  We have numerically studied the evolution of the heavy ions that expand in a
cold background plasma at a large scale. Two typical collective behaviors of
the heavy ions are identified with the conditions where only the traversing
heavy ion's initial total mass is different. Our work has demonstrated that a
difference in the initial total mass of the moving heavy ions is able to induce
completely different collective behaviors of the plasma. The simulation is
performed via the hybrid model, in which the ions and electrons are treated as
classical particles and mass-less fluid, respectively. Due to the imbalance of
the electric and magnetic force on the heavy ions, these particles will evolve
into different collective patterns at the later time. These patterns manifest a
rather different stopping behavior of the moving ions and an opposite drifting
direction of the electron fluid at the rim of the expanding plasma. Further
numerical and analytical calculations show that the imbalance depends not only
on the number densities of the plasma ions, but also on the spatial variations
of the magnetic fields. Our work reveals that the collective behavior of the
heavy ions is highly non-linear, and the non-linearity is able to induce
different phenomena in the evolution of the system at a large scale.
