Editorial: Magnetic Flux Ropes: From the Sun to the Earth and Beyond

Rui Liu, Jie Zhang, Yuming Wang, Hongqiang Song
2020 Frontiers in Astronomy and Space Sciences  
Editorial on the Research Topic: Magnetic Flux Ropes: From the Sun to the Earth and Beyond The eruptions in the solar atmosphere exhibit distinctly diverse patterns across a vast range of spatio-temporal scales, from ever-expanding large-scale coronal mass ejections (CMEs), to localized flares within active regions harboring sunspots, to collimated jets down to the resolution limit of modern telescopes. As the core structure of various eruptive phenomena in the solar atmosphere, magnetic flux
more » ... re, magnetic flux ropes, which are characterized by coherently twisted magnetic field lines, hold the key to understanding the physical mechanisms of solar eruptions and to our predictive capability of space weather. The purpose of this Frontiers Research Topic on magnetic flux ropes is to provide a forum to bring together multi-wavelength remote sensing and in-situ diagnostics, to integrate observation and numerical modeling, and to confront established models with new observations. The articles published in this Topic represent the most active fronts of research on a few important questions, namely, how flux ropes originate and evolve toward destabilization and beyond, how they are structured, and how they interact with each other and with surrounding magnetic fields and plasma. Below we briefly summarize the major results achieved by these articles. Solar filaments (or prominences if appearing above the solar limb) are an important indicator of magnetic flux ropes on the Sun, although it has been controversially debated how a filament is magnetically structured, more specifically, whether the dense filament mass is supported against gravity by magnetic dips in a flux rope or a sheared arcade. Since the coronal magnetic field is extremely difficult to measure, filament mass serves as a valuable field tracer, especially when the individual threads are resolved and their dynamic motions are monitored. In equilibrium, dense filament plasmas may only trace a portion of magnetic field lines, but when disturbed, they must flow dominantly along field lines in a low-β plasma environment. Mainly in chromospheric Hα filtergrams, signatures of flux ropes in the lower atmosphere have been detected by meter-class ground-based telescopes with a spatial resolution as high as 0.1 to 0.2 arcsec [see the review article by Wang and Liu, 2019] . Combining Doppler maps with flow maps in the plane of sky, [Awasthi and Liu, 2019] revealed a complex yet organized flow pattern inside a bubble underneath a prominence, which could be envisaged as counterstreaming mass motions in a helically distorted field resulting from the internal kink mode m 2. Magnetic twist is an inherent property of flux ropes. A CME flux rope is often envisaged to build up like an onion with nested layers of magnetic flux added sequentially as the eruption progresses, which
doi:10.3389/fspas.2020.605957 fatcat:zwojqhibr5cmtfg4bwazgqnjpy