scholarly journals Test Particle Energization by Current Sheets and Nonuniform Fields in Magnetohydrodynamic Turbulence

2004 ◽  
Vol 617 (1) ◽  
pp. 667-679 ◽  
Author(s):  
Pablo Dmitruk ◽  
W. H. Matthaeus ◽  
N. Seenu
Keyword(s):  
Test Particle ◽  
Magnetohydrodynamic Turbulence ◽  
Current Sheets ◽  
Particle Energization

Particle energization inside plasmoids: numerical and analytical investigations

2021 ◽  
Author(s):  
Xiaozhou Zhao ◽  
Rony Keppens ◽  
Fabio Bacchini
Keyword(s):  
Test Particle ◽  
Large Scale ◽  
Mass Density ◽  
Magnetic Islands ◽  
Chaotic Flow ◽  
Reynolds Decomposition ◽  
Particle Simulations ◽  
Particle Energization ◽  
Periodic Setting ◽  
A Current

<div> <div> <div> <p>In an idealized system where four magnetic islands interact in a two-dimensional periodic setting, we follow the detailed evolution of current sheets forming in between the islands, as a result of an enforced large-scale merging by magnetohydrodynamic (MHD) simulation. The large-scale island merging is triggered by a perturbation to the velocity field, which drives one pair of islands move towards each other while the other pair of islands are pushed away from one another. The "X"-point located in the midst of the four islands is locally unstable to the perturbation and collapses, producing a current sheet in between with enhanced current and mass density. Using grid-adaptive resistive magnetohydrodynamic (MHD) simulations, we establish that slow near-steady Sweet-Parker reconnection transits to a chaotic, multi-plasmoid fragmented state, when the Lundquist number exceeds about 3×10<sup>4</sup>, well in the range of previous studies on plasmoid instability. The extreme resolution employed in the MHD study shows significant magnetic island substructures. Turbulent and chaotic flow patters are also observed inside the islands. We set forth to explore how charged particles can be accelerated in embedded mini-islands within larger (monster)-islands on the sheet. We study the motion of the particles in a MHD snapshot at a fixed instant of time by the Test-Particle Module incorporated in AMRVAC (). The planar MHD setting artificially causes the largest acceleration in the ignored third direction, but does allow for full analytic study of all aspects leading to the acceleration and the in-plane, projected trapping of particles within embedded mini-islands. The analytic result uses a decomposition of the test particle velocity in slow and fast changing components, akin to the Reynolds decomposition in turbulence studies. The analytic results allow a complete fit to representative proton test particle simulations, which after initial non-relativistic motion throughout the monster island, show the potential of acceleration within a mini-island beyond (√2/2)c≈0.7c, at which speed the acceleration is at its highest efficiency. Acceleration to several hundreds of GeVs can happen within several tens of seconds, for upward traveling protons in counterclockwise mini-islands of sizes smaller than the proton gyroradius.</p> </div> </div> </div><div></div><div></div>

scholarly journals On the compressibility effect in test particle acceleration by magnetohydrodynamic turbulence

2016 ◽  
Vol 23 (8) ◽  
pp. 082305 ◽  
Author(s):  
C. A. González ◽  
P. Dmitruk ◽  
P. D. Mininni ◽  
W. H. Matthaeus
Keyword(s):  
Particle Acceleration ◽  
Test Particle ◽  
Magnetohydrodynamic Turbulence ◽  
Compressibility Effect

scholarly journals STATISTICAL ANALYSIS OF CURRENT SHEETS IN THREE-DIMENSIONAL MAGNETOHYDRODYNAMIC TURBULENCE

2013 ◽  
Vol 771 (2) ◽  
pp. 124 ◽  
Author(s):  
Vladimir Zhdankin ◽  
Dmitri A. Uzdensky ◽  
Jean C. Perez ◽  
Stanislav Boldyrev
Keyword(s):  
Statistical Analysis ◽  
Three Dimensional ◽  
Magnetohydrodynamic Turbulence ◽  
Current Sheets

scholarly journals Test Particle Acceleration in Three-dimensional Magnetohydrodynamic Turbulence

2003 ◽  
Vol 597 (1) ◽  
pp. L81-L84 ◽  
Author(s):  
P. Dmitruk ◽  
W. H. Matthaeus ◽  
N. Seenu ◽  
M. R. Brown
Keyword(s):  
Particle Acceleration ◽  
Test Particle ◽  
Three Dimensional ◽  
Magnetohydrodynamic Turbulence

scholarly journals Dynamic Alignment and Plasmoid Formation in Relativistic Magnetohydrodynamic Turbulence

2021 ◽  
Vol 923 (1) ◽  
pp. L13
Author(s):  
Alexander Chernoglazov ◽  
Bart Ripperda ◽  
Alexander Philippov
Keyword(s):  
Large Scale ◽  
Magnetic Energy ◽  
Magnetohydrodynamic Turbulence ◽  
Current Sheets ◽  
Guide Field ◽  
Tearing Instability ◽  
Decaying Turbulence ◽  
2D And 3D ◽  
Dynamic Alignment ◽  
Dynamic Formation

Abstract We present high-resolution 2D and 3D simulations of magnetized decaying turbulence in relativistic, resistive magnetohydrodynamics. The simulations show dynamic formation of large-scale intermittent long-lived current sheets being disrupted into plasmoid chains by the tearing instability. These current sheets are locations of enhanced magnetic-field dissipation and heating of the plasma. We find magnetic energy spectra ∝k −3/2, together with strongly pronounced dynamic alignment of Elsässer fields and of velocity and magnetic fields, for strong guide-field turbulence, whereas we retrieve spectra ∝k −5/3 for the case of a weak guide-field.

scholarly journals Test Particle Energization and the Anisotropic Effects of Dynamical MHD Turbulence

2017 ◽  
Vol 850 (1) ◽  
pp. 19 ◽  
Author(s):  
C. A. González ◽  
P. Dmitruk ◽  
P. D. Mininni ◽  
W. H. Matthaeus
Keyword(s):  
Test Particle ◽  
Mhd Turbulence ◽  
Particle Energization

scholarly journals Particle acceleration in coalescent and squashed magnetic islands

2020 ◽  
Vol 635 ◽  
pp. A116 ◽  
Author(s):  
Q. Xia ◽  
V. Zharkova
Keyword(s):  
Particle Acceleration ◽  
Current Sheet ◽  
Test Particle ◽  
Pitch Angle ◽  
Magnetic Islands ◽  
Current Sheets ◽  
Aspect Ratios ◽  
Energy Gains ◽  
Particle Approach ◽  
Accelerated Particles

Aims. Particles are known to have efficient acceleration in reconnecting current sheets with multiple magnetic islands that are formed during a reconnection process. Using the test-particle approach, the recent investigation of particle dynamics in 3D magnetic islands, or current sheets with multiple X- and O-null points revealed that the particle energy gains are higher in squashed magnetic islands than in coalescent ones. However, this approach did not factor in the ambient plasma feedback to the presence of accelerated particles, which affects their distributions within the acceleration region. Methods. In the current paper, we use the particle-in-cell (PIC) approach to investigate further particle acceleration in 3D Harris-type reconnecting current sheets with coalescent (merging) and squashed (contracting) magnetic islands with different magnetic field topologies, ambient densities ranging between 108 − 1012 m−3, proton-to-electron mass ratios, and island aspect ratios. Results. In current sheets with single or multiple X-nullpoints, accelerated particles of opposite charges are separated and ejected into the opposite semiplanes from the current sheet midplane, generating a strong polarisation electric field across a current sheet. Particles of the same charge form two populations: transit and bounced particles, each with very different energy and asymmetric pitch-angle distributions, which can be distinguished from observations. In some cases, the difference in energy gains by transit and bounced particles leads to turbulence generated by Buneman instability. In magnetic island topology, the different reconnection electric fields in squashed and coalescent islands impose different particle drift motions. This makes particle acceleration more efficient in squashed magnetic islands than in coalescent ones. The spectral indices of electron energy spectra are ∼ − 4.2 for coalescent and ∼ − 4.0 for squashed islands, which are lower than reported from the test-particle approach. The particles accelerated in magnetic islands are found trapped in the midplane of squashed islands, and shifted as clouds towards the X-nullpoints in coalescent ones. Conclusions. In reconnecting current sheets with multiple X- and O-nullpoints, particles are found accelerated on a much shorter spatial scale and gaining higher energies than near a single X-nullpoint. The distinct density and pitch-angle distributions of particles with high and low energy detected with the PIC approach can help to distinguish the observational features of accelerated particles.

scholarly journals Joule heating and anomalous resistivity in the solar corona

2009 ◽  
Vol 16 (3) ◽  
pp. 443-452 ◽  
Author(s):  
S. R. Spangler
Keyword(s):  
Solar Corona ◽  
Heating Rate ◽  
Joule Heating ◽  
Heliocentric Distance ◽  
Theoretical Estimate ◽  
Magnetohydrodynamic Turbulence ◽  
Volumetric Heating ◽  
Current Sheets ◽  
True Resistivity ◽  
Thermal Speed

Abstract. Recent radioastronomical observations of Faraday rotation in the solar corona can be interpreted as evidence for coronal currents, with values as large as 2.5×109 Amperes (Spangler, 2007). These estimates of currents are used to develop a model for Joule heating in the corona. It is assumed that the currents are concentrated in thin current sheets, as suggested by theories of two dimensional magnetohydrodynamic turbulence. The Spitzer result for the resistivity is adopted as a lower limit to the true resistivity. The calculated volumetric heating rate is compared with an independent theoretical estimate by Cranmer et al. (2007). This latter estimate accounts for the dynamic and thermodynamic properties of the corona at a heliocentric distance of several solar radii. Our calculated Joule heating rate is less than the Cranmer et al estimate by at least a factor of 3×105. The currents inferred from the observations of Spangler (2007) are not relevant to coronal heating unless the true resistivity is enormously increased relative to the Spitzer value. However, the same model for turbulent current sheets used to calculate the heating rate also gives an electron drift speed which can be comparable to the electron thermal speed, and larger than the ion acoustic speed. It is therefore possible that the coronal current sheets are unstable to current-driven instabilities which produce high levels of waves, enhance the resistivity and thus the heating rate.

Sign in / Sign up

Export Citation Format

Share Document