Correlation studies of the inclinations of the heliospheric current sheet with: II. 27 day and 13.5 day waves of the cosmic ray intensity

Abstract

The comparison of the amplitudes of 27-day (Amp27) and 13.5-day (Amp13) cosmic ray waves with the tilts, α, of heliospheric current sheet was studied during the period 1971–1995. Large Amp27 or Amp13 or both were observed following a relatively large excursions in α and large dips in the tilts, near the times of the interplanetary magnetic field (IMF) polarity reversals and also, during the declining phase of the solar activity cycles (SAC). The correlation between Amp13 and α dose not depend on the heliospheric magnetic field polarity, while the correlation and sensitivity of Amp27 to tilt changes are dependent on the solar polar magnetic field. The time variations of the energy spectrum of 27-day and 13.5-day modulations varied with SAC and depend on the inversions of the dipole solar polar magnetic field. The sensitivities of the Amp13 waves to α for both IMF polarity states are rigidity (R) dependent, with a power form of R−1.47±0.2 for the qA<0 and R−0.7±0.15 for the qA>0 epoch (positive solar polarity state). The variations spectra of the 27-day modulations revealed a clear dependence on the IMF polarity state, the spectra are harder during the period of 1981–1989, when qA<0, than during the epoch with qA>0.