Труды сотрудников ИВМ СО РАН

[Text] : статья / N.V. Erkaev, V.S. Semenov, H.K. Alexeev, H.K. Biernat // Physics of Plasmas. - 2001. - Vol. 8, № 11. - p. 4800-4811DOI 10.1063/1.1410112 . -
Аннотация: The reconnection rate is obtained for the simplest case of two-dimensional (2D) symmetric reconnection in an incompressible plasma. In the short note [Erkaev et al., Phys. Rev. Lett. 84, 1455 (2000)], the reconnection rate is found by matching the outer Petschek solution and the inner diffusion region solution. Here the details of the numerical simulation of the diffusion region are presented and the asymptotic procedure which is used for deriving the reconnection rate is described. The reconnection rate is obtained as a decreasing function of the diffusion region length. For a sufficiently large diffusion region scale, the reconnection rate becomes close to that obtained in the Sweet-Parker solution with the inverse square root dependence on the magnetic Reynolds number Re m , determined for the global size of the current sheet. On the other hand, for a small diffusion region length scale, the reconnection rate turns out to be very similar to that obtained in the Petschek model with a logarithmic dependence on the magnetic Reynolds number Re m . This means that the Petschek regime seems to be possible only in the case of a strongly localized conductivity corresponding to a small scale of the diffusion region. c 2001 American Institute of Physics.

http://icm.krasn.ru/refextra.php?id=1805,
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Держатели документа:
ИВМ СО РАН : 660036, Красноярск, Академгородок, 50, стр.44

Доп.точки доступа:
Semenov, V.S.; Семенов В.С.; Alexeev, H.K.; Алексеев Г.К.; Biernat, H.K.; Еркаев, Николай Васильевич

[Text] : статья / N.V. Erkaev, V.S. Semenov, H.K. Biernat // Nonlinear Processes in Geophysics. - 2002. - Vol. 9, № 2. - p. 131–138 . - ISSN 1023-5809
Аннотация: Magnetic reconnection is an important process providing a fast conversion of magnetic energy into thermal and kinetic plasma energy. In this concern, a key problem is that of the resistive diffusion region where the reconnec-tion process is initiated. In this paper, the diffusion region is associated with a nonuniform conductivity localized to a small region. The nonsteady resistive incompressible MHD equations are solved numerically for the case of symmetric reconnection of antiparallel magnetic fields. A Petschek type steady-state solution is obtained as a result of time relax-ation of the reconnection layer structure from an arbitrary initial stage. The structure of the diffusion region is studied for various ratios of maximum and minimum values of the plasma resistivity. The effective length of the diffusion re-gion and the reconnection rate are determined as functions of the length scale and the maximum of the resistivity. For suf-ficiently small length scale of the resistivity, the reconnection rate is shown to be consistent with Petschek's formula. By increasing the resistivity length scale and decreasing the re-sistivity maximum, the reconnection layer tends to be wider, and correspondingly, the reconnection rate tends to be more consistent with that of the Parker-Sweet regime.

Полный текст,
http://icm.krasn.ru/refextra.php?id=2434

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

Доп.точки доступа:
Semenov, V.S.; Семенов В. С.; Biernat, H.K.; Еркаев, Николай Васильевич

[Text] : статья / M.Desroche [et al.] // J. Geophys. Res-Space Phys. - 2013. - Vol. 118, Is. 6. - P3087-3095, DOI 10.1002/jgra.50294. - Cited References: 43. - The authors thank Chris Arridge for initially suggesting this project. The authors are thankful to Adam Masters, Bob Ergun, Jack Gosling, Martin Goldman, and Dmitri Uzdensky for helpful discussions and guidance. This work was supported by NASA's NESSF program. N.V. Erkaev acknowledges support by the RFBR grant No 12-05-00152-a. . - 9. - ISSN 2169-9380РУБ Astronomy & Astrophysics

Аннотация: Using idealized models of the magnetosheath and magnetospheric magnetic fields, plasma densities, and plasma flow, we test for the steady state viability of processes mediating the interaction between the solar wind and the magnetosphere of Saturn. The magnetopause is modeled as an asymmetric paraboloid with a standoff distance of approximate to 25R(S). We test where on the magnetopause surface largescale reconnection may be affected by either a shear flow or diamagnetic drift due to a pressure gradient across the magnetopause boundary. We also test for the onset of the KelvinHelmholtz instability. We find that, for the solar wind and magnetosphere states considered, reconnection is inhibited on the dawn flank due to the large shear flows in this region. Additionally, most of the dawn and dusk equatorial region of the magnetopause is KelvinHelmholtz unstable, due to the presence of the dense magnetospheric plasma sheet and weak magnetic fields on either side of the magnetopause. This study is a followup to a previously published study of the solar wind interaction with Jupiter's magnetosphere.


Доп.точки доступа:
Desroche, M.; Bagenal, F.; Delamere, P.A.; Erkaev, N.V.; Еркаев, Николай Васильевич; NASA's NESSF program; RFBR [12-05-00152-a]

/ M. Desroche [et al.] // J. Geophys. Res-Space Phys. - 2012. - Vol. 117. - Ст. A07202, DOI 10.1029/2012JA017621. - Cited References: 50. - The authors thank Chris Arridge for initially suggesting this project. The authors are thankful to Adam Masters, Bob Ergun, Jack Gosling, Martin Goldman, and Dmitri Uzdensky for helpful discussions and guidance. This work was supported by NASA's NESSF program and JUNO mission. . - ISSN 0148-0227РУБ Astronomy & Astrophysics

Аннотация: Using idealized models of the magnetosheath and magnetosphere magnetic fields, plasma densities, and plasma flow, we test for the steady state viability of processes mediating the interaction between the solar wind and the Jovian magnetosphere. The magnetopause is modeled as an asymmetric paraboloid with variable asymmetry. The subsolar standoff of the magnetopause has been shown to exhibit a bimodal probability distribution (Joy et al., 2002). Only the expanded magnetopause is considered, with a standoff of similar to 90 R-J. We test where on the magnetopause surface large-scale reconnection may be affected by either a shear flow or diamagnetic drift due to a pressure gradient across the magnetopause boundary. We also test for the onset of the Kelvin-Helmholtz instability. We find that reconnection is inhibited on the dawn flank due to the large shear flows in this region, regardless of magnetopause shape or interplanetary magnetic field orientation. The presence of a high energy plasma population in the magnetosphere may inhibit reconnection over much of the magnetopause area, except when the fields are antiparallel. Additionally, most of the dawn flank of the magnetopause is Kelvin-Helmholtz unstable, regardless of magnetopause asymmetry; and the dusk flank tailward of the planet is Kelvin-Helmholtz unstable when the magnetopause is highly oblate.


Доп.точки доступа:
Desroche, M.; Bagenal, F.; Delamere, P.A.; Erkaev, N.V.; Еркаев, Николай Васильевич

/ A. Divin [et al.] // J. Geophys. Res-Space Phys. - 2012. - Vol. 117. - Ст. A06217, DOI 10.1029/2011JA017464. - Cited References: 43. - The present work is supported partially by the Onderzoekfonds KU Leuven (Research Fund KU Leuven), by the NASA MMS grant NNX08AO84G and by the European Commission's Seventh Framework Programme (FP7/2007-2013) under the grant agreement 263340 (SWIFF project, www. swiff. eu) and 269198 - Geoplasmas (Marie Curie International Research Staff Exchange Scheme). Additional support is provided by RFBR grants 09-05-91000-ANF-a, 12-05-00152-a and 12-05-00918-a, Austrian Science Fund project T193-N16 and by SPSU grants 11.38.47.2011 and 11.38.84.2012. The simulations were conducted on the resources of the Vlaams Supercomputer Centrum (VSC) at the Katholieke Universiteit Leuven. The authors wish to thank the reviewers for their comments that helped to improve the manuscript. . - ISSN 2169-9380РУБ Astronomy & Astrophysics

Аннотация: The Sweet-Parker analysis of the inner electron diffusion region of collisionless magnetic reconnection is presented. The study includes charged particles motion near the X-line and an appropriate approximation of the off-diagonal term for the electron pressure tensor. The obtained scaling shows that the width of the inner electron diffusion region is equal to the electron inertial length, and that electrons are accelerated up to the electron Alfven velocity in X-line direction. The estimated effective plasma conductivity is based on the electron gyrofrequency rather than the binary collision frequency, and gives the extreme (minimal) value of the plasma conductivity similar to Bohm diffusion. The scaling properties are verified by means of Particle-in-Cell simulations. An ad hoc parameter needs to be introduced to the scaling relations in order to better match the theory and simulations.


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

[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 1070-664XРУБ 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.

[Text] / U. Taubenschuss [et al.] // Ann. Geophys. - 2010. - Vol. 28, Is. 5. - pp. 1075-1100, DOI 10.5194/angeo-28-1075-2010. - Cited References: 92. - The author appreciates financial support on behalf of the projects 06/9690 from the Austrian Research Community and A3-12T63/2007-1 from the Styrian government. Participation at the ISSS8 was made possible due to the travel fellowship of UCLA. Nikolai Erkaev acknowledges support by RFBR grants Nos. 07-05-00135 and 09-05-91000-ANF. Charles Farrugia received NASA grants NNG06GD41G and NNX08AD11G. Christian Mostl and Ute Amerstorfer work under FWF projects P20145N16 and P21051-N16 of the Austrian Science Foundation, respectively. . - ISSN 0992-7689РУБ Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: We investigate the propagation of magnetic clouds (MCs) through the inner heliosphere using 2.5-D ideal magnetohydrodynamic (MHD) simulations. A numerical solution is obtained on a spherical grid, either in a meridional plane or in an equatorial plane, by using a Roe-type approximate Riemann solver in the frame of a finite volume approach. The structured background solar wind is simulated for a solar activity minimum phase. In the frame of MC propagation, special emphasis is placed on the role of the initial magnetic handedness of the MC's force-free magnetic field because this parameter strongly influences the efficiency of magnetic reconnection between the MC's magnetic field and the interplanetary magnetic field. Magnetic clouds with an axis oriented perpendicular to the equatorial plane develop into an elliptic shape, and the ellipse drifts into azimuthal direction. A new feature seen in our simulations is an additional tilt of the ellipse with respect to the direction of propagation as a direct consequence of magnetic reconnection. During propagation in a meridional plane, the initial circular cross section develops a concave-outward shape. Depending on the initial handedness, the cloud's magnetic field may reconnect along its backside flanks to the ambient interplanetary magnetic field (IMF), thereby losing magnetic flux to the IMF. Such a process in combination with a structured ambient solar wind has never been analyzed in detail before. Furthermore, we address the topics of force-free magnetic field conservation and the development of equatorward flows ahead of a concave-outward shaped MC. Detailed profiles are presented for the radial evolution of magnetoplasma and geometrical parameters. The principal features seen in our MHD simulations are in good agreement with in-situ measurements performed by spacecraft. The 2.5-D studies presented here may serve as a basis under more simple geometrical conditions to understand more complicated effects seen in 3-D simulations.


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

[Text] / B.Harris [et al.] // Ann. Geophys. - 2013. - Vol. 31, Is. 10. - P1779-1789, DOI 10.5194/angeo-31-1779-2013. - Cited References: 26. - Work at UNH is supported by NASA Grants NNX10AQ29G and NNX13AP39G. N. V. Erkaev is supported by grant No. 12-05-00152-a from the Russian Foundation of Basic Research. . - ISSN 0992-7689РУБ Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: Acceleration of magnetosheath plasma resulting from the draping of the interplanetary magnetic field (IMF) around the magnetosphere can give rise to flow speeds that exceed that of the solar wind (V-SW) by up to similar to 60%. Three case event studies out of 34 identified events are described. We then present a statistical study of draping-related accelerations in the magnetosheath. Further, we compare the results with the recent theory of Erkaev et al. (2011, 2012). We present a methodology to help distinguish draping-related accelerations from those caused by magnetic reconnection. To rule out magnetopause reconnection at low latitudes, we focus mainly on the positive B-z phase during the passage of interplanetary coronal mass ejections (ICMEs), as tabulated in Richardson and Cane (2010) for 1997-2009, and adding other events from 2010. To avoid effects of high-latitude reconnection poleward of the cusp, we also consider spacecraft observations made at low magnetic latitudes. We study the effect of upstream Alfven Mach number (M-A) and magnetic local time (MLT) on the speed ratio V/V-SW. The comparison with theory is good. Namely, (i) flow speed ratios above unity occur behind the dawn-dusk terminator, (ii) those below unity occur on the dayside magnetosheath, and (iii) there is a good general agreement in the dependence of the V ratio on M-A.


Доп.точки доступа:
Harris, B.; Farrugia, C.J.; Erkaev, N.V.; Еркаев, Николай Васильевич; Torbert, R.B.; NASA [NNX10AQ29G, NNX13AP39G]; Russian Foundation of Basic Research [12-05-00152-a]

[Text] / D. B. Korovinskiy [et al.] // J. Geophys. Res-Space Phys. - 2008. - Vol. 113, Is. A4. - Ст. A04205, DOI 10.1029/2007JA012852. - Cited References: 56 . - ISSN 0148-0227РУБ Astronomy & Astrophysics

Аннотация: An analytical model of steady-state magnetic reconnection in a collisionless incompressible plasma is developed using the electron Hall MHD approximation. It is shown that the initial complicated system of equations may be split into a system of independent equations, and the solution of the problem is based on the solution of the Grad-Shafranov equation for a magnetic potential. This equation is found to be fundamental for the whole problem analysis. An electric field potential jump across the electron diffusion region and the separatrices is proved to be the necessary condition for steady- state reconnection. Besides of this fact, it is found that the protons in-plane motion obeys to Bernoulli law. The solution obtained demonstrates all essential Hall reconnection features, namely proton acceleration up to Alfven velocities and the formation of Hall current systems and a magnetic field structure as expected.


Доп.точки доступа:
Korovinskiy, D.B.; Semenov, V.S.; Erkaev, N.V.; Еркаев, Николай Васильевич; Divin, A.V.; Biernat, H.K.

[Text] / D. Korovinskiy [et al.] // Adv. Space Res. - 2008. - Vol. 41, Is. 10. - P1556-1561, DOI 10.1016/j.asr.2006.10.014. - Cited References: 13 . - ISSN 0273-1177РУБ Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: The problem of steady-state magnetic reconnection in an infinite current layer in collisionless, incompressible, nonresistive plasma, except of the electron diffusion region, is examined analytically using the electron Hall magnetohydrodynamics approach. It is found that this approach allows reducing the problem to the magnetic field potential finding, while last one has to satisfy the Grad-Shafranov equation. The obtained solution demonstrates all essential Hall reconnection features, namely proton acceleration up to Alfven velocities, the forming of Hall current systems and the magnetic field structure expected. It turns out that the necessary condition of steady-state reconnection to exist is an electric field potential jump across the electron diffusion region and the separatrices. Besides, the powerful mechanism of electron acceleration in X-line direction is required. It must accelerate electrons up to the electron Alfven velocity inside the diffusion region and on the separatrixes. This is a necessary condition for steady-state reconnection as well. (c) 2006 COSPAR. Published by Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Korovinskiy, D.; Semenov, V.S.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.; Penz, T.

[Text] / S. Muhlbachler [et al.] ; ed.: X. BlancoCano // COMPARATIVE MAGNETOSPHERES. 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. 11. - P2103-2107, DOI 10.1016/j.asr.2003.04.052. - Cited References: 10 . - ISBN 0273-1177РУБ Engineering, Aerospace + Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: During periods of a persistent southward interplanetary magnetic field, reconnection is initiated at the dayside magnetopause and flux is transported away to the nightside magnetosphere. This is the so-called phenomenon of magnetosphere erosion. In this paper, erosion at the terrestrial magnetopause is studied. A new theoretical approach to study erosion at the magnetopause on the basis of time-dependent reconnection is presented. We calculate the earthward motion of the magnetopause resulting from each reconnection pulse, together with the associated bow shock motion. Thus, the displacement of both boundary layers is presented. (C) 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Muhlbachler, S.; Semenov, V.S.; Biernat, H.K.; Erkaev, N.V.; Еркаев, Николай Васильевич; Kubyshkin, I.V.; Farrugia, C.J.; Langmayr, D.; Vogl, D.F.; BlancoCano, X. \ed.\

[Text] / D. Langmayr [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. - P780-783, DOI 10.1016/S0273-1177(03)00631-8. - Cited References: 4 . - ISBN 0273-1177РУБ Engineering, Aerospace + Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: It is well known that in contrast to the Alfven wave, which is propagating strictly along the direction of the magnetic field, a slow mode wave shows a deviation from the ambient magnetic field. This deviation is determined by the dispersion equation for the slow mode wave. With the help of this dispersion equation we present a theoretical study of the spatial and temporal evolution of an initial pressure disturbance in a homogeneous and constant background magnetic field. The main factor determining the amount of the deviation is the so-called plasma beta, i.e., the ratio of magnetic to thermal energy, which is investigated quantitatively. We obtain that for a low beta plasma, the disturbance propagates more or less strictly along the magnetic field. However, for increasing beta the disturbances across the magnetic field gets stronger. These results can be applied to magnetospheric phenomena, where slow shocks may play a role as a kind of energy carrier as in the case of the Io-Jupiter interaction or magnetic field line reconnection. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

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Доп.точки доступа:
Langmayr, D.; Erkaev, N.V.; Еркаев, Николай Васильевич; Semenov, V.S.; Macher, W.; Biernat, H.K.; Rucker, H.O.

[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 0273-1177РУБ 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.

[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 0032-0633РУБ 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.

[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 0273-1177РУБ 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.

[Text] / S. Muhlbachler [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. - P1113-1118, DOI 10.1016/S0273-1177(02)00033-9. - Cited References: 14 . - ISBN 0273-1177РУБ Engineering, Aerospace + Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: Magnetic reconnection is a process which allows topological different magnetic fields to interconnect. Thus, in magnetospheric context, reconnection is strongly associated with substorm phenomena. Because many observations show a difference between the pressure parallel and perpendicular to the magnetic field, it is reasonable to study the reconnection mechanism for the set of equations, involving a pressure tensor. Existing theoretical work for isotropic weak reconnection is extended for anisotropic theory. In particular, the reconnection associated discontinuities as the Alfven discontinuity, the slow shock, and the contact discontinuity are generalized for anisotropic pressure. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.


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

[Text] / N. V. Erkaev, V. S. Semenov, F. Jamitzky // Phys. Rev. Lett. - 2000. - Vol. 84, Is. 7. - P1455-1458, DOI 10.1103/PhysRevLett.84.1455. - Cited References: 16 . - ISSN 0031-9007РУБ Physics, Multidisciplinary

Аннотация: The reconnection rate for the canonical simplest case of steady-state two-dimensional symmetric reconnection in an incompressible plasma is found by matching of an outer Petschek solution and an internal diffusion region solution. The reconnection rate obtained naturally incorporates both Sweet-Parker and Petschek regimes; while the latter is possible only for a strongly localized resistivity.


Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Semenov, V.S.; Jamitzky, F.

[Text] / N. V. Erkaev, V. S. Semenov // PROCEEDINGS OF THE FIFTH INTERNATIONAL CONFERENCE ON SUBSTORMS. Ser. ESA SPECIAL PUBLICATIONS : ESA PUBLICATIONS DIVISION C/O ESTEC, 2000. - Vol. 443: 5th International Conference on Substorms (MAY 16-20, 2000, ST PETERSBURG, RUSSIA). - P161-164. - Cited References: 14 . - ISBN 0379-6566. - ISBN 92-9092-772-0РУБ Astronomy & Astrophysics

Аннотация: In the theory of magnetic reconnection there is the old problem: it is still unclear which conditions make Petschek-type reconnection to be possible and which are responsible for the Sweet-Parker regime. The fact is that numerical simulations were not able to reproduce solution of Petschek type but rather were in favor of Sweet-Parker solution unless the resistivity was localized in a small region. The problem of reconnection rate is connected with the matching of a solution for the diffusion region where dissipation is important, and solution for the convective zone where ideal MHD equations can be used. Using the nonsteady numerical MHD solution obtained for the diffusion region, we determine the reconnection rate as a function of time by matching of the outer Petschek solution and the internal diffusion region solution. The reconnection rate obtained naturally incorporates both Sweet-Parker and Petschek regimes, the latter seems to be possible only for the case with strongly localized resistivity.


Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Semenov, V.S.

[Text] / C. J. Farrugia [et al.] // J. Geophys. Res-Space Phys. - 1998. - Vol. 103, Is. A4. - P6703-6727DOI 10.1029/97JA03248. - Cited References: 39 . - РУБ Astronomy & Astrophysics

Аннотация: We present maximum growth rate charts of the Kelvin-Helmholtz (KH) and Rayleigh-Taylor (RT) instabilities at the dayside magnetopause (MP), considering two orientations of the interplanetary magnetic field (IMF) (due north and 30 degrees west of north). We input parameters in the plasma depletion layer calculated from an MHD code. We study both a sharp MP transition and an MP with an attached boundary layer ("thin" and "thick" approximations, respectively). Our analysis applies to wavelengths (lambda) from similar to 2 x 10(3) km to less than or equal to 9 R-E. Thin model results are as follows: For a stationary MP and due north IMF, the off-noon, low-latitude MP is very low shear (less than or equal to 10 degrees) and is substantially KH active. With an IMF inclined to north, extremely low shear, KH-active regions are confined to two strips, one in each hemisphere, where short lambda perturbations are generated, which propagate as surface ripples on the high-latitude, duskside MP. For a sunward accelerating magnetopause and IMF north, a large part of the MP is unstable. With an inclined IMF, the KH+RT unstable strips are broader and growth rates are higher. Thick model results are as follows: For IMF due north and a stationary MP, the middle-to high-latitude MP is stable. At middle to low latitudes, the inner edge of the boundary layer (IEBL) is active, except fora 2-hour local time band on either side of noon. For the inclined IMF, the MP is stable for long lambda, with activity for short lambda confined to two strips, as before, with slightly reduced growth rates. For the IEBL, a clear dawn-dusk asymmetry in KH activity is evident. When the MP accelerates sunward and the IMF points north, we have to consider also the lambda of the perturbation. For short lambda, growth rates are enhanced with respect to stationarity at both the NIP and the IEBL. While there are extensive regions of negligible growth at the MP, the entire IEBL is RT + KH unstable. We give an example of a long lambda perturbation where both interfaces are coupled and oscillate together. Finally, for an inclined IMF, we have at the MP unstable strips which are wider and have higher growth rates. The IEBL, by contrast, is completely destabilized, with larger growth rates than under stationary conditions.

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Доп.точки доступа:
Farrugia, C.J.; Gratton, F.T.; Bender, L.; Biernat, H.K.; Erkaev, N.V.; Еркаев, Николай Васильевич; Quinn, J.M.; Torbert, R.B.; Denisenko, V.V.; Денисенко, Валерий Васильевич

[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.