scattering, evidence has built up from solar wind observations that perpendicular diffusion leads to a significant angular spread of EPs up to $0.1$ GeV, both in longitudinal and latitudinal directions of the heliosphere [@Strauss.etal:17 and references therein]. On the other hand, longitudinal tracking of Ground Level Enhancement events, i.e. SEP events with typical particle energy $\gtrsim 1$ GeV, is not available for solar cycles prior to the current one ($24^{th}$) and in the current one an unusual lack of events (only $2$ so far) prevents statistically significant conclusions. We refer to a two-fold type of perpendicular diffusion (see, e.g., [@Fraschetti.Jokipii:11]). A first contribution is due to the meandering of field lines described by the diffusion coefficient $\kappa_\perp^{MFL}$, i.e., the fluctuation of the magnetic field in the direction perpendicular to the local average field (this contribution assumes that the particle is simply chained to the magnetic field lines and is dominated by large-scale fluctuations). The second contribution is the gradient/curvature drift diffusion ($\kappa_\perp^{D}$), due to the spatial variation of the turbulence $\delta B ({\bf x})$ bringing about a departure of the particle from the field line it was initially on.

In general, the perpendicular diffusion coefficient grows with the particle energy 