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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 21, issue 8
Ann. Geophys., 21, 1681-1689, 2003
https://doi.org/10.5194/angeo-21-1681-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 21, 1681-1689, 2003
https://doi.org/10.5194/angeo-21-1681-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.

  31 Aug 2003

31 Aug 2003

Low- and high-frequency spectral behavior of cosmic-ray intensity for the period 1953–1996

H. Mavromichalaki1, P. Preka-Papadema2, B. Petropoulos3, I. Tsagouri1, S. Georgakopoulos1, and J. Polygiannakis2 H. Mavromichalaki et al.
  • 1Nuclear and Particle Physics Sect., Physics Dept., University of Athens, Panepistimiopolis Zografos, 15783 Athens, Greece
  • 2Section of Astrophysics, Astronomy and Mechanics, Physics Dept., University of Athens, Panepistimiopolis Zografos, 15783 Athens, Greece
  • 3Research Center for Astronomy and Applied Mathematics, Academy of Athens, 14 Anagnostopoulou str., 10673 Athens, Greece

Abstract. A study of the cosmic-ray intensity power spectrum using the Climax Neutron Monitor data in the frequency range from 10-9 Hz to 10-7 Hz (which corresponds to periodicities from 11 years to a few months) during the period 1953–1996, was carried out by means of the successive approximations method of analysis and was compared against the power spectrum and the maximum entropy methods. The contributions of the time evolution of several peaks to the global one were obtained. Except for the well-known 11-year and the 1-year variations, peaks at 7.7, 5.5, 2 and 1.7 years are found. Several peaks with periods less than 10 months have appeared in our analysis, while the occurrence of 5.1 months is obtained in all the examined solar cycles with a strong signature in cycle 21. Transitions of these quasi-periodicities are seen in power spectra plots. Some of them can be attributed to the modulation of the cosmic ray intensity by solar activity. Others are sporadic and have been previously attributed to the interplanetary magnetic field. The results obtained support once again the argument regarding the difference in the solar activity between odd and even solar cycles.

Key words. Interplanetary physics (Cosmic rays, Interplanetary magnetic fields)

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