Strong horizontal photospheric magnetic field in a surface dynamo simulation

Context. Observations with the Hinode spectro-polarimeter have revealed strong horizontal internetwork magnetic fields in the quiet solar photosphere. Aims. We aim to interpret the observations with results from numerical simulations. Methods. Radiative MHD simulations of dynamo action by near-surface convection are analyzed with respect to the relation between vertical and horizontal magnetic field components. Results. The dynamo-generated fields show a clear dominance of the horizontal field in the height range where the spectral lines used for the Hinode observations are formed. The ratio between the averaged horizontal and vertical field components is consistent with the values derived from the observations. This behavior results from the intermittent nature of the dynamo field with polarity mixing on small scales in the surface layers. Conclusions. Our results provide further evidence that local near-surface dynamo action contributes significantly to the solar internetwork fields.