Diagram illustrating the shape of the column taken from the original PSI model, considered in this work. The blue shaded area corresponds to the original PSI model. The green shaded area corresponds to the selected column. The red square shows the boundary of the CBP model. The black circle shows the boundary between the corona and the inner solar atmosphere. Upper panel: YZ plane at X = 0, with the X-direction corresponding to the LoS. Lower panel: XZ plane for Y = 0. Figure not to scale.