Cross-field flow and electric potential in a plasma slab

Keyser, Johan De; Echim, Marius; Roth, M.

doi:10.5194/angeo-31-1297-2013

Cited by 14 publications

(13 citation statements)

References 33 publications

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“…Although there is a set of analytical models describing observed C‐ and S‐type magnetopause current sheets (Allanson et al, 2017; Artemyev, 2011; De Keyser et al, 2013; Harrison & Neukirch, 2009; Panov et al, 2011), investigation of plasma transport across the magnetopause require numerical simulations of dynamical systems. A small (kinetic) thickness of the magnetopause current sheet gives preference for such simulations to global hybrid models (Lin et al, 2014, 2017, Omidi et al, 2009, 2016), but combination of MHD simulations and test particle tracing (Peroomian, 2003; Peroomian & El‐Alaoui, 2008; Raeder et al, 2000) is also useful tool for such investigations.…”

Section: Discussionmentioning

confidence: 99%

Comparison of the Flank Magnetopause at Near‐Earth and Lunar Distances: MMS and ARTEMIS Observations

et al. 2020

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One of the main sources of magnetospheric particles is solar wind penetration through the magnetopause-a current sheet separating the cold, dense magnetosheath from the hot, rarified magnetospheric plasmas. The mechanism responsible for magnetosheath particle transport across the magnetopause has been better investigated for the near-Earth dayside magnetopause (contrary to the nightside), where it was found that such a transport is controlled by the current sheet thickness, structure, and dynamics. Because plasma properties and magnetic field intensity in the magnetosheath significantly change as a function of radial distance from the Earth, the current sheet characteristics are different near Earth and at distant nightside magnetopause. Comparative investigations between near-Earth and distant magnetopauses, however, require statistical observations at the two locations during the same time interval, that enable control for the same upstream solar wind driving conditions. In this paper, we perform such a study using the four Magnetosheric Multiscale (MMS) and two Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) probes to compare the characteristics of magnetic field and plasma populations during magnetopause crossings, which are separated by about 50 R E. We find that the current sheet profiles is similar at two locations. We also show that the magnetopause current sheet thickness scales with the local magnetosheath ion gyroradius. A weaker magnetic field on both sides of the current sheet is correlated with smaller current density at lunar distances.

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Section: Discussionmentioning

confidence: 99%

Comparison of the Flank Magnetopause at Near‐Earth and Lunar Distances: MMS and ARTEMIS Observations

et al. 2020

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“…According to MHD theory, plasma discontinuities are classified into tangential discontinuities (which separate two plasmas with different characteristics), rotational discontinuities (which move relative to the plasmas on the two sides, accelerating the plasma population that crosses them), and shock waves (Hudson, ; Landau & Lifshitz, ). This classification, however, does not describe a discontinuity's internal (kinetic) structure, which can vary, even for the same discontinuity type (see, e.g., Artemyev, ; De Keyser et al, ; Harrison & Neukirch, ; Panov et al, ; Vasko et al, ). Therefore, investigation of a discontinuity's contribution to charged particle heating and acceleration in the solar wind requires detailed observational information about its configuration.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Properties of Solar Wind Discontinuities at 1 AU Observed by ARTEMIS

2019

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Because solar wind plasma flow transports the entire spectrum of magnetic field fluctuations (from low-frequency inertial range to electron kinetic range), it is a natural laboratory for plasma turbulence investigation. Among the various wave modes and coherent plasma structures that contribute to this spectrum, one of the most important solar wind elements is ion-scale solar wind discontinuities. These structures, which carry very intense current, have been considered as a free energy source for plasma instabilities that contribute to solar wind heating. Investigations of such discontinuities have been mostly focused on their magnetic field signatures; much less is known about plasma kinetics around them. Using statistics of such discontinuities observed around the Earth (∼1 AU) by two spacecraft from the Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) mission, we demonstrate that they are accompanied by density and temperature variations with a spatial scale of tens of ion inertial lengths. Inversely correlated density and temperature variations suggest the discontinuity configuration is nearly force free. The discontinuities are typified by two spatial scales, an intense current layer (>1 nA/m 2), and a much broader current layer structure enveloping them. The magnetic field rotation occurs at the large scale, whereas at the small (inner) scale the plasma pressure gradients provide the pressure balance. We find that the electron kinetic behavior around the discontinuities strongly depends on electron energy: Whereas the pitch-angle distribution of near-thermal electrons (10-30 eV) changes significantly across discontinuities, hot (100-1,000 eV) electrons retain their properties on the two sides, suggesting they are able to cross the discontinuities freely. Exploring these and other kinetic characteristics of discontinuities, we discuss possible mechanisms of formation/evolution of these structures.

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“…These flow shears directly lead to multiple FAC sheets that join together in the cusp region in both hemispheres and field-aligned acceleration of electrons which create multiple cusp-aligned auroral arcs both in the polar cap and auroral oval. This is a general mechanism for the formation of auroral arcs due to field-aligned acceleration of electrons through the Knight’s current-voltage process ( 36 , 37 ) caused by the FAC sheets that are generated by the strong flow shears in the magnetosphere ( 31 , 32 , 39 – 41 ). With a roughly stable IMF and fast solar wind speed conditions, the stable and multiple transpolar arcs, presented in this paper, cannot be fully explained by the previous models or theories, for example, the twisting magnetotail model due to IMF B y switching ( 3 , 21 , 22 ), the model of tail reconnection during IMF northward nonsubstorm intervals ( 4 , 7 ), and the interchange instability model ( 18 , 19 ), as well as the simulation model of small-scale sun-aligned arcs on closed field lines ( 25 ).…”

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confidence: 99%

Multiple transpolar auroral arcs reveal insight about coupling processes in the Earth’s magnetotail

Zhang

Wang

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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A distinct class of aurora, called transpolar auroral arc (TPA) (in some cases called “theta” aurora), appears in the extremely high-latitude ionosphere of the Earth when interplanetary magnetic field (IMF) is northward. The formation and evolution of TPA offers clues about processes transferring energy and momentum from the solar wind to the magnetosphere and ionosphere during a northward IMF. However, their formation mechanisms remain poorly understood and controversial. We report a mechanism identified from multiple-instrument observations of unusually bright, multiple TPAs and simulations from a high-resolution three-dimensional (3D) global MagnetoHydroDynamics (MHD) model. The observations and simulations show an excellent agreement and reveal that these multiple TPAs are generated by precipitating energetic magnetospheric electrons within field-aligned current (FAC) sheets. These FAC sheets are generated by multiple-flow shear sheets in both the magnetospheric boundary produced by Kelvin–Helmholtz instability between supersonic solar wind flow and magnetosphere plasma, and the plasma sheet generated by the interactions between the enhanced earthward plasma flows from the distant tail (less than −100 RE) and the enhanced tailward flows from the near tail (about −20 RE). The study offers insight into the complex solar wind-magnetosphere-ionosphere coupling processes under a northward IMF condition, and it challenges existing paradigms of the dynamics of the Earth’s magnetosphere.

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Cross-field flow and electric potential in a plasma slab

Cited by 14 publications

References 33 publications

Comparison of the Flank Magnetopause at Near‐Earth and Lunar Distances: MMS and ARTEMIS Observations

Comparison of the Flank Magnetopause at Near‐Earth and Lunar Distances: MMS and ARTEMIS Observations

Kinetic Properties of Solar Wind Discontinuities at 1 AU Observed by ARTEMIS

Multiple transpolar auroral arcs reveal insight about coupling processes in the Earth’s magnetotail

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