[en] Calculations of column intensities are performed for a number of infrared transitions of the H-3(+) molecular ion, using a model atmosphere recently produced by Grodent et al. [2001. A self-consistent model of the jovian auroral thermal structure. J. Geophys. Res. 106, 12933-12952]. The line intensities integrated along the line of sight through the model atmosphere are first computed assuming that all of the emitting energy levels are in local thermodynamic equilibrium (LTE). These results are compared with those derived from a detailed balance calculation using a method recently proposed by Oka and Epp [2004. Non-thermal rotational distribution of H-3(+). Astrophys. J. In press]. It is shown that the population of excited vibrational levels starts to depart from that derived from LTE at attitudes higher than 500 km (above the jovian cloud tops). This effect has been noted previously by Kim et it. [1992. Densities and vibrational distribution of H-3(+) in the jovian auroral atmosphere. J. Geophys. Res. 97, 6093-6101]. By 2000 km, all of the excited vibrational levels are Populated at less than 10% of the expected LTE value. This has important implications for the jovian upper atmosphere. In particular, the H-3(+) cooling effect will be greatly reduced high in the atmosphere. Modelled LTE line emission is greater than that derived from non-LTE modelling. Comparison of the non-LTE modelling with recent spectral measurements of the jovian auroral/polar regions in the L- and K-infrared windows shows that the Grodent et al. [2001. A self-consistent model of the jovian auroral thermal structure. J. Geophys. Res. 106, 12933-12952] profile overestimates the measured line intensity by similar to 3. Allowing for this, the non-LTE modelling shows that the column densities derived from (quasi-)LTE treatment of the measured line intensities may underestimate the real H-3(+) abundance by a factor of between 6 and 200. This means that attempts to derive important ionospheric properties, such as conductivity and related energy inputs due to magnetosphere-ionosphere coupling, front observed spectra will need to take this into account, if they are not to be seriously in error. (c) 2005 Elsevier Inc. All rights reserved.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Melin, Henrik; University College London > Department of Physics and Astronomy > Atmospheric Physics Laboratory
Miller, Steve; University College London > Department of Physics and Astronomy > Atmospheric Physics Laboratory
Stallard, Tom; University College London > Department of Physics and Astronomy > Atmospheric Physics Laboratory
Grodent, Denis ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Language :
English
Title :
Non-LTE effects on H-3(+) emission in the jovian upper atmosphere
Publication date :
01 November 2005
Journal title :
Icarus
ISSN :
0019-1035
eISSN :
1090-2643
Publisher :
Academic Press Inc Elsevier Science, San Diego, United States - California
Bougher, S.W., Waite Jr., J.H., Majeed, T., Gladstone, G.R., 2005. Jupiter Thermospheric General Circulation Model (JTGCM). 1. Global structure and dynamics driven by auroral and Joule heating. J. Geophys. Res. In press
S.W.H. Cowley E.J. Bunce Origin of the main auroral oval in Jupiter's coupled magnetosphere-ionosphere system Planet. Space Sci. 49 2001 1067-1088
B.M. Dinelli S. Miller J. Tennyson Bands of H3+ up to 4ν2: Rovibrational transitions from first principles J. Mol. Spectrosc. 153 1992 718-725
P. Drossart 11 colleagues Detection of H3+ on Jupiter Nature 340 1989 539-541
P. Drossart B. Bézard S.K. Atreya J. Bishop J.H. Waite Jr. D. Boice Thermal profiles in the auroral regions of Jupiter J. Geophys. Res. 98 1993 18803-18810
P. Drossart J.-P. Maillard J. Caldwell J. Rosenqvist Line-resolved spectroscopy of the jovian H3(+) auroral emission at 3.5 micrometers Astrophys. J. 402 1993 L25-L28
D. Grodent J.H. Waite Jr. J.-C. Gérard A self-consistent model of the jovian auroral thermal structure J. Geophys. Res. 106 2001 12933-12952
J. Gustin 14 colleagues Jovian auroral spectroscopy with FUSE: Analysis of self-absorption and implications for electron precipitation Icarus 171 2004 336-355
Y.H. Kim J.L. Fox H.S. Porter Densities and vibrational distribution of H3+ in the jovian auroral atmosphere J. Geophys. Res. 97 1992 6093-6101
H.A. Lam N. Achilleos S. Miller J. Tennyson L.M. Trafton T.R. Geballe G.E. Ballester A baseline spectroscopic study of the infrared auroras of Jupiter Icarus 127 1997 379-393
J.-P. Maillard P. Drossart J.K.G. Watson S.J. Kim J. Caldwell H3+ fundamental band in Jupiter's auroral zones at high resolution from 2400 to 2900 inverse centimetres Astrophys. J. 363 1990 L37-L40
S. Miller J. Tennyson Calculated rotational and rovibrational transitions in the spectrum of H3+ Astrophys J. 335 1988 486-494
S. Miller R.D. Joseph J. Tennyson Infrared emissions of H3 + in the atmosphere of Jupiter in the 2.1 and 4.0 micron region Astrophys. J. 360 1990 L55-L58
S. Miller N. Achilleos G.E. Ballester H. Lam J. Tennyson T.R. Geballe L.M. Trafton Mid-to-low latitude H3+ emission from Jupiter Icarus 130 1997 57-67
S. Miller 10 colleagues The role of H3+ in planetary atmospheres Phil. Trans. R. Soc. 358 2000 2485-2502
G. Millward S. Miller T. Stallard A. Aylward N. Achilleos On the dynamics of the jovian ionosphere and thermosphere. III. The modelling of auroral conductivity Icarus 160 2002 95-107
G. Millward S. Miller T. Stallard N. Achilleos A.D. Aylward On the dynamics of the jovian ionosphere and thermosphere. IV. Ion-neutral coupling Icarus 173 2005 200-211
T. Oka E. Epp Non-thermal rotational distribution of H3 + Astrophys. J. 613 2004 349-354
T. Oka T.R. Geballe Observations of the 4 micron fundamental band of H3+ in Jupiter Astrophys. J. 351 1990 L53-L56
F.-S. Pan T. Oka Calculated forbidden rotational spectra of H3 + Astrophys. J. 305 1986 518-525
E. Raynaud E. Lellouch J.-P. Maillard G.R. Gladstone J.H. Waite Jr. B. Bézard P. Drossart T. Fouchet Spectro-imaging observations of Jupiter's 2-μm auroral emission. I. H3+ distribution and temperature Icarus 171 2004 133-152
T. Stallard S. Miller G. Millward R.D. Joseph On the dynamics of the jovian ionosphere and thermosphere. II. The measurement of H3 + vibrational temperature, column density, and total emission Icarus 156 2002 498-514