Schematic diagram of a bulk of bunches moving in the magnetosphere is shown in the left panel. The light solid blue line shows the slice in which electrons emit roughly the same phase. The unit vector of the LOS is denoted as n, while ϵ₁ and ϵ₂ denote the two polarization components. The geometry for instantaneous circular motion for a particle identified by ijk in a bunch is on the right. The trajectory lies on the β_0, ∥ − ϵ₁ plane. At the retarded time, t = 0, the electron is at the origin. The dotted trajectory shows an electron at the origin. The angle between the solid and dotted trajectory is χ_ij at t = 0. The angle between the LOS (z₀) and the trajectory plane is φ_k.