MMS Observations of FTE-Type Structures with Internal Magnetic Reconnection

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

<p>A bipolar magnetic variation B<sub>n</sub> 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.</p>

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

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

<p>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 Alfvénic 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.</p>

MAVEN Survey of Magnetic Flux Rope Properties in the Martian Ionosphere: Comparison with 3 Types of Formation Mechanisms

2021 ◽  
Author(s):  
Charles Bowers ◽  
James A. Slavin ◽  
Gina A. DiBraccio ◽  
Gangkai Poh ◽  
Takuya Hara ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Flux Rope ◽  
Formation Mechanisms ◽  
Magnetic Flux Rope ◽  
Martian Ionosphere

scholarly journals A Model of Solar X-ray Bright Points and Ephemeral Active Regions

1979 ◽  
Vol 32 (6) ◽  
pp. 671 ◽  
Author(s):  
JH Piddington
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Large Scale ◽  
Flux Rope ◽  
Active Regions ◽  
Activity Cycle ◽  
Solar Magnetic Fields ◽  
Flux Tubes ◽  
X Ray ◽  
Field System

Solar ephemeral active regions may provide a larger amount of emerging magnetic flux than the active regions themselves, and the origin and disposal of this flux pose problems. The related X-ray bright points are a major feature of coronal dynamics, and the two phenomena may entail a revision of our ideas of the activity cycle. A new large-scale subsurface magnetic field system has been suggested, but it is shown that such a system is neither plausible nor necessary. The emerging magnetic bipoles merely represent loops in pre-existing vertical flux tubes which are parts of active regions or the remnants of active regions. These loops result from the kink (or helical) instability in a twisted flux tube. Their observed properties are explained in terms of the flux-rope theory of solar fields. The model is extended to some dynamical effects in emerging loops. Further observations of ephemeral active regions may provide important tests between the traditional and flux-rope theories of solar magnetic fields.

scholarly journals A new trigger mechanism for coronal mass ejections

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.

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

2012 ◽  
Vol 30 (5) ◽  
pp. 761-773 ◽  
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.

scholarly journals Asymmetry in the current sheet and secondary magnetic flux ropes during guide field magnetic reconnection

2012 ◽  
Vol 117 (A7) ◽  
pp. n/a-n/a ◽  
Author(s):  
Rongsheng Wang ◽  
Rumi Nakamura ◽  
Quanming Lu ◽  
Aimin Du ◽  
Tielong Zhang ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Magnetic Flux Ropes ◽  
Guide Field ◽  
Flux Ropes

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

2018 ◽  
Vol 36 (2) ◽  
pp. 497-507 ◽  
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)

scholarly journals A magnetic reconnection model for hot explosions in the cool atmosphere of the Sun

2021 ◽  
Author(s):  
Lei Ni
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheet ◽  
Large Temperature ◽  
Formation Mechanisms ◽  
Line Profiles ◽  
Turbulent Structures ◽  
Plasma Parameters ◽  
Magnetic Diffusivity ◽  
Reconnection Region ◽  
Initial Plasma

&lt;p&gt;UV bursts and Ellerman bombs are transient brightenings observed in the low solar atmospheres of emerging flux regions. Observations have discovered the cospatial and cotemporal EBs and UV bursts, and their formation mechanisms are still not clear. The multi-thermal components with a large temperature span in these events challenge our understanding of magnetic reconnection and heating mechanisms in the low solar atmosphere. We have studied magnetic reconnection between the emerging and background magnetic fields. The initial plasma parameters are based on the C7 atmosphere model. After the current sheet with dense photosphere plasma is emerged to &lt;span tabindex=&quot;0&quot; role=&quot;presentation&quot; data-mathml='&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;&gt;&lt;mn&gt;0.5&lt;/mn&gt;&lt;/math&gt;'&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;0.5&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt; Mm above the solar surface, plasmoid instability appears. The plasmoids collide and coalesce with each other, which makes the plasmas with different densities and temperatures mixed up in the turbulent reconnection region. Therefore, the hot plasmas corresponding to the UV emissions and colder plasmas corresponding to the emissions from other wavelenghts can move together and occur at about the same height. In the meantime, the hot turbulent structures basically concentrate above &lt;span tabindex=&quot;0&quot; role=&quot;presentation&quot; data-mathml='&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;&gt;&lt;mn&gt;0.4&lt;/mn&gt;&lt;/math&gt;'&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;0.4&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt; Mm, whereas the cool plasmas extend to much lower heights to the bottom of the current sheet. These phenomena are consistent with the observations of Chen et al. 2019, ApJL. The synthesized Si IV line profiles are similar to the observed one in UV bursts, the enhanced wing of the line profiles can extend to about &lt;span tabindex=&quot;0&quot; role=&quot;presentation&quot; data-mathml='&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;&gt;&lt;mn&gt;100&lt;/mn&gt;&lt;/math&gt;'&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;100&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt; km s&lt;span tabindex=&quot;0&quot; role=&quot;presentation&quot; data-mathml='&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;&gt;&lt;msup&gt;&lt;mi&gt;&lt;/mi&gt;&lt;mrow class=&quot;MJX-TeXAtom-ORD&quot;&gt;&lt;mo&gt;&amp;#x2212;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;'&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;&amp;#8722;&lt;/span&gt;&lt;span&gt;1&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;. The differences are significant among the numerical results with different resolutions, which indicate that the realistic magnetic diffusivity is crucial to reveal the fine structures and realistic plasmas heating in these reconnection events. Our results also show that the reconnection heating contributed by ambipolar diffusion in the low chromosphere around the temperature minimum region is not efficient.&lt;/p&gt;

Local kinetic processes determining macroscopic properties of interlinked magnetic flux tubes

2020 ◽  
Author(s):  
Kyoung-joo Hwang ◽  
Jim Burch ◽  
Christopher Russell ◽  
Eunjin Choi ◽  
Kyunghwan Dokgo ◽  
...  
Keyword(s):  
Flux Rope ◽  
Transfer Event ◽  
Transient Phenomena ◽  
Flux Tubes ◽  
The Earth ◽  
Magnetic Flux Tubes ◽  
Kinetic Processes ◽  
Field Lines ◽  
Transient Structure ◽  
Northern And Southern Hemispheres

&lt;p&gt;One of the most important transient phenomena affecting the solar wind-Earth&amp;#8217;s magnetosphere coupling is non-steady dayside magnetic reconnection, observationally evidenced by a transient structure consisting of a bipolar magnetic-field component normal to the magnetopause. This signature, termed a flux-transfer-event (FTE), has been recently found to often consist of two interlinked flux tubes. The recent observations, particularly from the MMS spacecraft, showed a reconnecting current sheet between the interlaced flux tubes.&amp;#160;However, local kinetic processes between the flux tubes have not been understood&amp;#160;in the context of the broader FTE structure and evolution. An FTE observed by&amp;#160;MMS on 18 December, 2017 comprised two flux tubes of different topology. One includes field lines with their ends connected to the northern and southern hemispheres while the other includes field lines that are connected to the magnetosheath (and ultimately the Sun). Evidence for reconnection occurring at the interface of the two flux tubes indicates how interacting flux tubes evolve into a flux rope having helical magnetic topology connecting either both to the Earth or being completely open. This study&amp;#160;proposes a new aspect of&amp;#160;how micro-to-meso-scale dynamics occurring within FTEs determines the macroscale characteristics and evolution of the structures.&lt;/p&gt;

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