Solar magnetic polarity dependency of the cosmic ray diurnal variation

Abstract

AbstractCosmic rays (CRs) data observed through four neutron monitors and one muon telescope are used to study the solar diurnal variation (DV) from 1953 to 2010. The median primary rigidity of response, (Rm), for these detectors encompasses the range 16 ≤ Rm ≤ 60 GV of the galactic CRs spectrum. The phase angle observed with the lower rigidity station depends strongly on the solar magnetic field polarity reversal due to drift effect. However, the higher rigidity stations show an 11 year cycle. This cycle is evident in the shape of the cross‐correlation functions (CCFs) between the phase angle and the interplanetary magnetic field (IMF) parameters due to diffusion of galactic CRs by the IMF. The amplitude of the DV, IMF magnitude, and solar activity are larger, and the phase angle is later in hours for qA < 0 than for qA > 0. In addition, the amplitude is well correlated with the IMF magnitude. The amplitudes observed by the lower rigidity station peaks 2 years after the IMF magnitude reach maximum for qA < 0. The diurnal amplitude reaches minimum 2–3 years after the solar wind speed peak due to outward convection by solar wind along the helioequator. The phase angle of the higher rigidity station shifts toward the earliest hours, 2 years after the wind speed peaks for qA > 0. This shift is due to outward convection by solar wind that increases the radial component of the DV more than the East‐West component.