Ion temperature drop and quasi‐electrostatic electric field at the current sheet boundary minutes prior to the local current disruption

Liang, J.; Liu, W. W.; Donovan, E.

doi:10.1029/2009ja014357

Cited by 18 publications

(45 citation statements)

References 73 publications

(127 reference statements)

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“…12. The latter seems to line up with a result from a survey performed by Liang et al, [30] in the near-Earth plasma sheet. They studied cross-tail current disruption (CD) events and identified that "when the current sheet thickness is down to ion kinetic scales, the ions are demagnetized, and a quasi-electrostatic neutral sheetpointing electric field emerges (at the current sheet boundary) owing to the charge separation".…”

Section: Physics Of the Harang Discontinuity (Hd)supporting

confidence: 85%

Anatomy of the Pulsating Double Layer Source in the Earth's Magnetotail

Sarafopoulos¹

2015

JESTR

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This investigation is composed of an observational part, plus a new theoretical model interpreting the related exhibited satellite datasets through an entirely new approach concerning the substorm's ultimate excitation mechanism. First, we present a few representative case studies showing the B z component of the magnetic field to develop quasi-periodic negative deflections with periodicities ranging from T=15 to 60s in the central plasma sheet (CPS) with persistent tailward plasma flows. The wave activity of B z is much lower outside the CPS, while occasionally almost a monochromatic response is identified. In certain cases, a profound change of frequency is evident and happens most probably due to the Doppler-effect; there is a relation between the plasma velocity enhancement and the increase of frequency. When comparing the amplitude of Bz deflections to the lobe magnetic field, one plausibly may infer that the deflections reflect the very dynamics of the source itself. Therefore, we put forward the concept about "a pulsating source", and more specifically, we adopt the pulsating "twin Double Layer (DL) structure" as the ultimate mechanism converting magnetic energy to kinetic. The DL acts either as a resistor or a capacitor and the twin-DL structure approximately behaves in a way similar to the cardiac cycle with repeated, rhythmic contractions and expansions. The contraction phase represents the abrupt local thinning of the plasma sheet (PS) that terminates explosively, heating the plasma and accelerating energetic particles. The expansion phase corresponds to a local distention of the source, which also terminates explosively. The DLs are oppositely polarized depending on the range of Rc whether it fulfills the condition r gi ≤ R c < 9 r gi or r ge < R c < r gi , where r gi (r ge) and R c are the ion (electron) gyro-radius and the curvature radius of the local magnetic field, respectively. In more detail, the "akis structure", as it was earlier introduced by Sarafopoulos [1, 2] and further elaborated in this work, repetitively forms DLs that undergo a transition from depolarization to repolarization in each of the consecutive cycles. The collapse of the dissipation region (leading to local dipolarization) seems to occur when r ge < Rc < 9r ge. Large scale Boström's type II field aligned currents (FACs) flow and neutralize the net charges produced by "charge separation processes" within the twin-DL structure; thus the whole structure principally operates (under favorable conditions) like a huge resonant RLC-type circuit. Actually the pulsating source is an integral part of that huge (resonating) circuit, wherein even the ionosphere obviously plays its vital role imposing a positive feedback. The author of this study believes that Faraday's law can be experimentally validated with his suggested model more reliably than with the alternative X-type magnetic reconnection model incorporating the concept of "magnetic diffusion". The presently proposed "akis structure" embedded in the whole magnetotail's current sy...

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Section: Physics Of the Harang Discontinuity (Hd)supporting

confidence: 85%

Anatomy of the Pulsating Double Layer Source in the Earth's Magnetotail

Sarafopoulos¹

2015

JESTR

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“…Such bell‐shaped T i profiles were obtained by Catapano et al [] for the special type of ion velocity distributions. Similar profiles could be resulted from some combination of hot (current carrying) particle population and cold background population (see corresponding CS model in Yoon and Lui [] and Liang et al []). The scenario of plasma parameter projection along magnetic field lines predicts that the ion population observed at CS boundaries around r ∼ 10 R E with T B <3 keV travels along magnetic field lines from the distant tail r > 45 R E , where T 0 <3 keV.…”

Section: Discussionmentioning

confidence: 65%

Ion density and temperature profiles along (X_GSM) and across (Z_GSM) the magnetotail as observed by THEMIS, Geotail, and ARTEMIS

et al. 2017

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Characteristics of the two‐dimensional configuration of the magnetotail current sheet are important for modeling magnetotail motion/evolution and charged particle energization. Because of the magnetotail current sheet's dynamical nature, however, simultaneous plasma and magnetic field measurements at different radial distances are required to reveal this configuration. Simultaneous observations of the magnetotail current sheet from Time History of Events and Macroscale Interactions during Substorms (THEMIS) D (around 10RE downtail), Geotail (around 30RE downtail), and Acceleration, Reconnection, Turbulence and Electrodynamics of the Moons Interaction with the Sun (ARTEMIS) P1 (around 55RE downtail) are used to study distributions of plasma (ion) density and temperature along (Earth‐Sun direction) and across (north‐south direction) the magnetotail. Fourteen events (each including several current sheet crossings at different downtail distances) are studied. We demonstrate that the plasma temperature along and across the magnetotail varies more significantly than plasma density does. The temperature decrease from equatorial plane to current sheet boundaries is a major contributor to the cross‐tail pressure balance. The Alfven velocity VA,B calculated at the current sheet boundaries increases significantly toward the Earth from 700 km/s at lunar orbit ∼55RE to 2200 km/s around ∼10RE downtail. The corresponding energy EA=mpVA,B2 (mp is the proton mass) is 4 times larger than the plasma temperature T0 in the magnetotail's equatorial plane, whereas the ratio EA/T0 is constant along the magnetotail. The plasma temperature T0 measured around lunar orbit in the magnetotail agrees well with the simultaneously measured energy of solar wind protons mpVnormalSW2/2 (VSW is the solar wind speed).

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“…The real configuration could be of course more complicated. In addition to these two particle groups a “third” relatively cold plasma component with substantial density is often observed [ Liang et al , 2009; Artemyev et al , 2009]. Zhou et al [2009] and Liu et al [2010] modeled current sheets from the THEMIS observations, creating background sheets with much colder plasma.…”

Section: Discussionmentioning

confidence: 99%

Embedded current sheets in the Earth’s magnetotail

et al. 2011

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[1] In this investigation we introduce and discuss quantitative parameters of a thin current sheet embedded in the background plasma sheet. We use Cluster statistics and empirical models, as well as self-consistent simulations, to understand the formation and development of embedded current sheets, in particular in the course of substorms. Data and theory show that the embedded sheet thickness is of the order of a proton larmor radius, a constraint equivalent to magnetic flux conservation. The embedded sheet can be essentially described by two dimensionless parameters B 0 /B ext and F 0 /F ext . B 0 is the magnetic field at the embedded sheet boundary, B ext is the field at the boundary of the background plasma sheet, and F 0 and F ext are magnetic flux values. During the growth phase current density in embedded sheet and B 0 increase, while thickness decreases. Sheets with the most intense currents (large B 0 ) are observed after onset. The self-consistent anisotropic sheet model, including both electron and proton currents and combined with the Harris-type background shows that when the proton-scale embedded sheet becomes sufficiently thin, an electron-scale current sheet can appear inside it due to enhanced electron curvature drift.

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Ion temperature drop and quasi‐electrostatic electric field at the current sheet boundary minutes prior to the local current disruption

Cited by 18 publications

References 73 publications

Anatomy of the Pulsating Double Layer Source in the Earth's Magnetotail

Anatomy of the Pulsating Double Layer Source in the Earth's Magnetotail

Ion density and temperature profiles along (X_GSM) and across (Z_GSM) the magnetotail as observed by THEMIS, Geotail, and ARTEMIS

Embedded current sheets in the Earth’s magnetotail

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Ion temperature drop and quasi‐electrostatic electric field at the current sheet boundary minutes prior to the local current disruption

Cited by 18 publications

References 73 publications

Anatomy of the Pulsating Double Layer Source in the Earth's Magnetotail

Anatomy of the Pulsating Double Layer Source in the Earth's Magnetotail

Ion density and temperature profiles along (XGSM) and across (ZGSM) the magnetotail as observed by THEMIS, Geotail, and ARTEMIS

Embedded current sheets in the Earth’s magnetotail

Contact Info

Product

Resources

About

Ion density and temperature profiles along (X_GSM) and across (Z_GSM) the magnetotail as observed by THEMIS, Geotail, and ARTEMIS