Characteristics of enhanced and low-amplitude cosmic-ray diurnal variation

Cosmic-ray data from a high pressure integrating ionization chamber, obtained at Ottawa, for 129 complete days during September 1950 to July 1951 are subjected to rigorous statistical analysis. The barometric coefficient is −0.19% per mm. of Hg for the period covered by this analysis. The results also indicate a physically significant 24-hr. wave in cosmic-ray intensity, with an amplitude of 0.12% of the total intensity, having its maximum at about 10.40 a.m. local mean time. The existence of the semidiurnal wave, however, is not physically significant.

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PERIODICAL FLUCTUATION STUDIES OF COSMIC-RAY DIURNAL VARIATIONS DURING THE QUIET-SUN PERIOD 1962–64

Canadian Journal of Physics ◽

10.1139/p67-220 ◽

1967 ◽

Vol 45 (8) ◽

pp. 2733-2748 ◽

Cited By ~ 1

Author(s):

Masahiro Kodama

Keyword(s):

Diurnal Variation ◽

Solar Minimum ◽

Counting Rate ◽

Solar Rotation ◽

Rotation Period ◽

Cosmic Ray ◽

Diurnal Variations ◽

Statistical Studies ◽

Periodic Fluctuations ◽

Recurrence Tendency

Statistical studies of periodic fluctuations of the cosmic-ray diurnal variation have been performed, using neutron and meson component data obtained by the high-counting-rate cosmic-ray monitors at Deep River. The data cover an interval from May 1962 to October 1964, a period of descending solar activity ending near the solar minimum. It is shown that a 27-day recurrence tendency of the amplitude of the diurnal variation occasionally appears as well as shorter recurrent variations, ranging from one-half to one-sixth of the solar rotation period. The correlations of these fluctuations with some typical solar and terrestrial indices are examined in order to search for possible origins of the shorter recurrent variations. A possible connection with the Kp index exists.

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The solar semidiurnal variation of cosmic-ray intensity 70 m.w.e. underground

Canadian Journal of Physics ◽

10.1139/p68-364 ◽

1968 ◽

Vol 46 (10) ◽

pp. S839-S843 ◽

Cited By ~ 4

Author(s):

G. Cini-Castagnoli ◽

M. A. Dodero ◽

L. Andreis

Keyword(s):

Diurnal Variation ◽

Cosmic Ray ◽

Fermi Acceleration ◽

Sidereal Time ◽

Cosmic Ray Intensity ◽

Intensity Measurements ◽

Hourly Data ◽

Semidiurnal Variation ◽

Order Of Magnitude ◽

Different Depths

Cosmic-ray intensity measurements have been carried out during the last year at a depth of 70 m.w.e. in the Monte dei Cappuccini laboratory in Torino, using solid vertical semicubical scintillator telescopes with a total area of 2 m2. Hourly data for 245 days corrected for barometric changes have been analyzed for the solar, apparent sidereal, and antisidereal daily variations whose harmonics are as follows:[Formula: see text]The true sidereal diurnal variation is estimated to have an amplitude of 0.019% with a time of maximum at 1720 h local sidereal time. The solar diurnal variation at different depths underground follows the energy dependence calculated with Axford's theory. The solar semidiurnal variation shows instead a fairly constant value at different μ energies. Its order of magnitude agrees with that expected as a result of Fermi acceleration in collisions of primaries moving in roughly solar and antisolar directions with solar wind inhomogeneities.

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