scholarly journals Particle Acceleration in Collisionless Magnetic Reconnection

2001 ◽  
Vol 203 ◽  
pp. 555-557
Author(s):  
P. K. Browning ◽  
G. E. Vekstein
Keyword(s):  
Magnetic Field ◽  
Field Component ◽  
Charged Particles ◽  
Energy Spectra ◽  
Uniform Field ◽  
Two Dimensional ◽  
Point Field ◽  
Field Geometry ◽  
Collisionless Reconnection ◽  
Accelerated Particles

We investigate the acceleration of charged particles in the framework of collisionless reconnection. A steady reconnection scenario is considered, with a two dimensional X-point magnetic field geometry having also a uniform field component transverse to the plane of the X-point field, and an inductive electric field generating an inflow of particles. Test particle trajectories are studied, and the energy spectra of the accelerated particles are determined.

A physical description of magnetic helicity evolution in the presence of reconnection lines

1991 ◽  
Vol 46 (1) ◽  
pp. 179-199 ◽  
Author(s):  
Andrew N. Wright ◽  
Mitchell A. Berger
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Magnetic Reynolds Number ◽  
Magnetic Helicity ◽  
Two Dimensional ◽  
Flux Tubes ◽  
Physical Description ◽  
Reconnection Region ◽  
Field Geometry ◽  
Field Lines

The dissipation of relative magnetic helicity due to the presence of a resistive reconnection region is considered. We show that when the reconnection region has a vanishing cross-section, helicity is conserved, in agreement with previous studies. It is also shown that in two-dimensional systems reconnection can produce highly twisted reconnected flux tubes. Reconnection at a high magnetic Reynolds number generally conserves helicity to a good approximation. However, reconnection with a small Reynolds number can produce significant dissipation of helicity. We prove that helicity dissipation in two-dimensional configurations is associated with the retention of some of the inflowing magnetic flux by the reconnection region, vr. When the reconnection site is a simple Ohmic conductor, all of the magnetic field parallel to the reconnection line that is swept into vr is retained. (In contrast, the inflowing magnetic field perpendicular to the line is annihilated.) We are able to relate the amount of helicity dissipation to the retained flux. A physical interpretation of helicity dissipation is developed by considering the diffusion of magnetic field lines through vr. When compared with helicity-conserving reconnection, the two halves of a reconnected flux sheet appear to have slipped relative to each other parallel to the reconnection line. This provides a useful method by which the reconnected field geometry can be constructed: the incoming flux sheets are ‘cut’ where they encounter vr, allowed to slip relative to each other, and then ‘pasted’ together to form the reconnected flux sheets. This simple model yields estimates for helicity dissipation and the flux retained by vr in terms of the amount of slippage. These estimates are in agreement with those expected from the governing laws.

Two-Dimensional Melting of Magnetic Bubble Arrays: A Continuous Hexatic-To-Liquid Transition

1991 ◽  
Vol 248 ◽  
Author(s):  
R. Seshadri ◽  
R. M. Westervelt
Keyword(s):  
Magnetic Field ◽  
Imaging Techniques ◽  
Topological Defects ◽  
Gradient Field ◽  
Uniform Field ◽  
Two Dimensional ◽  
Bias Magnetic Field ◽  
Liquid Transition ◽  
Bubble Density ◽  
Dc Bias

AbstractArrays of two-dimensional magnetic bubbles in thin garnet films undergo a hexatic-toliquid transition as a function of bubble density controlled by an applied spatially uniform dc bias magnetic field that opposes the magnetization in the bubbles. The phase transition is driven by topological point defects. The bubbles are observed directly using optical microscopy and digital imaging techniques. In the presence of a linear gradient in the dc bias magnetic field the hexatic-to-liquid transition occurs spatially in the direction of the gradient. As the system goes from hexatic to liquid, a continuous decrease in bubble density accompanied by a continuous disordering of the array is observed along the gradient direction. This continuous disordering persists even after the system is allowed to equilibrate for very long periods of time, indicating that the hexatic-to-liquid transition is continuous at equilibrium. Dynamics of topological defects observed in the gradient field correspond to those observed in the uniform field.

TWO-DIMENSIONAL COULOMB INTERACTIONS IN A MAGNETIC FIELD

1999 ◽  
Vol 11 (03) ◽  
pp. 361-382
Author(s):  
JINGBO XIA
Keyword(s):  
Magnetic Field ◽  
Essential Spectrum ◽  
Landau Level ◽  
Charged Particles ◽  
Two Dimensional ◽  
Coulomb Interactions

We consider the 2D Hamiltonian of N charged particles in a magnetic field. We show how the Coulomb interactions cause the first Landau level to split in the essential spectrum.

scholarly journals A weak turbulence theory for incompressible magnetohydrodynamics

2000 ◽  
Vol 63 (5) ◽  
pp. 447-488 ◽  
Author(s):  
S. GALTIER ◽  
S. V. NAZARENKO ◽  
A. C. NEWELL ◽  
A. POUQUET
Keyword(s):  
Magnetic Field ◽  
Kinetic Equations ◽  
Turbulence Theory ◽  
Energy Spectra ◽  
Weak Turbulence ◽  
Two Dimensional ◽  
Wave Interactions ◽  
Weak Turbulence Theory ◽  
The Magnetic Field ◽  
Incompressible Magnetohydrodynamics

We derive a weak turbulence formalism for incompressible magnetohydrodynamics. Three-wave interactions lead to a system of kinetic equations for the spectral densities of energy and helicity. The kinetic equations conserve energy in all wavevector planes normal to the applied magnetic field B0ê∥. Numerically and analytically, we find energy spectra E± ∼ kn±⊥, such that n+ + n− = −4, where E± are the spectra of the Elsässer variables z± = v ± b in the two-dimensional case (k∥ = 0). The constants of the spectra are computed exactly and found to depend on the amount of correlation between the velocity and the magnetic field. Comparison with several numerical simulations and models is also made.

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