We are in the process of updating the DRUM statistics and the number of downloads reported in DRUM records only reflects downloads from June 2014 to the present. The previous numbers have not been lost and we are in the process adding them to the total. Please contact firstname.lastname@example.org if you have any questions.
N-body Simulations with Cohesion in Dense Planetary Rings
Richardson, Derek C
MetadataShow full item record
This dissertation is primarily focused on exploring whether weak cohesion among icy particles in Saturn's dense rings is consistent with observations--and if so, what limits can be placed on the strength of such cohesive bonds, and what dynamical or observable consequences might arise out of cohesive bonding. Here I present my numerical method that allows for N-body particle sticking within a local rotating frame ("patch")--an approach capable of modeling hundreds of thousands or more colliding bodies. Impacting particles can stick to form non-deformable but breakable aggregates that obey equations of rigid body motion. I then apply the method to Saturn's icy rings, for which laboratory experiments suggest that interpenetration of thin, frost-coated surface layers may lead to weak bonding if the bodies impact at low speeds--speeds that happen to be characteristic of the rings. This investigation is further motivated by observations of structure in the rings that could be formed through bottom-up aggregations of particles (i.e., "propellers" in the A ring, and large-scale radial structure in the B ring). This work presents the implementation of the model, as well as results from a suite of 100 simulations that investigate the effects of five parameters on the equilibrium characteristics of the rings: speed-based merge and fragmentation limits, bond strength, ring surface density, and patch orbital distance (specifically the center of either the A or B ring), some with both monodisperse and polydisperse particle comparison cases. I conclude that the presence of weak cohesion is consistent with observations of the A and B rings, and present a range of parameters that reproduce the observed size distribution and maximum particle size. The parameters that match observations differ between the A and B rings, and I discuss the potential implications of this result. I also comment on other observable consequences of cohesion for the rings, such as optical depth and scale height effects, and discuss the unlikelihood that very large objects are grown bottom-up from cohesion of smaller ring particles. Lastly, I include a brief summary of other projects in ring dynamics I have undertaken before and during my thesis work.