  We develop a non-perturbative model for valence parton distribution functions
(PDFs) based on the mean field interactions of valence quarks in the nucleonic
interior. The main motivation for the model is to obtain a mean field
description of the valence quarks as a baseline to study the short range
quark-quark interactions that generate the high $x$ tail of PDFs. The model is
based on the separation of the valence three-quark cluster and residual system
in the nucleon. Then the nucleon structure function is calculated within the
effective light-front diagrammatic approach introducing nonperturbative
light-front valence quark and residual wave functions. Within the model a new
relation is obtained between the position, $x_p$, of the peak of $xq_V(x)$
distribution of the valence quark and the effective mass of the residual
system, $m_R$, in the form: $x_{p} \approx {1\over 4} (1-{m_R\over m_N})$ at
starting $Q^2$. This relation explains the difference in the peak positions for
d- and u- quarks through the expected difference of residual masses for valence
d- and u- quark distributions. The parameters of the model are fixed by fitting
the calculated valence quark distributions to the phenomenological PDFs. This
allowed us to estimate the overall mean field contribution in baryonic and
momentum sum rules for valence d- and u- quarks. Finally, the evaluated
parameters of the non-perturbative wave functions of valence 3q-cluster and
residual system can be used in calculation of other quantities such as nucleon
form factors, generalized partonic and transverse momentum distributions.
