An analytic parameterization of self-gravity wakes in Saturn's rings, with application to occultations and propellers - Astrophysics > Earth and Planetary AstrophysicsReportar como inadecuado




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Abstract: We have developed a semi-analytic method of parameterizing N-body simulationsof self-gravity wakes in Saturn-s rings, describing their properties by meansof only 6 numbers: 3 optical depths and 3 weighting factors. These numbers areobtained using a density-estimation procedure that finds the frequencies ofvarious values of local density within a simulated ring patch.Application of our parameterization to a suite of N-body simulations impliesthat the distribution of local optical depths is trimodal, rather than bimodalas previous authors have assumed. Rings dominated by self-gravity wakes appearto be mostly empty space.The implications of this result for the analysis of occultation data are moreconceptual than practical. The only adjustment needed is that the modelparameter $\tau {gap}$ should be interpreted as representing the area-weightedaverage optical depth within the gaps or inter-wake regions.The most significant consequence of our results applies to the question ofwhy -propeller- structures observed in the mid-A ring are seen asrelative-bright features, even though the most prominent features of simulatedpropellers are regions of relatively low density. We find preliminaryquantitative support for the hypothesis that propellers would be bright if theyinvolve a local and temporary disruption of self-gravity wakes, flooding theregion with more -photometrically active- material i.e., material that cancontribute to the rings- local optical depth even though the overall densityis lower, and thus raising their apparent brightnesses in agreement withobservations. We suggest that this mechanism be tested by future detailednumerical models.



Autor: Matthew S. Tiscareno, Randall P. Perrine, Derek C. Richardson, Matthew M. Hedman, John W. Weiss, Carolyn C. Porco, Joseph A. Burn

Fuente: https://arxiv.org/







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