Characteristics of enhanced and low-amplitude cosmic-ray diurnal variation |
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Authors: | A. G. Ananth K. Kudela D. Venkatesan |
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Affiliation: | (1) Institute for Space Physics, Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada, T2N IN2;(2) Present address: The Indian Space Research Organization, HQ, Antariksh Bhavan, Bangalore, India;(3) Present address: The Institute of Experimental Physics, SAS, Koice, Slovakia |
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Abstract: | The occurrence of a large number of high- and low-amplitude cosmic-ray diurnal wave trains during the two solar cycles (20 and 21) over the years 1965–1990 has been examined as a function of solar activity. The high-amplitude days with the time of maximum in the 18:00 hr corotation direction do not indicate any significant correlation with solar activity. But, the low-amplitude days are inversely correlated with solar activity and the time of maximum shifts to earlier hours ( 15:00 hr direction). The slope of the power-specrum density roughly characterized by power spectral index n in the high-frequency range 3.5 x 10–5 Hz to 8.3 x 10–4 Hz (time scales of 20 min to 8 hr) is different for the two classes of events. A suggestion is made that the enhanced and low-amplitude cosmic-ray diurnal variations are produced by different types of interplanetary magnetic field distributions. |
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