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Summary: ICARUS25, ~35-338 (1975)
The Role of Hydrocarbons in the Ionospheres of the Outer Planets
S. K. ATREYA AND T. M. DONAHUE
Department el Atmospheric and OceanicScience, Univeralty of Michigan,
Ann Arbor, Michigan 48106
Received December 9, 1974
The role of hydrocarbons as a possible sink for H + and Ha+ ions in the lower
ionosphere ofthe outer planets is examined. Calculations indicate that H +and I-Is+
are efficiently converted to hydrocarbon ions on reaction with methane. The
terminal ions, CH5+ and C2Hs+ are rapidly neutralized in dissociative recombi-
nation with electrons. Extreme ultraviolet photolysis of hydrocarbons as a poten-
tial additional source of lower elevation ions is investigated.
INTRODUCTION
McElroy (1973) first raised the possi-
bility that protons in the Jovian ionos-
phere may be efficiently removed at lower
altitudes by reaction with methane. In
our last paper on the model ionospheres of
Saturn, Uranus and Neptune (Atreya and
Donahue, 1975) we mentioned that H +
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