For typical coronal mean mass $m_i$ we have $\lambda_n(T_\lambda) \simeq 47 \,\mathrm{Mm}\,(T_\lambda/\mathrm{MK})$ [@Aschwanden:2004].

Since we know the density along the plumes from SUMER observations and we know the 3D height from the stereoscopic reconstructions, we can fit these two variables, $n_{\rm e}$ and $h$ to derive $T_{\lambda}$ and $n_0$ in Equation \[equ:ne\_h\]. In Figure \[fig:sumer\_fit\], we present the results of fits based on Equation \[equ:ne\_h\] to the density stratification of plumes 0, 1, 2. The calculated density scale height is given along with the corresponding temperature $T_{\lambda}$ and the electron temperature deduced from SUMER $T_{\rm s}$ in Figure \[fig:sumer\_fit\]. We have invariably $T_\lambda > T_{\rm s}$. The fits describe the data reasonably well suggesting that they are consistent with hydrostatic equilibrium.

Discussion and outlook
======================

We have reconstructed the three dimensional geometry of ten polar plumes using simultaneous observations by the two *STEREO* spacecraft. For two different days, the locations of the footpoints of ten plumes and their inclinations were determined. Even though the statistical basis is small, we find that the plumes we could detect from the EUV images are homogeneously distributed over the polar cap. For both cases, the deviation of the plumes to the local meridian plane 