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Mid-term periodicities of cosmic ray intensitiesc

Galactic cosmic ray intensities (GCRs) observed by five neutron monitors (NMs) have been used to study cosmic ray modulations between 1971 and 2007. The influence of interplanetary magnetic polarity (IMF) states has been studied for the A 0 epochs. A comparison of the spectra for both positive IMF polarities indicated different solar origins. The spectra have different power amplitudes and most peaks of different locations. In addition, the differences in the cosmic ray modulations, conditions for solar activity minima and maxima periods are probably associated with the influence of drift effects. The observed differences are related to the 22-year cycle in heliospheric modulations of cosmic rays, leading to the different shapes of CR maxima and the hysteresis effect. Accordingly, drift effects dependent on the polarity of the global solar magnetic field may play a significant role in the observed differences between maxima and minima periods. The drift mechanism is enhanced during periods of low to moderate SA, i.e., around solar cycle minima, during negative polarity periods, when A | Journal of Advanced Research 2011 2 137-147 Cairo University Journal of Advanced Research ORIGINAL ARTICLE Mid-term periodicities of cosmic ray intensities Mohamed A. El-Borie a Naglaa A. Aly b Amr El-Taher b a Physics Department Faculty of Science Alexandria University Moharam Bak P.O. 21511 Egypt b Physics and Chemistry Department Faculty of Education Alexandria University Al-Shatby Egypt Received 9 April 2010 revised 25 August 2010 accepted 26 August 2010 Available online 26 November 2010 KEYWORDS Astroparticle-nuclear physics Galactic cosmic rays Solar activity Ultra low-frequency power spectra Abstract Galactic cosmic ray intensities GCRs observed by five neutron monitors NMs have been used to study cosmic ray modulations between 1971 and 2007. The influence of interplanetary magnetic polarity IMF states has been studied for the A 0 and A 0 epochs. A comparison of the spectra for both positive IMF polarities indicated different solar origins. The spectra have different power amplitudes and most peaks of different locations. In addition the differences in the cosmic ray modulations conditions for solar activity minima and maxima periods are probably associated with the influence of drift effects. The observed differences are related to the 22-year cycle in heliospheric modulations of cosmic rays leading to the different shapes of CR maxima and the hysteresis effect. Accordingly drift effects dependent on the polarity of the global solar magnetic field may play a significant role in the observed differences between maxima and minima periods. The drift mechanism is enhanced during periods of low to moderate SA i.e. around solar cycle minima during negative polarity periods when A 0. 2010 Cairo University. Production and hosting by Elsevier B.V. All rights reserved. Introduction Study of the modulation of galactic cosmic rays GCRs is important because of its potential for revealing the subtle fea- Corresponding author. Tel. 20 16 5042670 fax 203 391 1794. E-mail .