Let u and v be distributions in D′(U). Assume that there is no point (x, k) in WF(u) such that (x, −k) belongs to WF(v), then the product uv can be defined. (Lars Hörmander)

Thank you @bathalf15320 , but I am not sur if the product r_n^2 is well defined in the sens of generalized functions, for exemple the Heaviside function verifies that H.H = H but the product H.H is not well defined becuse does not satisfy the leibniz rule.