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Venus nighttime hydrogen bulgeThe concentration of atomic hydrogen in the Venus thermosphere near 165 km altitude and approximately 18 deg north latitude has been derived from Pioneer Venus in situ measurements of H(+), O(+), O and CO2 concentrations, under the assumption of chemical equilibrium. Altitude profiles of derived H concentration suggest that chemical equilibrium prevails to an altitude of at least 200 km on the dayside and to 165 km on the nightside. Measurements below these limits were made by the ion and neutral mass spectrometers on the orbiter spacecraft between December 1978 and July 1979, while periapsis traversed a complete diurnal cycle. The hydrogen concentration is found to rise sharply at both terminators from a dayside value of approximately 50,000/cu cm, and to exhibit an asymmetric nightside distribution with a peak density in the predawn sector approximately 400 times greater than the dayside value. Analysis suggests that wind-induced diffusion, combined with exospheric return flow, can account for the observed hydrogen behavior. The large day-night temperature contrast enhances advective transport, which produces the large H concentration diurnal variation; the shift of the H concentration nighttime maximum toward dawn is caused by atmospheric superrotation.
Document ID
19810029999
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Brinton, H. C.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Taylor, H. A., Jr.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Niemann, H. B.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Mayr, H. G.
(NASA Goddard Space Flight Center Laboratory for Planetary Atmospheres, Greenbelt, Md., United States)
Nagy, A. F.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Cravens, T. E.
(Michigan, University Ann Arbor, Mich., United States)
Strobel, D. F.
(U.S. Navy, Naval Research Laboratory, Washington D.C., United States)
Date Acquired
August 11, 2013
Publication Date
November 1, 1980
Publication Information
Publication: Geophysical Research Letters
Volume: 7
Subject Category
Lunar And Planetary Exploration
Accession Number
81A14403
Distribution Limits
Public
Copyright
Other

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