On the twists of interplanetary magnetic flux ropes observed at 1 AU

Abstract

Magnetic flux ropes (MFRs) are one kind of fundamental structures in the solar physics, and involved in various eruption phenomena. Twist, characterizing how the magnetic field lines wind around a main axis, is an intrinsic property of MFRs, closely related to the magnetic free energy and stableness. So far it is unclear how much amount of twist is carried by MFRs in the solar atmosphere and in heliosphere and what role the twist played in the eruptions of MFRs. Contrasting to the solar MFRs, there are lots of in-situ measurements of magnetic clouds (MCs), the large-scale MFRs in interplanetary space, providing some important information of the twist of MFRs. Thus, starting from MCs, we investigate the twist of interplanetary MFRs with the aid of a velocity-modified uniform-twist force-free flux rope model. It is found that most of MCs can be roughly fitted by the model and nearly half of them can be fitted fairly well though the derived twist is probably over-estimated by a factor of 2.5. By applying the model to 115 MCs observed at 1 AU, we find that (1) the twist angles of interplanetary MFRs generally follow a trend of about $0.6\frac{l}{R}$ radians, where $\frac{l}{R}$ is the aspect ratio of a MFR, with a cutoff at about $12\pi$ radians AU${}^{-1}$, (2) most of them are significantly larger than $2.5\pi$ radians but well bounded by $2\frac{l}{R}$ radians, (3) strongly twisted magnetic field lines probably limit the expansion and size of MFRs, and (4) the magnetic field lines in the legs wind more tightly than those in the leading part of MFRs. These results not only advance our understanding of the properties and behavior of interplanetary MFRs, but also shed light on the formation and eruption of MFRs in the solar atmosphere. A discussion about the twist and stableness of solar MFRs are therefore given.

accepted by JGR, 20 pages, 10 figures, 2 tables

References in corpus (4)

• Global and local expansion of magnetic clouds in the inner heliosphere
• Structures of Interplanetary Magnetic Flux Ropes and Comparison with Their Solar Sources
• Linking two consecutive nonmerging magnetic clouds with their solar sources
• Investigating plasma motion of magnetic clouds at 1 AU through a velocity-modified cylindrical force-free flux rope model

Cited by in corpus (16)

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• Uncovering Erosion Effects on Magnetic Flux Rope Twist
• Prominence fine structures in weakly twisted and highly twisted magnetic flux ropes
• A Helicity-Based Method to Infer the CME Magnetic Field Magnitude in Sun and Geospace: Generalization and Extension to Sun-Like and M-Dwarf Stars and Implications for Exoplanet Habitability
• Formation of episodic jets and associated flares from black hole accretion systems
• Modeling a Coronal Mass Ejection from an Extended Filament Channel. II. Interplanetary Propagation to 1 au
• Investigating The Cross-section of Coronal Mass Ejections Through the Study of Non-Radial Flows with STEREO/PLASTIC
• Untwisting Jets Related to Magnetic Flux Cancellation
• Analysis of the Helical Kink Stability of Differently Twisted Magnetic Flux Ropes
• Investigation on the Spatiotemporal Structures of Supra-Arcade Spikes
• Re-analysis of Lepping's Fitting Method for Magnetic Clouds: Lundquist Fit Reloaded
• Magnetic field extrapolation in active region well comparable with observations in multiple layers
• Interaction of Trappist-1 exoplanets with coronal mass ejections: Joule heating, Poynting fluxes and the role of magnetic fields
• Evolution of reconnection flux during eruption of magnetic flux ropes