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    Ideal Magnetohydrodynamic Flow Around a Blunt Body under Anisotropic Pressure
[Text]. - Electronic data (106 Kb)
. - Режим доступа: http://icm.krasn.ru/refextra.php?id=1472. - Электрон. версия печ. публикации . - Режим доступа: http://library.krasn.ru/trudy/2000/1472erkaev_PHP03413_eng.pdf (Полный текст) : статья / Erkaev N.V., Biernat H.K., Farrugia C.J. - Electronic data (106 Kb) // Physics of Plasmas. - 2000. - Vol. 7, № 7. - p. 3413-3420
ГРНТИ

Аннотация: The plasma flow past a blunt obstacle in an ideal magnetohydrodynamic ~MHD! model is studied, taking into account the tensorial nature of the plasma pressure. Three different closure relations are explored and compared with one another. The first one is the adiabatic model proposed by Chew, Goldberger, and Low. The second closure is based on the mirror instability criterion, while the third depends on an empirical closure equation obtained from observations of solar wind flow past the Earth's magnetosphere. The latter is related with the criterion of the anisotropic ion cyclotron instability. In the presented model, the total pressure, defined as the sum of magnetic pressure and perpendicular plasma pressure, is assumed to be a known function of Cartesian coordinates. The calculation is based on the Newtonian approximation for the total pressure along the obstacle and on a quadratic behavior with distance from the obstacle along the normal direction. Profiles of magnetic field strength and plasma parameters are presented along the stagnation stream line between the shock and obstacle of an ideal plasma flow with anisotropy in thermal pressure and temperature.

http://icm.krasn.ru/refextra.php?id=1472,
Полный текст

Держатели документа:
ИВМ СО РАН : 660036, Красноярск, Академгородок, 50, стр.44

Доп.точки доступа:
Biernat, H.K.; Farrugia, C.J.; Еркаев, Николай Васильевич

    Model of electron pressure anisotropy in the electron diffusion region of collisionless magnetic reconnection
[Text] / A. Divin [et al.] // Phys. Plasmas. - 2010. - Vol. 17, Is. 12. - Ст. 122102, DOI 10.1063/1.3521576. - Cited References: 42. - The present work is supported partially by the Onderzoekfonds KU Leuven (Research Fund KU Leuven) and by the European Commission's Seventh Framework Programme (FP7/2007-2013) under grant Agreement No. 218816 (SOTERIA project, www.soteria- space.eu). Additional support is provided by RFBR (Grant No. 09-05-91000-ANF-a). V.S.S. thanks ISSI for hospitality and financial support. The simulations were conducted on the resources of the Vlaams Supercomputer Centrum (VSC) at the Katholieke Universiteit Leuven. . - ISSN 1070-664X
РУБ Physics, Fluids & Plasmas

Аннотация: A new model of the electron pressure anisotropy in the electron diffusion region in collisionless magnetic reconnection is presented for the case of antiparallel configuration of magnetic fields. The plasma anisotropy is investigated as source of collisionless dissipation. By separating electrons in the vicinity of the neutral line into two broad classes of inflowing and accelerating populations, it is possible to derive a simple closure for the off-diagonal electron pressure component. The appearance of these two electron populations near the neutral line is responsible for the anisotropy and collisionless dissipation in the magnetic reconnection. Particle-in-cell simulations verify the proposed model, confirming first the presence of two particle populations and second the analytical results for the off-diagonal electron pressure component. Furthermore, test-particle calculations are performed to compare our approach with the model of electron pressure anisotropy in the inner electron diffusion region by Fujimoto and Sydora [Phys. Plasmas 16, 112309 (2009)]. (C) 2010 American Institute of Physics. [doi:10.1063/1.3521576]


Доп.точки доступа:
Divin, A.; Markidis, S.; Lapenta, G.; Semenov, V.S.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.

    Variations of magnetic field and plasma parameters in the magnetosheath related to reconnection pulses
[Text] / N. V. Erkaev [et al.] // STREAMERS, SLOW SOLAR WIND, AND THE DYNAMICS OF THE MAGNETOSPHERE. Ser. ADVANCES IN SPACE RESEARCH : PERGAMON-ELSEVIER SCIENCE LTD, 2004. - Vol. 33: 2nd World Space Congress/34th COSPAR Scientific Assembly (OCT 10-19, 2002, HOUSTON, TX), Is. 5. - P784-788, DOI 10.1016/S0273-1177(03)00646-X. - Cited References: 13 . - ISBN 0273-1177
РУБ Engineering, Aerospace + Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: The interplanetary magnetic field is enhanced in a thin layer near the magnetopause which is called the magnetic barrier or plasma depletion layer. The magnetic energy stored in the magnetic barrier can be released during the process of magnetic field reconnection. Using ideal magnetohydrodynamics and assuming a sudden decrease of the magnetic field near the magnetopause due to the reconnection pulse, we analyze the model variations of the plasma parameters and the magnetic field at the magnetosheath. For a given reconnection rate and calculated parameters of the magnetic barrier, we derive the duration of a reconnection pulse as a function of the solar wind parameters. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Farrugia, C.J.; Biernat, H.K.; Langmayr, D.

    The role of the magnetic barrier in the solar wind-magneto sphere interaction
[Text] / N. V. Erkaev, C. J. Farrugia, H. K. Biernat // Planet Space Sci. - 2003. - Vol. 51, Is. 12. - P745-755, DOI 10.1016/S0032-0633(03)00111-9. - Cited References: 36 . - ISSN 0032-0633
РУБ Astronomy & Astrophysics

Аннотация: The magnetized solar wind carries a large amount of energy but only a small fraction of it enters the magnetosphere and powers its dynamics. Numerous observations show that the interplanetary magnetic field (IMF) is a key parameter regulating the solar wind-magnetosphere interaction. The main factor determining the amount of energy extracted from the solar wind flow by the magnetosphere is the plasma flow structure in the region adjacent to the sunward side of the magnetopause. While compared to the energy of the solar wind flow the IMF magnetic energy is relatively weak, it is considerably enhanced in a thin layer next to the dayside magnetopause variously called the plasma depletion layer or magnetic barrier. Important features of this barrier/layer are (i) a pile-up of the magnetic field with (ii) a concurrent decrease of density, (iii) enhancement of proton temperature anisotropy, (iv) asymmetry of plasma flow caused by magnetic field tension. and (v) characteristic wave emissions (ion cyclotron waves). Importantly, the magnetic barrier can be considered as an energy source for magnetic reconnection. While the steady-state magnetic barrier has been extensively examined, non-steady processes therein have only been addressed by a few authors. We discuss here two non-steady aspects related to variations of the magnetic barrier caused by (i) a north-to-south rotation of the IMF, and (ii) by pulses of magnetic field reconnection at the magnetopause. When the IMF rotates smoothly from north-to-south, a transition layer is shown to appear in the magnetosheath which evolves into a thin layer bounded by sharp gradients in the magnetic field and plasma quantities. For a given reconnection rate and calculated parameters of the magnetic barrier, we estimate the duration and length scale of a reconnection pulse as a function of the solar wind parameters. Considering a sudden decrease of the magnetic field near the magnetopause caused by the reconnection pulse, we study the relaxation process of the magnetic barrier. We find that the relaxation time is longer than the duration of the reconnection pulse for large Alfved-Mach numbers. (C) 2003 Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Farrugia, C.J.; Biernat, H.K.

    The solution of the Rankine-Hugoniot equations for fast shocks in an anisotropic kappa distributed medium
[Text] / D. F. Vogl [et al.] // Planet Space Sci. - 2003. - Vol. 51, Is. 12. - P715-722, DOI 10.1016/S0032-0633(03)00108-9. - Cited References: 28 . - ISSN 0032-0633
РУБ Astronomy & Astrophysics

Аннотация: In this paper, we concentrate on the analysis of the anisotropic Rankine-Hugoniot equations for perpendicular and oblique fast shocks. In particular, as additional information to the anisotropic set of equations, the threshold conditions of the fire-hose and mirror instability are used to bound the range of the pressure anisotropy downstream of the discontinuity. These anisotropic threshold conditions of the plasma instabilities are obtained via a kinetic approach using a generalized Lorentzian distribution function, the so-called kappa distribution function. Depending on up-stream conditions, these instabilities further define stable and unstable regions with regard to the pressure anisotropy downstream of the shock. The calculations are done for different upstream Alfven Mach numbers. We found that low values of the parameter kappa reduce the pressure anisotropy downstream of the shock. (C) 2003 Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Vogl, D.F.; Langmayr, D.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.; Farrugia, C.J.; Muhlbachler, S.

    The anisotropic jump equations for oblique fast shocks in a kappa distributed medium
[Text] / D. F. Vogl [et al.] // HELIOSPHERE AT SOLAR MAXIMUM. Ser. ADVANCES IN SPACE RESEARCH : PERGAMON-ELSEVIER SCIENCE LTD, 2003. - Vol. 32: D1 1/D2 1/E3 1 Symposium of COSPAR Scientific Commission D held at the 34th COSPAR Scientific Assembly/2nd Space Congress (OCT 10-19, 2002, HOUSTON, TEXAS), Is. 4. - P519-523, DOI 10.1016/S0273-1177(03)00336-3. - Cited References: 18 . - ISBN 0273-1177
РУБ Engineering, Aerospace + Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: In this paper, we concentrate on the solution of the anisotropic Rankine-Hugoniot equations for inclined fast shocks taking into account a new approach in closing the set of equations. In particular, the threshold conditions of the fire-hose and that of the mirror instability, obtained in a kinetic approach using the so-called kappa distribution function, are used to bound the range of the pressure anisotropy downstream of the discontinuity. We study the variation of the density across the shock for a given Alfven Mach number and upstream pressure anisotropy and find that the parameter kappa is most sensitive to stable plasma conditions, i.e. low values of kappa reduce the pressure anisotropy downstream of the discontinuity. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Vogl, D.F.; Langmayr, D.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.; Farrugia, C.J.; Muhlbachler, S.

    Petschek shocks of reconnection for anisotropic pressure
[Text] / H. K. Biernat [et al.] // COMPARATIVE RECONNECTION STUDIES AT THE SUN AND IN PLANETARY MAGNETOSPHERES. Ser. ADVANCES IN SPACE RESEARCH : PERGAMON-ELSEVIER SCIENCE LTD, 2002. - Vol. 29: D0 1-E3 1 Symposium of COSPAR Scientific Commission D held at the 33rd COSPAR Scientific Assmbly (JUL, 2000, WARSAW, POLAND), Is. 7. - P1069-1074, DOI 10.1016/S0273-1177(02)00023-6. - Cited References: 12 . - ISBN 0273-1177
РУБ Engineering, Aerospace + Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: Many observations show a difference between the pressure parallel and perpendicular to the magnetic field. Thus it is reasonable to study the Petschek reconnection mechanism for the set of equations allowing for pressure anisotropy. We study the simplest case of so-called Petschek shocks, where the Alfven discontinuity and the slow shock degenerate to one discontinuity. More specifically, we consider switch-off shocks, where the magnetic field on the downstream side vanishes in lowest order, so that the plasma is isotropic on that side. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.


Доп.точки доступа:
Biernat, H.K.; Muhlbachler, S.; Semenov, V.S.; Erkaev, N.V.; Еркаев, Николай Васильевич; Vogl, D.F.; Ivanova, V.V.

    Anisotropic magnetosheath: Comparison of theory with Wind observations near the stagnation streamline
[Text] / C. J. Farrugia [et al.] // J. Geophys. Res-Space Phys. - 2001. - Vol. 106, Is. A12. - P29373-29385, DOI 10.1029/2001JA000034. - Cited References: 42 . - ISSN 0148-0227
РУБ Astronomy & Astrophysics

Аннотация: We carry out a first comparison with spacecraft measurements of our recent three-dimensional, one-fluid magnetohydrodynamic (MHD) model for the anisotropic magnetosheath [Erkaev et al., 1999], using data acquired by the Wind spacecraft on an inbound magnetosheath pass on December 24, 1994. The spacecraft trajectory was very close to the stagnation streamline, being displaced by less than 1/2 hour from noon and passing at low southern magnetic latitudes (similar to4.5degrees). All quantities downstream of the bow shock are obtained by solving the Rankine-Hugoniot equations taking the pressure anisotropy into account. In this application of our model we close the MHD equations by a "bounded anisotropy" ansatz using for this purpose the inverse correlation between the proton temperature anisotropy, A(p) (equivalent to T-pperpendicular to/T-pparallel to - 1) and the proton plasma beta parallel to the magnetic field beta(pparallel to) observed on this pass when conditions are steady. In the model the total perpendicular pressure is prescribed and not obtained self-consistently. For all quantities studied we find very good agreement between the predicted and the observed profiles, indicating that the bounded anisotropy method of closing the magnetosheath equations, first suggested by Denton et al. [1994], is valid and reflects the physics of the magnetosheath well. We assess how sensitive our model results are to different parameters in the A(p) = alpha(0)beta(pparallel to)(-alpha1) (alpha(1) 0) relation, taking for al the two limiting values (0.4, 0.5) resulting from the two-dimensional hybrid simulations of Gary et al. [1997], and varying alpha(0) in the range 0.6 - 0.8. Input solar wind conditions are as measured on this pass. In general, the model profiles depend more strongly on alpha(0) than on al. In particular, decreasing alpha(0) narrows the width of the plasma depletion layer (PDL) and widens the mirror stable region. For the lowest value of alpha(0) the mirror stable region extends sunward of the outer edge of the PDL. For the other two values of alpha(0) and regardless of the value of al, it is contained within the PDL. Finally, we also study phenomenological double-polytropic laws and find polytropic indices gamma(perpendicular to) approximate to 1 and gamma(parallel to) approximate to 1.5. These results agree well with those of Hau et al. [1993] inferred from Active Magnetospheric Particle Tracer Explorers/ Ion Release Module data on a crossing of the near-subsolar magnetosheath.


Доп.точки доступа:
Farrugia, C.J.; Erkaev, N.V.; Еркаев, Николай Васильевич; Vogl, D.F.; Biernat, H.K.; Oieroset, M.; Lin, R.P.; Lepping, R.P.

    Analysis of mirror modes convected from the bow shock to the magnetopause
[Text] / N. V. Erkaev [et al.] // Planet Space Sci. - 2001. - Vol. 49, Is. 13. - P1359-1364, DOI 10.1016/S0032-0633(01)00057-5. - Cited References: 22 . - ISSN 0032-0633
РУБ Astronomy & Astrophysics

Аннотация: Spacecraft observations confirm the existence of mirror fluctuations in the magnetosheath. The mirror instability occurs in an anisotropic magnetized plasma when the difference between perpendicular and parallel (with respect to the magnetic field) plasma pressure exceeds a threshold depending on the perpendicular plasma beta. The anisotropy of the plasma pressure increases from the shock to the magnetopause as a result of magnetic field line stretching. This gives rise to plasma fluctuations which in turn lead to a relaxation between parallel and perpendicular temperatures. Mirror perturbations do not propagate and are convected with plasma flow along the streamlines. Using an anisotropic steady-state MHD flow model, we calculate the growth of mirror fluctuations from the bow shock to the magnetopause along the subsolar streamline. For the anisotropic MHD model, we use the empirical closure equation suitable for the AMPTE/IRM observations. The amplitudes of mirror fluctuations, which are obtained as a function of distance from the magnetopause, are directly compared with AMPTE/IRM observations on October 24, 1985. With regard to both the amplification of the magnetic field and the plasma density oscillations, as well as the location of maximum amplitudes, model calculations are in good agreement with values obtained from the AMPTE/IRM data. (C) 2001 Elsevier Science Ltd. All rights reserved.


Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Schaffenberger, W.; Biernat, H.K.; Farrugia, C.J.; Vogl, D.F.

    Jump conditions for pressure anisotropy and comparison with the Earth's bow shock
[Text] / D. F. Vogl [et al.] // Nonlinear Process Geophys. - 2001. - Vol. 8: 25th General Assembly of the European-Geophysical-Society (APR, 2000, NICE, FRANCE), Is. 3. - P167-174. - Cited References: 16 . - ISSN 1023-5809
РУБ Geochemistry & Geophysics + Meteorology & Atmospheric Sciences

Аннотация: Taking into account the pressure anisotropy in the solar wind, we study the magnetic field and plasma parameters downstream of a fast shock, as functions of upstream parameters and downstream pressure anisotropy. In our theoretical approach, we model two cases: a) the perpendicular shock and b) the oblique shock. We use two threshold conditions of plasma instabilities as additional equations to bound the range of pressure anisotropy. The criterion of the mirror instability is used for pressure anisotropy P (perpendicular to)/P (parallel to) 1. Analogously, the criterion of the fire-hose instability is taken into account for pressure anisotropy P-perpendicular to/P-parallel to 1. We found that the variations of the parallel pressure, the parallel temperature, and the tangential component of the velocity are most sensitive to the pressure anisotropy downstream of the shock. Finally, we compare our theory with plasma and magnetic field parameters measured by the WIND spacecraft.


Доп.точки доступа:
Vogl, D.F.; Biernat, H.K.; Erkaev, N.V.; Еркаев, Николай Васильевич; Farrugia, C.J.; Muhlbachler, S.

    Jump conditions at fast shocks in an anisotropic magnetized plasma
[Text] / D. F. Vogl [et al.] // PLANETARY MAGNETOSPHERES. Ser. ADVANCES IN SPACE RESEARCH : ELSEVIER SCIENCE BV, 2001. - Vol. 28: D3 1/C3 3 Symposium of COSPAR Scientific Commission D held at the 33rd COSPAR Scientific Assembly (JUL, 2000, WARSAW, POLAND), Is. 6. - P851-856, DOI 10.1016/S0273-1177(01)00503-8. - Cited References: 12 . - ISBN 0273-1177
РУБ Engineering, Aerospace + Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: In this paper we report on the variations of the magnetic field strength and the plasma parameters across a fast shock as functions of upstream Alfven Mach numbers and pressure anisotropy downstream of the shock. In our study we consider an oblique shock where the angle between the magnetic field vector and the normal vector upstream of the shock is chosen to be 45degrees. We further use two threshold conditions of plasma instabilities as additional equations to bound the range of the pressure anisotropy, p(perpendicular to)/p(\\), i.e., the criterion of the mirror instability and that of the fire-hose instability. We found that the variations of the parallel pressure, the parallel temperature, as well as the tangential component of the velocity are most sensitive to the pressure anisotropy downstream of the shock, whereas the variations of the plasma density, the normal velocity, the magnetic field strength, and perpendicular pressure and temperature with respect to the magnetic field show much less pronounced dependence on the anisotropy. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.


Доп.точки доступа:
Vogl, D.F.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.; Muhlbachler, S.; Farrugia, C.J.

    MHD effects of the solar wind flow around planets
[Text] / H. K. Biernat [et al.] // Nonlinear Process Geophys. - 2000. - Vol. 7: 24th General Assembly of the European-Geophysical-Society (APR 19-23, 1999, THE HAGUE, NETHERLANDS), Is. 03.04.2013. - P201-209. - Cited References: 34 . - ISSN 1023-5809
РУБ Geochemistry & Geophysics + Meteorology & Atmospheric Sciences

Аннотация: The study of the interaction of the solar wind with magnetized and unmagnetized planets forms a central topic of space research. Focussing on planetary magnetosheaths, we review some major developments in this field. Magnetosheath structures depend crucially on the orientation of the interplanetary magnetic field, the solar wind Alfven Mach number, the shape of the obstacle (axisymmetric/non-axisymmetric, etc.), the boundary conditions at the magnetopause (low/high magnetic shear), and the degree of thermal anisotropy of the plasma. We illustrate the cases of Earth, Jupiter and Venus. The terrestrial magnetosphere is axisymmetric and has been probed in situ by many spacecraft. Jupiter's magnetosphere is highly non-axisymmetric. Furthermore, we study magnetohydrodynamic effects in the Venus magnetosheath.


Доп.точки доступа:
Biernat, H.K.; Erkaev, N.V.; Еркаев, Николай Васильевич; Farrugia, C.J.; Vogl, D.F.; Schaffenberger, W.

    Three-dimensional, one-fluid, ideal MHD model of magnetosheath flow with anisotropic pressure
[Text] / N. V. Erkaev, C. J. Farrugia, H. K. Biernat // J. Geophys. Res-Space Phys. - 1999. - Vol. 104, Is. A4. - P6877-6887, DOI 10.1029/1998JA900134. - Cited References: 29 . - ISSN 0148-0227
РУБ Astronomy & Astrophysics

Аннотация: We present a three-dimensional, one-fluid, steady state magnetohydrodynamic (MHD) model of magnetosheath flow near the subsolar line with unequal plasma pressures perpendicular (P-perpendicular to) and parallel (P-parallel to) to the magnetic field (P-perpendicular to P-parallel to) Aside from an assumption on the total pressure normal to the magnetopause, our analytical-numerical method is completely general and is an extension of our isotropic, "magnetic string" MHD model, which we describe in detail here. The MHD equations are closed by a relation between P-perpendicular to and P-parallel to as in the Bounded Anisotropy Model [Denton et al., 1994] corresponding to the threshold of the electromagnetic proton cyclotron wave instability. We take an IMF oriented perpendicular to the solar wind velocity. As boundary conditions, we have Rankine-Hugoniot relations at the bow shock and a no-flow condition at the magnetopause. We obtain steady state profiles of the magnetic field and plasma parameters for upstream sonic and Alfven Mach numbers equal to 10, and compare them with the isotropic case (P-parallel to = P-perpendicular to). Anisotropy slightly thickens the magnetosheath. In the anisotropic model, the density, the parallel and perpendicular temperatures, plasma pressures, and betas all decrease toward the magnetopause. Isotropic profiles lie between those of quantities perpendicular and parallel to the field. Anisotropy has considerable effect on the density profile, which lies below that in the isotropic limit throughout the magnetosheath. Density depletion results from stretching of magnetic field lines, which is caused by field-aligned plasma flow. Approaching the magnetopause, the tangential component of velocity parallel to the magnetic field decreases, while the tangential component perpendicular to the magnetic field increases. These are features characterizing a stagnation line flow at the magnetopause. The acceleration along the magnetic field is produced by the gradient of P-parallel to and the mirror force, which depends on anisotropy. They both make substantial contributions and are responsible for the changes we see;from isotropy. The acceleration perpendicular to magnetic field is also larger than in the case of isotropy and is caused by the gradient of total pressure, the magnetic strength, and the mirror force. In addition, acceleration in both directions is affected by the decreasing density.


Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Farrugia, C.J.; Biernat, H.K.

    Plasma depletion layer model for low Alfven Mach number: Comparison with ISEE observations
[Text] / C. J. Farrugia [et al.] // J. Geophys. Res-Space Phys. - 1997. - Vol. 102, Is. A6. - P11315-11324DOI 10.1029/97JA00410. - Cited References: 29 . -
РУБ Astronomy & Astrophysics

Аннотация: Together with the magnetic shear across the magnetopause, the solar wind Alfven Mach number, M-A infinity plays a central role in determining the structure of the magnetosheath. Recent theoretical modeling has shown, in particular, that as M-A infinity decreases, the region adjacent to the sunward side of the magnetopause where the interplanetary magnetic field (IMF) exerts a strong influence on the flow (i.e., the so-called ''plasma depletion layer''), is no longer confined to a thin layer similar to 0.3 Earth radii (R-E) thick but occupies an increasingly larger fraction of the magnetosheath. Furthermore, the model predicts the possibility of a plasma depletion layer for low M-A infinity, irrespective of the size of the magnetic shear at the magnetopause, In this paper we study three examples of low latitude ISEE 2 passes through the dayside magnetosheath near noon: December 3, 1979; October 5, 1979; and November 11, 1979, In all three examples, MA, was lower than normal. During the December 3 pass (which we treat qualitatively), we find evidence of a plasma depletion layer when the IMF was pointing south, On the other two passes (which we study quantitatively), the interplanetary magnetic field was strongly northward pointing, leading to low magnetic shear at the respective magnetopause crossings, The October 5 pass was under steady interplanetary conditions and we find good agreement between theory and data, Temporal variations of the interplanetary medium during the November 11 pass necessitated an extension of the steady state theory to encompass piecewise steady (on average) interplanetary conditions, Better agreement with the data results when the theory is extended further to correct the total pressure at the sunward side of the magnetopause by integrating the magnetic tension term across the layer. For wide plasma depletion layers, this correction can be substantial.


Доп.точки доступа:
Farrugia, C.J.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.; Lawrence, G.R.; Elphic, R.C.

    Equations of the dynamics of a liquid crystal under the influence of weak mechanical and thermal perturbations
/ V. M. Sadovskii // AIP Conference Proceedings. - 2014. - Vol. 1629: 6th International Conference for Promoting the Application of Mathematics in Technical and Natural Sciences, AMiTaNS 2014 (26 June 2014 through 1 July 2014, ) Conference code: 109043. - P311-318, DOI 10.1063/1.4902287 . -

Кл.слова (ненормированные):
dynamics -- micropolar medium -- Nematic liquid crystal -- thermal conductivity -- viscoelasticity -- waves of rotational motion

Аннотация: The paper is devoted to the construction of the simplified mathematical model of thermomechanical behavior of a liquid crystal under the influence of weak mechanical and thermal perturbations. This model is based on the nonlinear equations of a micropolar viscoelastic medium with rotating particles. To describe small strains and finite rotations of molecules, the hypothesis of the dependence of potential energy on the volume change, on the angle of relative rotation and on the entropy is used in the framework of the method of internal thermodynamic parameters. The heat conduction process is described taking into account the anisotropy of a material due to the difference in coefficients of thermal conductivity along the axis of orientation of the particles and in the transverse direction. Separate equation for the tangential stress is obtained from the simplified model, which is useful for the analysis of the recently discussed issues of orientational thermoelasticity and resonant excitation of liquid crystals.

Scopus,
Полный текст (доступен только в локальной сети),
WOS

Держатели документа:
Institute of Computational Modeling, SB RAS, Akademgorodok 50/44Krasnoyarsk, Russian Federation

Доп.точки доступа:
Sadovskii, V.M.; Садовский, Владимир Михайлович

    Modeling of elastic waves in a blocky medium based on equations of the Cosserat continuum
/ V. M. Sadovskii, O. V. Sadovskaya // Wave Mot. - 2015. - Vol. 52. - P138-150, DOI 10.1016/j.wavemoti.2014.09.008 . - ISSN 0165-2125

Кл.слова (ненормированные):
Blocky medium -- Compliant interlayer -- Cosserat continuum -- Dynamic elasticity

Аннотация: Based on the equations of the dynamics of piecewise-homogeneous elastic material, parallel computational algorithms are developed to simulate the process of stress and strain wave propagation in amedium consisting of alarge number of blocks interacting through compliant interlayers. Computations of waves caused by localized impulse perturbations show that such amedium can be considered as isotropic only in the case of sufficiently thin interlayers. In the case of relatively thick interlayers, the anisotropy effects are observed which consist in the appearance of elongated wave fronts along the coordinate directions and characteristic oscillations of velocities and stresses because of the rotational motion of blocks. For the description of waves in ablocky medium with thin interlayers, the equations of the isotropic Cosserat continuum are applicable. As the thickness of interlayers increases, the orthotropic Cosserat continuum theory which takes into account the symmetry of elastic properties relative to the coordinate planes can be applied. By comparing the elastic wave velocities in the framework of piecewise-homogeneous model and continuum model, a simple method is obtained to estimate the mechanical parameters of the orthotropic Cosserat continuum modeling ablocky medium. In two-dimensional formulation of the orthotropic model the computational algorithm and the program system are worked out for the analysis of propagation of elastic waves. The comparison showed good qualitative agreement between the results of computations of waves caused by localized impulses, in the framework of the model of ablocky medium with compliant interlayers and the model of orthotropic Cosserat continuum.

Scopus,
WOS

Держатели документа:
Institute of Computational Modeling, Siberian Branch, Russian Academy of Sciences, Akademgorodok 50/44Krasnoyarsk, Russian Federation

Доп.точки доступа:
Sadovskii, V.M.; Sadovsky V.M.; Sadovskaya, O.V.; Садовская, Оксана Викторовна

    Analysis of Elastic Waves in Blocky Media Using the Equations of Cosserat Continuum
[Text] / O. V. Sadovskaya, V. M. Sadovskii // AIP Conference Proceedings. - 2015. - Vol. 1648: International Conference on Numerical Analysis and Applied Mathematics (SEP 22-28, 2014, Rhodes, GREECE). - Ст. UNSP 630006, DOI 10.1063/1.4912864. - Cited References:5 . - ISSN 0094-243X
РУБ Mathematics, Applied + Physics, Applied

Кл.слова (ненормированные):
Dynamics -- Elasticity -- Anisotropy -- Blocky medium -- Compliant interlayer -- Cosserat continuum -- Rotational motion -- Shock wave -- Finite-difference -- scheme -- Parallel computational algorithm

Аннотация: Wave processes in blocky media with a large number of elastic blocks, interacting through compliant interlayers, are described by the equations of a piecewise-homogeneous isotropic elastic medium and by the equations of an orthotropic Cosserat continuum. Parallel program systems for numerical implementation of 2D dynamic problems on wave propagation in blocky media are worked out. Computations demonstrating the anisotropy of a blocky medium even for a sufficiently small thickness of interlayers were performed on supercomputers with cluster architecture.

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Держатели документа:
SB RAS, Inst Computat Modeling, Krasnoyarsk 660036, Russia

Доп.точки доступа:
Sadovskaya, O.V.; Садовская, Оксана Викторовна; Sadovskii, V.M.; Садовский, Владимир Михайлович

    Reynolds-averaged modeling of turbulent flows of power-law fluids
[Text] / A. A. Gavrilov, V. Y. Rudyak // J. Non-Newton. Fluid Mech. - 2016. - Vol. 227. - P45-55, DOI 10.1016/j.jnnfm.2015.11.006. - Cited References:24. - This work was supported by the Russian Scientific Foundation (Contract no. 14-19-00312). . - ISSN 0377-0257. - ISSN 1873-2631
РУБ Mechanics

Аннотация: The paper presents a novel Reynolds-averaged turbulence model for flows of power-law fluid. The model uses the elliptic relaxation approach to capture the near-wall turbulence anisotropy. The turbulence model for Newtonians fluids is modified by introducing closed approximations of correlations between velocity and viscosity fluctuations. The approximation for non-Newtonian extra stress is derived with the assumption of smallness of molecular viscosity fluctuations. A closed model for the averaged molecular viscosity is derived which takes into account its nonlinear dependence on the shear rate. Validation of the model against the direct numerical simulation (DNS) data for power-law fluids flows in the pipe demonstrates that new model is able to predict the main features of the non-Newtonian turbulence. Mean velocity, turbulent energy and averaged molecular viscosity distributions agree well with DNS data. (c) 2015 Published by Elsevier B.V.

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Держатели документа:
ICM SB RAS, Inst Thermophys SB RAS, Krasnoyarsk Branch, 50-44 Akad Gorodok, Krasnoyarsk 660036, Russia.
Novosibirsk State Univ Architecture & Civil Engn, 113 Leningradskaya Str, Novosibirsk 630008, Russia.

Доп.точки доступа:
Gavrilov, Andrey A.; Rudyak, Valeriy Ya; Russian Scientific Foundation [14-19-00312]

    Acoustic approximation of the governing equations of liquid crystals under weak thermomechanical and electrostatic perturbations
/ V. Sadovskii, O. Sadovskaya // Advances in Mechanics of Microstructured Media and Structures : Springer Verlag, 2018. - Vol. 87. - P297-341, DOI 10.1007/978-3-319-73694-5_17 . -

Аннотация: A simplified mathematical model of thermomechanical behavior of a liquid crystal in nematic phase under weak mechanical and thermal perturbations as a micropolar viscoelastic medium with rotating particles is constructed. This model is based on the assumption that potential energy of elastic deformation depends on four parameters—the change in volume, angle of relative rotation of particles, first invariant of curvature measure and entropy. The heat conduction process is described taking into account the anisotropy of a material due to the difference in coefficients of thermal conductivity along the axis of orientation of particles and in the transverse direction. Influence of electric field on the layer of a liquid crystal is modeled by means of the equations of electrostatics for an inhomogeneous anisotropic medium. In the plane formulation, the parallel computational algorithm is worked out on the basis of splitting method with respect to spatial variables, Godunov’s gap decay method, Ivanov’s method of constructing finite-difference schemes with controlled dissipation properties and method of straight lines for finding electric field. The algorithm is implemented using the CUDA technology for computer systems with graphics accelerators. Results of computations of wave motions demonstrating the efficiency of proposed method and algorithm are represented. It is shown that the effect of orientational thermoelasticity of a liquid crystal in the form of re-orientation of particles in an inhomogeneous temperature field can only be evident in the presence of tangential stresses at the boundary. The modes of resonance excitation in a liquid crystal at the eigenfrequency of rotational motion of particles are analyzed numerically. © Springer International Publishing AG, part of Springer Nature 2018.

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Держатели документа:
Siberian Branch of the Russian Academy of Sciences, Institute of Computational Modeling, Akademgorodok 50/44, Krasnoyarsk, Russian Federation

Доп.точки доступа:
Sadovskii, V.; Sadovskaya, O.
539.3, 519.63
Н 25

    Наномодифицирование полимерного связующего с целью повышения свойств углепластиковых материалов
[Текст] : статья / Г. Г. Крушенко, О. А. Исеева // Сибирский журнал науки и технологий. - 2017. - Т. 18, № 3. - С. 651-657 . - ISSN 2587-6066
   Перевод заглавия: Nano modification of polymer binder with the aim of improving the properties of carbon fibre materials
УДК

Аннотация: Одной из проблем космического машиностроения является снижение массы деталей, узлов и механизмов как собственно космического аппарата, так и средств доставки его на орбиту, т. е. ракеты-носителя. Прогрессивным решением этой проблемы является применение так называемых сетчатых (анизогридных - anisogrid) конструкций. В настоящее время сетчатые конструкции, материалом для которых является угле- пластик, широко применяются в космической технике для изготовления различных пустотелых трубчатых и конических конструкций космических аппаратов. Наиболее распространенным способом изготовления угле- пластиковых сетчатых конструкций является их намотка из углеродных волокон. Однако при всех положи- тельных качествах углепластиковых конструкций, в связи с однонаправленностью их структуры, их эффек- тивное использование возможно только при одноосном нагружении, когда растягивающие и сжимающие напряжения совпадают с направлением волокон. В случае сложного сопротивления или изгиба, когда в мате- риале возникает сложное напряженное состояние, могут произойти разрушения как от действия скалывающих касательных напряжений, так и от нормальных напряжений. Строгая ориентация волокон в одном направле- нии обусловливает анизотропию физико-механических свойств однонаправленных композитов. При нагрузке, приложенной нормально к направлению волокон, происходит разрушение углепластиковой конструкции прак- тически без ее предварительной пластической деформации. Проблема повышения механических свойств угле- пластиковых материалов успешно решается в результате введения в полимерное связующее нанопорошков различных химических соединений. Этот процесс называется наномодифицированием. Причем в этом плане наиболее эффективным оказались углеродные нанопорошки, включая наноалмазы.
One of the problems in space engineering is the reduction of masses parts, assemblies and mechanisms as the actual spacecraft, and the means to deliver it to the orbit, i. e. booster. Progressive solution of this problem is the use of so- called net (anisogrid) structures. And currently mesh structure, the material for which is carbon fiber, are widely used in space technology for the manufacture of hollow tubular and conical designs of the spacecraft. The most common method of making carbon mesh designs is the winding of carbon fibers. However, with all the positive qualities of CFRP structures, in connection with the pointedness of their structure, and their effective use is possible only under uniaxial loading when tensile and compressive stresses coincide with the fiber direction. In the case of complex resis- tance or bending when the material occurs in the complex stress state can cause the destruction, as from the action of shear stresses and normal stresses. Strict fiber orientation in one direction leads to anisotropy of physical and mechanical properties of unidirectional composites. When the load applied normal to the direction of the fibers is destroyed by carbon fiber construction practically without preliminary plastic deformation. The problem of improving the mechanical properties of the CFRP materials was successfully solved by introducing in the polymer binder nano- powders of different chemical compounds - a process called nanomodification. And, in this regard, the most effective was the carbon nanopowders, including nanodiamonds.

РИНЦ

Держатели документа:
Институт вычислительного моделирования СО РАН
Сибирский государственный университет науки и технологий имени академика М. Ф. Решетнева

Доп.точки доступа:
Крушенко, Г.Г.; Krushenko G.G.; Исеева, О.А.; Iseeva O.A.