Panel a: variation of v_T with ℓ. Various curves represent E = 2.71 (solid black line) E = 1.71 (long dashedblue line) and E = 1.04 (dashed red line). Panel b: v_T as a functionof E for different ℓ = 2.85 (solid black line) and 0.8 (dashed red line). Panel c: amplification factor A_m with E of jets flowing out through a radiation field of ℓ = 0.8. All panels have ξ = 1. The “e”-type(solid line) and “f”-type (dotted line) jets are also marked.