Decomposition of the Lorentz force into magnetic pressure gradient and magnetic tension. Variations in the magnetic pressure gradient, G_ϕ, (blue) and magnetic tension, T_ϕ, (red) along the azimuthal coordinate, ϕ, are indicated in Fig. 2 (outermost arc) and were inferred from GREGOR (top) and Hinode (middle) observations, as well as from 3D MHD simulations (bottom). Values for the latter have been divided by a factor of five.