Equilibrium magnetic flux tube model embedded in the background atmosphere. The red and blue lines outline some selected magnetic field lines that cross the photosphere at 40 km and 70 km from the tube axis, respectively. The color gradient illustrates the density stratification from the photosphere (brown) to the low corona (yellow). The transition region height is marked by a horizontal, semitransparent plane. For visualization purposes, the horizontal and vertical directions are not to scale.