2001ApJ...548L.221R

The extremely faint, temperature-sensitive ``auroral'' emission line [N II] λ5755 has been detected from the low-density ionized gas along the sight line toward l=130°.0, b=-7°.5 using the Wisconsin Hα Mapper. The intensity of this emission line, relative to the red nebular line [N II] λ6584, is found to be twice that observed in bright, classical H II regions surrounding O stars. This implies that the electron temperature of the ionized gas along this sight line is about 2000 K higher than the H II regions and that the enhanced [N II] λ6584/Hα and [S II] λ6716/Hα intensity ratios in this low-density gas are due at least in part to an elevated temperature.