The origin of amplitude synchronization (AS), or amplitude envelope synchronization, as a peculiar form of strong correlation between amplitudes of oscillators is studied by using a model of coupled Landau-Stuart periodic oscillators. We find that the AS extensively occurs within the traditional phase drift region, and the amplitude correlation does not change with variation of the coupling strength but is dampened with increase of the frequency mismatch. The AS appears only at weak couplings and before the occurrence of phase synchronization (PS), and the oscillator amplitude is modulated by its phase. This study could build a solid foundation for AS, which has not drawn much attention in the nonlinear dynamics field before, providing a clear physical picture for synchronization including not only PS, but also AS, and arousing general interest in many interdisciplinary fields, such as neuronal systems, laser dynamics, nanomechanical resonators, and power systems, etc., where phase and amplitude are always mutually influenced and both are important.

• Received 8 November 2019
• Revised 6 January 2020
• Accepted 28 January 2020

DOI:https://doi.org/10.1103/PhysRevE.101.022210