Scaling of asymmetric magnetic reconnection: General theory and collisional simulations

Cassak, P. A.; Shay, M. A.

doi:10.1063/1.2795630

Cited by 450 publications

(808 citation statements)

References 52 publications

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“…For full generality, we first perform the analysis on asymmetric reconnection and then take the symmetric limit for application to this study. Our analysis is similar to previous Sweet-Parker analyses of asymmetric reconnection 4,7 . Figure 1 shows a schematic of the energy fluxes into and out of the diffusion region.…”

Section: Theorysupporting

confidence: 78%

Electron heating during magnetic reconnection: A simulation scaling study

et al. 2014

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1Electron bulk heating during magnetic reconnection with symmetric inflow conditions is examined using kinetic particle-in-cell (PIC) simulations. Inflowing plasma parameters are varied over a wide range of conditions, and the increase of electron temperature is measured in the exhaust well downstream of the x-line. The degree of electron heating is well correlated with the inflowing Alfvén speed c Ar based on the reconnecting magnetic field through the relation ∆T e = 0.033 m i c 2 Ar , where ∆T e is the increase in electron temperature. For the range of simulations performed, the heating shows almost no correlation with inflow total temperature T tot = T i + T e or plasma β. An out-of-plane (guide) magnetic field of similar magnitude to the reconnecting field does not affect the total heating, but it does quench perpendicular heating, with almost all heating being in the parallel direction. These results are qualitatively consistent with a recent statistical survey of electron heating in the dayside magnetopause (Phan et al, Geophys. Res. Lett., 40, doi:10.1002/grl.50917, 2013), which also found that ∆T e was proportional to the inflowing Alfvén speed. The net electron heating varies very little with distance downstream of the x-line.The simulations show at most a very weak dependence of electron heating on the ion to electron mass ratio. In the antiparallel reconnection case, the largely parallel heating is eventually isotropized downstream due a scattering mechanism such as stochastic particle motion or instabilities. The simulation size is large enough to be directly relevant to reconnection in the Earth's magnetosphere, and the present findings may prove to be universal in nature with applications to the solar wind, the solar corona, and other astrophysical plasmas. The study highlights key properties that must be satisfied by an electron heating mechanism: (1) Preferential heating in the parallel direction; (2) Heating proportional to m i c 2 Ar ; (3) At most a weak dependence on electron mass; and (4) An exhaust electron temperature that varies little with distance from the x-line. a) shay@udel.edu 2

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Section: Theorysupporting

confidence: 78%

Electron heating during magnetic reconnection: A simulation scaling study

et al. 2014

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“…͑17͔͒. This result has been used in a series of subsequent publications [1][2][3] and the same result has also been obtained in a similar way in a paper by different authors at about the same time. 4 If we repeat their analysis based on Eqs.…”

supporting

confidence: 64%

Comment on “Scaling of asymmetric magnetic reconnection: General theory and collisional simulations” [Phys. Plasmas 14, 102114 (2007)]

2009

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“…We assume incompressible plasma flow and anti-parallel magneticflux tubes of equal field strength |B x |. The situation could be generalized to allow for compressible plasma and asymmetric field strengths (Cassak & Shay 2007), flux tubes intersecting at an angle or with a shared component of magnetic field (guide field) B z (Linton et al 2001), twisted flux tubes with magnetic helicity (Zweibel & Rhoads 1995), etc. All of these are relevant for applications, but we keep the setup simple in order to make the new ideas clear.…”

Section: Large-scale Magnetic Reconnectionmentioning

confidence: 99%

Fast Magnetic Reconnection and Spontaneous Stochasticity

Eyink

Lazarían²,

Vishniac

2011

ApJ

183

260

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Magnetic field lines in astrophysical plasmas are expected to be frozen-in at scales larger than the ion gyroradius. The rapid reconnection of magnetic-flux structures with dimensions vastly larger than the gyroradius requires a breakdown in the standard Alfvén flux-freezing law. We attribute this breakdown to ubiquitous MHD plasma turbulence with power-law scaling ranges of velocity and magnetic energy spectra. Lagrangian particle trajectories in such environments become "spontaneously stochastic," so that infinitely many magnetic field lines are advected to each point and must be averaged to obtain the resultant magnetic field. The relative distance between initial magnetic field lines which arrive at the same final point depends upon the properties of two-particle turbulent dispersion. We develop predictions based on the phenomenological Goldreich & Sridhar theory of strong MHD turbulence and on weak MHD turbulence theory. We recover the predictions of the Lazarian & Vishniac theory for the reconnection rate of large-scale magnetic structures. Lazarian & Vishniac also invoked "spontaneous stochasticity," but of the field lines rather than of the Lagrangian trajectories. More recent theories of fast magnetic reconnection appeal to microscopic plasma processes that lead to additional terms in the generalized Ohm's law, such as the collisionless Hall term. We estimate quantitatively the effect of such processes on the inertial-range turbulence dynamics and find them to be negligible in most astrophysical environments. For example, the predictions of the Lazarian & Vishniac theory are unchanged in Hall MHD turbulence with an extended inertial range, whenever the ion skin depth δ i is much smaller than the turbulent integral length or injection-scale L i .

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Scaling of asymmetric magnetic reconnection: General theory and collisional simulations

Cited by 450 publications

References 52 publications

Electron heating during magnetic reconnection: A simulation scaling study

Electron heating during magnetic reconnection: A simulation scaling study

Comment on “Scaling of asymmetric magnetic reconnection: General theory and collisional simulations” [Phys. Plasmas 14, 102114 (2007)]

Fast Magnetic Reconnection and Spontaneous Stochasticity

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