Tuesday, July 27, 2010

Ring Dynamics Work

While the summer session is just about ended for my research students, there continue to be interesting results that they are documenting on the wiki. Cameron is doing timing results on the lock graph. He is comparing it to the older lock grid for some different simulations. The results aren't exactly what would have been predicted. He'll finish out the week looking at some other systems.

Crosby has gone back to looking at the silicate hiding simulations. He had looked at the A ring previously. Now he is looking at the B ring simulations. There are unexpected results here as well. In the A ring he found that the reflected light was only showing silicate with 25% of the amount of silicates present. So if 4% of the particles were silicate, only 1% of the light would be coming off silicate particles. This 25% was consistent across 4%, 2%, and 1% silicate fractions. The B ring simulations are confusing because it isn't a constant fraction. A lot more exploration is needed here. he'll also have to look at the C ring simulations that have been done.

Lastly, I continue to look at moonlet stability. On a suggestion from Matt Tiscareno I looked at stability without the background. This showed me that I had upped my time step too high based on stuff I did earlier this summer looking for optimal speed. However, there is still a story here. I found the break point in density for where a lattice of equal sized particles is stable at 130,000km. This is a higher density than what was found by Porco, et al. (2007) for a bunch of rubble on a single large core. I took the lowest density value for which I got a stable moonlet alone and dropped in into the background. The simulation hasn't gone all that far, but it is already apparent that the moonlet is being broken up by collisions. Here again there is a lot more work to do. In fact, it looks like this might be an area that Crosby uses for his senior thesis. It has the advantage that the simulations looking at stability in moonlets without background are fairly small simulations and he can run a bunch of them. He has done a little bit to document the experiments that he will look at running.