Context : Recent spectro-polarimetric observations have provided detailed measurements of magnetic field , velocity and intensity during events of magnetic field intensification in the solar photosphere .

Aims : By comparing with synthetic observations derived from MHD simulations , we aim to discern the physical processes underlying the observations , as well as to verify the simulations and the interpretation of the observations .

Methods : We consider the temporal evolution of the relevant physical quantities for three cases of magnetic field intensification in a numerical simulation .
In order to compare with observations , we calculate Stokes profiles and take into account the spectral and spatial resolution of the spectropolarimeter ( SP ) on board Hinode .
We determine the evolution of the intensity , magnetic flux density and zero-crossing velocity derived from the synthetic Stokes parameters , using the same methods as applied to the Hinode/SP observations to derive magnetic field and velocity information from the spectro-polarimetric data .

Results : The three events considered show a similar evolution : advection of magnetic flux to a granular vertex , development of a strong downflow , evacuation of the magnetic feature , increase of the field strength and the appearance of the bright point .
The magnetic features formed have diameters of 0.1-0.2″ .
The downflow velocities reach maximum values of 5-10 km/s at \tau = 1 .
In the largest feature , the downflow reaches supersonic speed in the lower photosphere .
In the same case , a supersonic upflow develops approximately 200 s after the formation of the flux concentration .
We find that synthetic and real observations are qualitatively consistent and , for one of the cases considered , agree very well also quantitatively .
The effect of finite resolution ( spatial smearing ) is most pronounced in the case of small features , for which the synthetic Hinode/SP observations miss the bright point formation and also the high-velocity downflows during the formation of the smaller magnetic features .

Conclusions : The observed events are consistent with the process of field intensification by flux advection , radiative cooling , and evacuation by strong downflow found in MHD simulations .
The quantitative agreement of synthetic and real observations indicates the validity of both the simulations and the interpretations of the spectro-polarimetric observations .