On relation of the long period galactic cosmic rays intensity variations with the interplanetary magnetic field turbulence

Abstract

We study a relationship of the exponent γ of the rigidity R spectrum δD(R)D(R) of the galactic cosmic rays (GCR) intensity variations δD(R)D(R)∝R-γ and the exponent νy of the power spectral density (PSD) of the By component of the interplanetary magnetic field (IMF) (PSD=Pf-νy, where P is power and f is frequency) in the range of the frequency f ≈ 4 × 10−6–10−5 Hz. For this purpose we use data of neutron monitors and the IMF in the period of 1967–2002. We show that the rigidity spectrum of the long-period variations of the GCR intensity is hard in the minimum epochs of solar activity (γ ≈ 0.6) when the exponent νy of the PSD of the IMF is higher (νy ≈ 1.9), and is soft in the maximum epochs (γ ≈ 1.2), when the exponent νy is relatively lower (νy ≈ 1.4). We ascribe these features to the essential rearrangement of the structure of the IMF turbulence during the 11-year cycle of solar activity assuming that the IMF turbulence is homogeneous and isotropy for time scales τ > 1 day. We reveal the relationships among rigidity spectrum exponent γ, exponent νy and the power P of the PSD of the IMF turbulence in different epochs of solar activity. We suppose that the changes of the structure of the IMF turbulence versus solar activity (manifesting in the changes of the exponent γ of the rigidity R spectrum of the GCR intensity variations) is one of the important reasons of the 11-year variation of the GCR intensity for the rigidity of the GCR particles, to which neutron monitors are respond.