103
JournalPhysical review letters
Issue number7
StatePublished - Feb 19 2021

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)


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