  Macroscopic parameters as well as precise information on the random force
characterizing the Langevin type description of the nuclear fusion process
around the Coulomb barrier are extracted from the microscopic dynamics of
individual nucleons by exploiting the numerical simulation of the improved
quantum molecular dynamics. It turns out that the dissipation dynamics of the
relative motion between two fusing nuclei is caused by a non-Gaussian
distribution of the random force. We find that the friction coefficient as well
as the time correlation function of the random force takes particularly large
values in a region a little bit inside of the Coulomb barrier. A clear
non-Markovian effect is observed in the time correlation function of the random
force. It is further shown that an emergent dynamics of the fusion process can
be described by the generalized Langevin equation with memory effects by
appropriately incorporating the microscopic information of individual nucleons
through the random force and its time correlation function.
