Electric current density as a function of frequency and wave number for relativistic streaming instability and interacting plasma bunches in the plasma reference frame. Both instabilities are selected in the time interval ω_pt = 0 − 3500. Subluminal waves, which do not contribute to the emission, are set to zero. Dashed magenta lines: light lines k = ±ω/c. Positive wave numbers correspond to the direction away from the star.