H2 spectroscopy and a diurnally changing cloud on Jupiter

Cindy C. Cunningham, Donald M. Hunten, Martin G. Tomasko

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

A large number of specific areas of Jupiter have been observed at wavelengths chosen for their different absorptive properties. The weak broadband (5 Å/pixel) CH4 absorptions (6190 and 7270 Å) probe the deep cloud layer at the 2- to 4-bar level. The high resolution (∼50 mÅ/pixel) 3-0 H2 quadrupole wavelengths probe to about 1-2 bars and the strongest CH4 band at 8900 Å probes the upper haze layer and the top of the NH3 cloud around 200-450 mbars. This paper concerns the 3-0 S(0) and S(1) lines of hydrogen at which wavelengths of three separate longitudes were tracked as they rotated from one limb to the other. The June 1983 data has been modeled at seven different latitudes so that spatial and temporal variability can be tested. The gradual increase in the measured equivalent widths of the H2 quadrupole lines from the east limb to the west limb is most likely indicative of a diurnal change in the vertical cloud structure. Such a variation is shown to be consistent with the properties of a convective layer driven by internal heat, with solar heat deposited at the top. The average models representing the belt regions require somewhat thinner optical depths for the upper ammonia clouds (τcl = 3-4.5) than the zones (τcl = 5.5-6.5) or the equatorial region (τcl = 6.5-7). Some constraints can be placed on the thermodynamic state of the hydrogen. A model atmosphere with only normal hydrogen (ortho-H2 to para-H2 of 3 : 1) is not able to fit both of the 3-0 lines simultaneously. Model atmospheres with most of the hydrogen in a state of equilibrium fit the two lines much better. It is also possible to produce a reasonable average fit to both lines with small amounts of disequilibrium hydrogen in the upper atmosphere such as that measured by B.J. Conrath and P.J. Geirasch (1984, Icarus 57, 184-204) with the IRIS Voyager data. These models cannot be distinguished from those that incorporate only equilibrium hydrogen at all levels.

Original languageEnglish (US)
Pages (from-to)324-350
Number of pages27
JournalIcarus
Volume75
Issue number2
DOIs
StatePublished - Aug 1988

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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