, Volume 205, Issue 1, pp 165-175

Time Evolution of low-Frequency Periodicities in Cosmic ray Intensity

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


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.