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Advances in Astronomy
Volume 2012 (2012), Article ID 834247, 9 pages
http://dx.doi.org/10.1155/2012/834247
Research Article

New Insights on Cosmic Ray Modulation through a Joint Use of Nonstationary Data-Processing Methods

1Dipartimento di Fisica, Università della Calabria, 87036 Rende (CS), Italy
2IAPS, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
3Liquid Crystal Laboratory, INFM, Ponte P. Bucci Cubo 33B, 87036 Rende (CS), Italy

Received 3 August 2012; Accepted 31 October 2012

Academic Editor: Badruddin

Copyright © 2012 A. Vecchio et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The time variability of the cosmic ray (CR) intensity, recorded by the Climax neutron monitor and covering the period 1953–2004, has been analyzed by the joint application of the wavelet and the empirical mode decomposition (EMD) analyses. Dominant time scales of variability are found at ~11 yr, ~22 yr, ~6 yr and in the range of the quasi-biennial oscillations (QBOs). The combination of the 11 yr cycle and QBOs explains the Gnevychev Gap (GG) phenomenon and many step-like decreases characterizing the CR modulation. The additional scales of variability at ~22 yr and ~6 yr are responsible for other features of the long-term CR trend, such as the intensity flat-topped profile, following the maxima of even-numbered cycles during positive polarity state of the heliosphere ( ). Comparison with basic time scales of variability derived from the sunspot area (SA) allows the association of the 11 yr cycle and QBOs with solar activity variations, whereas the other two modes with the drift effects govern the CR entrance in the heliosphere.