On the peculiar features of the instantaneous angular distribution of synchrotron radiation

The instantaneous angular distribution of synchrotron radiation is investigated. The radiation space is divided into two parts. The first part of the space is the interior of a cone with the apex located at the point of a radiating charge, the angular span being $2\alpha_0$ and the central axis oriented along the instantaneous velocity of the charge. The second part of the space is the complement of the first part in the entire space. It is shown that the radiation in the ultrarelativistic limit is entirely contained in the first part of the space, and the radiation in the second part (with a non-zero $\alpha_0$) vanishes.