Astrophysics and Space Sciences Transactions www.astrophys-space-sci-trans.net 1810-6528 1810-6536 4 2 2008 10.5194/astra-4-59-2008 http://www.astrophys-space-sci-trans.net/4/59/2008/ http://www.astrophys-space-sci-trans.net/4/59/2008/astra-4-59-2008.html http://www.astrophys-space-sci-trans.net/4/59/2008/astra-4-59-2008.pdf 59 63 2008-12-04 Forbush decrease of the galactic cosmic ray intensity: experimental study and theoretical modeling M. V. Alania A. Wawrzynczak Institute of Math. and Physics of University of Podlasie, Siedlce, Poland Institute of Geophysics, Georgian Academy of Sciences, Tbilisi, Georgia Institute of Computer Science of University of Podlasie, Siedlce, Poland We study the temporal changes of the power law rigidity spectrum of the Forbush decrease (Fd) of the galactic cosmic ray (GCR) intensity. We show that the power law rigidity spectrum of Fd for the period of 6–20 November 2004 found by neutron monitors and ground muon telescopes experimental data, gradually is hardening during the decreasing phase of the intensities and then steadily is softening during the recovery phase. A relation of the rigidity spectrum exponent of the Fd of the GCR intensity with the exponent of the power spectral density (PSD) of the components of the interplanetary magnetic field (IMF) turbulence is established. We develop three dimensional (3-D) non stationary model of the Fd and show that the results of the theoretical modeling are in good agreement with the experimental data. We suppose that temporal changes of the rigidity spectrum exponent of the Fd of GCR intensity can be used to calculate the exponent of the PSD of the IMF turbulence for the arbitrary period, which is not achievable by the in situ measurements of the IMF. Ahluwalia,~H S. and Fikani,~M M.: Cosmic ray detector response to transient solar modulation: Forbush decreases, J. Geophys. Res., 112, A08105, 2007. Alania,~M V. and Iskra,~K.: Features of the solar wind large-scale structure in the different periods of solar activity based on the variations of cosmic rays, Adv. Space Res., 16, 241–244, 1995. Alania,~M V., Iskra,~K., and Siluszyk,~M.: New index of long-term variations of galactic cosmic ray intensity, Adv. in Space Res., 41, 267–274, 2008. Bieber,~J W., Matthaeus,~W H., Smith,~C W., Wanner,~W., Kallenrode,~M.-B., and Wibberenz,~G.: Proton and electron mean free paths: The Palmer consensus, Revised Astrophys. J., 420, 294–306, 1994. Burlaga, L. F.: Interplanetary Magnetohydrodynamics, Oxford Univ. Press, New York, 1995. Cane,~H V.: Coronal Mass Ejections and Forbush Decreases, Space Sci. Rev., 93, 55–77, 2000. Dorman,~L.: Cosmic Rays in the Earth's Atmosphere and Underground, Kluwer Academic Publishers, Dordrecht, 2004. Droge,~W.: Solar Particle Transport In A Dynamical Quasi-Linear Theory, Astrophys. J., 589, 1027–1039, 2003. Forbush,~S E.: On the Effects in Cosmic-Ray Intensity Observed During the Recent Magnetic Storm, Phys. Rev., 51, 1108–1109, 1937. Hasselman,~K. and Wibberentz,~G.: Scattering of charged particles by random electromagnetic field, Z. Gephys., 34, 353–388, 1968. Jokipii, J. R.: Cosmic-Ray Propagation, I. Charged Particles in a Random Magnetic Field, Astrophys. J., 146, 480–487, 1966. Jokipii, J. R.: Propagation of Cosmic Rays in the Solar Wind, Rev. Geophys. Space Phys., 9, 27–87, 1971. Kudela,~K., Storini,~M., Hofer,~M Y., and Belov,~A.: Cosmic Rays in Relation to Space Weather, Space Science Rev., 93, 153–174, 2000.\vadjust Matthaeus,~W H., Qin,~G., Bieber,~J W., and Zank,~G P.: Nonlinear Collisionless Perpendicular Diffusion Of Charged Particles, Astrophys. J., 590, 53–56, 2003. Parker, E. N.: The passage of energetic charged particles through interplanetary space, Planet. and Space Sci., 13, 9–49, 1965. Qin, G.: Nonlinear Parallel Diffusion of Charged Particles: Extension to the Nonlinear Guiding Center Theory, Astrophys. J., 656, 217–221, 2007. Shalchi,~A. and Schlickeiser,~R.: The parallel mean free path of heliospheric cosmic rays in composite Slab/two-dimensional geometry, I. The damping model of dynamical turbulence, Astrophys. J., 604, 861–873, 2004. Shalchi, A., Bieber,~J W., Matthaeus,~W H., and Qin,~G.: Nonlinear Parallel and Perpendicular Diffusion of Charged Cosmic Rays in Weak Turbulence, Astrophys. J., 616, 617–629, 2004. Toptygin, I. N.: Cosmic rays in interplanetary magnetic fields, Dordrecht, D. Reidel Publishing Co., 1985. 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, 325–334, 2008.