The reflection spectrum of the torus around AGN is characterized by X-ray fluorescent lines , which are most prominent for type II AGN .
A clumpy torus allows photons reflected from the back-side of the torus to leak through the front free-of-obscuration regions .
Therefore , the observed X-ray fluorescent lines are sensitive to the clumpiness of the torus .
We analyse a sample of type II AGN observed with Chandra HETGS , and measure the fluxes for the Si \hbox { K } \alpha~ { } and Fe \hbox { K } \alpha~ { } lines .
The measured \mbox { Fe~ { } K } \alpha / \mbox { Si~ { } K } \alpha~ { } ratios , spanning a range between 5 - 60 , are far smaller than the ratios predicted from simulations of smooth tori , indicating that the tori of the studied sources have clumpy distributions rather than smooth ones .
Compared with simulation results of clumpy tori with a half-opening angle of 60 ^ { \circ } , the Circinus galaxy has a \mbox { Fe~ { } K } \alpha / \mbox { Si~ { } K } \alpha~ { } ratio of \sim 60 , which is close to the simulation results for N = 5 , where N is the average number of clumps along the line of sight .
The \mbox { Fe~ { } K } \alpha / \mbox { Si~ { } K } \alpha~ { } ratios of the other sources are all below the simulation results for N = 2 .
Overall , it shows that the non-Fe fluorescent lines in the soft X-ray band are a potentially powerful probe of the clumpiness of the torus around AGN .