Astrophysics and Space Sciences Transactions www.astrophys-space-sci-trans.net 1810-6528 1810-6536 4 1 2008 10.5194/astra-4-31-2008 http://www.astrophys-space-sci-trans.net/4/31/2008/ http://www.astrophys-space-sci-trans.net/4/31/2008/astra-4-31-2008.html http://www.astrophys-space-sci-trans.net/4/31/2008/astra-4-31-2008.pdf 31 34 2008-07-08 27-day variations of the galactic cosmic ray intensity and anisotropy M. V. Alania A. Gil R. Modzelewska Institute of Math. And Physics of University of Podlasie, 3 Maja 54, 08-110 Siedlce, Poland Institute of Geophysics, Georgian Academy of Sciences, Tbilisi, Georgia We study the 27-day variations of the galactic cosmic ray (GCR) intensity and three dimensional (3-D) anisotropy in different polarity periods of the solar magnetic cycle. We found that the larger amplitudes of the 27-day variations of the galactic cosmic ray anisotropy and intensity in the minimum epochs of solar activity for the <i>A</i>>0 polarity period than for the <i>A</i><0 period are related with the heliolongitudinal asymmetry of the solar wind velocity. We reveal the long-lived (~22 years) active region of the heliolongitudes being the sources of the long-lived 27-day variation of the solar wind velocity during the <i>A</i>>0 polarity period. The 27-day variation of the GCR 3-D anisotropy has a sporadic character; it appears and disappears as wave packages (wave oscillations) with an average duration of 4–6 solar rotations. We found that the rigidity R power law spectrum of the amplitudes (<i>A</i>27) of the 27-day variation of the GCR intensity (<i>A</i>27 &#x221D; <i>R</i><sup>&minus;&gamma;</sup>) is hard (&gamma;=0.54&plusmn;0.11) in the <i>A</i>>0 polarity period (1996–1997) and is soft (&gamma;=0.95&plusmn;0.12) in the <i>A</i><0 period (1986–1987). Belov,~A V., Eroshenko,~E A., and Yudahin,~K F.: Isotropic and anisotropic cosmic-ray variations in March – June 1991, Izvestia RAN, ser. Fiz., 59, 4, 79–85, 1995. \bibitem[Burger and Hitge(2004)] burger04 Burger,~R A. and Hitge,~M.: The effect of a Fisk-Type heliospheric magnetic field on cosmic-ray modulation, Astrophys. J., 617, 73–76, 2004. \bibitem[Gil and Alania(2001)] gil01 Gil,~ A. and Alania,~M V.: 27- day variations of cosmic rays for the minima epochs of solar activity: experimental and 3-D drift modeling results, Proc. 27th ICRC, 9, 3725–3728, 2001. \bibitem[Gil et al.(2005)] gil05 Gil,~A., Iskra,~K., Modzelewska,~R., and Alania,~M V.: On the 27-day variations of the galactic cosmic ray anisotropy and intensity for different periods of solar magnetic cycle, Adv. Space Res., 35, 687–690, 2005. \bibitem[Krymsky et al.(1966)] krymsky66 Krymsky,~G F., Kuzmin,~A I., Chirkov,~N P.,Krivoshapkin,~P A., and Skripin,~G V.: Cosmic ray distribution and reception vectors of detectors I, Geomagn. and Aeronomy, 6, 991–996, 1966. \bibitem[Krymsky et al.(1967)] krymsky67 Krymsky,~G F., Kuzmin,~A I., Chirkov,~N P., Krivoshapkin,~P A., and Skripin,~G V.: Cosmic ray distribution and reception vectors of detectors II, Geomagn. and Aeronomy, 7, 11–16, 1967. \bibitem[Neugebauer et al.(2000)] neugebauer00 Neugebauer,~M., Smith,~E J., Ruzmaikin,~A., Feynman,~J., and Vaughan,~A H.: The solar magnetic field and the solar wind: Existence of preferred longitudes, J. Geophys. Res., 105, 2315–2324, 2000. \bibitem[Otnes and Enochson(1972)] otnes Otnes,~R K. and Enochson,~L.: Digital Time Series Analysis, John Wiley and Sons Inc., New York, 1972. \bibitem[Richardson et al.(1999)] richardson99 Richardson,~I G., Cane,~H V., and Wibberenz,~G.: A 22-year dependence in the size of near-ecliptic corotating cosmic ray depressions during five solar minima, J. Geophys. Res., 104, 12 549–12 553, 1999. \bibitem[Roberts et al.(2007)] roberts07 Roberts,~D A., Giacalone,~J., Jokipii,~J R., Goldstein,~M L., and Zepp,~T D.: Spectra of polar heliospheric fields and implications for field structure, J. Geophys. Res., 112, A8, doi:10.1029/2007JA012247, A08103, 2007. \bibitem[Ruzmaikin et al.(2001)] ruzmaikin01 Ruzmaikin,~A., Feynman,~J., Neugebauer,~M., and Smith,~E J.: Preferred solar longitudes with signatures in the solar wind, J. Geophys. Res., 106, 8363–8370, 2001. Wawrzynczak,~A. and Alania,~M V.: Peculiarities of galactic cosmic ray Forbush effects during October November 2003, Adv. in Space Res., 35, 682–686, 2005. Wawrzynczak,~A. and Alania,~M V.: Modeling of the recurrent Forbush effect of the galactic cosmic ray intensity and comparison with the experimental data, Adv. in Space Res., 41, 1, 325–334, 2008.