the angle $\beta$ between the LOS from the Earth and the plumes’ orientation were calculated. They range from $65.7^{\circ}$ to $128.6^{\circ}$ for plume 3 and 8 being almost perpendicular to the view direction of the Earth. For the angle $\gamma$ off the meridian plane, we found for all ten plumes a maximum departure of $14.2^{\circ}$. This indicates that the magnetic azimuthal component $B_\varphi$ was very small on the polar cap during the time of our observations. The deviation of the plume projection to the solar radial direction $\widehat{\mathbf{e_r}}$ is calculated and represented by the angle $\psi$. This angle in general becomes larger with increasing distance of the footpoint from the pole as shown in the upper panel of Figure \[fig:dipole\_tan\]. This means that the plumes do not converge to the solar center, which is consistent with the 2D results [@DeForest:etal:1997; @Fisher:Guhathakurta:1995]. They found the plumes/rays appear to diverge radially from a point between the solar center and the respective pole.

In addition, we compared the 3D plume structure which outlines the coronal magnetic field with the assumption of a dipole with its axis along the solar rotation axis. In this case the plume’s inclination angle $i$ and the footpoint latitude 