Origin of some anisotropic tailward flows in the plasma sheet

Wanliss, J. A.; Sydora, R. D.; Rostoker, G.; Rankin, R.

doi:10.5194/angeo-20-1559-2002

Cited by 7 publications

(7 citation statements)

References 89 publications

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“…With the equilibrium current sheet model treated as the initial condition, test‐particle simulations can now be carried out to reproduce the observed evolution of the ion distributions (shown in Figures 2d–2f) as the front approaches. As was shown by Zhou et al [2009a], the modeled ion distributions are associated with the ion distributions at later times, on the basis of Liouville's theorem [e.g., Schwartz et al , 1998; Wanliss et al , 2002]. In other words, the ion distributions f ( r , v , t ) at time t can be determined by tracing the ion trajectories backward in time to obtain their initial locations r 0 and velocities v 0 within the modeled equilibrium at t 0 and equating f with the corresponding f ( r 0 , v 0 , t 0 ) values [ Zhou et al , 2009a].…”

Section: Simulations and Discussionmentioning

confidence: 99%

Accelerated ions ahead of earthward propagating dipolarization fronts

et al. 2010

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[1] We report on the evolving ion distributions associated with the arrival of an earthward propagating dipolarization front in the near-Earth magnetotail using Time History of Events and Macroscale Interactions during Substorms (THEMIS). Ion distributions exhibit steady duskward anisotropy well before the front arrival, suggesting thin current sheet formation at ∼11 R E , during the growth phase of a moderate geomagnetic substorm. As the dipolarization front moves closer, an additional, earthward streaming ion population appears, resulting in an earthward velocity moment. This population eventually overwhelms the preexisting duskward anisotropy and merges with the earthward convecting bulk flow once the dipolarization front arrives. Test-particle simulations show that the observed ion evolution is consistent with a picture of ions reflected and accelerated by the approaching front and moving ahead of it.Citation: Zhou, X.-Z., V. Angelopoulos, V. A. Sergeev, and A. Runov (2010), Accelerated ions ahead of earthward propagating dipolarization fronts,

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Section: Simulations and Discussionmentioning

confidence: 99%

Accelerated ions ahead of earthward propagating dipolarization fronts

et al. 2010

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“…Our approach to simulate the precursor flows ahead of DFs is based on Liouville's theorem [ Birn and Hesse , ; Schwartz et al ., ; Wanliss et al ., ; Zhou et al ., ; Marchand , ]. First, we use a two‐dimensional, Schindler‐type equilibrium [ Schindler , ] current sheet, with the magnetic field obtained from the magnetic vector potential given by…”

Section: Backward Tracing Liouville Simulationsmentioning

confidence: 99%

Characteristics of high‐latitude precursor flows ahead of dipolarization fronts

Zhou

Runov

et al. 2017

JGR Space Physics

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Dipolarization fronts (DFs), earthward propagating structures in the magnetotail current sheet characterized by sharp enhancements of northward magnetic field, are capable of converting electromagnetic energy into particle kinetic energy. The ions previously accelerated and reflected at the DFs can contribute to plasma flows ahead of the fronts, which have been identified as DF precursor flows in both the near‐equatorial plasma sheet and far from it, near the plasma sheet boundary. Using observations from the THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft, we show that the earthward particle and energy flux enhancements ahead of DFs are statistically larger farther away from the neutral sheet (at high latitudes) than in the near‐equatorial region. High‐latitude particle and energy fluxes on the DF dawnside are found to be significantly greater than those on the duskside, which is opposite to the dawn‐dusk asymmetries previously found near the equatorial region. Using forward and backward tracing test‐particle simulations, we then explain and reproduce the observed latitude‐dependent characteristics of DF precursor flows, providing a better understanding of ion dynamics associated with dipolarization fronts.

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“…With the initial condition determined, test particle simulations can then be carried out under prescribed electric and magnetic fields, as the second step, to simulate the evolution of ion distributions [ Zhou et al , 2009a]. Here the association between the ion distributions in the initial equilibrium and those at later times is provided by Liouville's theorem [ Schwartz et al , 1998; Wanliss et al , 2002]. In other words, the ion distributions f ( r , v , t ) at time t can be obtained by tracing ion trajectories backward in time to identify their initial locations r 0 and velocities v 0 within the modeled equilibrium at t 0 and equating f ( r , v , t ) with the corresponding f ( r 0 , v 0 , t 0 ) values.…”

Section: Simulationsmentioning

confidence: 99%

On the nature of precursor flows upstream of advancing dipolarization fronts

et al. 2011

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[1] Earthward propagating dipolarization fronts, interpreted as thin, vertical current sheets that separate plasmas of different origins in the Earth's magnetotail, are embedded within flow bursts, often near the leading edge of bursty bulk flows. Observations have also shown that bursty bulk flow onset typically precedes dipolarization front arrival by ∼1 min. Ion distribution functions reveal that earthward flows in advance of front arrival are often caused by the appearance of a new ion population atop a preexisting plasma sheet component. Particle simulations suggest that this second population, which contributes most to the plasma velocity, is composed of ions that have been reflected at and accelerated by the approaching front. We propose that in the presence of a finite upstream B z field, the reflected ions would be confined in a region with a size comparable to the ion thermal gyroradius over the upstream B z . THEMIS observations confirm that the measured time difference dt between the appearance of earthward plasma flows and the dipolarization front arrival is consistent with the predicted size of the ion accessibility region.Citation: Zhou, X.-Z., V. Angelopoulos, V. A. Sergeev, and A. Runov (2011), On the nature of precursor flows upstream of advancing dipolarization fronts,

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Origin of some anisotropic tailward flows in the plasma sheet

Cited by 7 publications

References 89 publications

Accelerated ions ahead of earthward propagating dipolarization fronts

Accelerated ions ahead of earthward propagating dipolarization fronts

Characteristics of high‐latitude precursor flows ahead of dipolarization fronts

On the nature of precursor flows upstream of advancing dipolarization fronts

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