Magnetic Flux Ropes in the Solar Corona: Structure and Evolution toward Eruption

TL;DR

This paper reviews the structure and evolution of magnetic flux ropes in the solar corona, emphasizing their role in eruptions and space weather, by integrating observations and modeling to understand their formation and development.

Contribution

It provides a comprehensive review of coronal flux ropes, highlighting an initiation mechanism involving plasmoid coalescence into a seed flux rope leading to CMEs.

Findings

Identification of flux ropes as key to solar eruptions

Mechanism of flux rope formation via plasmoid coalescence

Correlation between flux rope evolution and CME initiation

Abstract

Magnetic flux ropes are characterized by coherently twisted magnetic field lines, which are ubiquitous in magnetized plasmas. As the core structure of various eruptive phenomena in the solar atmosphere, flux ropes hold the key to understanding the physical mechanisms of solar eruptions, which impact the heliosphere and planetary atmospheres. Strongest disturbances in the Earth's space environments are often associated with large-scale flux ropes from the Sun colliding with the Earth's magnetosphere, leading to adverse, sometimes catastrophic, space-weather effects. However, it remains elusive as to how a flux rope forms and evolves toward eruption, and how it is structured and embedded in the ambient field. The present paper addresses these important questions by reviewing current understandings of coronal flux ropes from an observer's perspective, with emphasis on their structures and nascent evolution toward solar eruptions, as achieved by combining observations of both remote sensing and in-situ detection with modeling and simulation. It highlights an initiation mechanism for coronal mass ejections (CMEs) in which plasmoids in current sheets coalesce into a `seed' flux rope whose subsequent evolution into a CME is consistent with the standard model, thereby bridging the gap between microscale and macroscale dynamics.