A Precise Measurement of the Sidereal Anisotropy of Cosmic-Rays Near 1500 GV.
Abstract
The Utah underground muon detector has monitored the muon flux produced by primary cosmic rays having a median rigidity of 1500 GV for most of the 2.2 yr interval since 1 Jan 1978. The detector, located 507 hg/cm('2) underground, consists of 300 plastic scintillation counters arranged in three layers separated by 75 g/cm('2) of concrete absorber. With 37.3 m('2) of sensitive area per layer, the 3-layer coincidence rate is 4.7/sec. Right ascension resolution is about 15(DEGREES). In principle, no declination information is available from such experiments. When an event occurs, an on-line computer reads all of the latches, tallies recognizable single muon events in any one of 1900 channels, and records summaries every half-hour. More complicated events are recorded verbatim for off-line analysis. Detailed study of various event rates demonstrates that the detector operates in a stable and predictable manner. Discrete Fourier transform (DFT) techniques are applied to the problems of picking out stationary sinusoidal signals buried in noise and of understanding the temperature induced fluctuations in the muon flux. A sidereal anisotropy in the relative intensity is found, with a first harmonic amplitude (2.4('+1.5)) x 10('-4) with its maximum at (alpha) = 2('h).0 (+OR-) 1('h).9. After corrections for latitude and the motion of the solar system relative to the local interstellar medium, this amplitude corresponds to a cosmic ray streaming velocity v cos (delta) = (40('+19)) km/s towards (alpha) = 3('h).5 (+OR-) 1('h).5. The second harmonic amplitude is (2.0('+1.2)) x 10('-4) with maxima at 8('h).2(20('h).2) (+OR-) 1('h).0. No higher harmonics are observed.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1980
- Bibcode:
- 1980PhDT.........6C
- Keywords:
-
- Physics: Astronomy and Astrophysics;
- Anisotropy;
- Cosmic Rays;
- Flux Density;
- Muons;
- Radiation Measurement;
- Fourier Transformation;
- Harmonic Analysis;
- Radiation Detectors;
- Space Radiation