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Fine‐structure physical chemistry modeling of Uranus H 2 X quadrupole emission
Author(s) -
Hallett J. T.,
Shemansky D. E.,
Liu X.
Publication year - 2005
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2004gl021327
Subject(s) - uranus , physics , population , planet , atomic physics , electron , astrophysics , nuclear physics , demography , sociology
A new hydrogen physical chemistry model has been developed at the fine‐structure level for application to the giant outer planet thermospheres. The model is applied to Uranus because observations of dayglow H 2 X 1 Σ g + ( v ) quadrupole and H 3 + vibration‐rotation emission made at NASA IRTF and UKIRT provide critical constraints for thermospheric modeling. The observed H 3 + vibration‐rotation emission infers an H 3 + dominant ionosphere, predicted only for non‐LTE H 2 X ( v : J ). Excitation mechanisms explored are solar and non‐solar electron energy deposition. Non‐solar electron forcing is constrained by the EUV H 2 Lyman and Werner band emission measured by Voyager UVS. Analysis indicates that non‐solar electrons are dominant in the energy budget required to predict the observed thermospheric temperature profile. The modeled H 2 X quadrupole emission infers that an additional mechanism is required to excite the H 2 X ( v = 1) population. Non‐thermal H produced in dissociative excitation of H 2 X is a primary candidate.