Unipolar versus bipolar internetwork flux appearance

Small-scale internetwork (IN) magnetic fields are considered to be the main ingredient of the quiet Sun magnetism. For this reason, it is crucial to understand how they appear on the solar surface. Here, we employ a high-resolution, high-sensitivity, long-duration Hinode/NFI magnetogram sequence to analyze the appearance modes and spatio-temporal evolution of individual magnetic elements inside a supergranular cell at the disk center. From visual identification of flux patches and magnetofrictional simulations, we show that there are two distinct populations of IN flux concentrations: unipolar patches and bipolar features. They both appear uniformly over the solar surface. However, we argue that unipolar flux concentrations are formed by coalescence of the background flux, while bipolar features truly represent the emergence of new flux on the solar surface. Magnetic bipoles emerge at a higher rate than unipolar features (68 as opposed to 55~Mx~cm$^{-2}$~day$^{-1}$), and provide about 70\% of the total instantaneous IN flux detected in the interior of the observed supergranule.