Title: Temporal evolution of 1.68 y periodicity in cosmic rays
Author: Anna Antalova
Affil: Institute of the Experimental Physics, Watson street 47, 04353 Kosice, The Slovak Republic
Email: antalova@ta3.sk
Authors: K.Kudela (the first), J.Rybák(the second)
Affils: Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatr. Lomnica, The Slovak Republic
Abstract: Wavelet transform allows to make inspection of the temporal evolution of given periodicities in the signal independently of its stationarity. The long cosmic ray time series of neutron monitor data at different cutoff rigidities are used to deduce the time profile of selected periodicities for the period from 1953 until 1999. While for the periodicity 1.3 years its density is dominant around the year 1991 independently of cutoff rigidity, there is a tendency of organizing the density of 1.68 years periodicity according to rigidity if the two most pronounced peaks are assumed, namely that around 1982 (A) and that around 1991 (B). Four stations (Calgary, Climax, Lomnicky Stit and Huancayo/Haleakala) are indicating the ratio of A/B is changing with the increasing rigidity, from 1:0.6 at Calgary down to 1:1.55 for Huancayo/Haleakala. The causes of this effect are discussed and compared with earlier papers on 1.68 year periodicity. Torrence and Compo wavelet transform procedure is used.