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We are re-examining the problem of stellar migration in disc galaxies from adiffusion perspective. We use for the first time the formulation of thediffusion rates introduced by \citet{1979PhR....52..263C}, applied to bothenergy $E$ and angular momentum $L_\mathrm{z}$ in self-consistent N$-$bodyexperiments. We limit our study to the evolution of stellar discs well afterthe formation of the bar, in a regime of adiabatic evolution. We show thatdistribution functions of Chirikov diffusion rates have similar shapesregardless the simulations, but different slopes for energy and angularmomentum. Distribution functions of derived diffusion time scales $T_D$ havealso the same form for all simulations, but are different for $T_D(E)$ and$T_D(L_\mathrm{z})$. Diffusion time scales are strongly dependent on$L_\mathrm{z}$. $T_D(E) \lesssim 1$~Gyr in a $L_\mathrm{z}$ range roughlydelimited by the set of stellar bar resonances (between the Ultra HarmonicResonance and the Outer Lindblad Resonance). Only particles with low$L_\mathrm{z}$ have $T_D(L_\mathrm{z}) \lesssim 10$ Gyr, i.e. the simulationlength. In terms of mass fraction, 35 to 42% turn out to diffuse energy in acharacteristic time scale shorter than 10 Gyr, i.e. simulations length, while60 to 64% undergo the diffusion of the angular momentum on the same time scale.Both the diffusion of $L_\mathrm{z}$ and $E$ are important in order to graspthe full characterisation of the radial migration process, and we showed thatdepending on the spatial region considered, one or the other of the twodiffusions dominates.

Stellar migration in galaxy discs using the Chirikov diffusion rate