Horizontal force balance in a vertical slice of a magnetic field concentration for the F star. Left: plot of the bolometric intensity. The selected magnetic element is highlighted by the green rectangle. The red contours represent areas with B²/8π > p_gas. Right: map of B_ɀ in the x-plane with the horizontal axis in Mm and the vertical axis in the number of pressure scale heights above (negative) and below (positive) the 〈τ〉 = 1 height. The dark red, red, and yellow contours show the iso log₁₀ τ =1,0,−1 surfaces, respectively. The line plot on top shows the diagonal terms of the total stress tensor (see Eq. (1) and Sect. 4.1 for details). An animation is available online.