Viva! I usually come upon this statement: " Since B is solenoidal, it can be split into Toroidal and Poloidal parts, i.e, B=Bt+Bp, where Bt=curl(Tr) and Bp=curlcurl(Pr)" How can I prove this?? I think it is somehow related with the stokes theorem... Looking forward for someone to explain me this, once for all. Cheers!