Abstract It has been commonly accepted that the bulk velocity of extragalactic jets varies in all directions. We examined the synchrotron radiation of a jet with velocity structure in the direction perpendicular to its axis and found that the spectral energy distribution (SED) is not strongly influenced by this circumstance, that there is only a small increase in the emission intensity and almost no shift in the peak frequency. For objects with smaller inclined angles θ0 between the jet axis and the line of our sight, such as Blazars, the effect is more important. When θ0 exceeds a critical value there is no longer any change in the SED. To compare the bulk speed with different velocity structure, an equivalent speed <β> is defined which would reproduce the same spectral profile. There possibly exists a stress fμ (y) between layers of the outflow when the velocity is not the same in the jet.

Keywords galaxies: jets --- radiation mechanisms: non-thermal --- methods: numerical

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