Magnetic mirror structures associated with magnetopause flux ropes investigated with Mangnetospheric Multiscale misson (MMS)

Magnetic reconnection is a fundamental plasma physics process which governs energy and mass transfer from the solar wind into the Earth&#8217;s magnetosphere. Electron acceleration during reconnection has been widely investigated with multiple mechanisms proposed. Many of these mechanisms involve flux ropes: twisted magnetic field structures formed during reconnection. Drake et al. 2006 suggest that contracting magnetic islands (or flux ropes in 3D) could trap and energise electrons by a Fermi acceleration process.Whilst previous missions have observed and characterised flux ropes, the temporal resolution of the data was typically not great enough to study structures in detail, particularly on electron scales. Here we investigate magnetopause flux ropes using data from NASA&#8217;s four spacecraft Magnetospheric Multiscale mission (MMS). MMS measures the thermal electron and ion 3D distribution at 30 msec and 150 msec time resolution, respectively, and at spacecraft separations down to a few kilometers.We focus on electron pitch angle distributions and examine how they can be used to investigate magnetopause flux ropes. In particular, the distributions are used to identify electron trapping in magnetic mirror structures on the magnetospheric edge of the flux ropes. These features are found to have extended 3D structure along the body of the flux rope. We evaluate possible formation mechanisms, such as the mirror instability, and potential electron acceleration mechanisms, such as betatron and Fermi acceleration. Magnetic mirror structures could represent an important particle acceleration feature for flux ropes and magnetic reconnection.

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Energetic electron acceleration during magnetic reconnection

10.5194/egusphere-egu2020-1945 ◽

2020 ◽

Author(s):

Huishan Fu

Keyword(s):

Numerical Simulations ◽

Magnetic Reconnection ◽

Magnetic Energy ◽

Energetic Electron ◽

Electron Acceleration ◽

Particle Energy ◽

Acceleration Process ◽

The Earth

During magnetic reconnection, magnetic energy is explosively converted to particle energy and consequently electrons are accelerated to hundreds of keV that are dangerous to spacecraft and astronauts. To date, how and where the acceleration happens during reconnection is still unknown. Also, how efficient can the acceleration be remains a puzzle. Using spacecraft measurements (e.g., Cluster and MMS) and numerical simulations, many attempts have been made to answer these questions during the last twenty years. In this talk, I will briefly review these progresses and then show our recent results in understanding these issues. Specifically, I will (1) report a super-efficient electron acceleration by magnetic reconnection in the Earth&#8217;s magnetotail, during which electron fluxes are enhanced by 10000 times within 30 seconds; (2) discuss the mechanisms leading to super-efficient electron acceleration; (3) report the first evidence of electron acceleration at a reconnecting magnetopause, during which the acceleration process is nonadiabatic; and (4) report electron acceleration in the

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A new trigger mechanism for coronal mass ejections

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038781 ◽

2020 ◽

Vol 644 ◽

pp. A137

Author(s):

A. W. James ◽

L. M. Green ◽

L. van Driel-Gesztelyi ◽

G. Valori

Keyword(s):

Magnetic Flux ◽

Magnetic Reconnection ◽

Extreme Ultraviolet ◽

Flux Rope ◽

Active Regions ◽

Magnetic Activity ◽

Trigger Mechanism ◽

Magnetic Flux Rope ◽

Left Handed ◽

Flux Ropes

Context. Many previous studies have shown that the magnetic precursor of a coronal mass ejection (CME) takes the form of a magnetic flux rope, and a subset of them have become known as “hot flux ropes” due to their emission signatures in ∼10 MK plasma. Aims. We seek to identify the processes by which these hot flux ropes form, with a view of developing our understanding of CMEs and thereby improving space weather forecasts. Methods. Extreme-ultraviolet observations were used to identify five pre-eruptive hot flux ropes in the solar corona and study how they evolved. Confined flares were observed in the hours and days before each flux rope erupted, and these were used as indicators of episodic bursts of magnetic reconnection by which each flux rope formed. The evolution of the photospheric magnetic field was observed during each formation period to identify the process(es) that enabled magnetic reconnection to occur in the β < 1 corona and form the flux ropes. Results. The confined flares were found to be homologous events and suggest flux rope formation times that range from 18 hours to 5 days. Throughout these periods, fragments of photospheric magnetic flux were observed to orbit around each other in sunspots where the flux ropes had a footpoint. Active regions with right-handed (left-handed) twisted magnetic flux exhibited clockwise (anticlockwise) orbiting motions, and right-handed (left-handed) flux ropes formed. Conclusions. We infer that the orbital motions of photospheric magnetic flux fragments about each other bring magnetic flux tubes together in the corona, enabling component reconnection that forms a magnetic flux rope above a flaring arcade. This represents a novel trigger mechanism for solar eruptions and should be considered when predicting solar magnetic activity.

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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.

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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)

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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.

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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.

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The birth of a coronal mass ejection

Science Advances ◽

10.1126/sciadv.aau7004 ◽

2019 ◽

Vol 5 (3) ◽

pp. eaau7004 ◽

Cited By ~ 11

Author(s):

Tingyu Gou ◽

Rui Liu ◽

Bernhard Kliem ◽

Yuming Wang ◽

Astrid M. Veronig

Keyword(s):

Magnetic Reconnection ◽

Coronal Mass Ejection ◽

Current Sheet ◽

Magnetic Structure ◽

Coronal Mass Ejections ◽

Flux Rope ◽

Evolutionary Path ◽

X Ray ◽

Flux Ropes ◽

Mass Ejection

The Sun’s atmosphere is frequently disrupted by coronal mass ejections (CMEs), coupled with flares and energetic particles. The coupling is usually attributed to magnetic reconnection at a vertical current sheet connecting the flare and CME, with the latter embedding a helical magnetic structure known as flux rope. However, both the origin of flux ropes and their nascent paths toward eruption remain elusive. Here, we present an observation of how a stellar-sized CME bubble evolves continuously from plasmoids, mini flux ropes that are barely resolved, within half an hour. The eruption initiates when plasmoids springing from a vertical current sheet merge into a leading plasmoid, which rises at increasing speeds and expands impulsively into the CME bubble, producing hard x-ray bursts simultaneously. This observation illuminates a complete CME evolutionary path capable of accommodating a wide variety of plasma phenomena by bridging the gap between microscale and macroscale dynamics.

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TOPOLOGICAL HELICITY FOR FRAMED LINKS

Journal of Knot Theory and Its Ramifications ◽

10.1142/s0218216504003664 ◽

2004 ◽

Vol 13 (08) ◽

pp. 1007-1019

Author(s):

ELIZABETH L. BOUZARTH ◽

DAVID RICHESON

Keyword(s):

Magnetic Flux ◽

Magnetic Reconnection ◽

Equivalence Relation ◽

Flux Rope ◽

Equivalence Classes ◽

Magnetic Flux Rope ◽

Flux Ropes

We introduce topological helicity, an invariant for oriented framed links. Topological helicity provides an elementary means of computing helicity for a magnetic flux rope by measuring its knotting, linking, and twisting. We present an equivalence relation, reconnection-equivalence, for framed links and prove that topological helicity is a complete invariant for the resulting equivalence classes. We conclude by showing that one can use magnetic reconnection to transform one collection of linked flux ropes into another collection if and only if they have the same helicity.

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Observations of an Electron-only Magnetic Reconnection within a macroscopic Flux Rope in the Magnetotail

10.5194/egusphere-egu2020-2841 ◽

2020 ◽

Author(s):

Hengyan Man ◽

Meng Zhou ◽

Yongyuan Yi ◽

Zhihong Zhong ◽

Xiaohua Deng

Keyword(s):

Electric Field ◽

Magnetic Reconnection ◽

Current Sheet ◽

Large Scale ◽

Energy Transport ◽

Flux Rope ◽

Space Plasmas ◽

Positive Energy ◽

Guide Field ◽

Flux Ropes

It is widely accepted that flux ropes play important roles in the momentum and energy transport in space plasmas. Recent observations found that magnetic reconnection occurs at the interface between two counter flows around the center of flux ropes. In this presentation, we report a novel observation by MMS that reconnection occurs at the edge of a large-scale flux rope, the cross-section of which was about 2.5 Re. The flux rope was observed at the dusk side in Earth&#8217;s magnetotail and was highly oblique with its axis proximity along the XGSM direction. We found an electron-scale current sheet near the edge of this flux rope. The Hall magnetic and electric field, super-Alfv&#233;nic electron outflow, parallel electric field and positive energy dissipation were observed associated with the current sheet. All the above signatures indicate that MMS detected a reconnecting current sheet in the presence of a large guide field. Interestingly, ions were not coupled in this reconnection, akin to the electron-only reconnection observed in the magnetosheath turbulence. We suggest that the electron-scale current sheet was caused by the strong magnetic field perturbation inside the flux rope. This result will shed new lights for understanding the multi-scale coupling associated with flux ropes in space plasmas.

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MMS Observations of FTE-Type Structures with Internal Magnetic Reconnection

10.5194/egusphere-egu2020-15878 ◽

2020 ◽

Author(s):

Rungployphan Kieokaew ◽

Benoit Lavraud ◽

Naïs Fargette

Keyword(s):

Magnetic Flux ◽

Magnetic Reconnection ◽

Current Sheet ◽

Flux Rope ◽

Formation Mechanisms ◽

Transfer Event ◽

Flux Tubes ◽

Magnetospheric Multiscale ◽

Spacecraft Data ◽

Upstream Solar Wind

A bipolar magnetic variation Bn with enhanced core and total fields in spacecraft data are recognized as a Flux Transfer Event (FTE) signature, which corresponds to the passage of a magnetic flux rope structure. Recent literature reported Magnetospheric Multiscale (MMS) observations of FTE signatures with magnetic reconnection signatures at the central current sheet. Among reported cases, electron pitch angle distributions (ePAD) in the suprathermal energy range show different features on either side of the reconnecting current sheet, indicating different magnetic connectivities. This structure is interpreted as interlinked/interlaced flux tubes, possibly formed by converging jets toward the central current sheet that in turn enhance magnetic flux pile-up and facilitate reconnection at the current sheet separating the two flux tubes. By surveying similar events using MMS data, we found some FTE-type structures with reconnection signatures at the central current sheet but with homogeneous ePAD of suprathermal electrons across the structures. Thus, these structures are inconsistent with interlinked flux tubes, but rather a regular flux rope. This leads to a question of how reconnection can occur in those single flux ropes, and their relation with interlinked flux tubes. In this work, we investigate properties of these structures and their related upstream solar-wind conditions. Formation mechanisms of such structures and how reconnection can occur will be discussed.

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