  Galaxy clusters are connected at their peripheries to the large scale
structures by cosmic filaments that funnel accreting material. These
filamentary structures are studied to investigate both environment-driven
galaxy evolution and structure formation and evolution. In the present work, we
probe in a statistical manner the azimuthal distribution of galaxies around
clusters as a function of the cluster-centric distance, the cluster richness,
and the galaxy activity (star-forming or passive).We perform a harmonic
decomposition in large photometric galaxy catalogue around 6400 SDSS clusters
with masses M >1e14 solar masses, in the redshift range of 0.1< z <0.3. The
same analysis is performed on the mock galaxy catalogue from the light-cone of
Magneticum hydrodynamical simulation.
  We use the multipole analysis to quantify asymmetries in the 2-D galaxy
distribution. In the inner cluster regions at R <2 R500, we confirm that the
galaxy distribution traces an ellipsoidal shape, which is more pronounced for
richest clusters. In the clusters' outskirts (R= [2-8]R500), filamentary
patterns are detected in harmonic space with a mean angular scale m_mean=
4.2+/-0.1. Massive clusters seem to have a larger number of connected filaments
than low massive ones. We also find that passive galaxies appear to better
trace the filamentary structures around clusters, even if the contribution of
SF ones tend to increase with the cluster-centric distance, suggesting a
gradient of galaxy activity in filaments around clusters.
