Context : Important information on the evolution of the jet can be obtained by comparing the physical state of the plasma at its propagation through the broad-line region ( where the jet is most likely formed ) into the intergalactic medium , where it starts to significantly decelerate .

Aims : We compare the constraints on the physical parameters in the innermost ( \leq pc ) and outer ( \geq kpc ) regions of the 3C 120 jet by means of a detailed multiwavelength analysis and theoretical modeling of their broadband spectra .

Methods : The data collected by Fermi LAT ( \gamma -ray band ) , Swift ( X-ray and ultraviolet bands ) and Chandra ( X-ray band ) are analyzed together and the spectral energy distributions are modeled using a leptonic synchrotron and inverse Compton model , taking into account the seed photons originating inside and outside of the jet .
The model parameters are estimated using the Markov Chain Monte Carlo method .

Results : The \gamma -ray flux from the inner jet of 3C 120 was characterized by rapid variation from MJD 56900 to MJD 57300 .
Two strong flares were observed on April 24 , 2015 when , within 19.0 minutes and 3.15 hours the flux was as high as ( 7.46 \pm 1.56 ) \times 10 ^ { -6 } { photon\ > cm ^ { -2 } \ > s ^ { -1 } } and ( 4.71 \pm 0.92 ) \times 10 ^ { -6 } { photon\ > cm ^ { -2 } \ > s ^ { -1 } } respectively , with \geq 10 \sigma .
During these flares the apparent isotropic \gamma -ray luminosity was L _ { \gamma } \simeq ( 1.20 - 1.66 ) \times 10 ^ { 46 } \ > { erg\ > s ^ { -1 } } which is not common for radio galaxies .
The broadband emission in the quiet and flaring states can be described as synchrotron self-Compton emission while inverse Compton scattering of dusty torus photons can not be excluded for the flaring states .
The X-ray emission from the knots can be well reproduced by inverse Compton scattering of cosmic microwave background photons only if the jet is highly relativistic ( since even when \delta = 10 still U _ { e } / U _ { B } \geq 80 ) .
These extreme requirements can be somewhat softened assuming the X-rays are from the synchrotron emission of a second population of very-high-energy electrons .

Conclusions : We found that the jet power estimated at two scales is consistent , suggesting that the jet does not suffer severe dissipation , it simply becomes radiatively inefficient .