In:
Journal of Geophysical Research: Planets, American Geophysical Union (AGU), Vol. 104, No. E9 ( 1999-09-25), p. 21997-22024
Abstract:
Titan's lower ionosphere (from 1 to 400 km) has been studied with a one‐dimensional ion‐neutral model. In this region of the atmosphere, galactic cosmic rays (GCRs) are the main ionization source. They penetrate to the deeper atmosphere and ionize the neutral constituents of Titan's atmosphere (mainly N 2 , CH 4 , Ar, H 2 , and CO) to produce N 2 + , N + , Ar + , CH 4 + , CH 3 + , CH 2 + , H 2 + , H + , and CO + . Fast reactions with the neutrals convert these ions into ions such as CH 5 + , C 2 H 5 + , and N 2 H + . Different pathways are proposed to obtain the ion and electron densities. The most abundant ions are cluster ions, like CH 5 + ·CH 4 , HCO + ·H 2 , and HCNH + ·C 2 H 4 , and long chain hydrocarbon ions. In atmospheres very rich in N 2 , such as Titan's, ions like H 4 C 7 N + and CH 3 CNH + also represent an important contribution to the total positive ion density. Three‐body reactions may play an important role in the dense atmosphere of Titan, and special attention is devoted to them. The calculated electron density in the lower atmosphere reaches a peak of ≈ 2150 cm −3 at an altitude of 90 km.
Type of Medium:
Online Resource
ISSN:
0148-0227
DOI:
10.1029/1998JE001001
Language:
English
Publisher:
American Geophysical Union (AGU)
Publication Date:
1999
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