A Measurement Of The Solar And Sidereal Cosmic-ray Anisotropy At E0 ∼ 1014 Ev

The results of the measurement of the cosmic-ray solar and sidereal anisotropies at primary energy E0 ≈ 1014 eV performed by the EAS-TOP Extensive Air Shower array (Campo Imperatore, National Gran Sasso Laboratories, 2005 m above sea level, latitude 42°.5 N are presented. The measurement includes 4 years of data taking (1990, 1992, 1993, 1994) for a total of 1.3 × 109 events and is performed at two different mean primary energies: E0v ≈ 1.5 × 1014 eV and E0i ≈ 2.5 × 1014 eV. The two results are compatible (within 2 σ) and can therefore be combined. The obtained amplitude and phase of the first harmonic in sidereal time are (in the equatorial plane) Asid, δ=0, (E0 ≈ 2 × 1014 eV) = (3.73 ± 0.57) × 10-4 and sid = 1.82 ± 0.49 hr local sidereal time, with significance 6.5 a. The amplitude of the anisotropy exhibits the expected cos δ dependence. A first harmonic in solar time compatible with the expected Compton-Getting effect due to the motion of revolution of the Earth around the Sun is observed with significance 7.3 σ. The corresponding measured amplitude and phase (also in the equatorial plane) are Asol, δ=0° = (4.06 ± 0.55) × 10-4 and sol = 4.92 ± 0.53 hr, the expected values being 4.7 × 10-4 and 6.0 hr. Different checks of stability of the detectors and consistency of the data are presented. © 1996. The American Astronomical Society. All rights reserved.4701 PART I501505Aglietta, M., (1986) Nuovo Cimento, 9 C, p. 262. , EAS-TOP Collaboration(1993) Proc, 23d Int. Cosmic-Ray Conf. (Calgary), 2, p. 65(1993) Nucl. Instrum. Methods a, 336, p. 310(1993) Proc. 23d Int. Cosmic-Ray Conf. (Calgary)., 4, p. 247(1995) Proc. 24th Int. Cosmic-Ray Conf. (Rome), 2, p. 800Alexeenko, V.V., (1981) Proc. 17th Int. Cosmic-Ray Conf. (Paris), 2, p. 146(1993) Proc. 23d Int Cosmic-Ray Conf. (Calgary), 1, p. 483Andreyev, Y., (1987) Proc. 20th Int Cosmic-Ray Conf. (Moscow), 2, p. 22Bergamasco, L., (1990) Proc. 21st Int. Cosmic-Ray Conf. (Adelaide), 6, p. 372Compton, A.H., Getting, I.A., (1935) Phys. Rev., 47, p. 817(1995) Proc. 24th Int Cosmic-Ray Conf. (Rome), 2, p. 732Parley, F.J.M., Storey, J.R., (1954) Proc. Phys. Soc., A, 67, p. 996Fenton, A.G., (1976) Proc. International Cosmic-Ray Symposium on High-energy Cosmic-Ray Modulation, p. 313. , ed. Cosmic-Ray Laboratory (Tokyo:Univ. Tokyo)Gombosi, T., (1975) Nature, 255, p. 687Kiraly, P., (1979) Nuovo Cimento, 2, p. 7Linsey, J., (1983) Proc. 18th Int. Cosmic-Ray Conf. (Bangalore), 12, p. 135Nagashima, K., (1989) Nuovo Cimento, 12, p. 69