let us dub it the  model. Both the  and  models are actually particular cases of the  model, but put the emphasis on different physical processes at low rigidity. In the following, we provide the details of these three configurations.

### : the paradigmatic model {#sssec:big}

The  model includes a double-break diffusion coefficient, as well as convection and reacceleration. Its minimal version fixes the non-relativistic parameter $\eta=1$, while a non-minimal configuration may allow $\eta$ to vary. The latter case will actually help justify the former one independently from theoretical arguments. Therefore, the  model stands for the most general configuration describing the propagation equation, , and which allows us to probe the low-rigidity processes with the largest flexibility and complexity. This model has a total of 6 (7) parameters in the minimal (non-minimal) configuration, which are recalled in .

### : the minimal (double-break diffusion) model {#sssec:slim}

The  model is a subpart of , which discards convection and reacceleration as major players at low rigidity ($V_{\rm A}=V_{\rm c}=0$ km/s), but instead insists on relating low-rigidity features to changes in the magnetic turbulence properties. It also assumes a standard scaling in the non-relativistic regime, with $\eta=1$. This model, though very minimal, will be 