  Within the Hadron-String Dynamics (HSD) transport approach we study the
suppression pattern of charmonia at RHIC with respect to centrality and
rapidity employing various model concepts such as variants of the 'comover
absorption' model or the 'charmonium melting' scenario. We find that especially
the ratio of the forward to mid-rapidity nuclear modification factors of J/Psi
(R_AA (forward) / R_AA (mid)) cannot be explained by the interactions with
'formed' comoving mesons or by the 'color screening mechanism' alone. Only when
incorporating interactions of the c or c-bar quark with a pre-hadronic medium
satisfactory results are obtained. A detailed comparison to the PHENIX data
demonstrates that non-hadronic interactions are mandatory to describe the
narrowing of the J/Psi rapidity distribution from p+p to central Au+Au
collisions. The Psi' to J/Psi ratio is found to be crucial in disentangling the
different charmonium absorption scenarios especially in the RHIC energy range.
Furthermore, a comparison of the transport calculations to the statistical
model of Gorenstein and Gazdzicki as well as the statistical hadronization
model of Andronic et al. shows differences in the energy dependence as well as
centrality dependence of the J/Psi to pion ratio which may be exploited
experimentally to disentangle different concepts. We find additionally that the
collective flow of charm in the HSD transport appears compatible with the data
at SPS energies but substantially underestimates the data at top RHIC energies
such that the large elliptic flow v_2 of charm seen experimentally has to be
attributed to early interactions of non-hadronic degrees of freedom.
