Features of the equinox of Saturn in 2010
| 1Vidmachenko, AP 1Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Kyiv, Ukraine |
| Kinemat. fiz. nebesnyh tel (Online) 2021, 37(1):57-70 |
| https://doi.org/10.15407/kfnt2021.01.057 |
| Start Page: Dynamics and Physics of Bodies of the Solar System |
| Language: Ukrainian |
Abstract: The equator of Saturn is inclined to the orbital plane at an angle of 26.75° with a period of revolution around the Sun of 29.45 years. Due to the eccentricity of the e = 0.056 orbit, its southern hemisphere receives 25 % more energy from the Sun than the northern one, since the perihelion of orbit — Saturn passes during the summer epoch in the southern hemisphere, and aphelion — during summer in the northern hemisphere. This affects the physical characteristics and vertical structure of the atmosphere. We registered changes on Saturn and related them to the seasonal influx of solar energy. For the analysis, we used the results of observations at the equinox moments in 1966, 1980, 1995 and 2010. Latitudinal differences in methane absorption across the disk showed significant asymmetries between the northern and southern hemispheres. Moreover, the change in absorption in the opposite hemispheres occurs in different ways. In identical conditions of the previous history of the planet in 1966 and 1995. — absorption in the northern summer hemisphere was greater than in the southern one. The opposite effect was observed in 1980 when absorption was large in the southern summer hemisphere. The last equinox on Saturn was in 2009. We assumed that it would be similar to the results of 1980. However, in contrast to the pronounced asymmetry of absorption in the hemispheres in 1966, 1980 and 1995. — in the equinox of 2009, the difference in absorption between the hemispheres is almost absent. Moreover, in the northern winter hemisphere, absorption did not decrease, but in the summer southern hemisphere it increased markedly. The very same equinox of 2009 differed in that, unlike the previous three equinoxes, there was a minimum of solar activity. Combined observations of Voyager in 1980 and Cassini in 2010 showed that in one Saturnian year — the tropical atmosphere in the tropopause warmed up by 10 K. Taking into account these differences and the fact that in 2010 the solar activity index R = 0, and in 1980 — more than 150, we estimate that the radiative constant of the hydrogen-helium atmosphere of Saturn is about 4.5 Earth years. And warming in the tropopause changed atmospheric stratification and stability, and influenced the large-scale dynamics of the upper troposphere in 2010. |
| Keywords: atmosphere, equinox, methane absorption, Saturn, seasonal changes |
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