Time Evolution of low-Frequency Periodicities in Cosmic ray Intensity |
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| Authors: | K Kudela J Rybák A Antalová M Storini |
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| Institution: | (1) IEP/SAS, Watsonova 47, SK-04353 Ko ice, Slovak Republic;(2) Astronomical Institute/SAS, SK-05960 Tatranská Lomnica, Slovak Republic;(3) Area di Ricerca Roma-Tor Vergata, IFSI/CNR, Via del Fosso del Cavaliere |
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| Abstract: | The long-time series of daily means of cosmic-ray intensity observed by four neutron monitors at different cutoff rigidities (Calgary, Climax, Lomnický  tít and Huancayo/Haleakala) were analyzed by means of the wavelet transform method in the period range   60 to 1000 days. The contributions of the time evolution of three quasi-periodic cosmic-ray signals (150 d, 1.3 yr and 1.7 yr) to the global one are obtained. While the 1.7-yr quasi-periodicity, the most remarkable one in the studied interval, strongly contributes to the cosmic ray intensity profile of solar cycle 21 (particularly in 1982), the 1.3-yr one, which is better correlated with the same periodicity of the interplanetary magnetic field strength, is present as a characteristic feature for the decreasing phases of the cycles 20 and 22. Transitions between these quasi-periodicities are seen in the wavelet power spectra plots. Obtained results support the claimed difference in the solar activity evolution during odd and even solar activity cycles. |
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