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Detection of interstellar pick-up hydrogen in the solar systemInterstellar hydrogen ionized primarily by the solar wind has been detected by the Solar Wind Ion Composition Spectrometer instrument on the Ulysses spacecraft at a distance of 4.8 AUs from the sun. This 'pick-up' hydrogen is identified by its distinct velocity distribution function, which drops abruptly at twice the local solar wind speed. From the measured fluxes of pick-up protons and singly charged helium, the number densities of neutral hydrogen and helium in the distant regions of the solar system are estimated to be 0.077 +/- 0.015 and 0.013 +/- 0.003 per cu cm, respectively.
Document ID
Document Type
Reprint (Version printed in journal)
Gloeckler, G. (Maryland Univ. College Park, United States)
Geiss, J. (NASA Headquarters Washington, DC United States)
Balsiger, H. (Bern Univ. Switzerland)
Fisk, L. A. (NASA Office of Space Science and Applications Washington, United States)
Galvin, A. B. (NASA Headquarters Washington, DC United States)
Ipavich, F. M. (Maryland Univ. College Park, United States)
Ogilvie, K. W. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Von Steiger, R. (Bern Univ. Switzerland)
Wilken, B. (Max-Planck-Inst. fuer Aeronomie Katlenburg-Lindau, Germany)
Date Acquired
August 16, 2013
Publication Date
July 2, 1993
Publication Information
Publication: Science
Volume: 261
Issue: 5117
ISSN: 0036-8075
Subject Category
Funding Number(s)
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