Lyapunov and diffusion timescales in the solar neighborhood

TL;DR

This paper estimates the Lyapunov and diffusion timescales in models of the solar neighborhood, showing that chaos can facilitate Sun's migration within the Milky Way, with implications for galactic dynamics.

Contribution

It provides the first estimates of Lyapunov and diffusion timescales in models including Galactic bar and spiral arms perturbations, highlighting the role of chaos in stellar migration.

Findings

Lyapunov times are typically around 10 Galactic years.

Galactic chaos is usually non-adiabatic, with only narrow parameter ranges being adiabatic.

Diffusion times can be short enough to allow Sun's migration from inner Galaxy regions.

Abstract

We estimate the Lyapunov times (characteristic times of predictability of motion) in Quillen's models for the dynamics in the solar neighborhood. These models take into account perturbations due to the Galactic bar and spiral arms. For estimating the Lyapunov times, an approach based on the separatrix map theory is used. The Lyapunov times turn out to be typically of the order of 10 Galactic years. We show that only in a narrow range of possible values of the problem parameters the Galactic chaos is adiabatic; usually it is not slow. We also estimate the characteristic diffusion times in the chaotic domain. In a number of models, the diffusion times turn out to be small enough to permit migration of the Sun from the inner regions of the Milky Way to its current location. Moreover, due to the possibility of ballistic flights inside the chaotic layer, the chaotic mixing might be even far more effective and quicker than in the case of normal diffusion. This confirms the dynamical possibility of Minchev and Famaey's migration concept.