An Analysis of 17 Years of<i>Voyager</i>Observations of the Diffuse Far‐Ultraviolet Radiation Field

Abstract

We have systematically reduced 17 years of data from the V oyager ultraviolet spectrometer (UVS) archives, from which we have obtained 431 spectra that place useful limits on the diuse far-ultraviolet radiation Ðeld between 912 and 1100 We observe a large range in brightnesses ranging from upperA . limits of 30 photons cm~2 s~1 sr~1 The diuse background is correlated with the integrated T D-1A ~1. Ñux near the line of sight but shows no correlation with N(H I). We place a 1 p upper limit of 30 photons cm~2 s~1 sr~1 on the level of an isotropic extragalactic continuum.A ~1 We have modeled and characterized the observed heliospheric H I and He I emission lines in the outer solar system as a function of heliospheric distance, apex angle from the direction of the inÑowing inter-stellar wind, and time as speciÐed by subspacecraft solar intensity. This modeling adequately reproduces observed intensities over a range of heliospheric distances of 15È50 AU, for an unrestricted range of look directions, and for a 12 year period (covering 1 solar cycle). Subject headings: diuse radiation È ultraviolet: ISM 1.