Synchrotron Radiation
It is worth briefly discussing some extreme results that come out of the previous discussion about linearly accelerating charges. When a charge travels in a circular path, at least some component of the acceleration is centripetal and has magnitude v2/R, where R is the radius of the path. Again in this case, radiation is most strongly emitted perpendicular to the acceleration. When the motion is uniformly circular, the emission is entirely tangent to the path.
As the velocity increases, so does the centripetal acceleration and due to relativistic effects, emission is almost entirely in the forward direction with any emission that would be in the backward direction almost completely nullified.