  A diffuse non-thermal component has now been observed in massive merging
clusters. To better characterise this component, and to extend analyses done
for massive clusters down to a lower mass regime, we are conducting a
statistical analysis over a large number of X-ray clusters (from ROSAT based
catalogues). By means of their stacked radio and X-ray emissions, we are
investigating correlations between the non-thermal and the thermal baryonic
components. We will present preliminary results on radio-X scaling relations
with which we aim to probe the mechanisms that power diffuse radio emission ;
to better constrain whether the non-thermal cluster properties are compatible
with a hierarchical framework of structure formation ; and to quantify the
non-thermal pressure.
