The right-hand side is the sum of the electric fields associated with the velocity and the acceleration of the charged particle. The velocity field depends only upon β β while the acceleration field depends on both β β and β β ˙ ˙ and the angular relationship between the two. Since the velocity field is proportional to 1 / R 2 , it falls off very quickly with distance. On the other hand, the acceleration field is proportional to 1 / R , which means that it falls off more slowly with distance. Because of this, the acceleration field is representative of the radiation field and is responsible for carrying most of the energy away from the charge.