The Kelvin–Helmholtz instability (KHI) is a velocity shear-driven magnetohydrodynamic (MHD) instability ubiquitously observed throughout the universe: from the solar atmosphere to heliospheric boundaries. It is a key mechanism for energy transport across planetary boundaries in solar wind–magnetosphere coupling, by producing nonlinearly rolled-up vortices, turbulence, and magnetic reconnection. KHI has been observed at the magnetopauses of Earth and other magnetized planets, including Jupiter, Saturn, Uranus, and Neptune, as well as in the induced magnetospheres of unmagnetized bodies such as Venus, Mars, and Pluto. Its presence in the solar wind itself further illustrates its broad role in driving plasma mixing and energy redistribution across planetary systems. Despite decades of observation and modeling, open questions remain about the conditions that control its onset, nonlinear evolution, and cross-scale effects on particle dynamics and boundary structures. Recent multi-point measurements, improved simulation methods, and data-driven approaches have narrowed some of these gaps, but connecting global-scale flows with kinetic-scale processes remains a major challenge.

This Research Topic covers how the Kelvin–Helmholtz instability drives energy transfer, plasma transport, and dissipation in solar wind–planet interactions. It brings together observational, theoretical, numerical, and experimental work to explain the multi-scale processes behind KHI evolution and its role in global magnetospheric dynamics. We invite contributions addressing how turbulence, reconnection, and wave-particle interactions connect through KHI-driven processes, as well as comparative studies across planetary and interplanetary environments. A key goal is to identify physical principles that link local kinetic phenomena with large-scale boundary behavior across different astrophysical settings.

To build on current understanding of the multiscale dynamics of the Kelvin-Helmholtz instability and its role in heliospheric and planetary systems, we welcome original research, review, mini review, brief research report, and perspective articles addressing, but not limited to, the following themes:

• Observational evidence of KHI across planetary magnetospheres and induced boundary layers.
• Theoretical and numerical modeling of KHI initiation, growth, and vortex evolution.
• Cross-scale coupling and energy cascade from global flows to kinetic dissipation.
• Energy conversion processes within Kelvin-Helmholtz waves and vortices.
• Relationships among KHI, turbulence, and magnetic reconnection.
• Impact of KHI on particle heating, transport, and plasma mixing in the solar wind.
• Comparative studies of KHI dynamics across different planetary and heliospheric conditions.
• Machine learning and data-driven approaches to identifying and characterizing KHI signatures.
• Implications of KHI-induced processes for space weather forecasting and magnetospheric variability.

Are you interested in contributing a manuscript to this Research Topic?

Kelvin–Helmholtz Instability and Energy Transfer Across Heliospheric and Planetary Boundaries