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The Far Ultraviolet Background

Kulkarni, S. R. (2021) The Far Ultraviolet Background. . (Unpublished)

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The diffuse far-ultraviolet (FUV) background has received considerable attention from astronomers since the seventies. 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 (extra-galactic background light, EBL) and a component of unknown origin (and referred to as the "offset" component). During the eighties, 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 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.

Item Type:Report or Paper (Discussion Paper)
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Kulkarni, S. R.0000-0001-5390-8563
Additional Information:Attribution 4.0 International (CC BY 4.0). What follows is an incomplete list of these who helped me. For help with ISM & Atomic Physics: Ronald Reynolds; Michael Shull, University of Colorado at Boulder; E. Sterl Phinney, California Institute of Technology. For help with FUV background: Jayant Murthy, Indian Institute of Astrophysics. For help with Aeronomy, SOHO and Voyager missions: Edwin J. Mierkiewicz & Matthew D. Zettergren, Embry-Riddle Aeronautical University; I. I. Baliukin, Space Research Institute (IKI), Moscow; and E. C. Stone, Project Scientist for Voyager Mission. For help with CHIANTI: Nikolaus Zen Prusinski, California Institute of Technology. For detector physics: Roger Smith, Caltech Optical Observatories. For feedback: Ilaria Caiazzo, California Institute of Technology; Bruce Draine, Princeton University; Jerry Edelstein & Christopher McKee, University of California at Berkeley; and Kevian Stassun, Vanderbilt University, Finally, I am most grateful to Robert Benjamin,University of Wisconsin at Madison; Hannah Earnshaw, California Institute of Technology; Eran Ofek, Weizmann, Institute of Science; and Michael Shull, University of Colorado at Boulder for careful reading and constructive feedback.
Group:Astronomy Department, Division of Geological and Planetary Sciences
Record Number:CaltechAUTHORS:20220104-233149999
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112705
Deposited By: George Porter
Deposited On:10 Jan 2022 23:41
Last Modified:02 Jun 2023 01:18

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