Analysis of pioneer venus orbiter ultraviolet spectrometer lyman. alpha. data from near the subsolar region

Journal Article · Tue Mar 01 04:00:00 EST 1988 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA093iA03p01766· OSTI ID:6050981

Paxton, L J; Anderson, Jr, D E ^[1]; Stewart, A I.F. ^[2]

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1. E.O. Hulburt Center for Space Research, Washington, DC (United States)
2. Univ. of Colorado, Boulder (United States)

Atomic hydrogen is an important tracer not only of global atmospheric behavior, but also of the evolutionary processes which modify a planetary atmosphere. One of the most important questions in the field of the evolution of planetary atmospheres is whether or not Venus at one time had an ocean. The answer is directly related to the present, and past, escape flux of atomic hydrogen. Techniques for determining the abundance of atomic hydrogen are somewhat limited, and those for determining the flux of escaping hydrogen even more so. Pioneer Venus Orbiter ultraviolet spectrometer data from 20 orbits which span 3 years have been analyzed to determine the atomic hydrogen number density and vertical flux at the exobase as a function of solar zenith angle, F{sub 10.7} index, and spacecraft latitude. From 1979 through 1981 the exobase number density n{sub c} and flux {phi}{sub c} are remarkably constant at n{sub c} = 6.0 {+-} 1.5 {times} 10{sup 4} cm{sup {minus}3} and {phi}{sub c} = 7.5 {+-} 1.5 {times} 10{sup 7} cm{sup {minus}2} s{sup {minus}1} in the subsolar region. The integrated vertical column density above 110 km is 3.6 {+-} 1 {times} 10{sup 13} cm{sup {minus}2}. An empirical relationship is determined between the line center solar flux at H Lyman {alpha}, {pi}F{sub o}, and the F{sub 10.7} index. At 1 AU, {pi}F{sub o} = (2.0 + 1.1 {times} 10{sup {minus}2}F{sub 10.7}) {times} 10{sup 11} photons cm{sup {minus}2} s{sup {minus}1} {angstrom}{sup {minus}1}.

• OSTI ID: 6050981
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 93:A3; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

660000* -- Physics-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
AIRGLOW
ATMOSPHERES
CALCULATION METHODS
CHEMICAL COMPOSITION
DATA ANALYSIS
DENSITY
ELEMENT ABUNDANCE
ELEMENTS
HYDROGEN
LYMAN LINES
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
NONMETALS
PHYSICAL PROPERTIES
PLANETARY ATMOSPHERES
PLANETARY EVOLUTION
PLANETS
SEAS
SOLAR SYSTEM EVOLUTION
SPECTROMETERS
SURFACE WATERS
ULTRAVIOLET SPECTROMETERS
VENUS PLANET