Forcing Planets to Evolve: Interactions Between Uranus and Neptune at Late Stages of Dynamical Evolution

In early Solar System numerical simulations, where chaos is a primary driver, it is difficult to explore parameter space in a systematic way. In such simulations, stable configurations are hard to come by, and often require special fine-tuning. In addition, it is infeasible to run suites of well-resolved, realistic simulations with a disk of massive particles to drive planetary evolution where enough particles remain to represent the transneptunian populations to robustly statistically compare with observations. To complement state of the art full N-body simulations, we develop a method to artificially control each planet's orbital elements independently from each other, which when carefully applied, can be used to test a wider suite of models. We modify two widely used publicly available N-body integrators: (1) the C code, \texttt{REBOUND} and (2) the FORTRAN code, \texttt{Mercury6.2}. We show how the application of specific fictitious forces within numerical integrators can be used to tightly control planetary evolution to more easily explore migration and orbital excitation and damping. This tool allows us to replicate the impact a massive planetesimal disk would have on the planets, without actually including the massive planetesimals, thus decreasing the chaos and simulation runtime. We demonstrate the utility of this tool by applying it to the coupled orbital evolution of Uranus and Neptune, and show that Neptune's eccentricity damping and radial outward migration have the appropriate affect on Uranus' eccentricity.