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

• Main Authors: Gorham, PW, Ludwig, A, Deaconu, C, Cao, P, Allison, P, Banerjee, O, Batten, L, Bhattacharya, D, Beatty, JJ, Belov, K, Binns, WR, Bugaev, V, Chen, CH, Chen, P, Chen, Y, Clem, JM, Cremonesi, L, Dailey, B, Dowkontt, PF, Fox, BD, Gordon, JWH, Hast, C, Hill, B, Hsu, SY, Huang, JJ, Hughes, K, Hupe, R, Israel, MH, Liu, TC, Macchiarulo, L, Matsuno, S, McBride, K, Miki, C, Nam, J, Naudet, CJ, Nichol, RJ, Novikov, A, Oberla, E, Olmedo, M, Prechelt, R, Rauch, BF, Roberts, JM, Romero-Wolf, A, Rotter, B, Russell, JW, Saltzberg, D, Seckel, D, Schoorlemmer, H, Shiao, J, Stafford, S, Stockham, J, Stockham, M, Strutt, B, Sutherland, MS, Varner, GS, Vieregg, AG, Wang, SH, Wissel, SA
• Format: Article in Journal/Newspaper
• Language: English
• Published: AMER PHYSICAL SOC 2021
• Subjects: Antarctic; The Antarctic; Antarc*
• Online Access: https://discovery.ucl.ac.uk/id/eprint/10131170/1/PhysRevLett.126.071103.pdf; https://discovery.ucl.ac.uk/id/eprint/10131170/

ANITA’s fourth long-duration balloon flight in 2016 detected 29 cosmic-ray (CR)-like events on a background of 0.37 + 0.27 − 0.17 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.