Turbulence in the outer heliosphere

TL;DR

This paper reviews observational evidence, modeling advances, and challenges related to turbulence in the outer heliosphere and local interstellar medium, highlighting its role in particle processes and heliospheric dynamics.

Contribution

It provides a comprehensive overview of turbulence in the outer heliosphere, integrating recent observations and modeling efforts to address existing knowledge gaps.

Findings

Turbulence influences particle populations and energetic processes in the heliosphere.

Voyager, New Horizons, and IBEX data suggest turbulence is critical at the heliospheric interface.

Modeling efforts are advancing but still face open challenges in understanding turbulence dynamics.

Abstract

The solar wind (SW) and local interstellar medium (LISM) are turbulent media. Their interaction is governed by complex physical processes and creates heliospheric regions with significantly different properties in terms of particle populations, bulk flow and turbulence. Our knowledge of the solar wind turbulence \nature and dynamics mostly relies on near-Earth and near-Sun observations, and has been increasingly improving in recent years due to the availability of a wealth of space missions, including multi-spacecraft missions. In contrast, the properties of turbulence in the outer heliosphere are still not completely understood. In situ observations by Voyager and New Horizons, and remote neutral atom measurements by IBEX strongly suggest that turbulence is one of the critical processes acting at the heliospheric interface. It is intimately connected to charge exchange processes responsible for the production of suprathermal ions and energetic neutral atoms. This paper reviews the observational evidence of turbulence in the distant SW and in the LISM, advances in modeling efforts, and open challenges.