  Highly relativistic jets are most probably driven by strong magnetic fields
and launched from the accretion disk surrounding a central black hole. Applying
the jet flow parameters (velocity, density, temperature) calculated from the
magnetohydrodynamic (MHD) equations, we derive the thermal X-ray luminosity
along the inner jet flow in the energy range 0.2-10.1 keV. Here, we concentrate
on the case of Galactic microquasars emitting highly relativistic jets. For a 5
solar masses central object and a jet mass flow rate of 10^{-8} solar
masses/year we obtain a jet X-ray luminosity L_x ~ 10^{33} erg\sec. Emission
lines of Fe XXV and Fe XXVI are clearly visible. Relativistic effects such as
Doppler shift and Doppler boosting were considered for different inclinations
of the jet axis. Due to the chosen geometry of the MHD jet the inner X-ray
emitting part is not yet collimated. Therefore, depending on the viewing angle,
the Doppler boosting does not play a major role in the total spectra.
