Plasma sheet thickness and electric currents

Kaufmann, Richard L.; Ball, B. M.; Paterson, W. R.; Frank, L. A.

doi:10.1029/2000ja000284

Cited by 44 publications

(79 citation statements)

References 38 publications

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“…The tendency for a component of the bulk flow to point away from midnight has been noted previously [Kaufmann et al, 2001;Wang et al, 2006]. This behavior suggests a source of plasma near midnight associated with flow toward the neutral sheet from the outer plasma sheet and the subsequent flow away from midnight in the neutral sheet.…”

Section: Energy Transport Sorted By F Cmentioning

confidence: 83%

Ion heat flux and energy transport near the magnetotail neutral sheet

Kaufmann

Paterson

2008

J. Geophys. Res.

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[1] Ten-year averages of energy transport rates near the neutral sheet showed that the enthalpy flux density or thermal energy term Q T = (5/2)PV was the largest, where P is the isotropic pressure and V is the bulk flow velocity. The ion heat flux, q i , was the next largest term. Sorting data using a magnetic flux transport parameter showed that q i could become dominant during periods of slow flow. Both q i and the ion bulk velocity V i were duskward on the dusk side of the neutral sheet. This relationship is characteristic of crosstail drift and a heat flux that can be attributed to the energy dependent gradient and curvature drifts. The q i and V i vectors often pointed in different directions on the dawn side. The x component of q i on the dawn side pointed tailward, suggesting entry through the magnetopause of a suprathermal ion component. On the dusk side the q ix plots that were sorted using a magnetic flux transport parameter showed evidence of plasma sheet reconnection. The long-term averaged x component of Q T pointed earthward almost everywhere in the neutral sheet, and was attributed to periods of very fast plasma flow. The cross-tail component of Q T was separated into two contributions. One part of Q Ty involved a common drift away from midnight during both earthward and tailward fast flows. This feature suggests that thermal energy and plasma flow from the outer plasma sheet toward the neutral sheet near midnight, and then toward the flanks. The other part of Q Ty involved a differential duskward drift during fast earthward flows and a dawnward drift during fast tailward flows. The incremental E fields that would produce such convection point tailward during the fastest earthward flows and earthward during the fastest tailward flows. The dependencies of V i , q i and Q T on the interplanetary magnetic field (IMF) clock angle also were studied. Both V i and Q T were reduced when the IMF was northward and the neutral sheet plasma became cold and dense. However, no dependence of q i on the IMF direction was seen. This shows that the generation of a cold dense plasma sheet does not substantially change the distribution of the suprathermal ions that are most important in the production of q i .Citation: Kaufmann, R. L., and W. R. Paterson (2008), Ion heat flux and energy transport near the magnetotail neutral sheet,

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Section: Energy Transport Sorted By F Cmentioning

confidence: 83%

Ion heat flux and energy transport near the magnetotail neutral sheet

Kaufmann

Paterson

2008

J. Geophys. Res.

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“…Values of the current density resulting from the linear estimation of the ∇×B are underestimated, because of the relatively large inter-spacecraft separation during the 2001 tail period, however, typically they are by a factor of 2 larger than the values obtained by analysis of longer crossings (3.5 nA/m 2 , Zhang et al, 2005) and statistical values of the current density in the plasma sheet, calculated from measured ion and electron moments (1-3 nA/m 2 , Kaufmann et al, 2001). …”

Section: Discussionmentioning

confidence: 99%

Electric current and magnetic field geometry in flapping magnetotail current sheets

et al. 2005

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Abstract. Using four-point magnetic field measurements by the Cluster spacecraft, we statistically analyze the magnetic field and electric current configurations during rapid crossings of the current sheet observed in July-October 2001 at geocentric distances of 19 R E . The database includes 78 crossings, specially selected to apply multi-point data analysis techniques to calculate vector derivatives. Observed bipolar variations of j z , often with |j z |>j y , indicate that the electric currents follow kinks of the current sheet. The current density varies between 5-25 nA/m 2 . The half-thickness of the current sheet during flapping varies over a wide range, from 1 to 20 ion thermal gyroradii (L cp , calculated from average temperature and lobe magnetic field for each crossing). We found no relationship between the tilt angle of the current sheet normal and the half-thickness. In 68 cases the magnetic field curvature vector has a positive (earthward) X-component. Ten cases with a negative (tailward) curvature, associated with reconnection, were detected within 0

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“…Besides, the main convection component in the middle tail during the quiet periods (without BBFs) is the dawn-dusk drift velocity. Taking into account the substantial contribution of the fast flows to the convection, we can expect that the vortex plasma motion, accompanying the BBFs, plays a significant role in the formation of a cross-tail component of the average convection pattern (Hori et al, 2000;Kaufmann et al, 2001). …”

Section: Discussionmentioning

confidence: 99%

“…Our survey of individual events shows that during the isolated V x enhancement above the average level (that is, above several tens km/s, according to Kaufmann et al, 2001), the V y flows often display a complicated variation at smaller time-scale. In this case the episodes with V y >V thr are shorter than those with V x >V thr for the same threshold value.…”

Section: Relationship Of Large V Y Events With the High-speed Plasma mentioning

confidence: 99%

“…Sergeev and Lennartsson, 1988;Borodkova et al, 2002). Recently, the average plasma sheet flow pattern in the XY plane was obtained by Hori et al (2000) and Kaufmann et al (2001) by averaging the Geotail velocity measurement for a few years. An important feature of this average pattern is the large flow velocity (100-200 km/s) in the region X<−15 R E , −5 R E <Y <10 R E , where a significant V y component is also observed.…”

Section: Introductionmentioning

confidence: 99%

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Cross-tail velocity component in the plasma sheet fast flows

Dmitrieva

2008

Ann. Geophys.

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Abstract. The flux transfer in the magnetotail plasma sheet is mainly provided by the tail-aligned fast plasma flows (Bursty Bulk Flows -BBFs). In this paper we study the events with a large cross-tail velocity component, including their occurrence and relationship to the standard BBFs. We found out that a significant part of large V y events are a subgroup connected with the BBFs propagation. The maximal deviation of the velocity vector from the X direction (about 40-50 degrees, on average) is observed near the BBFs' leading front in the sheath, where the fast flow interacts with surrounding plasma. The average variation of the velocity direction in the vicinity of the BBF resembles a plasma vortex. Our results support the model, in which the BBF represents a polarized, bubble-like flux tube, propagating through the plasma sheet.

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Plasma sheet thickness and electric currents

Cited by 44 publications

References 38 publications

Ion heat flux and energy transport near the magnetotail neutral sheet

Ion heat flux and energy transport near the magnetotail neutral sheet

Electric current and magnetic field geometry in flapping magnetotail current sheets

Cross-tail velocity component in the plasma sheet fast flows

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