Abstract

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.

中文翻译：

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土星大气中气溶胶体积散射系数的高度依赖性。二、北半球的纬度带

摘要

已经确定了土星北半球五个纬度带的气溶胶体积散射系数的高度依赖性，并且已经构建了在 0.06-10.0 bar 大气压力范围内气溶胶成分的可能垂直结构。为此，作者早先对 2015 年对北纬 17° N、33° N、49° N、66° N 和 80° N 纬度带进行的巨行星分光光度测量分析的结果。使用了 727 nm 和 619 nm 处的甲烷吸收带。已经发现气溶胶是土星大气在所考虑范围的高度水平上无处不在的成分，而没有纯粹的气体夹层的迹象。我们确定了气溶胶体积散射系数的最大值，大约 ≈2 × 10⁻⁶ cm ^-1，在北纬49°的中纬度带和最小的带，大约≈1 × 10 ^-8 cm ^-1，在 80° N 的近极带中。在考虑的大气高度范围内，我们检测到气溶胶增稠（聚类）的四个区域，其中气溶胶体积散射系数达到最高值。土星大气层中最厚的气溶胶层粒子在约 0.06 巴的压力下被发现。随着更深地浸入大气中，气溶胶体积散射系数增长到最大值。在这里，在所有考虑的纬度带中，除了在 80° N 处，在最高海拔处形成了两个气溶胶团；在这些星团中，气溶胶体积散射系数在海拔 ≈0.26 和 ≈0.45 bar 的压力下达到最大值。这些簇在高度上被一个密度较小的气溶胶夹层隔开。在更深的大气层中，在 ≈0.45−2.0 bar 之间的压力水平下，气溶胶体积散射系数显着降低。在这个大气区域，在所有考虑的纬度带中，除了 80° N 处，发现了连续第三个气溶胶簇。在那里，气溶胶体积散射系数的最大值位于~1.0 bar 的压力水平附近。在更深的层中，大气压力约为 ≈2.0-6.0 bar，有第四个连续的气溶胶簇。它的高度显着延长，其上部和下部的气溶胶体积散射系数的最大值分别位于 2.7 和 4.4 巴的压力水平附近。在模型计算中，我们使用了以下气溶胶粒子参数：粒度分布由修正的伽马函数描述；该分布的有效半径和方差分别为 1.4 μm 和 0.07；复折射率的实部为1.44。气溶胶的这些模型特征被认为接近于 66° N 纬度带中所考虑高度和纬度带中约 0.06-1.5 bar 压力范围内土星真实大气中粒子的平均参数33° N。同时，在 17° N 和 49° N 带中所有考虑的大气高度水平上，模型和实际气溶胶粒子参数之间可能存在显着差异的迹象被揭示。