Self‐consistent current sheet structures in the quiet‐time magnetotail

Holland, D. L.; Chen, James

doi:10.1029/93gl01976

Cited by 44 publications

(46 citation statements)

References 16 publications

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“…We consider moderate turbulence levels, and we pay attention to the anisotropy of the injected ion distribution function, that is to the ratio =v th /v D between the thermal velocity v th and the drift velocity of ions along the average magnetic field v D . We find that also influences the current sheet profile: for sufficient fluctuation levels the double current peak is formed, while moderately large values of lead to the formation of diamagnetic (negative) current wings, as predicted by self-consistent kinetic studies in the absence of turbulence (Holland and Chen, 1993;Malova et al, 2000;Zelenyi et al, 2000). Conversely, for small values of the negative current wings disappear.…”

Section: Introductionmentioning

confidence: 72%

“…Hence, the influence of turbulence is not simply pitch angle scattering, but comprises a diffusive slowing of ordered motion. Clearly, the scenario is different in the absence of turbulence, when the whole current profile depends on the anisotropy and on the way the current sheet is populated (Holland and Chen, 1993;Zelenyi et al, 2000Zelenyi et al, , 2002aSitnov et al, 2003).…”

Section: Numerical Resultsmentioning

confidence: 99%

“…In this connection, we notice that a number of current sheet equilibria based on current carrying ions have been developed. By varying the drift velocity v D of the transient ion distribution function (see later), Holland and Chen (1993) obtained selfconsistent solutions with a thin current sheet embedded in a thicker plasma sheet. Thin current sheets with double peaks from about 11 to 14 R E downtail were obtained by Delcourt and Belmont (1998) by means of test particles evolving in the Tsyganenko 89 magnetic field model.…”

Section: Introductionmentioning

confidence: 99%

“…By making use of the quasi-adiabatic invariant of motion I z =(2π) −1 mv z dz (Büchner and Zelenyi, 1989), and considering anisotropic ion distribution functions, a series of self-consistent Vlasov current sheet structures were developed by Kropotkin et al (1997); Sitnov et al (2000); Malova et al (2000); Zelenyi et al (2000). Solutions were obtained which also describe the magnetic overshoots which are associated with the diamagnetic current wings (Holland and Chen, 1993;Malova et al, 2000;Zelenyi et al, 2000). Indeed, Cluster data of the 26 September crossing are particularly stimulating because the magnetic overshoots are observed (i) by more than one spacecraft, (ii) repeatedly by a single spacecraft, and (iii) on both sides of the current sheet.…”

Section: Introductionmentioning

confidence: 99%

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Double peak structure and diamagnetic wings of the magnetotail current sheet

et al. 2004

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Abstract. Recent Cluster observations in the magnetotail at about 20 Earth radii downtail have unambiguously shown that sometimes the current sheet is bifurcated, i.e. it is divided in two layers. We report numerical simulations of the ion dynamics in a quasi-neutral sheet in the presence of magnetic turbulence, which is often observed in the magnetotail, and for various anisotropies of the ion distribution function. Ions are injected at the boundary of the simulation box with a velocity distribution corresponding to a shifted Maxwellian. The simulation parameters, are adjusted to be similar to those of Cluster observations. We find that even for moderate fluctuation levels, the computed current density profile develops a double peak, in agreement with the observations. By varying the anisotropy of the injected distribution function, we are able to reproduce, for weak anisotropy, the magnetic field overshoots which are sometimes observed prior to magnetotail traversals. Therefore, we suggest an ion current profile with a double peak due to magnetic turbulence, and with possible diamagnetic current wings, present in the case of weak anisotropy of the ion distribution function.

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Section: Introductionmentioning

confidence: 72%

Section: Numerical Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Double peak structure and diamagnetic wings of the magnetotail current sheet

et al. 2004

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“…More recent work has improved on the above models by including the full particle dyn;~mics with Bn ~ 0 using simulation techniques [Burkhart et al, 1992;Pritchett andCor.oniti, 1992, 1995;Holland and Chen, 1993;Harold and Chen, 1996;Hesse et al, 1996] or approximations of particle orbits assuming Bn/ Ba « 1 [Kropotkin et al, 1997;Sitnov et al, 2000]. These works identified the quantity VD/Vth as an important parameter, where Vth is the thermal speed of the asymptotic source particle distributions.…”

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confidence: 99%

A Hybrid Kinetic Model of Asymmetric Thin Current Sheets with Sheared Flows in a Collisionless Plasma

Chen¹,

Sabtoro²,

Szabó³

et al. 2010

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PublIC reporting burden lor tIliS COllection of Information IS estimated to average 1 hOll' per response. Including tile ame lor revt8Wlng nslruClions. searching eXisting data sources. gathenng and maintaining tile data needed. -and completing-and reviewing ABS'rRACTA new model of eqUilibrium current sheets in a coIIisionless plasma incorporating ion flows that are asymmetric and sheared across the current sheet is developed. Ions are treated as single particles and electrons as a massless fluid. The resulting current sheet is a Vlasov equilibrium satisfy:ing Ampere's law. The current sheet thickness is shown to be of the order of the ion Larmor radius. It is found that the structure of the current sheet depends on the distribution function of the ions entering the current sheet. A characteristic feature of this class of equilibria is that the pressure tensor is anisotropic and nondiagonal while the reversing component of the magnetic field is similar to the hyperbolic tangent Harris field. lhe results show that the asymmetric sheared ion momentum flows as well as the off-diagonal pressure tensor elements play an essential role in the force balance. The model is applied to current sheets co-moving with the solar wind and is directly compared with high-resolution WIND MFI magnetic field data and WIND 3DP particle data. The agreement is good. The theoretical results are scalable to collisionless plasmas in different regimes. SUBJECT TERMS

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Earth's distant magnetotail current sheet near and beyond lunar orbit

et al. 2015

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We analyze the structure of the Earth magnetotail current sheet (CS) in middle, X∈[−50,−20] RE, and distant, X∈[−100,−80] RE, regions using data set of 573 CS crossings by Geotail in 1994–1995. For a subset of 213 CSs we determine the CS thickness L, average current density j0, and velocity vD=j0/en0 (n0 is the ion number density). We find similar dawn‐dusk distributions of CS parameters for middle and distant tail: L is about 3000 km at the dusk flank and grows up to 12,000 km toward the dawn flank; j0 grows toward the dusk flank by a factor of 2–3; and the most intense CSs (with higher vD) are observed near midnight. We show that ion‐scale CSs with the thickness of several ion thermal gyroradii (say less than seven) are observed in middle and distant tail in more than 50% of crossings. For observed CSs electrons likely provide the dominant contribution to the current density. We divide the subset into intense and weak CSs (using parameter vD). Weak CSs have thickness of about 20 ion thermal gyroradii and Bz of about 1.5 nT. Intense CSs have thickness of about 3–7 thermal gyroradii and much smaller Bz implying more stretched field line configuration. Intense CSs are accompanied by fast ion flows: vD is larger for larger amplitudes of ion bulk velocity vx that is likely due to larger contribution of Speiser ions. The properties of the CS in middle and distant tail are compared with those found for the near‐Earth tail.

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Self‐consistent current sheet structures in the quiet‐time magnetotail

Cited by 44 publications

References 16 publications

Double peak structure and diamagnetic wings of the magnetotail current sheet

Double peak structure and diamagnetic wings of the magnetotail current sheet

A Hybrid Kinetic Model of Asymmetric Thin Current Sheets with Sheared Flows in a Collisionless Plasma

Earth's distant magnetotail current sheet near and beyond lunar orbit

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