  The 11-year and 22-year modulation of galactic cosmic rays (GCRs) in the
inner heliosphere are studied using a numerical model developed by Qin and Shen
in 2017. Based on the numerical solutions of Parker's transport equations, the
model incorporates a modified Parker heliospheric magnetic field, a locally
static time delayed heliosphere, and a time-dependent diffusion coefficients
model in which an analytical expression of the variation of magnetic turbulence
magnitude throughout the inner heliosphere is applied. Furthermore, during
solar maximum, the solar magnetic polarity is determined randomly with the
possibility of $A>0$ decided by the percentage of the north solar polar
magnetic field being outward and the south solar polar magnetic field being
inward. The computed results are compared with several GCR observations, e.g.,
IMP 8, SOHO/EPHIN, Ulysses, Voyager 1 \& 2, at various energies and show good
agreement. It is shown that our model has successfully reproduced the 11-year
and 22-year modulation cycles.
