Observations of diffuse galactic H alpha and forbidden N II emission

A study has been made of the intensities and radial velocities of faint galactic H alpha and forbidden N II 6584-emission lines not associated with any known bright H II regions. Although some (about 10%) of the observed radiation may be scattered galactic light from bright H II regions in the galactic plane, most of the radiation appears to be produced by an ionized component of the interstellar gas which is distributed throughout the interstellar medium within the three nearby galactic spiral arms. In the local Orion arm the emitting gas has a temperature between 3000 and 8000 K and mean square electron density approximately equal to 0.05 cm to the minus 6th power in the galactic plane, while in the Perseus and Sagittarius arms the mean square electron density is equal to about 0.1 and 0.9 cm to the minus 6th power, respectively.