Evolution of Plasma Composition in an Eruptive Flux Rope

Abstract Magnetic flux ropes are bundles of twisted magnetic field enveloping a central axis. They harbor free magnetic energy and can be progenitors of coronal mass ejections (CMEs). However, identifying flux ropes on the Sun can be challenging. One of the key coronal observables that has been shown to indicate the presence of a flux rope is a peculiar bright coronal structure called a sigmoid. In this work, we show Hinode EUV Imaging Spectrometer observations of sigmoidal active region (AR) 10977. We analyze the coronal plasma composition in the AR and its evolution as a sigmoid (flux rope) forms and erupts as a CME. Plasma with photospheric composition was observed in coronal loops close to the main polarity inversion line during episodes of significant flux cancellation, suggestive of the injection of photospheric plasma into these loops driven by photospheric flux cancellation. Concurrently, the increasingly sheared core field contained plasma with coronal composition. As flux cancellation decreased and a sigmoid/flux rope formed, the plasma evolved to an intermediate composition in between photospheric and typical AR coronal compositions. Finally, the flux rope contained predominantly photospheric plasma during and after a failed eruption preceding the CME. Hence, plasma composition observations of AR 10977 strongly support models of flux rope formation by photospheric flux cancellation forcing magnetic reconnection first at the photospheric level then at the coronal level.

Download Full-text

Direct evidence of secondary reconnection inside filamentary currents of magnetic flux ropes in magnetic reconnection

10.5194/egusphere-egu2020-1671 ◽

2020 ◽

Author(s):

Shimou Wang ◽

Quanming Lu

Keyword(s):

Energy Dissipation ◽

Magnetic Flux ◽

Magnetic Reconnection ◽

Current Sheet ◽

Magnetic Energy ◽

Flux Rope ◽

Plasma Jets ◽

Magnetic Flux Ropes ◽

Flux Ropes ◽

Reconnecting Current Sheet

Magnetic reconnection is a fundamental plasma process, by which magnetic energy is explosively released in the current sheet to energize charged particles and to create bi-directional Alfv&#233;nic plasma jets. A long-outstanding issue is how the stored magnetic energy is rapidly released in the process. Numerical simulations and observations show that formation and interaction of magnetic flux ropes dominate the evolution of the reconnecting current sheet. Accordingly, most volume of the reconnecting current sheet is occupied by the flux ropes and energy dissipation primarily occurs along their edges via the flux rope coalescence. Here, for the first time, we present in-situ evidence of magnetic reconnection inside the filamentary currents which was driven possibly by electron vortices inside the flux ropes. Our results reveal an important new way for energy dissipation in magnetic reconnection.

Download Full-text

Eruptions and flaring activity in emerging quadrupolar regions

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936246 ◽

2019 ◽

Vol 630 ◽

pp. A134 ◽

Cited By ~ 3

Author(s):

P. Syntelis ◽

E. J. Lee ◽

C. W. Fairbairn ◽

V. Archontis ◽

A. W. Hood

Keyword(s):

Current Sheet ◽

Flux Tube ◽

Flux Rope ◽

Active Regions ◽

Solar Interior ◽

Magnetic Flux Ropes ◽

Solar Observations ◽

Flux Ropes ◽

Polarity Inversion Line ◽

Field Lines

Context. Solar observations suggest that some of the most dynamic active regions are associated with complex photospheric magnetic configurations such as quadrupolar regions, and especially those that have a δ-spot configuration and a strong polarity inversion line (PIL). Aims. We study the formation and eruption of magnetic flux ropes in quadrupolar regions. Methods. We performed 3D magnetohydrodynamics simulations of the partial emergence of a highly twisted flux tube from the solar interior into a non-magnetised stratified atmosphere. We introduced a density deficit at two places along the length of the subphotospheric flux tube to emerge as two Ω-shaped loops, forming a quadrupolar region. Results. At the photosphere, the emerging flux forms two initially separated bipoles, which later come in contact, forming a δ-spot central region. Above the two bipoles, two magnetic lobes expand and interact through a series of current sheets at the interface between them. Two recurrent confined eruptions are produced. In both cases, the reconnection between sheared low-lying field lines forms a flux rope. The reconnection between the two lobes higher in the atmosphere forms field lines that retract down and push against the flux rope, creating a current sheet between them. It also forms field lines that create a third magnetic lobe between the two emerged lobes, that later acts as a strapping field. The flux rope eruptions are triggered when the reconnection between the flux ropes and the field above the ropes becomes efficient enough to remove the tension of the overlying field. These reconnection events occur internally in the quadrupolar system, as the atmosphere is non-magnetised. The flux rope of the first, weaker, eruption almost fully reconnects with the overlying field. The flux rope of the second, more energetic, eruption is confined by the overlying strapping field. During the second eruption, the flux rope is enhanced in size, flux, and twist, similar to confined-flare-to-flux-rope observations. Proxies of the emission reveal the two erupting filaments channels. A flare arcade is only formed in the second eruption owing to the longer lasting and more efficient reconnection at the current sheet below the flux rope.

Download Full-text

Spiky electric and magnetic field structures in flux rope experiments

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1721343115 ◽

2018 ◽

Vol 116 (37) ◽

pp. 18239-18244 ◽

Cited By ~ 1

Author(s):

W. Gekelman ◽

S. W. Tang ◽

T. DeHaas ◽

S. Vincena ◽

P. Pribyl ◽

...

Keyword(s):

Magnetic Field ◽

Laboratory Experiments ◽

Magnetic Energy ◽

Flux Rope ◽

Building Blocks ◽

Counting Method ◽

Magnetic Flux Ropes ◽

Flux Ropes ◽

Corona Of The Sun ◽

Probability Density Function Pdf

Magnetic flux ropes are structures that are common in the corona of the sun and presumably all stars. They can be thought of as the building blocks of solar structures. They have been observed in Earth’s magnetotail and near Mars and Venus. When multiple flux ropes are present magnetic field line reconnection, which converts magnetic energy to other forms, can occur when they collide. The structure of multiple magnetic ropes, the interactions between multiple ropes, and their topological properties such as helicity and writhing have been studied theoretically and in laboratory experiments. Here, we report on spiky potential and magnetic fields associated with the ropes. We show that the potential structures are chaotic for a range of their temporal half-widths and the probability density function (PDF) of their widths resembles the statistical distribution of crumpled paper. The spatial structure of the magnetic spikes is revealed using a correlation counting method. Computer simulation suggests that the potential structures are the nonlinear end result of an instability involving relative drift between ions and electrons.

Download Full-text

Study of flux-rope characteristics at sub-astronomical-unit distances using the Helios 1 and 2 spacecraft

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1189 ◽

2020 ◽

Vol 495 (2) ◽

pp. 1566-1576

Author(s):

Anil Raghav ◽

Sandesh Gaikwad ◽

Yuming Wang ◽

Zubair I Shaikh ◽

Wageesh Mishra ◽

...

Keyword(s):

Magnetic Flux ◽

Magnetic Energy ◽

Ambient Medium ◽

Flux Rope ◽

Magnetic Clouds ◽

Astronomical Unit ◽

Magnetic Flux Ropes ◽

Flux Ropes ◽

External Conditions ◽

Internal Properties

ABSTRACT Magnetic flux ropes observed as magnetic clouds near 1 au have been extensively studied in the literature and their distinct features are derived using numerous models. These studies summarize the general characteristics of flux ropes at 1 au without providing an understanding of the continuous evolution of the flux ropes from near the Sun to 1 au. In the present study, we investigate 26 flux ropes observed by the Helios 1 and 2 spacecraft (from 0.3 to 1 au) using the velocity-modified Gold–Hoyle model. The correlation and regression analyses suggest that the expansion speed, poloidal speed, total magnetic helicity and twist per au of the flux rope are independent of heliospheric distance. The study implies that the aforementioned features are more strongly influenced by their internal properties compared with external conditions in the ambient medium. Moreover, the poloidal magnetic flux and magnetic energy of the studied flux ropes exhibit power-law dependence on heliospheric distance. A better understanding of the underlying physics and corroboration of these results is expected from the Parker Solar Probe measurements in the near future.

Download Full-text

Confined and Eruptive Catastrophes of Solar Magnetic Flux Ropes Caused by Mass Loading and Unloading

The Astrophysical Journal ◽

10.3847/1538-4357/ac1fef ◽

2021 ◽

Vol 921 (2) ◽

pp. 172

Author(s):

Quanhao Zhang ◽

Rui Liu ◽

Yuming Wang ◽

Xiaolei Li ◽

Shaoyu Lyu

Keyword(s):

Magnetic Flux ◽

Total Mass ◽

Large Scale ◽

Magnetic Energy ◽

Flux Rope ◽

Mass Loading ◽

Magnetic Flux Ropes ◽

Flux Ropes ◽

Loading And Unloading ◽

Rope System

Abstract It is widely accepted that coronal magnetic flux ropes are the core structures of large-scale solar eruptive activities, which have a dramatic impact on the solar-terrestrial system. Previous studies have demonstrated that varying magnetic properties of a coronal flux rope system could result in a catastrophe of the rope, which may trigger solar eruptive activities. Since the total mass of a flux rope also plays an important role in stabilizing the rope, we use 2.5 dimensional magnetohydrodynamic numerical simulations in this article to investigate how a flux rope evolves as its total mass varies. It is found that an unloading process that decreases the total mass of the rope could result in an upward (eruptive) catastrophe in the flux rope system, during which the rope jumps upward and the magnetic energy is released. This indicates that mass unloading processes could initiate the eruption of the flux rope. Moreover, when the system is not too diffusive, there is also a downward (confined) catastrophe that could be caused by mass loading processes via which the total mass accumulates. The magnetic energy, however, is increased during the downward catastrophe, indicating that mass loading processes could cause confined activities that may contribute to the storage of energy before the onset of coronal eruptions.

Download Full-text

Observations of photospheric magnetic structure below a dark filament using the Hinode Spectro-Polarimeter

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psz014 ◽

2019 ◽

Vol 71 (2) ◽

Author(s):

Takaaki Yokoyama ◽

Yukio Katsukawa ◽

Masumi Shimojo

Keyword(s):

Magnetic Structure ◽

Flux Rope ◽

Transverse Field ◽

Optical Telescope ◽

Polarity Inversion ◽

Normal Orientation ◽

Normal Polarity ◽

East Limb ◽

Polarity Inversion Line ◽

Dark Filament

Abstract The structure of the photospheric vector magnetic field below a dark filament on the Sun is studied using the observations of the Spectro-Polarimeter attached to the Solar Optical Telescope onboard Hinode. Special attention is paid to discriminating between two suggested models, a flux rope or a bent arcade. “Inverse polarity” orientation is possible below the filament in a flux rope, whereas “normal polarity” can appear in both models. We study a filament in the active region NOAA 10930, which appeared on the solar disk during 2006 December. The transverse field perpendicular to the line of sight has a direction almost parallel to the filament spine with a shear angle of 30°, the orientation of which includes the 180° ambiguity. To know whether it is in the normal orientation or in the inverse one, the center-to-limb variation is used for the solution under the assumption that the filament does not drastically change its magnetic structure during the passage. When the filament is near the east limb, we found that the line-of-site magnetic component below the filament is positive, while it is negative near the west limb.This change of sign indicates that the horizontal photospheric field perpendicular to the polarity inversion line beneath the filament has an “inverse-polarity”, which indicates a flux-rope structure of the filament supporting field.

Download Full-text

Observations of magnetic flux ropes during magnetic reconnection in the Earth's magnetotail

Annales Geophysicae ◽

10.5194/angeo-30-761-2012 ◽

2012 ◽

Vol 30 (5) ◽

pp. 761-773 ◽

Cited By ~ 38

Author(s):

A. L. Borg ◽

M. G. G. T. Taylor ◽

J. P. Eastwood

Keyword(s):

Magnetic Flux ◽

Magnetic Reconnection ◽

Electron Flux ◽

Energetic Electron ◽

Flux Rope ◽

Clear Correlation ◽

Particle Measurements ◽

Magnetic Flux Ropes ◽

Flux Ropes ◽

Show Evidence

Abstract. We present an investigation of magnetic flux ropes observed by the four Cluster spacecraft during periods of magnetic reconnection in the Earth's magnetotail. Using a list of 21 Cluster encounters with the reconnection process in the period 2001–2006 identified in Borg et al. (2012), we present the distribution and characteristics of the flux ropes. We find 27 flux ropes embedded in the reconnection outflows of only 11 of the 21 reconnection encounters. Reconnection processes associated with no flux rope observations were not distinguishable from those where flux ropes were observed. Only 7 of the 27 flux ropes show evidence of enhanced energetic electron flux above 50 keV, and there was no clear signature of the flux rope in the thermal particle measurements. We found no clear correlation between the flux rope core field and the prevailing IMF By direction.

Download Full-text

The evolution of magnetic flux ropes in sheared plasma flows

Journal of Plasma Physics ◽

10.1017/s0022377800008394 ◽

2000 ◽

Vol 64 (1) ◽

pp. 41-55 ◽

Cited By ~ 2

Author(s):

J. M. SCHMIDT ◽

P. J. CARGILL

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Shear Layer ◽

Cross Section ◽

Circular Cross Section ◽

Flux Rope ◽

Plasma Pressure ◽

Magnetic Flux Ropes ◽

Flux Ropes ◽

The Magnetic Field

The evolution of magnetic flux ropes in a sheared plasma flow is investigated. When the magnetic field outside the flux rope lies parallel to the axis of the flux rope, a flux rope of circular cross-section, whose centre is located at the midpoint of the shear layer, has its shape distorted, but remains in the shear layer. Small displacements of the flux-rope centre above or below the midpoint of the shear layer lead to the flux-rope being expelled from the shear layer. This motion arises because small asymmetries in the plasma pressure around the flux-rope boundary leads to a force that forces the flux rope into a region of uniform flow. When the magnetic field outside the flux rope lies in a plane perpendicular to the flux-rope axis, the flux rope and external magnetic field reconnect with each other, leading to the destruction of the flux rope.

Download Full-text

Non-Gaussianity and cross-scale coupling in interplanetary magnetic field turbulence during a rope–rope magnetic reconnection event

Annales Geophysicae ◽

10.5194/angeo-36-497-2018 ◽

2018 ◽

Vol 36 (2) ◽

pp. 497-507 ◽

Cited By ~ 1

Author(s):

Rodrigo A. Miranda ◽

Adriane B. Schelin ◽

Abraham C.-L. Chian ◽

José L. Ferreira

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Magnetic Reconnection ◽

Coherent Structures ◽

Flux Rope ◽

Inertial Subrange ◽

Order Moment ◽

Magnetic Flux Ropes ◽

Flux Ropes ◽

Non Gaussian

Abstract. In a recent paper (Chian et al., 2016) it was shown that magnetic reconnection at the interface region between two magnetic flux ropes is responsible for the genesis of interplanetary intermittent turbulence. The normalized third-order moment (skewness) and the normalized fourth-order moment (kurtosis) display a quadratic relation with a parabolic shape that is commonly observed in observational data from turbulence in fluids and plasmas, and is linked to non-Gaussian fluctuations due to coherent structures. In this paper we perform a detailed study of the relation between the skewness and the kurtosis of the modulus of the magnetic field |B| during a triple interplanetary magnetic flux rope event. In addition, we investigate the skewness–kurtosis relation of two-point differences of |B| for the same event. The parabolic relation displays scale dependence and is found to be enhanced during magnetic reconnection, rendering support for the generation of non-Gaussian coherent structures via rope–rope magnetic reconnection. Our results also indicate that a direct coupling between the scales of magnetic flux ropes and the scales within the inertial subrange occurs in the solar wind. Keywords. Space plasma physics (turbulence)

Download Full-text

Magnetic Reconnection in the Corona as a Source of Switchbacks in the Solar Wind

10.5194/egusphere-egu21-2865 ◽

2021 ◽

Author(s):

James Drake ◽

Oleksiy Agapitov ◽

Marc Swisdak ◽

Sam Badman ◽

Stuart Bale ◽

...

Keyword(s):

Solar Wind ◽

Magnetic Reconnection ◽

Coronal Hole ◽

Flux Rope ◽

Magnetic Flux Ropes ◽

Guide Field ◽

Large Numbers ◽

Flux Ropes ◽

Environment Characteristic ◽

Field Lines

The observations from the Parker Solar Probe during the first perihelion revealed large numbers of local reversals in the radial component of the magnetic field with associated velocity spikes. Since the spacecraft was magnetically connected to a coronal hole during the closest approach to the sun, one possible source of these spikes is magnetic reconnection between the open field lines in the coronal hole and an adjacent region of closed flux. Reconnection in a low beta environment characteristic of the corona is expected to be bursty rather than steady and is therefore capable of producing large numbers of magnetic flux ropes with local reversals of the radial magnetic field that can propagate outward large radial distances from the sun. Flux ropes with a strong guide field produce signatures consistent with the PSP observations. We have carried out simulations of "interchange" reconnection in the corona and have explored the local structure of flux ropes embedded within the expanding solar wind. We have first established that traditional interchange reconnection cannot produce the switchbacks since bent field lines generated in the corona quickly straighten. The simulations have been extended to the regime dominated by the production of multiple flux ropes and we have established that flux ropes are injected into the local solar wind. Local simulations of reconnection are also being carried out to explore the structure of flux ropes embedded in the solar wind for comparison with observations. Evidence is presented that flux rope merging may be ongoing and might lead to the high aspect ratio of the switchback structures measured in the solar wind.

Download Full-text