EVOLUTION OF THE COSMIC-RAY ANISOTROPY ABOVE 10 ¹⁴ eV

Abstract

The amplitude and phase of the cosmic-ray anisotropy are well established experimentally between 10 11 eV and 10 14 eV. The study of their evolution in the energy region 10 14-10 16 eV can provide a significant tool for the understanding of the steepening ("knee") of the primary spectrum. In this Letter, we extend the EAS-TOP measurement performed at E 0 ≈ 10 14 eV to higher energies by using the full data set (eight years of data taking). Results derived at about 10 14 and 4 × 10 14 eV are compared and discussed. Hints of increasing amplitude and change of phase above 10 14 eV are reported. The significance of the observation for the understanding of cosmic-ray propagation is discussed.

Cosmic rays and stochastic magnetic reconnection in the heliotail

“…This anisotropy was observed in the Northern Hemisphere from energies of tens to several hundreds GeV with muon detectors (Nagashima et al, 1998;Munakata et al, 2010), and in the multi-TeV energy range with Tibet ASγ array (Amenomori et al, 2006(Amenomori et al, , 2011a, Super-Kamiokande (Guillian et al, 2007), Milagro (Abdo et al, 2009) and ARGO-YBJ (Zhang, 2009;Shuwang, 2011). An anisotropy was also observed at an energy in excess of about 100 TeV with the EAS-TOP shower array (Aglietta et al, 2009). Recently similar observations were reported in the Southern Hemisphere at energies of 10s to 100s TeV with the IceCube Observatory (Abbasi et al, 2010(Abbasi et al, , 2012.…”

Cosmic-Ray Small-Scale Anisotropies and Local Turbulent Magnetic Fields

“…Above the energy range where cosmic rays are directly affected by inner heliospheric processes (see, e.g., Florinski et al 2013;Manuel et al 2014;Florinski et al 2015), a statistically significant anisotropy has been observed by a variety of experiments, sensitive to different energy ranges (from tens of GeV to a few PeV), located on or below the Earth's surface in the northern hemisphere (Nagashima et al 1998;Hall et al 1999;Amenomori et al 2005Amenomori et al , 2006Guillian et al 2007;Abdo et al 2009;Aglietta et al 2009;Zhang et al 2009;Munakata et al 2010;Amenomori et al 2011;de Jong et al 2011;Cui et al 2011;Bartoli et al 2015) and in the southern hemisphere (Abbasi et al 2010a(Abbasi et al , 2011a(Abbasi et al , 2012bAartsen et al 2013b).…”

Medium scale anisotropy in the TeV cosmic ray flux observed by ARGO-YBJ

“…However, a number of experiments observed an energydependent nondipolar ''large''-scale anisotropy (LSA) in the sidereal time frame with an amplitude of about 10 À4 -10 À3 , revealing the existence of two distinct broad regions: an excess distributed around 40 to 90 in right ascension (commonly referred to as the ''tail-in'' excess because of the position consistent with the direction of the heliotail) and a deficit (the ''loss cone'') around 150 to 240 in right ascension (R.A.) [3][4][5][6][7][8][9]. The origin of this anisotropy of Galactic CRs is still unknown.…”