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Spectral Analysis of HST-STIS Observations of Jovian UV Auroral Emissions
Gladstone, G. R.; Gérard, Jean-Claude; Gustin, Jacques et al.
2005Annual DPS meeting
 

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Abstract :
[en] Spectral observations of Jupiter's far-ultraviolet (FUV) auroral emissions are commonly used to determine a ``color ratio, - defined as I(155-162nm) / I(123-130nm), which provides an estimate for the peak emission altitude of the aurora and thus, assuming an accurate model atmosphere, for the mean energy of precipitating electrons. This is because the nascent emission spectrum resulting from electron impact on H[SUB]2[/SUB] is relatively unchanging over a wide range of energy, so that differential absorption by overlying CH[SUB]4[/SUB] is the primary modifier of the spectral shape of the emergent FUV emissions. This method is analogous to that used at Earth, with N[SUB]2[/SUB] LBH auroral emissions instead of H[SUB]2[/SUB] Lyman and Werner bands and differential absorption by O[SUB]2[/SUB] rather than methane. More detailed simulations of Jupiter's FUV auroral spectra can be used to place useful constraints on higher hydrocarbons, such as acetylene and ethane. Here we present a spectral analysis of HST-STIS G140L observations taken in September 1999, which include a region with the largest color ratio yet observed (i.e., the deepest aurora). A non-linear least squares model fit to the data is used to search for the presence of several important overlying hydrocarbons with strong and distinctive FUV absorption cross sections, e.g., CH[SUB]4[/SUB], C[SUB]2[/SUB]H[SUB]2[/SUB], C[SUB]2[/SUB]H[SUB]4[/SUB], C[SUB]2[/SUB]H[SUB]6[/SUB], CH[SUB]3[/SUB]C[SUB]2[/SUB]H, C[SUB]3[/SUB]H[SUB]8[/SUB], C[SUB]4[/SUB]H[SUB]2[/SUB], C[SUB]2[/SUB]H[SUB]2[/SUB], and C[SUB]4[/SUB]H[SUB]10[/SUB]. We gratefully acknowledge support from NASA through grant NNG05GG97G.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Gladstone, G. R.;  SwRI
Gérard, Jean-Claude  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Gustin, Jacques ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Grodent, Denis  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Clarke, J. T.;  Boston U.
Language :
English
Title :
Spectral Analysis of HST-STIS Observations of Jovian UV Auroral Emissions
Publication date :
01 August 2005
Event name :
Annual DPS meeting
Event organizer :
American Astronomical Society
Audience :
International
Commentary :
37
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