Analysis of time‐dependent reconnection in compressible plasmas

Semenov, V. S.; Drobysh, O. A.; Heyn, Martin

doi:10.1029/98ja00677

Cited by 10 publications

(8 citation statements)

References 15 publications

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“…In particular, the length scale (in the z direction) of the sheet is macroscopic (being several Earth radii in length) while the thickness along the Sun‐Earth line is about a tenth of an Earth radius. Further, we see no indication that the current sheet has disintegrated into a system of MHD discontinities (slow mode shocks, rotational discontinuities, and contact discontinuities), as predicted by Petschek‐like theories where the dissipation is localized to a microscopic region around the stagnation point [ Heyn et al , 1988; Heyn and Semenov , 1996; Semenov et al , 1998].…”

Section: Resultsmentioning

confidence: 54%

A new look at driven magnetic reconnection at the terrestrial subsolar magnetopause

Dorelli¹

2004

J. Geophys. Res.

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[1] The physics of steady driven magnetic reconnection at Earth's subsolar magnetopause is addressed. Three-dimensional, global magnetohydrodynamics (MHD) simulations of the magnetopause are compared with analytical solutions of the resistive MHD equations [Sonnerup and Priest, 1975] corresponding to magnetic field annihilation driven by an incompressible stagnation point flow. The simulations demonstrate that under steady southward interplanetary magnetic field conditions and when the plasma resistivity is spatially uniform, subsolar magnetopause reconnection occurs in long, thin Sweet-Parker current sheets via a flux pileup mechanism [Sonnerup and Priest, 1975;Priest and Forbes, 1986] (rather than in Petschek slow shock configurations). Magnetic energy piles up upstream of the magnetopause current sheet to accommodate the sub-Alfvénic solar wind inflow. The scaling of the pileup with Lundquist number, S, is consistent (approximately / S 1/4 ) with that predicted by the analytical, incompressible stagnation point flow solutions (though there are small corrections due to plasma compressibility in the simulations). Since there is a finite energy in the magnetosheath available to drive the magnetic pileup (and associated rapid magnetic reconnection), we expect the pileup to saturate and the reconnection rate to drop as the upstream plasma pressure drops to accommodate the pileup. Thus we expect the reconnection to stall, the rate vanishing in the limit S ! 1. We discuss the role of Hall electric fields in allowing the magnetic pileup to saturate before the reconnection begins to stall, permitting Alfvénic reconnection to occur in thin current sheets in the limit S ! 1.

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Section: Resultsmentioning

confidence: 54%

A new look at driven magnetic reconnection at the terrestrial subsolar magnetopause

Dorelli¹

2004

J. Geophys. Res.

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“…[2] Magnetic reconnection is believed to be a crucial process controlling plasma dynamics in the magnetosphere. Its occurrence in the magnetotail was predicted theoretically and verified by observations [e.g., Sonnerup, 1979;Semenov et al, 1998;Nagai et al, 2001].…”

Section: Introductionmentioning

confidence: 57%

“…Its occurrence in the magnetotail was predicted theoretically and verified by observations [e.g., Sonnerup, 1979;Semenov et al, 1998;Nagai et al, 2001].…”

Section: Introductionmentioning

confidence: 91%

Cluster observations of currents in the plasma sheet during reconnection

Alexeev

Owen

Fazakerley

et al. 2005

Geophysical Research Letters

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[1] We present Cluster PEACE observations of parallel electron currents near a reversal of accelerated ion flows which indicated that the spacecraft were in the vicinity of an active reconnection X-line (XL). Moments calculated from the PEACE electron spectrometer 3D 4s resolution data are analysed. We surveyed the electron current structure to reveal their dependence on distance from the neutral sheet (NS). The electron density and the magnetic field component parallel to the lobe magnetic field were selected as proxies of the distance to the NS. We found that earthward from the XL the electron parallel current switches direction: tailward closer to the NS and earthward nearer to the lobe. On the interface between the tailward and earthward currents we found a narrow layer of strong earthward current. At the same place the largest transverse magnetic disturbances were detected. The observed current structure is consistent with the collisionless reconnection model. However, tailward of the XL no such structure was evident in the data.Citation: Alexeev, I.

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“…The outflow region is bounded by branches of a bifurcated current sheet. This scheme is supported by MHD simulations [e.g., Ugai and Tsuda , 1977; Sato and Hayashi , 1979] and analytical solutions [e.g., Semenov et al , 1998].…”

Section: Introductionmentioning

confidence: 99%

Current sheet structure near magnetic X‐line observed by Cluster

Runov

Nakamura

Baumjohann

et al. 2003

Geophysical Research Letters

256

262

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[1] During the interval 0947 -0951 UT on 1 October 2001, when Cluster was located at X GSM = À16.4 R E near Z GSM = 0 in the pre-midnight magnetotail, the Cluster barycenter crosses the neutral sheet four times. High speed proton flow, with reversal from tailward to Earthward, was detected during the crossings. Using a linear gradient/curl estimator technique we estimate current density and magnetic field curvature within the crossings. These observations exhibit the tailward passage of an X-line over the Cluster tetrahedron. These current sheet has a bifurcated structure in the regions of tailward and earthward flows and a flat and/or slightly bifurcated thin current sheet in between. A distinct quadrupolar Hall magnetic field component was observed.

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Analysis of time‐dependent reconnection in compressible plasmas

Cited by 10 publications

References 15 publications

A new look at driven magnetic reconnection at the terrestrial subsolar magnetopause

A new look at driven magnetic reconnection at the terrestrial subsolar magnetopause

Cluster observations of currents in the plasma sheet during reconnection

Current sheet structure near magnetic X‐line observed by Cluster

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