Chaos-induced resistivity in the magnetic null region: A nonlinear mechanism of collisionless dissipation

Numata, Ryusuke; Yoshida, Zensho

doi:10.1103/physreve.68.016407

Cited by 11 publications

(40 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the roles of spatial anomalous diffusion arising from waveparticle interactions versus the role of ions nongyrotropy in generating resistivity in RCS of having widths of ion and MHD scales need further studies. We point out that Singh and Subramanian 24 compared the chaos-induced resistivity 22,23 with the resistivity given by the KAW-induced anomalous diffusion for solar flare reconnections and find comparable resistivities; these resistivities are much lower than that needed for reconnection in the magnetosphere and can be attributed to D $ 10 5 -10 6 m 2 /s for the solar coronal plasma with T e $ 100 eV and B $ 10-50 nT.…”

Section: Conclusion and Discussionmentioning

confidence: 78%

“…A novel study by Numata and Yoshida 22,23 found that the motion of charged particles in a confined region near the reconnection X-line is highly chaotic and their exit from this region gives collisionless resistivity. They used test-particle simulations to study the dynamics of electrons and ions, showing that the chaotic motion in conjunction with the exit of some of the particles energized by the reconnection electric field from the core of the diffusion region contributes to an anomalous resistivity.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Origins of effective resistivity in collisionless magnetic reconnection

Singh

2014

Physics of Plasmas

View full text Add to dashboard Cite

The mechanisms that provide effective resistivity for supporting collisonless magnetic reconnection have remained unsettled despite numerous studies. Some of these studies demonstrated that the electron pressure nongyrotropy generates the resistivity (g npg ) in the electron diffusion region (EDR). We derive an analytical relation for the effective resistivity (g kin ) by momentum balance in a control volume in the EDR. Both g npg and g kin mutually compare well and they also compare well with the resistivity required to support reconnection electric field E rec in multi-dimensional particle-in-cell simulations as well as in satellite observations when reconnection occurs in an EDR. But they are about an order of magnitude or so smaller than that required when the reconnection occurred in a much wider reconnecting current sheet (RCS) of half width (w) of the order of the ion skin depth (d i ), observed in the Earth magnetosphere. The chaos-induced resistivity reported in the literature is found to be even more deficient. We find that for reconnection in RCS with w $ d i , anomalous diffusion, such as the universal Bhom diffusion and/or that arising from kinetic Alfven waves, could fairly well account for the required resistivity. V C 2014 AIP Publishing LLC. [http://dx.

show abstract

Section: Conclusion and Discussionmentioning

confidence: 78%

mentioning

confidence: 99%

Origins of effective resistivity in collisionless magnetic reconnection

Singh

2014

Physics of Plasmas

View full text Add to dashboard Cite

show abstract

“…In the absence of strong particle collisions, this effective conductivity can support the reconnection process (Horton, 1997;Numata and Yoshida, 2002) and results in the formation of magnetic islands in the outflow regions. The amplitude of the corresponding effective collision frequency ν eff is proportional to the decay rate β of the number of particles in the current sheet (Numata and Yoshida, 2003). The estimate for the β parameter can be obtained from simple approximations of the time evolution of the number of particles initially injected to the current sheet.…”

Section: Discussionmentioning

confidence: 99%

Chaotic Charged Particle Motion and Acceleration in Reconnected Current Sheet

et al. 2014

View full text Add to dashboard Cite

We investigate charged particle dynamics and acceleration in the current sheet located in the reconnection outflow region. We consider parameter ranges corresponding to current sheets in the solar corona. We demonstrate a new effect of fast chaotization of charged particle motion due to effective geometrical destruction of adiabatic invariants in current sheets in the presence of a quite strong sheared magnetic field and a finite electric field. This fast chaotization results in particle acceleration and enhancement of effective collisionless conductivity. Additionally, chaotization of charged particle motion could lead to particle escape from the current sheet and corresponding formation of field-aligned beams. We also discuss different regimes of charged particle motion in the reconnected current sheet for wide parameter ranges.

show abstract

“…In collisionless plasmas, where the collision mean free path can approach the system scales, anomalous sources of resistivity have been proposed [ Dupree , ; Horton and Tajima , ; Yoshida et al , ; Numata and Yoshida , ]. Resistivity can be enhanced by wave‐particle interactions [ Ji et al , ; Drake and Lee , ], stochasticity/turbulence in the magnetic fields [ Kulpa‐Dybel et al , ], and single particle motion in spatially varying magnetic fields [ Speiser , ; Lyons and Speiser , ; Horton and Tajima , ; Numata and Yoshida , []]. Lower hybrid waves have often been observed during reconnection process [ Bale et al , ].…”

Section: Introductionmentioning

confidence: 99%

Collisionless resistivity in a bifurcated current sheet

Andriyas

Spencer

2014

JGR Space Physics

View full text Add to dashboard Cite

The collisionless resistivity due to charged particle chaos in spatially inhomogeneous magnetic fields is calculated for two frequently observed magnetotail current sheets, the X line, and a bifurcated current sheet (BCS) over varying strengths of cross-tail electric field. The calculation is done for two charged species, protons and O + ions, found in the magnetotail specially during active times. Chaotic behavior of the particles is studied for the chaos parameter ≈ 1 defined by Buchner and Zelenyi (1989) as the square root of minimum radius of curvature to the maximum particle gyroradius. The surface of section plot and maximal Lyapunov exponents are analyzed to compare the particle behavior in the two magnetic field topologies. It is found that the particle behavior in a BCS is chaotic around the two humps located at ±z 0 and that the configuration is more chaotic than the X line (maximum Lyapunov exponent for X line is around 0.25 compared to 0.34 for BCS). The collisionless resistivity is calculated using the technique developed by Numata and Yoshida (2003). The method relies on a phenomenological equivalence between the particle loss rate from the chaos region and rate of change of momentum in the chaos region under steady state conditions. Rapid decay of the particles from the chaos region is modeled with exponential fits, and it is found that a double exponent is needed for O + ions in an X line and for both species in the BCS. The resistivity thus calculated is found to be 9-10 orders of magnitude higher than the Spitzer resistivity.

show abstract

Chaos-induced resistivity in the magnetic null region: A nonlinear mechanism of collisionless dissipation

Cited by 11 publications

References 13 publications

Origins of effective resistivity in collisionless magnetic reconnection

Origins of effective resistivity in collisionless magnetic reconnection

Chaotic Charged Particle Motion and Acceleration in Reconnected Current Sheet

Collisionless resistivity in a bifurcated current sheet

Contact Info

Product

Resources

About