On Turbulent Reconnection

Kim, Eun Jin; Diamond, P. H.

doi:10.1086/321628

Cited by 46 publications

(53 citation statements)

References 32 publications

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“…A number of papers have attempted to treat turbulent magnetic reconnection by the formal methods of mean-field electrodynamics (MFE), e.g., Strauss 1988 andKim &Diamond 2001. Before we address these works in any detail, let us briefly discuss the relationships of LV99 itself to MFE.…”

Section: Alternative Ideas On the Role Of Turbulence In Magnetic Recomentioning

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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Section: Alternative Ideas On the Role Of Turbulence In Magnetic Recomentioning

confidence: 99%

Fast Magnetic Reconnection and Spontaneous Stochasticity

Eyink

Lazarían²,

Vishniac

2011

ApJ

183

260

View full text Add to dashboard Cite

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“…Turbulent reconnection models are still under debate. For instance, Kim & Diamond (2001) concluded that the effect of hyperresistivity is negligible with respect to turbulent diffusivity and that, despite turbulence, the global reconnection rate (that scales as in the Sweet & ParkerYtype reconnection) cannot be given by a simple sum of local reconnection events (as claimed by Lazarian & Vishniac 1999); hence, fast global reconnection cannot be achieved. It has also been proposed that, as the CS is stretched with the CME propagation, recurrent secondary tearing instabilities occurring at different spatial scales lead to a fractal (i.e., scale-free) CS structure (Fig.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic Detection of Turbulence in Post‐CME Current Sheets

Бемпорад

2008

Astrophysical Journal

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Plasma in post-CME current sheets (CSs) is expected to be highly turbulent because of the tearing and coalescence instability and/or local microscopic instabilities. For this reason, in the last decade the inconsistency between the observed ($10 4 Y10 5 km) and the expected ($1Y10 m) CS thickness has been tentatively explained in many MHD models as a consequence of plasma turbulence that should be able to significantly broaden the CS. However, from the observational point of view, little is known about this subject. A few post-CME CSs have been observed in UVCS spectra as a strong emission in the high-temperature [ Fe xviii] line, usually unobservable in the solar corona. In this work, published data on post-CME CSs observed by UVCS are reanalyzed, concentrating for the first time on the evolution of turbulence derived from the nonthermal broadening of the [Fe xviii] line profiles. Derived turbulent speeds are on the order of $60 km s À1 a few hours after the CME and slowly decay down to $30 km s À1 in the following 2 days. From this evolution the anomalous diffusivity due to microinstabilities has been estimated, and the scenario of multiple small-scale reconnections is tested. Results show that the existence of many ($10 À11 to 10 À17 CS m À3 ) microscopic CSs (CSs) of small sizes ($10Y10 4 m) could explain not only the high CS temperatures but also the much larger observed thickness of macroscopic CSs, thanks to turbulent broadening.

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“…[16][17][18][19][20][21][22][23][24][25] Other studies have shown that laminar neutral sheet reconnection is unstable to two-dimensional linear perturbations via a three-step transition-to-turbulence process. 15,26,27 Here, we investigate a slightly different aspect of the problem, namely how sensitive initial states known to produce reconnection dynamics are to the addition of small-scale turbulence.…”

Section: Introductionmentioning

confidence: 99%

The impact of small-scale turbulence on laminar magnetic reconnection

2007

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Initial states in incompressible two-dimensional magnetohydrodynamics that are known to lead to strong current sheets and ͑laminar͒ magnetic reconnection are modified by the addition of small-scale turbulent perturbations of various energies. The evolution of these states is computed with the aim of ascertaining the influence of the turbulence on the underlying laminar solution. Two main questions are addressed here: ͑1͒ What effect does small-scale turbulence have on the energy dissipation rate of the underlying solution? ͑2͒ What is the threshold turbulent perturbation level above which the original laminar reconnective dynamics is no longer recognizable. The simulations show that while the laminar dynamics persist the dissipation rates are largely unaffected by the turbulence, other than modest increases attributable to the additional small length scales present in the new initial condition. The solutions themselves are also remarkably insensitive to small-scale turbulent perturbations unless the perturbations are large enough to undermine the integrity of the underlying cellular flow pattern. Indeed, even initial states that lead to the evolution of small-scale microscopic sheets can survive the addition of modest turbulence. The role of a large-scale organizing background magnetic field is also addressed.

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On Turbulent Reconnection

Cited by 46 publications

References 32 publications

Fast Magnetic Reconnection and Spontaneous Stochasticity

Fast Magnetic Reconnection and Spontaneous Stochasticity

Spectroscopic Detection of Turbulence in Post‐CME Current Sheets

The impact of small-scale turbulence on laminar magnetic reconnection

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