The Far Ultraviolet Background
  The diffuse far-ultraviolet (FUV) background has received considerable
attention from astronomers since the 1970's. The initial impetus came from the
hope of detecting UV radiation from the hot intergalactic medium. The central
importance of the FUV background to the physics (heating and ionization) of the
diffuse atomic phases motivated the next generation of experiments. The
consensus view is that the diffuse FUV emission at high latitudes has three
components: stellar FUV reflected by dust grains (diffuse Galactic light or
DGL), FUV from other galaxies and the intergalactic medium (extra-galactic
background light or EBL) and a component of unknown origin (and referred to as
the "offset" component). During the1980's, there was some discussion that
decaying dark matter particles produced FUV radiation. In this paper I
investigate production of FUV photons by conventional sources: line emission
from Galactic Hot Ionized Medium, two-photon emission from the Galactic Warm
Ionized Medium and low-velocity shocks, and Lyman-beta fluorescence of hydrogen
at several locales in the Solar System (the interplanetary medium, the
exosphere and the thermosphere of Earth). I conclude that two thirds and
arguably all of the offset component can be explained by the sum of the
radiation from the processes listed above.
