The top panel shows the ratio of the azimuthal and vertical components of the magnetic field strength at each height from the midplane. The purple jagged line represents 〈B _y /B _z 〉. We also plot 〈B _y 〉/〈B _z 〉 in green for comparison. The bottom panel presents the effective column densities that cosmic-ray particles have to go through from the closer surface to reach the corresponding heights. The dashed curves are the vertical column densities that are used in the conventional estimates, and the dotted horizontal line represents the attenuation length of cosmic rays.