Temperature anisotropies of electrons and two-component protons in the dusk plasma sheet

Nishino, Masaki N.; Fujimoto, M.; Terasawa, T.; Ueno, G.; Maezawa, K.; Mukai, T.; Saito, Y.

doi:10.5194/angeo-25-1417-2007

Cited by 11 publications

(14 citation statements)

References 56 publications

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“…Figures 2i–2k show the total, parallel and perpendicular components of the ion and electron temperatures, as well as their ratios. Compatible with previous boundary layer observations for higher M A [ Hasegawa et al , 2003; Nishino et al , 2007a], electrons show parallel temperature anisotropy in the boundary layers while ions are more isotropic. By contrast, ions have a perpendicular anisotropy in the magnetosheath while electrons are more isotropic.…”

Section: Discussionsupporting

confidence: 87%

Tracing solar wind plasma entry into the magnetosphere using ion‐to‐electron temperature ratio

Lavraud

Borovsky

Génot

et al. 2009

Geophysical Research Letters

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When the solar wind Mach number is low, typically such as in magnetic clouds, the physics of the bow shock leads to a downstream ion‐to‐electron temperature ratio that can be notably lower than usual. We utilize this property to trace solar wind plasma entry into the magnetosphere by use of Cluster measurements in the vicinity of the dusk magnetopause during the passage of a magnetic cloud at Earth on November 25, 2001. The ion‐to‐electron temperature ratio was indeed low in the magnetosheath (Ti/Te ∼ 3). In total, three magnetopause boundary layer intervals are encountered on that day. They all show that the low ion‐to‐electron temperature ratio can be preserved as the plasma enters the magnetosphere, and both with and without the observation of Kelvin‐Helmholtz activity. This suggests that the ion‐to‐electron temperature ratio in the magnetopause boundary layer, which is usually high, is not prescribed by the heating characteristics of the plasma entry mechanism that formed these boundary layers. In the future, this property may be used to (1) further trace plasma entry into inner regions and (2) determine the preferred entry mechanisms if other theoretical, observational and simulation works can give indications on which mechanisms may alter this ratio.

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Section: Discussionsupporting

confidence: 87%

Tracing solar wind plasma entry into the magnetosphere using ion‐to‐electron temperature ratio

Lavraud

Borovsky

Génot

et al. 2009

Geophysical Research Letters

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“…In contrast, under northward IMF, the E 0 distribution for the single component plasma sheet is similar to the distribution of E 0c for the dual component plasma sheet ( Figure 9A). Given that the cold dense plasma sheet is reported for northward IMF and thought to form through the entry of cold plasma into the tail [e.g., Fujimoto et al, 1998;Nishino et al, 2007a], our results could be interpreted as showing that the hot population is generally present in the plasma sheet but the cold component increases with increasing duration of northward IMF. The distributions of the A parameters are consistent with this: The modal A c for northward IMF is higher than that for southward IMF, while the modal A h for northward IMF is lower than that for southward IMF (Figures 9c and 9d).…”

Section: Discussionmentioning

confidence: 65%

“…Transport through the flank magnetopause, perhaps via reconnection in rolled‐up Kelvin‐Helmholtz vortices [ Hasegawa et al , ], is thought to be responsible for the presence of cold ions in the magnetotail under northward IMF. Cold electrons with a dominant parallel component have been observed contemporaneously with the two component ion plasma sheet [ Nishino et al , ] and indeed close to a Kelvin‐Helmholtz vortex [ Nishino et al , ], so it is possible that the persistent cold component reported here also has a magnetosheath source.…”

Section: Discussionmentioning

confidence: 66%

Sources of electron pitch angle anisotropy in the magnetotail plasma sheet

et al. 2013

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[1] We survey the properties of electron pitch angle distributions in the magnetotail plasma sheet at a distance between 15 and 19 R E from the Earth, using data from the Plasma Electron and Current Experiment (PEACE) instrument. We limit our survey to those pitch angle distributions measured when the interplanetary magnetic field (IMF) had been steadily northward or steadily southward for the previous 3 h. We find that, at sub-keV energies, the plasma sheet electron pitch angle distribution has an anisotropy such that there is a higher differential energy flux of electrons in the (anti-) field-aligned directions. Fitting the measured pitch angle distributions with both a single and two component kappa distribution reveals that this anisotropy is the result of the presence of a second, cold, component of electrons that is observed more often than not, and occurs during both the northward and southward IMF intervals. We present evidence that suggests the cold electron component has an ionospheric, rather than magnetosheath, source and is linked to the large-scale field-aligned current systems that couple the magnetosphere and ionosphere.

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“…[58] Also, Nishino et al [2007] show by using data from Geotail that bidirectional ion beams with each component showing strong perpendicular heating, which probably arises from magnetic reconnection, are observed in the vortex that rolled-up in the tail-LLBL during northward IMF conditions. While the ion beams are observed inside the magnetopause, such ions are cold, and therefore probably of the magnetosheath origin.…”

Section: Observations Of Type I Reconnectionmentioning

confidence: 99%

Structure of an MHD‐scale Kelvin‐Helmholtz vortex: Two‐dimensional two‐fluid simulations including finite electron inertial effects

2008

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[1] Our two-dimensional two-fluid simulations including finite electron inertial effects of an MHD-scale Kelvin-Helmholtz (KH) vortex show that the plasma mixing and transport across the Earth's tail-magnetopause during northward interplanetary magnetic field (IMF) conditions can be caused by the coupling between the KH vortex and magnetic reconnection. First, it is found by systematical two-dimensional simulations under various fundamental conditions that two types of magnetic reconnection are driven in a KH vortex that are crucial factors for determining the structure of the KH vortex itself. One, named ''type I reconnection,'' occurs in the case where the magnetic field components along the k vector of Kelvin-Helmholtz instability (KHI) are antiparallel across the velocity shear layer (antiparallel case). Another, named ''type II reconnection,'' is driven in the case where the velocity shear is strong enough to produce highly rolled-up KH vortices and highly stretched field lines therein (strong KHI case). It is also found that type I reconnection leads directly to plasma mixing across the shear layer and that type II reconnection forms magnetic islands and plasma contained in these magnetic islands can be transferred from one side to the other across the shear layer. Next, linear analyses of the Earth's magnetopause-like cases under northward IMF show that the antiparallel case is obtained rather commonly and also that there is a significant possibility that the strong KHI case may be important. Furthermore, two-fluid simulations of the magnetopause-like cases actually show the occurrence of type I and type II reconnection in two dimensions. These results indicate that type I and type II reconnection may play a substantial role in the plasma mixing and transport across the magnetopause.

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Temperature anisotropies of electrons and two-component protons in the dusk plasma sheet

Cited by 11 publications

References 56 publications

Tracing solar wind plasma entry into the magnetosphere using ion‐to‐electron temperature ratio

Tracing solar wind plasma entry into the magnetosphere using ion‐to‐electron temperature ratio

Sources of electron pitch angle anisotropy in the magnetotail plasma sheet

Structure of an MHD‐scale Kelvin‐Helmholtz vortex: Two‐dimensional two‐fluid simulations including finite electron inertial effects

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