Cluster observation of a bifurcated current sheet

Runov, A.; Nakamura, R.; Baumjohann, W.; Zhang, T. L.; Volwerk, M.; Eichelberger, Hans; Balogh, A.

doi:10.1029/2002gl016136

Cited by 160 publications

(216 citation statements)

References 13 publications

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“…Karimbadi et al (2003) showed by full particle and hybrid simulations that the velocity shear, resulting from the presence of secondary ion population, drives the ion-ion kink (IIK) mode instability, which produces B x variations similar to the observed, and a displacement of the current peak from the sheet center to lobes. The calculated wavelength (2.8 R E ) and period (90 s) are close to the values which were found by Runov et al (2003) and Sergeev et al (2003).…”

Section: Discussionsupporting

confidence: 68%

“…4) show that the current density is larger near the current sheet-lobe boundary than in the centre (B x =0). As was shown by Runov et al (2003) the current sheet has a bifurcated structure with off-center maximum of the vertical gradient of the magnetic field during this interval. It was also found that the set of B x variations during interval C is caused by waves propagating in the +Y direction polarized in Y −Z plane.…”

Section: Introductionmentioning

confidence: 95%

“…The spatial structure of the magnetic field gradient during this interval was studied by Runov et al (2003). It was found that the current density has a maximum value at B x ∼0, which is expected from standard models.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper we extend the analysis by Runov et al (2003) of the bifurcated current sheet, observed by Cluster on 29 August 2001, using solar wind data, ground-based data and data from the Cluster/CIS (Rème et al , 2001) records, H e -and H p -components from the GOES-10 spacecraft during 06:00-12:00 UT.…”

Section: Introductionmentioning

confidence: 99%

“…Runov et al (2003) studied the orientation and structure of the current sheet during 10:55-11:07 UT on 29 August 2001 by the analysis of multi-point magnetic field measurements. Using the Cluster tetrahedron configuration the vertical magnetic field gradient was estimated as a difference between X GSM components of the magnetic field, measured by three spacecraft, forming a triangle in a plane approximately parallel to the magnetic equator and fourth spacecraft, located 1700 km southward.…”

Section: Introductionmentioning

confidence: 99%

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Properties of a bifurcated current sheet observed on 29 August 2001

et al. 2004

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Abstract. Ion density, velocity and temperature, measured by Cluster spacecraft in the plasma sheet during an isolated substorm at 10:20-11:15 UT, 29 August 2001 are discussed. The Custer/CODIF data for subinterval 10:55-11:03 UT, during which a bifurcation of the current sheet was detected, are studied in particular. It is shown that ion density and temperature have a plateau-like profile in the central part of the bifurcated current sheet. An enhanced proton flow directed in positive Y GSM was detected during the selected subinterval. Other components of proton bulk velocity are found to be negligibly small, i.e. the structure is likely not directly associated with magnetic reconnection. Alternative models, including ion anisotropy and localized magnetic turbulence, which result in a two-peak profile of the current density, are discussed briefly.

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Section: Discussionsupporting

confidence: 68%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Properties of a bifurcated current sheet observed on 29 August 2001

et al. 2004

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Collisionless resistivity in a bifurcated current sheet

Andriyas

Spencer

2014

JGR Space Physics

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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.

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Revisit of Alfvén ballooning modes in isotropic, ideal MHD plasmas: Effect of diamagnetic condition

John

Hirose

2014

JGR Space Physics

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Alfvén ballooning modes provide an important mechanism to explain explosive phenomena in regions where field lines transit from dipole-like to taillike shapes. However, commonly used analytical results were unable to recover Alfvén modes in uniform plasmas and basic ballooning mode in inhomogeneous plasmas. We rigidly revisited previous work on isotropic, ideal magnetospheric plasmas and found where the problems occurred. This paper shows accurate expressions of the ballooning modes. Under the dimagnetic condition (an infinite k y ), the modes have two groups depending on the relations of the three equilibrium parameters: plasma , pressure gradient k p , and magnetic curvature k c (magnetic gradient k B is no more than a tenth of k c and thus neglected in magnetotail plasma). If the constraint is relaxed (a finite k y ), the dispersion relation includes the following: (1) the fast compressional Alfvén branch; (2) two groups of ballooning instabilities: Group 1 appears when k p is independent of , and Group 2 emerges when k c is independent of ; and (3) in Group 1, a critical exists above which the wave mode becomes unstable, while the perpendicular wave number (k ⟂ ) affects the instability by modulating the critical values; by contrast, in Group 2, there is no critical , and the wave keeps its original stable or unstable mode, while k ⟂ has a critical value above which the wave mode becomes unstable.

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Cluster observation of a bifurcated current sheet

Cited by 160 publications

References 13 publications

Properties of a bifurcated current sheet observed on 29 August 2001

Properties of a bifurcated current sheet observed on 29 August 2001

Collisionless resistivity in a bifurcated current sheet

Revisit of Alfvén ballooning modes in isotropic, ideal MHD plasmas: Effect of diamagnetic condition

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