On the statistical convergence of N-body simulations of the Solar System

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Hauptverfasser: Rein, Hanno, Brown, Garett, Kanda, Mei
Format: Preprint
Veröffentlicht: 2025
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author Rein, Hanno
Brown, Garett
Kanda, Mei
author_facet Rein, Hanno
Brown, Garett
Kanda, Mei
contents Most direct N-body integrations of planetary systems use a symplectic integrator with a fixed timestep. A large timestep is desirable in order to speed up the numerical simulations. However, simulations yield unphysical results if the timestep is too large. Surprisingly, no systematic convergence study has been performed on long (Gyr) timescales. In this paper we present numerical experiments to determine the minimum timestep one has to use in long-term integrations of the Solar System in order to recover the system's fundamental secular frequencies and instability rate. We find that timesteps of up to 32 days, i.e. a third of Mercury's orbital period, yield physical results in an ensemble of 5 Gyr integrations. We argue that the chaotic diffusion that drives the Solar System's long-term evolution dominates over numerical diffusion and timestep resonances. Our results bolster confidence that the statistical results of most simulations in the literature are indeed physical and provide guidance on how to run time and energy efficient simulations while making sure results can be trusted.
format Preprint
id arxiv_https___arxiv_org_abs_2507_04987
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the statistical convergence of N-body simulations of the Solar System
Rein, Hanno
Brown, Garett
Kanda, Mei
Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
Numerical Analysis
Most direct N-body integrations of planetary systems use a symplectic integrator with a fixed timestep. A large timestep is desirable in order to speed up the numerical simulations. However, simulations yield unphysical results if the timestep is too large. Surprisingly, no systematic convergence study has been performed on long (Gyr) timescales. In this paper we present numerical experiments to determine the minimum timestep one has to use in long-term integrations of the Solar System in order to recover the system's fundamental secular frequencies and instability rate. We find that timesteps of up to 32 days, i.e. a third of Mercury's orbital period, yield physical results in an ensemble of 5 Gyr integrations. We argue that the chaotic diffusion that drives the Solar System's long-term evolution dominates over numerical diffusion and timestep resonances. Our results bolster confidence that the statistical results of most simulations in the literature are indeed physical and provide guidance on how to run time and energy efficient simulations while making sure results can be trusted.
title On the statistical convergence of N-body simulations of the Solar System
topic Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
Numerical Analysis
url https://arxiv.org/abs/2507.04987