Time Evolution of low-Frequency Periodicities in Cosmic ray Intensity
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- Kudela, K., Rybák, J., Antalová, A. et al. Solar Physics (2002) 205: 165. doi:10.1023/A:1013869322693
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The long-time series of daily means of cosmic-ray intensity observed by four neutron monitors at different cutoff rigidities (Calgary, Climax, Lomnický Štít 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.