  We study the pre-equilibrium dipole response in the charge-asymmetric
reaction $^{132}$Sn+$^{58}$Ni at $E_{lab}=10$ MeV/A, within a semi-classical
transport model employing effective interactions for the nuclear mean-field. In
particular, we adopt the recently introduced SAMi-J Skyrme interactions, whose
parameters are specifically tuned to improve the description of spin-isospin
properties of nuclei. Within the same framework, we also discuss
pre-equilibrium nucleon emission. Our results show that both mechanisms, i.e.,
pre-equilibrium dipole oscillations and nucleon emission, are sensitive to the
symmetry energy below the saturation density $\rho_0$ (in the range
$0.6\rho_0-\rho_0$), to the effective mass and to the nucleon-nucleon cross
section. Finally, a covariant analysis is applied to study the correlations
between the model parameters and observables of experimental interest.
