Long wavelength limit of the 2D photonic crystal

We solve {\bf analytically} the multiple scattering equations for the two dimensional photonic crystals in the long wavelength limit. Different approximations of the electric and magnetic susceptibilities are presented from a unified pseudopotential point of view. The nature of the so called plasmon-polariton bands are clarified. Its frequency as a function of the wire radius is discussed. The corresponding tunable ``magnetic surface plasmon'' band is pointed out.