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Rarefaction

About: Rarefaction is a research topic. Over the lifetime, 1852 publications have been published within this topic receiving 26943 citations.


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TL;DR: In this paper, the physical processes that take place in a multi-component plasma set in expansion by a minority of energetic electrons are discussed, and simple analytical models are confirmed in numerical simulations where the ions are described kinetically, and the electrons assume the Boltzmann distribution.
Abstract: We discuss the physical processes, which take place in a multi-component plasma set in expansion by a minority of energetic electrons. The expansion is in the form of a collisionless rarefaction wave associated with three types of electrostatic shocks. Each shock manifests itself in a potential jump and in the spatial separation of plasma species. The shock front associated with the proton–electron separation sets the maximum proton velocity. Two other shocks are due to the hot–cold electron separation and the light–heavy ion separation. They result in the light ion acceleration and their accumulation in the phase space. These structures open possibilities for control of the number and the energy spectrum of accelerated ions. Simple analytical models are confirmed in numerical simulations where the ions are described kinetically, and the electrons assume the Boltzmann distribution.

78 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the fine structure of rarefaction wave and blowup arising in third-order nonlinear dispersive equations and showed that two basic Riemann problems for Eq. (0.1) with the initial data exhibit a shock wave (u(x, t) ≡ S� −(x)) and a smooth rare faction wave (for S�� +), respectively.
Abstract: Shock waves and blowup arising in third-order nonlinear dispersive equations are studied. The underlying model is the equation in (0.1) $$ u_t = (uu_x )_{xx} in\mathbb{R} \times \mathbb{R}_ + . $$ It is shown that two basic Riemann problems for Eq. (0.1) with the initial data $$ S_ \mp (x) = \mp \operatorname{sgn} x $$ exhibit a shock wave (u(x, t) ≡ S −(x)) and a smooth rarefaction wave (for S +), respectively. Various blowing-up and global similarity solutions to Eq. (0.1) are constructed that demonstrate the fine structure of shock and rarefaction waves. A technique based on eigenfunctions and the nonlinear capacity is developed to prove the blowup of solutions. The analysis of Eq. (0.1) resembles the entropy theory of scalar conservation laws of the form u t + uu x = 0, which was developed by O.A. Oleinik and S.N. Kruzhkov (for equations in x ∊ ℝ N ) in the 1950s–1960s.

76 citations

Journal ArticleDOI
TL;DR: Examining the images corresponding to rarefaction regions in order to establish the range of behaviors that occur under these known conditions, which then act as a benchmark against which the compression region images can be compared, show relatively consistent properties of the main oval auroras.
Abstract: [1] We provide a first detailed discussion of the relation between the set of Jovian UV auroral images observed by the Hubble Space Telescope (HST) in December 2000 to January 2001 and simultaneous interplanetary data obtained by Cassini during its Jupiter flyby. Examination of the interplanetary data surrounding all seven HST observation intervals shows that by chance six of them correspond to solar wind rarefaction regions, which follow compressions by periods of ∼2 to ∼6 days. Only one imaging interval, on 13 January 2001, corresponds to a compression region of generally elevated, but highly variable, solar wind dynamic pressure and interplanetary field strength. We have thus first examined the images corresponding to rarefaction regions in order to establish the range of behaviors that occur under these known conditions, which then act as a benchmark against which the compression region images can be compared. The rarefaction region images show relatively consistent properties of the main oval auroras, though differing in detail from interval to interval. The polar auroras show more variability, with the patchy (“swirl”) auroras in the central region sometimes forming a diffuse ring structure and at other times being more uniformly distributed, while the “active region” auroras at dusk vary markedly from weak emissions to bright arc-like forms, the latter possibly being associated with intervals within ∼2–3 days of a previous solar wind compression. The two images obtained in the compression region on 13 January 2001 then show remarkably different properties in all the auroral components. The main oval is found to be brighter over its whole length by factors of two to three compared with the rarefaction region images, while its position remains essentially unchanged, close to the usual reference oval. However, bright contiguous “active region” auroras in the postnoon and dusk sector then widen the overall auroral distribution in that sector by up to ∼5° in the poleward direction. The region of patchy polar auroras is also found to expand to cover essentially the whole of the remaining area of the polar cap, with a much-narrowed darker zone just poleward of the main oval in the dawn and prenoon sector. We discuss whether these enhanced emissions are characteristic of the few-day compression region as a whole or of more localized conditions occurring within the compression region and conclude that the latter is more likely. Examination of the relevant interplanetary data then shows that the brightened images are associated with an interval of significant magnetospheric dynamics, involving a modest compression of the magnetosphere followed by an extended major expansion.

76 citations

Journal ArticleDOI
TL;DR: In this article, a one-dimensional model for thinning of the plasma sheet is developed on the basis of launching a fast mode MHD rarefaction wave propagating in the tailward direction along the surface.

75 citations

Journal ArticleDOI
TL;DR: In this article, a second-order slipping model incorporating pressure gradient is proposed and investigated, and the numerical results obtained using the new slipping model are presented and compared well with available experimental data and numerical results from other references.
Abstract: A numerical study of flow in micro channels and micro pipes is described. The simulations are performed by solving Navier-Stokes equations with a slip velocity boundary condition, using the LU-TVD implicit algorithm. A second-order slipping model incorporating pressure gradient is proposed and investigated. The numerical results obtained using the new slipping model are presented and found to compare well with available experimental data and numerical results from other references.Our computations also show that compressibility and the rarefied effects of gas flows are present in both micro channel and micro pipe flows. It is also found that the effect of rarefaction tends to mitigate the negative curvature of pressure distribution that can be attributed to compressibility.

74 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20224
2021105
202064
201964
201864
201773