Cluster as current sheet surveyor in the magnetotail

Narita, Yasuhito; Nakamura, R.; Baumjohann, W.

doi:10.5194/angeo-31-1605-2013

Cited by 17 publications

(15 citation statements)

References 22 publications

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“…The Harris current sheet model [ Harris , ] is the one‐dimensional equilibrium solution to the Maxwell‐Vlasov equation that describes the planetary magnetotail magnetic field structure in the

Z_{normalM normalS normalM}^{'}

direction. It has been used extensively in magnetotail studies by Cluster [e.g., Nakamura et al ., ; Narita et al ., ] and reconnection simulations [e.g., Birn et al ., ]. The relationship between B X and the cross‐tail current density ( J Y ) is given by

B_{X} ((), z) = B_{0} normaltan h ((), \frac{z - z_{0}}{L})

J_{Y} ((), z) = \frac{B_{0}}{μ_{0} L} normalsec h^{2} ((), \frac{z - z_{0}}{L})

where B 0 is the asymptotic lobe field, z 0 is the north‐south position of the CS center, and L is the characteristic half‐thickness of the CS.…”

Section: Discussionmentioning

confidence: 99%

Mercury's cross‐tail current sheet: Structure, X‐line location and stress balance

Poh

Slavin

Jia

et al. 2017

Geophysical Research Letters

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The structure, X‐line location, and magnetohydrodynamic (MHD) stress balance of Mercury's magnetotail were examined between −2.6 < XMSM < −1.4 RM using MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) measurements from 319 central plasma sheet (CPS) crossings. The mean plasma β in the CPS calculated from MESSENGER data is ~ 6. The CPS magnetic field was southward (i.e., tailward of X‐line) ~ 2–18% of the time. Extrapolation of downtail variations in BZ indicates an average X‐line location at −3 RM. Modeling of magnetic field measurements produced a cross‐tail current sheet (CS) thickness, current density, and inner CS edge location of 0.39 RM, 92 nA/m2 and −1.22 RM, respectively. Application of MHD stress balance suggests that heavy planetary ions may be important in maintaining stress balance within Mercury's CPS. Qualitative similarities between Mercury's and Earth's magnetotail are remarkable given the differences in upstream conditions, internal plasma composition, finite gyro‐radius scaling, and Mercury's lack of ionosphere.

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Z_{normalM normalS normalM}^{'}

B_{X} ((), z) = B_{0} normaltan h ((), \frac{z - z_{0}}{L})

J_{Y} ((), z) = \frac{B_{0}}{μ_{0} L} normalsec h^{2} ((), \frac{z - z_{0}}{L})

where B 0 is the asymptotic lobe field, z 0 is the north‐south position of the CS center, and L is the characteristic half‐thickness of the CS.…”

Section: Discussionmentioning

confidence: 99%

Mercury's cross‐tail current sheet: Structure, X‐line location and stress balance

Poh

Slavin

Jia

et al. 2017

Geophysical Research Letters

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“…Dunlop et al 2002Dunlop et al , 2005Haaland et al 2004;Panov et al 2006); the magnetotail current sheet (e.g. Runov et al 2006;Nakamura et al 2008;Narita et al 2013); the ring current and inner magnetosphere (e.g. Vallat et al 2005;Shen et al 2014;Yang et al 2016); field-aligned currents (FAC, e.g.…”

Section: Key Regions Covered By Related Methodologymentioning

confidence: 99%

Multi-spacecraft Current Estimates at Swarm

Dunlop

Yang

Yang³

et al. 2019

Ionospheric Multi-Spacecraft Analysis Tools

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In this chapter the application of the curlometer technique to various regions of the inner magnetosphere and upper ionosphere and for special circumstances of sampling is described. The basic technique is first outlined, together with the caveats of use, covering: the four-spacecraft technique, its quality factor and limitations; the lessons learnt from Cluster data, together with issues of implementation, scale size and stationarity, and description of the key regions covered by related methodology. Secondly, the application to the Earth's ring current region is outlined, covering: the application of Cluster crossings to survey the ring current; the use of the MRA (magnetic rotation analysis) method for field curvature analysis; the use of THEMIS (Time History of Events and Macroscale Interactions during Sub-storms mission) three-spacecraft configurations to sample the ring current, and future use of MMS (Magnetospheric MultiScale mission) and Swarm data, i.e. the case of small separations. Thirdly, the application of the technique to the low altitude regions covered by Swarm is outlined, covering: the extension of the method to stationary signals; the use of special configurations and adjacent times to achieve 2, 3, 4, 5 point analysis; the use of the extended 'curlometer' with Swarm close configurations to compute 3-D current density, and a brief indication of the computation of current sheet orientation implied by 2-spacecraft correlations. Fourthly, the direct coordination of Cluster and Swarm to check the scaling and coherence of field-aligned currents (FACs) is outlined.

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“…The use of nearly 7 years THEMIS data allowed us to assess basic properties of the current sheet for the first time. The four‐spacecraft Cluster mission has revealed a vertical profile of the tail current sheet by direct measurements during current sheet crossings and has shown the presence of a non‐Harris current sheet [e.g., Runov et al ., ; Asano et al ., ; Narita et al ., ]. In these studies, the obtained current sheet structure was based on a limited number of event‐based studies.…”

Section: Discussionmentioning

confidence: 99%

THEMIS two‐point measurements of the cross‐tail current density: A thick bifurcated current sheet in the near‐Earth plasma sheet

Saito

2015

JGR Space Physics

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The basic properties of the near‐Earth current sheet from 8 RE to 12 RE were determined based on Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations from 2007 to 2013. Ampere's law was used to estimate the current density when the locations of two spacecraft were suitable for the calculation. A total of 3838 current density observations were obtained to study the vertical profile. For typical solar wind conditions, the current density near (off) the central plane of the current sheet ranged from 1 to 2 nA/m2 (1 to 8 nA/m2). All the high current densities appeared off the central plane of the current sheet, indicating the formation of a bifurcated current sheet structure when the current density increased above 2 nA/m2. The median profile also showed a bifurcated structure, in which the half thickness was about 3 RE. The distance between the peak of the current density and the central plane of the current sheet was 0.5 to 1 RE. High current densities above 4 nA/m2 were observed in some cases that occurred preferentially during substorms, but they also occurred in quiet times. In contrast to the commonly accepted picture, these high current densities can form without a high solar wind dynamic pressure. In addition, these high current densities can appear in two magnetic configurations: tail‐like and dipolar structures. At least two mechanisms, magnetic flux depletion and new current system formation during the expansion phase, other than plasma sheet compression are responsible for the formation of the bifurcated current sheets.

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Cluster as current sheet surveyor in the magnetotail

Cited by 17 publications

References 22 publications

Mercury's cross‐tail current sheet: Structure, X‐line location and stress balance

Mercury's cross‐tail current sheet: Structure, X‐line location and stress balance

Multi-spacecraft Current Estimates at Swarm

THEMIS two‐point measurements of the cross‐tail current density: A thick bifurcated current sheet in the near‐Earth plasma sheet

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