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

<p>One of the most important transient phenomena affecting the solar wind-Earth’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. However, local kinetic processes between the flux tubes have not been understood in the context of the broader FTE structure and evolution. An FTE observed by 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 proposes a new aspect of how micro-to-meso-scale dynamics occurring within FTEs determines the macroscale characteristics and evolution of the structures.</p>

scholarly journals Ion velocity distributions within the LLBL and their possible implication to multiple reconnections

2004 ◽  
Vol 22 (1) ◽  
pp. 213-236 ◽  
Author(s):  
O. L. Vaisberg ◽  
L. A. Avanov ◽  
T. E. Moore ◽  
V. N. Smirnov
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Tube ◽  
Magnetic Flux Tube ◽  
Flux Tubes ◽  
Different Types ◽  
Subsolar Point ◽  
Magnetic Flux Tubes ◽  
Ion Velocity ◽  
Field Lines

Abstract. We analyze two LLBL crossings made by the Interball-Tail satellite under a southward or variable magnetosheath magnetic field: one crossing on the flank of the magnetosphere, and another one closer to the subsolar point. Three different types of ion velocity distributions within the LLBL are observed: (a) D-shaped distributions, (b) ion velocity distributions consisting of two counter-streaming components of magnetosheath-type, and (c) distributions with three components, one of which has nearly zero parallel velocity and two counter-streaming components. Only the (a) type fits to the single magnetic flux tube formed by reconnection between the magnetospheric and magnetosheath magnetic fields. We argue that two counter-streaming magnetosheath-like ion components observed by Interball within the LLBL cannot be explained by the reflection of the ions from the magnetic mirror deeper within the magnetosphere. Types (b) and (c) ion velocity distributions would form within spiral magnetic flux tubes consisting of a mixture of alternating segments originating from the magnetosheath and from magnetospheric plasma. The shapes of ion velocity distributions and their evolution with decreasing number density in the LLBL indicate that a significant part of the LLBL is located on magnetic field lines of long spiral flux tube islands at the magnetopause, as has been proposed and found to occur in magnetopause simulations. We consider these observations as evidence for multiple reconnection Χ-lines between magnetosheath and magnetospheric flux tubes. Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; solar wind-magnetosphere interactions)

scholarly journals Nonlinear theory of non-axisymmetric resonant slow waves in straight magnetic flux tubes

2000 ◽  
Vol 64 (5) ◽  
pp. 579-599 ◽  
Author(s):  
I. BALLAI ◽  
R. ERDÉLYI ◽  
M. GOOSSENS
Keyword(s):  
Solar Phys ◽  
Normal Component ◽  
Mhd Equations ◽  
Mhd Waves ◽  
Mean Flow ◽  
Slab Geometry ◽  
Flux Tubes ◽  
Magnetic Flux Tubes ◽  
Field Lines ◽  
Connection Formulae

Nonlinear resonant slow magnetohydrodynamic (MHD) waves are studied in weakly dissipative isotropic plasmas for a cylindrical equilibrium model. The equilibrium magnetic field lines are unidirectional and parallel with the z axis. The nonlinear governing equations for resonant slow magnetoacoustic (SMA) waves are derived. Using the method of matched asymptotic expansions inside and outside the narrow dissipative layer, we generalize the connection formulae for the Eulerian perturbation of the total pressure and for the normal component of the velocity. These nonlinear connection formulae in dissipative cylindrical MHD are an important extention of the connection formulae obtained in linear ideal MHD [Sakurai et al., Solar Phys. 133, 227 (1991)], linear dissipative MHD [Goossens et al., Solar Phys. 175, 75 (1995); Erdélyi, Solar Phys. 171, 49 (1997)] and in nonlinear dissipative MHD derived in slab geometry [Ruderman et al., Phys. Plasmas4, 75 (1997)]. These generalized connection formulae enable us to connect the solutions at both sides of the dissipative layer without solving the MHD equations in the dissipative layer. We also show that the nonlinear interaction of harmonics in the dissipative layer is responsible for generating a parallel mean flow outside the dissipative layer.

scholarly journals Nonthermal filamentary radio features within 20 pc of the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 369-373 ◽  
Author(s):  
M. R. Morris ◽  
J.-H. Zhao ◽  
W. M. Goss
Keyword(s):  
Galactic Center ◽  
Galactic Plane ◽  
Pulsar Wind Nebulae ◽  
Flux Tubes ◽  
Deep Imaging ◽  
Point Reflection ◽  
Predominant Orientation ◽  
Magnetic Flux Tubes ◽  
Field Lines ◽  
Sgr A

AbstractDeep imaging of the Sgr A complex at 6 cm wavelength with the B and C configurations of the Karl G. Jansky VLA† has revealed a new population of faint radio filaments. Like their brighter counterparts that have been observed throughout the Galactic center on larger scales, these filaments can extend up to ∼10 parsecs, and in most cases are strikingly uniform in brightness and curvature. Comparison with a survey of Paschen-α emission reveals that some of the filaments are emitting thermally, but most of these structures are nonthermal: local magnetic flux tubes illuminated by synchrotron emission. The new image reveals considerable filamentary substructure in previously known nonthermal filaments (NTFs). Unlike NTFs previously observed on larger scales, which tend to show a predominant orientation roughly perpendicular to the Galactic plane, the NTFs in the vicinity of the Sgr A complex are relatively randomly oriented. Two well-known radio sources to the south of Sgr A – sources E and F – consist of numerous quasi-parallel filaments that now appear to be particularly bright portions of a much larger, strongly curved, continuous, nonthermal radio structure that we refer to as the “Southern Curl”. It is therefore unlikely that sources E and F are Hii regions or pulsar wind nebulae. The Southern Curl has a smaller counterpart on the opposite side of the Galactic center – the Northern Curl – that, except for its smaller scale and smaller distance from the center, is roughly point-reflection symmetric with respect to the Southern Curl. The curl features indicate that some field lines are strongly distorted, presumably by mass flows. The point symmetry about the center then suggests that the flows originate near the center and are somewhat collimated.

scholarly journals Superoscillations in solar MHD waves and their possible role in heating coronal loops

2018 ◽  
Vol 614 ◽  
pp. A145 ◽  
Author(s):  
A. López Ariste ◽  
M. Facchin
Keyword(s):  
Cross Sections ◽  
Mhd Waves ◽  
Coronal Loops ◽  
Heating Rates ◽  
Flux Tubes ◽  
Magnetoacoustic Waves ◽  
Kink Wave ◽  
Magnetic Flux Tubes ◽  
Field Lines ◽  
Wave Modes

Aims. We aim to study the presence of superoscillations in coronal magnetoacoustic (MHD) waves and their possible role in heating coronal loops through the strong and localised gradients that they generate on the wave. Methods. An analytic model is built for the transition between sausage and kink wave modes propagating along field lines in the corona. We compute in this model the local frequencies, the wave gradients, and the associated heating rates due to compressive viscosity. Results. We find superoscillations associated with the transition between wave modes accompanying the wave dislocation that shifts through the wave domain. Frequencies ten times higher than the normal frequency are found. This means that a typical three-minute coronal wave will oscillate locally in 10 to 20 s. Such high frequencies bring up strong gradients that efficiently dissipate the wave through compressive viscosity. We compute the associated heating rates; locally, they are very strong, largely compensating typical radiative losses. Conclusions. We find a new heating mechanism associated to magnetoacoustic waves in the corona. Heating due to superoscillations only happens along particular field lines with small cross sections, comparable in size to coronal loops, inside the much larger magnetic flux tubes and wave propagation domain.

scholarly journals Interhemispheric conjugate effect in longitude variations of mid-latitude ion density

2020 ◽  
Author(s):  
Yiding Chen ◽  
Libo Liu ◽  
Huijun Le ◽  
Hui Zhang
Keyword(s):  
Solar Minimum ◽  
Neutral Wind ◽  
Ion Density ◽  
Flux Tubes ◽  
The Earth ◽  
Defense Meteorological Satellite Program ◽  
June Solstice ◽  
Magnetic Flux Tubes ◽  
First Time ◽  
Meteorological Satellite

<p>Interhemispheric coupling between the northern and southern mid-lattitude ionosphere through the plasmasphere is difficult to confirm directly from observations. A possible result induced by this coupling is interhemispheric conjugacy of the mid-latitude ionosphere. In this paper, interhemispheric conjugate effect in longitude variations of mid-latitude total ion density (N<sub>i</sub>) is presented, for the first time, using the Defense Meteorological Satellite Program (DMSP) measurements; northern and southern N<sub>i</sub> longitude variations at 21:30 LT are similar between magnetically conjugate mid-latitudes around solar minimum June Solstice of 1996. The conjugate effect after sunset also occurs around the June Solstice in other solar minimum years but disappears when solar activity increases. We suggested that mid-latitude interhemispheric coupling is responsible for the conjugate effect. Neutral wind induced ionospheric transport causes topside longitude variations via upward diffusion at summer mid-latitudes; this further induces similar longitude variations of topside N<sub>i</sub> at winter mid-latitudes via the summer to winter interhemispheric coupling. The conjugate effect occurs only inside the plasmapause where magnetic flux tubes are closed and the plasma in these tubes can stably corotate with the Earth. The conjugate effect not only proves mid-latitude interhemispheric coupling through the plasmasphere, but also implies that neutral wind induced transport can affect ionospheric coupling to the plasmasphere at mid-latitudes.</p>

scholarly journals Decay of trefoil and other magnetic knots

2010 ◽  
Vol 6 (S274) ◽  
pp. 461-463 ◽  
Author(s):  
Simon Candelaresi ◽  
Fabio Del Sordo ◽  
Axel Brandenburg
Keyword(s):  
Magnetic Flux ◽  
Magnetic Energy ◽  
Field Configuration ◽  
The Other ◽  
Flux Tubes ◽  
Trefoil Knot ◽  
Magnetic Flux Tubes ◽  
Field Lines

AbstractTwo setups with interlocked magnetic flux tubes are used to study the evolution of magnetic energy and helicity on magnetohydrodynamical (MHD) systems like plasmas. In one setup the initial helicity is zero while in the other it is finite. To see if it is the actual linking or merely the helicity content that influences the dynamics of the system we also consider a setup with unlinked field lines as well as a field configuration in the shape of a trefoil knot. For helical systems the decay of magnetic energy is slowed down by the helicity which decays slowly. It turns out that it is the helicity content, rather than the actual linking, that is significant for the dynamics.

scholarly journals Flux quanta, magnetic field lines, merging – some sub-microscale relations of interest in space plasma physics

2011 ◽  
Vol 29 (6) ◽  
pp. 1121-1127 ◽  
Author(s):  
R. A. Treumann ◽  
R. Nakamura ◽  
W. Baumjohann
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Quantum Mechanical ◽  
Space Plasma Physics ◽  
Flux Tubes ◽  
Magnetic Diffusion ◽  
Macro Scale ◽  
Magnetic Flux Tubes ◽  
Field Lines ◽  
The Given

Abstract. We clarify the notion of magnetic field lines in plasma by referring to sub-microscale (quantum mechanical) particle dynamics. It is demonstrated that magnetic field lines in a field of strength B carry single magnetic flux quanta Φ0=h/e. The radius of a field line in the given magnetic field B is calculated. It is shown that such field lines can merge and annihilate only over the length ℓ∥ of their strictly anti-parallel sections, for which case we estimate the power generated. The length ℓ∥ becomes a function of the inclination angle θ of the two merging magnetic flux tubes (field lines). Merging is possible only in the interval 12πθ≤π. This provides a sub-microscopic basis for "component reconnection" in classical macro-scale reconnection. We also find that the magnetic diffusion coefficient in plasma appears in quanta D0m=eΦ0/me=h/me. This lets us conclude that the bulk perpendicular plasma resistivity is limited and cannot be less than η0⊥=μ0eΦ0/me=μ0h/me~10−9 Ohm m. This resistance is an invariant.

scholarly journals Dual-spacecraft reconstruction of a three-dimensional magnetic flux rope at the Earth's magnetopause

2015 ◽  
Vol 33 (2) ◽  
pp. 169-184 ◽  
Author(s):  
H. Hasegawa ◽  
B. U. Ö. Sonnerup ◽  
S. Eriksson ◽  
T. K. M. Nakamura ◽  
H. Kawano
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Three Dimensional ◽  
Flux Rope ◽  
Angle Distribution ◽  
Generation Process ◽  
Transfer Event ◽  
Magnetic Flux Rope ◽  
First Results ◽  
Field Lines

Abstract. We present the first results of a data analysis method, developed by Sonnerup and Hasegawa (2011), for reconstructing three-dimensional (3-D), magnetohydrostatic structures from data taken as two closely spaced satellites traverse the structures. The method is applied to a magnetic flux transfer event (FTE), which was encountered on 27 June 2007 by at least three (TH-C, TH-D, and TH-E) of the five THEMIS probes near the subsolar magnetopause. The FTE was sandwiched between two oppositely directed reconnection jets under a southward interplanetary magnetic field condition, consistent with its generation by multiple X-line reconnection. The recovered 3-D field indicates that a magnetic flux rope with a diameter of ~ 3000 km was embedded in the magnetopause. The FTE flux rope had a significant 3-D structure, because the 3-D field reconstructed from the data from TH-C and TH-D (separated by ~ 390 km) better predicts magnetic field variations actually measured along the TH-E path than does the 2-D Grad–Shafranov reconstruction using the data from TH-C (which was closer to TH-E than TH-D and was at ~ 1250 km from TH-E). Such a 3-D nature suggests that the field lines reconnected at the two X-lines on both sides of the flux rope are entangled in a complicated way through their interaction with each other. The generation process of the observed 3-D flux rope is discussed on the basis of the reconstruction results and the pitch-angle distribution of electrons observed in and around the FTE.

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>

Linear Visco-Resistive Computations of Magnetohydrodynamic Waves: I. The Code and Test Cases

1994 ◽  
Vol 144 ◽  
pp. 503-505
Author(s):  
R. Erdélyi ◽  
M. Goossens ◽  
S. Poedts
Keyword(s):  
Resonant Absorption ◽  
Numerical Code ◽  
Mhd Waves ◽  
Test Cases ◽  
Numerical Accuracy ◽  
Element Discretization ◽  
Flux Tubes ◽  
Magnetohydrodynamic Waves ◽  
Viscosity Coefficients ◽  
Magnetic Flux Tubes

AbstractThe stationary state of resonant absorption of linear, MHD waves in cylindrical magnetic flux tubes is studied in viscous, compressible MHD with a numerical code using finite element discretization. The full viscosity tensor with the five viscosity coefficients as given by Braginskii is included in the analysis. Our computations reproduce the absorption rates obtained by Lou in scalar viscous MHD and Goossens and Poedts in resistive MHD, which guarantee the numerical accuracy of the tensorial viscous MHD code.

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