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[10.09] The mapping of longitudinal-latitudinal variations of the methane absorption on Jupiter

V.G. Tejfel (Fessenkov Astrophysical Institute)

In November-December 1999 a special observational program was run during four nights to study the probable longitudinal variations of the methane absorption bands 619, 725, 798 (CH₄ + NH₃ ), and 887 nm on different latitudes using the CCD-spectra of central meridian, recorded automatically with time interval 3 minutes. General number of processed spectra is 380. All longitudes of Jupiter were observed twice. The values of the central depths R in four absorption bands were calculated after prleminary procedure, when the CCD-spectra of Jupiter were divided on the spectra of Saturn's ring, recorded at the same nights. The computerized atlas of longitudinal and latitudinal values of Rn on Jupiter have been prepared and used for detailed analysis. The measurements of longitudinal variations of Rn were done for 48 jovigraphic latitudes between 75 N and 75 S. The latitudinal differences are expressed clearly and may be considered as an evidence of nonsimilar circulating processes and the cloud density distribution on different effective depths of the weak and strong absorption bands formation. Main latitudinal differences, which are common for all longitudes, may be seen in the equatorial zone and neighbouring parts of NEB and SEB. Strongly expressed depression of R has a minimum at the planetographic latitude 1 S for CH₄ 887 and 725 nm band, but this minimum is shifted to 11 N at 798 nm band at all longitudes and disappeared at 619 nm band. Instead of depression we have the increase of the absorption in 619 nm towards maximum at 5-7 S. Secondary maximum of absorption take place near 57 N before sharp decrease of Rn towards North pole. The decrease of R towards South pole begins from 45-55 S . Most latitudes of Jupiter do not show local longitudinal differences of R more than about few per cent (less than 3-4 where the irregular oscillations of R are some more (to about 5 are most noticeable local decrease of absorption within southern part of GRS (L2 =72 deg , PHI=21- 35 S) and increase on longitudes L2 = 40-80 deg at PHI=7-19 S). The last increase appears only at 798 nm and repeated on the next series of measurements. This anomaly may be probably connected with ammonia absorption in this band.