Scaling of Relativistic Shear Flows with Bulk Lorentz Factor

We compare Particle-in-Cell simulation results of relativistic electron-ion shear flows with different bulk Lorentz factors, and discuss their implications for spine-sheath models of blazar versus gamma-ray burst (GRB) jets. Specifically, we find that most properties of the shear boundary layer scale with the bulk Lorentz factor: the lower the Lorentz factor, the thinner the boundary layer, and the weaker the self-generated fields. Similarly, the energized electron spectrum peaks at an energy near the ion drift energy, which increases with bulk Lorentz factor, and the beaming of the accelerated electrons gets narrower with increasing Lorentz factor. This predicts a strong correlation between emitted photon energy, angular beaming and temporal variability with the bulk Lorentz factor. Observationally, we expect systematic differences between the high-energy emissions of blazars and GRB jets.