Study on Classical Electrodynamics Spin

There are two mutually exclusive concepts of the electrodynamics spin. According to the widespread concept, the spin density is proportional to the gradient of the electromagnetic energy density. Therefore, an unlimited plane wave of circular polarization does not contain spin, and a real wave, limited in space, carries all spin at its boundary, separately from energy. In contrast, according to the original concept, the spin density is proportional to the energy density, and the spin of plane waves is not related to the existence of the boundaries. Within the framework of this concept, we calculate the spin fluxes of plane waves in various situations and the previously unnoticed spin flux in the dipole radiation. The reason for the transition from this initial concept to the concept of a spin proportional to energy density gradient is discussed.