Time variations of cosmic ray electrons and nuclei between 1978 and 2004: Evidence for charge-dependent modulation organized by changes in solar magnetic polarity and current sheet tilt

Abstract

We have examined the 52-day average intensities of 1.2-GV electrons and positively charged nuclei of the same rigidity during the time period from 1978 to 2004. This time period covers a complete 22-year solar cycle plus data from 2000 to 2004 that can be used to examine the repetitive nature of the variations. The 11-year solar modulation changes both the electrons and nuclei intensities by similar overall factors ∼10 at 1.2 GV. Differences in the electron/nuclei modulation as exhibited by the e/nuclei ratios occur mainly between 1980-1984, 1990-1994, and 2000-2004. At these times the e/nuclei ratios increase or decrease by a factor ∼2 at 1.2 GV in close correspondence with the changes in solar magnetic polarity from positive to negative (1980) and negative to positive (1990). The e/nuclei ratio changes in 2000-2004 match those seen in 1980-1984, thus confirming the 22-year nature of the e/nuclei variations.