The figure shows the electrical field of a charged particle moving initially in the negative -direction with a constant velocity . At time it starts to accelerate uniformly in the positive -direction. The particle’s location at is labeled , its current position , and its virtual position at the current time . The dashed circle in the diagram is the location of the light cone emanating from at the current instant. Outside this light cone the particle’s field is simply a Lorentz contracted Coulomb field focused on , while inside the light cone the field is that of a uniformly accelerating charge with circular field lines.
