Movies proved to be a powerful and entertaining tool that we used to look at the data from our simulations.   There are two types of movies in our gallery. The first type gives a "bird's eye view" of the planetesimal disk and allows us to visualize overall trends in the disk density as it changes radially. The second type of movie that we used more often is one with two separate plots: a plot of the eccentricity vs. semi-major axis (a) and a plot of inclination vs. a. In the latter, the different colors and radius sizes represent different sizes of particles, and the filled circles characterize the largest particles. From the inclination and eccentricity movies we were able to troubleshoot multistepping problems and look at a picture of how the disk was growing.

      In this simulation we can see how resonances might develop in a planetesimal disk. We inserted a seed mass at 0.0028 AU, which is where Io currently orbits. We gave it a mass 1000 times that of Io, so that we could clearly and quickly see the resonances in the disk. The planetesimals were given no initial eccentricity or inclination. For parameter specifics, please refer to the ss.par parameter file and the ssic.par initial conditions file.

Extra massive Io effectively heats up the disk at the start of the simulation. The movie represents half of an earth year, or approximately 100 orbits of Io. Each frame represents 1/5 of an Io orbit.

      First and second order resonance peaks develop within the first two years. Look for 1:2 at 0.0044 AU, 2:3 at 0.00367 AU, and 3:5 at 0.00394 AU. Other resonances are either beyond the edge of the disk, or they are out of view due to the choice of the horizontal axis scale.

While we were exploring multistepping as an option to maximize the ratio of dynamical time to CPU time, we came across some difficulties that are discussed in detail in Challenges and Solutions. The initial problems with multistepping are especially evident here; the parameter which determines the step size is not properly adjusted and is affecting the behavior of the disk, encouraging growth at the "rungs."

This simulation attempted to establish resonance patterns in eccentricity and inclination distributions for the sake of comparison to those seen in multistepping simulations. A seed of mass equivalent to that of Io was placed at 0.0028 AU (Io's semi-major axis). While the disk was generally heated, distinct resonances did not appear. For more information, see both parameter files:   ss.par   &   ssic.par .

Jovian2

The growth of this single-stepping simulation provided a basis for comparison to other multistepping runs. This simulation included particle bouncing and merging. The growth pattern is quite different when we compare the run with perfect accretion (Galilean2).

Galilean2

In this single-stepping simulation particles are allowed only to merge, resulting in growth patterns visibly different from those of the previous simulation. For example, accretion takes place at a very high rate in the interior regions of the disk, as indicated by the relatively high number of large bodies inside 5*10^-3 AU. The more realistic scenario above (Jovian2) provides for moon formation at a higher relative rate in the outer regions.