Seasonal changes on Jupiter: 2. Influence of the planet exposure to the Sun

Аннотация

From our investigation of the behavior of changes in the visible brightness of Jupiter observed since 1850, it follows that the 22.3-year Hale magnetic cycle of solar activity produces the dominating influence on the processes taking place in the troposphere at a level of forming the upper boundary of clouds. The maximum values of the integral brightness of Jupiter fall on the solar cycle with the highest value of the Wolf number for the last 165 years (around 1957). The lowest estimates of brightness were obtained in 1855, when the Wolf number in the 12th solar-activity cycle was smallest. The analysis of the reflectance of Jupiter’s hemispheres in the visible spectral range for 1962–2015 revealed the alternating increase in the brightness of southern and northern tropical and middle regions for one rotation period of Jupiter about the Sun. Such a change in brightness and the increase in the activity of different hemispheres of the planet may indicate the periodic global alteration in the circulation system, the structure of cloud layers, and the overcloud haze. This suggests the interrelation between the observed variations in the reflectance of the considered latitudinal belts of Jupiter and the change in the axial tilts of the planet itself and its magnetic field to the orbital plane, i.e., the seasonal alteration in the atmosphere. The comparison of the temporal dependence of the activity factor A_j of the Jovian hemispheres in the visible spectral range with the change in the solar-activity index R shows that, from 1962 to 1995, these parameters almost synchronously changed, though the response of the visible cloud layer somewhat lagged behind the regime of exposure of the atmosphere to the Sun. The analysis shows that, when the planet is moving along the orbit, the reflectance of Jupiter’s hemispheres varies in response to the 21-percent change in the exposure of different hemispheres with a lag of 6 years. Such a lag coincides with the radiation- relaxation time of the hydrogen–helium atmosphere under the Jovian conditions. Desynchronization in their behavior that occurred after 1997 may be explained by the unbalanced influence of the three mentioned causes on the atmosphere of the planet.