Current sheets, plasmoids and flux ropes in the heliosphere. Part II: Theoretical aspects

TL;DR

This paper reviews the theoretical understanding of complex magnetic structures like current sheets, plasmoids, and flux ropes in the heliosphere, emphasizing their role in turbulence, reconnection, and particle acceleration.

Contribution

It provides a comprehensive analysis of the theoretical paradigms and numerical simulations of magnetic structures in the heliosphere, highlighting differences between 2D and 3D perspectives.

Findings

Magnetic reconnection is complex and occurs in turbulent environments.

3D structures provide a more accurate representation of heliospheric phenomena.

Numerical simulations reveal the stability and dynamics of current sheets and flux ropes.

Abstract

Our understanding of processes occurring in the heliosphere historically began with reduced dimensionality - one-dimensional (1D) and two-dimensional (2D) sketches and models, which aimed to illustrate views on large-scale structures in the solar wind. However, any reduced dimensionality vision of the heliosphere limits the possible interpretations of in-situ observations. Accounting for non-planar structures, e.g. current sheets, magnetic islands, flux ropes as well as plasma bubbles, is decisive to shed the light on a variety of phenomena, such as particle acceleration and energy dissipation. In part I of this review, we have described in detail the ubiquitous and multi-scale observations of these magnetic structures in the solar wind and their significance for the acceleration of charged particles. Here, in part II, we elucidate existing theoretical paradigms of the structure of the solar wind and the interplanetary magnetic field, with particular attention to the fine structure and stability of current sheets. Differences in 2D and 3D views of processes associated with current sheets, magnetic islands, and flux ropes are discussed. We finally review the results of numerical simulations and in-situ observations, pointing out the complex nature of magnetic reconnection and particle acceleration in a strongly turbulent environment.