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Title: EXPLORING THE POSSIBILITY OF O AND Ne CONTAMINATION IN ULYSSES OBSERVATIONS OF INTERSTELLAR HELIUM

We explore the possibility that interstellar O and Ne may be contributing to the particle signal from the GAS instrument on Ulysses, which is generally assumed to be entirely He. Motivating this study is the recognition that an interstellar temperature higher than any previously estimated from Ulysses data could potentially resolve a discrepancy between Ulysses He measurements and those from the Interstellar Boundary Explorer (IBEX). Contamination by O and Ne could lead to Ulysses temperature measurements that are too low. We estimate the degree of O and Ne contamination necessary to increase the inferred Ulysses temperature to 8500 K, which would be consistent with both the Ulysses and IBEX data given the same interstellar flow speed. We find that producing the desired effect requires a heavy element contamination level of ∼9% of the total Ulysses/GAS signal. However, this degree of heavy element contribution is about an order of magnitude higher than expected based on our best estimates of detection efficiencies, ISM abundances, and heliospheric survival probabilities, making it unlikely that heavy element contamination is significantly affecting temperatures derived from Ulysses data.
Authors:
 [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6]
  1. Naval Research Laboratory, Space Science Division, Washington, DC 20375 (United States)
  2. Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States)
  3. Space Research Centre of the Polish Academy of Sciences, Ul. Bartycka 18 A, 00-716 Warsaw (Poland)
  4. Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States)
  5. Max-Planck-Institute for Solar System Research, Katlenburg-Lindau (Germany)
  6. Southwest Research Institute, San Antonio, TX 78228 (United States)
Publication Date:
OSTI Identifier:
22520107
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 220; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ATOMS; DETECTION; EFFICIENCY; ELEMENT ABUNDANCE; HELIOSPHERE; HELIUM; INTERSTELLAR SPACE; NEON; OXYGEN; PROBABILITY; SUN; TEMPERATURE MEASUREMENT; VELOCITY