On the Altitude Dependence of the Aerosol Volume Scattering Coefficient in Saturn’s Atmosphere. II. Latitudinal Belts of the Northern Hemisphere

The altitude dependences of the aerosol volume-scattering coefficient have been determined for five latitudinal belts of the Northern hemisphere of Saturn, and the probable vertical structure of the aerosol component in a range of the atmospheric pressure at 0.06−10.0 bar has been constructed. For this purpose, the results of the authors' earlier analysis of the spectrophotometric measurements of the giant planet performed in 2015 for the latitudinal belts at 17° N, 33° N, 49° N, 66° N, and 80° N in the methane absorption bands at 727 nm and 619 nm were used. It has been found that aerosol is a ubiquitous component of Saturn’s atmosphere at altitude levels of the considered range, while there are no signs of purely gas interlayers. We determined the largest values of the aerosol volume-scattering coefficient, approximately ≈2 × 10⁻⁶ cm⁻¹, in the midlatitude belt at 49° N and the smallest ones, approximately ≈1 × 10⁻⁸ cm⁻¹, in the near-pole belt at 80° N. In the considered altitude range of the atmosphere, we detected four regions of the aerosol thickening (clustering), within which the aerosol volume-scattering coefficient reaches its highest values. Particles of the thickest aerosol layer in the atmosphere of Saturn were found at altitudes with a pressure of ≈0.06 bar. With immersing deeper into the atmosphere, the aerosol volume-scattering coefficient grows to the maximal values. Here, in all of the considered latitudinal belts except that at 80° N, two aerosol clusters are formed at the highest altitudes; within these clusters, the aerosol volume-scattering coefficient reaches its maximum at altitudes with a pressure of ≈0.26 and ≈0.45 bar. These clusters are separated in height by a less dense aerosol interlayer. In deeper atmospheric layers, at pressure levels between ≈0.45−2.0 bar, the aerosol volume-scattering coefficient significantly decreases. In this region of the atmosphere, in all of the considered latitudinal belts except that at 80° N, the third in succession cluster of aerosol was found. There, the maxima of the aerosol volume-scattering coefficient are located near a pressure level of ~1.0 bar. In even deeper layers, where the atmospheric pressure is approximately ≈2.0−6.0 bar, there is a fourth in succession cluster of aerosol. It is substantially extended in height, and the maxima of the aerosol volume-scattering coefficient in its upper and lower parts are located near pressure levels of 2.7 and 4.4 bar, respectively. In the model calculations, we used the following parameters of aerosol particles: the size distribution is described by a modified gamma function; the effective radius and the variance of this distribution are 1.4 μm and 0.07, respectively; and the real part of the complex refractive index is 1.44. These model characteristics of aerosols are considered as being close to the averaged parameters of particles in the real atmosphere of Saturn at the considered altitudes in the latitudinal belt at 66° N and in a pressure range of approximately 0.06−1.5 bar in the latitudinal belt at 33° N. At the same time, the signs of a possible significant difference between the model and real parameters of aerosol particles were revealed at all considered altitude levels of the atmosphere in the belts at 17° N and 49° N.