Interplanetary Magnetic Field Turbulence and Rigidity Spectrum of the Galactic Cosmic Rays Intensity Variation (1969–2011)

Abstract The present study investigates the relation between the rigidity R spectrum exponent γ of the galactic cosmic rays (GCR) flux changes ( δD ( R )/ D ( R ) ∝  R − γ ) and the exponents ν y and ν z of the power spectral density of the B y and B z components of the heliospheric magnetic field (HMF) fluctuations. Two parameters have been introduced: (1) the exponent γ demonstrating the rigidity dependence of long‐term changes of GCR flux on solar activity (SA) and (2) the exponents ν y and ν z signifying the state of turbulence which is divided of the B y and B z components. This study considers the period of time between 1969 and 2011 divided into four subperiods, according to the solar global magnetic field polarities: (I) 1969–1979, ( A  > 0) (positive polarity magnetic field lines are directed away from the Sun's northern hemisphere); (II) 1980–1988, ( A  < 0) (negative polarity magnetic field lines are directed toward the Sun's northern hemisphere); (III) 1991–2001, ( A  > 0); and (IV) 2002–2011, ( A  < 0). The paper finds that temporal changes of the resonant frequency ( f res ) of GCR protons in heliospheric magnetic field turbulence in relation to SA are mainly caused by variations of the induction of B components from year to year, while the contribution of the solar wind speed remains insignificant. The analyses of the four subperiods show that γ increases and ν y and ν z decrease in the periods of increased SA, and conversely, the γ decreases and ν y and ν z increase in the periods of reduced SA. The study concludes that the exponents γ , and ν y and ν z can be considered as important indices (proxies) for research on GCR transport in the heliosphere.