Measurement of the cosmicray sidereal anisotropy near 1500 GV
Abstract
A large underground muon detector has operated at an average rate of 4.47 Hz for most of a 2.7year interval, starting on Jan. 1, 1978, in a search for periodic variations in the cosmicray flux at a median rigidity of 1.5 x 10 to the 12th V. A peak with relative amplitude of 4.1 +1.2, 0.9 x 10 to the 4th is observed in the Fourier transform of data at the sidereal frequency, where the errors are 68% confidence limits based on an offcenter Rayleigh distribution. After correction for solar motion, the projected anisotropy is 6.4 +1.2, 1.0 x 10 to the 4th at the right ascension of 3.8 + or  0.7 h. Also observed are a second sidereal harmonic, with an amplitude of 2.8 +0.9, 0.7 x 10 to the 4th at the ascension 7.8 + or  1.0 h and a third harmonic of amplitude 2.3 +1.0, 0.7 x 10 to the 4th at 7.8 + or  1.4 h ascension. There is no discernible peak at the antisidereal frequency, and the small amplitude at the solar frequency implies an upper atmosphere diurnal temperature amplitude of less than about 0.1 C.
 Publication:

The Astrophysical Journal
 Pub Date:
 September 1981
 DOI:
 10.1086/159246
 Bibcode:
 1981ApJ...248.1166C
 Keywords:

 Anisotropic Media;
 Cosmic Rays;
 Muons;
 Particle Flux Density;
 Sidereal Time;
 Energy Spectra;
 Fourier Transformation;
 Frequency Response;
 Periodic Variations;
 Radiation Measurement;
 Space Radiation