Saturn's rings: Particle size distributions for thin layer models
Saturn's rings: Particle size distributions for thin layer models
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DOI：
10.1016/0019-1035(85)90074-0
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发表时间：
1985-12
期刊：
影响因子：
3.2
通讯作者：
H. Zebker;E. Marouf;G. Leonard Tyler
中科院分区：
文献类型：
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作者：
H. Zebker;E. Marouf;G. Leonard Tyler
土星环的物理厚度较小，要求使用具有有限多重散射的散射模型来解释射电掩星观测。新模型中近前向散射的可能阶数受到严格限制，允许较小的物理厚度，并且可用于将航海者 1 号对土星环 3.6 厘米和 13 厘米波长微波散射的观测与半径为 0.001 ≤ a ≤ 20 m 的粒子的环粒径分布函数 n(a) 联系起来。该有限散射模型给出了土星环八个区域的颗粒尺寸分布函数的解，这些区域表现出近似反立方幂律行为，颗粒半径的大尺寸截断范围从环 C 中的约 5 m 到环 A 部分的约 10 m。幂律指数在环 C 中约为 3.1，在卡西尼分区中约为 2.8，并且随着环 A 中的径向位置从 2.7 系统性地增加。 2.10Rsto 轻微 2.24Rs 时超过 3.0。假设粒子的物质密度为0.9 g/cm3，C环中相应的质量密度为32-43 kg/m2，卡西尼分区中的相应质量密度为188 kg/m2，A环中的相应质量密度为244-344 kg/m2。这些值比根据共振现象得出的一阶质量载荷估计值低 1 到 2 倍。鉴于测量和线性密度波模型中的不确定性，以及对比重不大于约 1 的冰粒子的有力论据，我们将这种差异解释为表明研究区域中可能存在差异，或散射结果、密度波现象或上述某种组合解释中的系统误差。
The small physical thickness of Saturn's rings requires that radio occultation observations be interpreted using scattering models with limited amounts of multiple scatter. A new model in which the possible order of near-forward scatter is strictly limited allows for the small physical thickness, and can be used to relate Voyager 1 observations of 3.6-and 13-cm wavelength microwave scatter from Saturn's rings to the ring particle size distribution function n(a), for particles with radius 0.001 ≤ a ≤ 20 m. This limited-scatter model yields solutions for particle size distribution functions for eight regions in Saturn's rings, which exhibit approximately inverse-cubic power-law behavior, with large-size cutoffs in particle radius ranging from about 5 m in ring C to about 10 m in parts of ring A. The power-law index is about 3.1 in ring C, about 2.8 in the Cassini division, and increases systematically with radial location in ring A from 2.7 at 2.10Rsto slightly more than 3.0 at 2.24Rs. Corresponding mass densities are 32–43 kg/m2in ring C, 188 kg/m2in the Cassini division, and 244–344 kg/m2in ring A, under the assumption that the material density of the particles is 0.9 g/cm3. These values are a factor of 1 to 2 lower than first-order mass loading estimates derived from resonance phenomena. In view of the uncertainties in the measurements and in the linear density wave model, and the strong arguments for icy particles with specific gravity not greater than about 1, we interpret this discrepancy as being indicative of possible differences in the regions studied, or systematic errors in the interpretation of the scattering results, the density wave phenomena, or some combination of the above.