Astrophysical jets from AGNs and microquasars are often relativistic and collimated. We study magnetic and radiative driving of jets to address these issues. The plasma is described by a relativistic equation of state which depends on the composition.
We show that the matter content may not affect the streamline of magnetically driven jets, but the poloidal velocity and temperature distribution strongly depend on the composition of the jet. We also discuss the salient features of radiatively driven jets.
Although consensus in the community precludes radiation driving to be an effective acceleration mechanism, we show that it is certainly not the case. For black holes surrounded by luminous discs, jets may be accelerated up to Lorentz factors of $\sim$ a few for baryon dominated jets. Interestingly, the terminal Lorentz factor may reach to a value of a few tens for lepton dominated jets. We also show that internal shocks driven by radiation are also possible in jets. Moreover, a temperature dependent scattering cross-section can produce relativistic jets that are launched with very low speeds and quite moderate temperatures, conditions which are expected in the inner region of the accretion discs. Although we have studied magnetic driving and radiative driving separately, it is apparent that both processes should be incorporated in order to solve the collimation and acceleration enigma of astrophysical jets.