Evidence for supersonic turbulence in the upper atmosphere of Jupiter

Science

Volumn 273, Issue 5278, 1996, Pages 1085-1087

  Emerich, Claude ^a   Jaffel, Lotfi Ben ^a   Clarke, John T ^b   Prangé, Renée ^a   Gladstone, G Randall ^c   Sommeria, Joel ^d   Ballester, Gilda ^b  

^a CNRS   (France)

^b UNIVERSITY OF MICHIGAN   (United States)

^c SOUTHWEST RESEARCH INSTITUTE   (United States)

^d UNIVERSITÉ DE LYON   (France)

Author keywords

[No Author keywords available]

Indexed keywords

HYDROGEN;

ARTICLE; ASTRONOMY; ATMOSPHERE; ATMOSPHERIC DISPERSION; METEOROLOGY; PRIORITY JOURNAL; TEMPERATURE MEASUREMENT; THERMODYNAMICS; TURBULENT FLOW; VELOCITY;

EID: 0029838224     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.273.5278.1085     Document Type: Article

References (24)

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9. L. Ben Jaffel et al., ibid. 20, 747 (1993).
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11. J. Sommeria, L. Ben Jaffel, R. Prangé, Icarus 119, 2 (1995).
12. C. Magnan, J. Quant. Spectrosc. Radiat. Transfer 16, 281 (1976).
13. M. L. Loucif and C. Magnan, Astron. Astrophys. 112, 287 (1982).
14. The automatic procedure to subtract the interorder background between the echelle orders is not adapted for measurements of a diffuse emission that fills the aperture. Consequently, the spectra were reduced without interorder background subtraction, and we later subtracted a constant background determined from adjacent wavelengths.
15. The automatic on-board correction for the effects of the motion of HST had been calculated in the initial reduction on the basis of erroneous coordinates for the moving targets. Consequently, the correct compensations were recalculated by the HST staff and then introduced into our data analysis of each individual spectrum. This procedure and the new Doppler corrections were validated by the spectrum obtained for the sky-background measurements: The central wavelength corresponding to the Ly-u resonance line was precisely located at its laboratory value of 1215.67 Å, within the experimental accuracy (about 0.008 Å) (Fig. 1).
16. The IPM and geocoronal H also contributed some extinction to the jovian signal before it was measured by HST. The jovian profile deduced from all of these corrections was almost equal to the raw measured profile (Fig. 1). This is so because of the opposite effects of a small background subtraction and of the geocoronal and IPM extinction. Finally, we improved the measured signal-to-noise ratio by binning the spectra by pairs of pixels (for exposures of 16 min) and by four pixels (for exposures of 4 min).
17. Each mean spectrum in Fig. 2 is the average of 16 elementary exposures of ≃1 min. Each subspectrum in Fig. 3 is the average of four of these elementary exposures.
18. The spectral line spread function is the wavelength width measured by the instrument when exposed to an extended monochromatic source illuminating the whole detector. If a quasi-monochromatic source illuminates only one of the eight diodes of the GHRS detector, the measured width may be as small as ∼0.07 Å/8 ∼ 0.009 Å.
19. One such cell within the GHRS Science slit corresponds to the projection on Jupiter's disk of one GHRS diode (in the dispersion axis) by eight diodes in the perpendicular axis.
20. 2.
21. C. Magnan, Astron. Astrophys. 144, 186 (1985).
22. 11 photons per square centimeter per second at 1 astronomical unit.
23. The fact that these models were able to roughly fit the profiles measured by IUE appears to be due to the much longer integration time of these observations, which averaged out the fine structure of any line profile (spectral or temporal) that the higher sensitivity of HST-GHRS is now able to detect almost instantaneously.
24. The work of C.E., L.B.J., and R.P. was supported by CNRS and the Institut National des Sciences de l'Univers (INSU). The work of J.C. and G.B. was supported under NASA grant STScl GO-5417.01-93A. The work of R.G. was supported under STScl grant GO-5417.02-93A. This work is based on observations with the NASA-European Space Agency HST, obtained at the STScl, which is operated by the Association of Universities for Research in Astronomy for NASA under contract NAS 5-26535.