Труды сотрудников ИВМ СО РАН

/ 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] / C.J. Farrugia [et al.] // J. Geophys. Res-Space Phys. - 2010. - Vol. 115. - Ст. A08227, DOI 10.1029/2009JA015128. - Cited References: 34. - The authors would like to thank David Burgess for helpful discussions. Part of this work was done when NVE was on a research visit to the Space Science Center of the University of New Hampshire, USA. This work is supported by NASA grants NNX08AD11G and NNG06GD41G, and also by RFBR grants 07-05-00135, 09-05-91000-ANF_a and by Program 16 of RAS. R. P. Lin has been supported in part by NASA grant NNX08AE34G at UC Berkeley, and the WCU grant (R31-10016) funded by the Korean Ministry of Education, Science and Technology. We thank D. J. McComas and H. J. Singer for the ACE plasma data and GOES magnetic field data, respectively, obtained through NASA cdaweb site. . - ISSN 0148-0227РУБ Astronomy & Astrophysics

Аннотация: While there are many approximations describing the flow of the solar wind past the magnetosphere in the magnetosheath, the case of perfectly aligned (parallel or antiparallel) interplanetary magnetic field (IMF) and solar wind flow vectors can be treated exactly in a magnetohydrodynamic (MHD) approach. In this work we examine a case of nearly-opposed (to within 15) interplanetary field and flow vectors, which occurred on October 24-25, 2001 during passage of the last interplanetary coronal mass ejection in an ejecta merger. Interplanetary data are from the ACE spacecraft. Simultaneously Wind was crossing the near-Earth (X similar to -13 Re) geomagnetic tail and subsequently made an approximately 5-hour-long magnetosheath crossing close to the ecliptic plane (Z = -0.7 Re). Geomagnetic activity was returning steadily to quiet, "ground" conditions. We first compare the predictions of the Spreiter and Rizzi theory with the Wind magnetosheath observations and find fair agreement, in particular as regards the proportionality of the magnetic field strength and the product of the plasma density and bulk speed. We then carry out a small-perturbation analysis of the Spreiter and Rizzi solution to account for the small IMF components perpendicular to the flow vector. The resulting expression is compared to the time series of the observations and satisfactory agreement is obtained. We also present and discuss observations in the dawnside boundary layer of pulsed, high-speed (v similar to 600 km/s) flows exceeding the solar wind flow speeds. We examine various generating mechanisms and suggest that the most likely cause is a wave of frequency 3.2 mHz excited at the inner edge of the boundary layer by the Kelvin-Helmholtz instability.


Доп.точки доступа:
Farrugia, C.J.; Erkaev, N.V.; Еркаев, Николай Васильевич; Torbert, R.B.; Biernat, H.K.; Gratton, F.T.; Szabo, A.; Kucharek, H.; Matsui, H.; Lin, R.P.; Ogilvie, K.W.; Lepping, R.P.; Smith, C.W.

[Text] / U.V. Amerstorfer [et al.] // Phys. Plasmas. - 2010. - Vol. 17, Is. 7. - Ст. 72901, DOI 10.1063/1.3453705. - Cited References: 26. - This work was supported by the FWF under Project No. P21051-N16 and also by the RFBR under Grant No. 09-05-91000-ANF_a. . - ISSN 1070-664XРУБ Physics, Fluids & Plasmas

Аннотация: Results of two-dimensional nonlinear numerical simulations of the magnetohydrodynamic Kelvin-Helmholtz instability are presented. A boundary layer of a certain width is assumed, which separates the plasma in the upper layer from the plasma in the lower layer. A special focus is given on the influence of a density increase toward the lower layer. The evolution of the Kelvin-Helmholtz instability can be divided into three different phases, namely, a linear growth phase at the beginning, followed by a nonlinear phase with regular structures of the vortices, and finally, a turbulent phase with nonregular structures. The spatial scales of the vortices are about five times the initial width of the boundary layer. The considered configuration is similar to the situation around unmagnetized planets, where the solar wind (upper plasma layer) streams past the ionosphere (lower plasma layer), and thus the plasma density increases toward the planet. The evolving vortices might detach around the terminator of the planet and eventually so-called plasma clouds might be formed, through which ionospheric material can be lost. For the special case of a Venus-like planet, loss rates are estimated, which are of the order of estimated loss rates from observations at Venus. (C) 2010 American Institute of Physics. [doi:10.1063/1.3453705]


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

[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] / H. Gunell [et al.] // Plasma Phys. Control. Fusion. - 2008. - Vol. 50, Is. 7. - Ст. 74018, DOI 10.1088/0741-3335/50/7/074018. - Cited References: 27 . - ISSN 0741-3335РУБ Physics, Fluids & Plasmas + Physics, Nuclear

Аннотация: We present measurements of oscillations in the electron density, ion density and ion velocity in the induced magnetosphere of Mars. The fundamental frequency of the oscillations is a few millihertz, but higher harmonics are present in the spectrum. The oscillations are observed in a region where there is a velocity shear in the plasma flow. The fundamental frequency is in agreement with computational results from an ideal-MHD model. An interpretation based on velocity-shear instabilities is described.


Доп.точки доступа:
Gunell, H.; Amerstorfer, U.V.; Nilsson, H.; Grima, C.; Koepke, M.; Franz, M.; Winningham, J.D.; Frahm, R.A.; Sauvaud, J.A.; Fedorov, A.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.; Holmstrom, M.; Lundin, R.; Barabash, S.

[Text] / H. K. Biernat [et al.] // Planet Space Sci. - 2007. - Vol. 55, Is. 12. - P1793-1803, DOI 10.1016/j.pss.2007.01.006. - Cited References: 28 . - ISSN 0032-0633РУБ Astronomy & Astrophysics

Аннотация: In this paper, the solar wind flow around Venus is modeled as a nondissipative fluid which obeys the ideal magnetohydrodynamic equations extended for mass loading processes. The mass loading parameter is calculated for four different cases, corresponding to solar minimum and maximum XUV flux and to nominal and low solar wind velocity. We get smooth profiles of the field and plasma parameters in the magnetosheath. Based on the results of this flow model, we investigate the occurrence of the Kelvin-Helmholtz (K-H) instability at the equatorial flanks of the ionopause of Venus. By comparing the instability growth time with the propagation time of the K-H wave, we find that the K-H instability can evolve at the ionopause for all four solar wind conditions. (C) 2007 Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Biernat, H.K.; Erkaev, N.V.; Еркаев, Николай Васильевич; Amerstorfer, U.V.; Penz, T.; Lichtenegger, H.I.M.

[Text] / U. V. Amerstorfer [et al.] // Planet Space Sci. - 2007. - Vol. 55, Is. 12. - P1811-1816, DOI 10.1016/j.pss.2007.01.015. - Cited References: 20 . - ISSN 0032-0633РУБ Astronomy & Astrophysics

Аннотация: In this paper, the Kelvin-Helmholtz instability is studied by solving the ideal MHD equations for a compressible plasma. A transition layer of finite thickness between two plasmas, across which the magnitude of the velocity and the density change, is assumed. Growth rates are presented for the transverse case, i.e., the flow velocity is perpendicular to the magnetic field. If only the velocity changes across the boundary layer and the density is kept constant, an important quantity affecting the growth of the Kelvin-Helmholtz instability is the magnetosonic Mach number, which characterizes compressibility. The growth rates for the case when both, the velocity and the density, change are very sensitive to the ratio of the upper plasma density to the lower plasma density: a decrease of the density ratio yields a decrease of the growth rate. Including a density profile is very important for the application of the Kelvin-Helmholtz instability to the solar wind flow around unmagnetized planets, e.g., Venus, where the plasma density increases from the magnetosheath to the ionosphere. (C) 2007 Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Amerstorfer, U.V.; Erkaev, N.V.; Еркаев, Николай Васильевич; Langmayr, D.; Biernat, H.K.

[Text] / T. Penz [et al.] // Planet Space Sci. - 2004. - Vol. 52, Is. 13. - P1157-1167, DOI 10.1016/j.pss.2004.06.001. - Cited References: 53 . - ISSN 0032-0633РУБ Astronomy & Astrophysics

Аннотация: Mars Global Surveyor detected cold electrons above the Martian ionopause, which can be interpreted as detached ionospheric plasma clouds. Similar observations by the Pioneer Venus Orbiter electron temperature probe showed also extreme spatial irregularities of electrons in the form of plasma clouds on Venus, which were explained by the occurrence of the Kelvin-Helmholtz instability. Therefore, we suggest that the Kelvin-Helmholtz instability may also detach ionospheric plasma clouds on Mars. We investigate the instability growth rate at the Martian ionopause resulting from the flow of the solar wind for the case where the interplanetary magnetic field is oriented normal to the flow direction. Since the velocity shear near the subsolar point is very small, this area is stable with respect to the Kelvin-Helmholtz instability. We found that the highest flow velocities are reached at the equatorial flanks near the terminator plane, while the maximum plasma density in the terminator plane appears at the polar areas. By comparing the instability growth rate with the magnetic barrier formation time, we found that the instability can evolve into a non-linear stage at the whole terminator plane but preferably at the equatorial flanks. Escape rates of O+ ions due to detached plasma clouds in the order of about 2 x 10(23)-3 x 10(24) s(-1) are found. Thus, atmospheric loss caused by the Kelvin-Helmholtz instability should be comparable with other non-thermal loss processes. Further, we discuss our results in view of the expected observations of heavy ion loss rates by ASPERA-3 on board of Mars Express. (C) 2004 Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Penz, T.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.; Lammer, H.; Amerstorfer, U.V.; Gunell, H.; Kallio, E.; Barabash, S.; Orsini, S.; Milillo, A.; Baumjohann, W.

[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. 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 0273-1177РУБ 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.

[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 1023-5809РУБ 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.

[Text] / C. J. Farrugia [et al.] // Adv. Space Res. - 2009. - Vol. 44, Is. 11. - P1288-1294, DOI 10.1016/j.asr.2009.07.003. - Cited References: 29. - Work supported by Project P20145-N16 and by I.2/04 Osterreichische Austauschdient. . - ISSN 0273-1177РУБ Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: Using a serendipitous configuration of the ACE and Wind spacecraft, we monitor the response of the distant geomagnetic tail (similar to-220 R(E)) to an abrupt, approx. fivefold pressure drop (from similar to 19.0 to similar to 3.5 nPa) at the front boundary of a magnetic cloud (MC) on November 20, 2003. The interplanetary data are from ACE in orbit around the L1 point. The far-tail observations are from Wind, which was nominally in the magnetosheath, separated from the Sun-Earth line by similar to 40 R(E). The magnetic field in the innermost sheath region of the MC had a large B(y) (similar to 30 nT) and substantial and variable flows lateral to the Sun-Earth line. There was also a significant northward field (similar to 35 nT), unique in the vicinity of this MC. These extreme values are reached in a filament forming the earliest relic of material accreted by the MC en route to Earth. The effects resulting from these on the far geomagnetic tail are: (1) expansion, (2) tail twisting, and (3) tail tilting. These extreme conditions were in part responsible for a crossing by Wind of a neutral sheet which is tilted by similar to 85 degrees to the ecliptic. Further, Wind made two successive excursions deep into the geomagnetic tail, in the first of which a tailward flow burst of similar to 1200 km/s was observed. The dayside part of the interaction of the sudden and large dynamic pressure drop with the bow shock is studied with a local 3D MHD simulation. This work is a contribution to the area ICME/MC-sheaths-magnetosheath interactions. (C) 2009 COSPAR. Published by Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Farrugia, C.J.; Erkaev, N.V.; Еркаев, Николай Васильевич; Maynard, N.C.; Richardson, I.G.; Sandholt, P.E.; Langmayr, D.; Ogilvie, K.W.; Szabo, A.; Taubenschuss, U.; Torbert, R.B.; Biernat, H.K.; NASA [NNG05GG25G, NNX08AD11G]; RFBR [07-05-00135]; RAS [2.16, 16.3]; Osterreichische Austauschdient [I.2/04]; [P20145-N16]

[Text] / U. V. Mostl [et al.] // Icarus. - 2011. - Vol. 216, Is. 2. - P476-484, DOI 10.1016/j.icarus.2011.09.012. - Cited References: 27. - This work is supported by the Austrian Science Fund Project P21051-N16 and also by RFBR Grant No. 09-05-91000-ANF_a. H.L. and H.G. are supported by the Helmholtz Association through the research alliance "Planetary Evolution and Life" and by the Austrian Science Fund Project I199-N16. M.Z. and D.K. are supported by the Austrian Science Fund Project I193-N16. . - ISSN 0019-1035РУБ Astronomy & Astrophysics

Аннотация: The Kelvin-Helmholtz instability gained scientific attention after observations at Venus by the spacecraft Pioneer Venus Orbiter gave rise to speculations that the instability contributes to the loss of planetary ions through the formation of plasma clouds. Since then, a handful of studies were devoted to the Kelvin-Helmholtz instability at the ionopause and its implications for Venus. The aim of this study is to investigate the stability of the two instability-relevant boundary layers around Venus: the induced magnetopause and the ionopause. We solve the 2D magnetohydrodynamic equations with the total variation diminishing Lax-Friedrichs algorithm and perform simulation runs with different initial conditions representing the situation at the boundary layers around Venus. Our results show that the Kelvin-Helmholtz instability does not seem to be able to reach its nonlinear vortex phase at the ionopause due to the very effective stabilizing effect of a large density jump across this boundary layer. This seems also to be true for the induced magnetopause for low solar activity. During high solar activity, however, there could occur conditions at the induced magnetopause which are in favour of the nonlinear evolution of the instability. For this situation, we estimated roughly a growth rate for planetary oxygen ions of about 7.6 x 10(25) s(-1), which should be regarded as an upper limit for loss due to the Kelvin-Helmholtz instability. (C) 2011 Elsevier Inc. All rights reserved.


Доп.точки доступа:
Mostl, U.V.; Erkaev, N.V.; Еркаев, Николай Васильевич; Zellinger, M.; Lammer, H.; Groller, H.; Biernat, H.K.; Korovinskiy, D.

[Text] / N. V. Erkaev [et al.] // J. Geophys. Res-Space Phys. - 2014. - Vol. 119, Is. 2. - P. 1121-1128, DOI 10.1002/2013JA019514. - Cited References: 23. - This work was done while NVE was on a research visit to the Space Science Center of UNH. This work is supported by RFBR grant N 12-05-00152-a and also by the Austrian "Fonds zur Forderung der wissenschaftlichen Forschung" under Project I 193-N16 and the "Verwaltungsstelle fur Auslandsbeziehungen" of the Austrian Academy of Sciences. Work by CJF was supported by NASA grants NNX10AQ29G and NNX13AP39G. NVE and CJF acknowledge the support by the International Space Science Institute (ISSI, Switzerland) and discussions within the ISSI Team 214 on Flow-Driven Instabilities of the Sun-Earth System. . - ISSN 2169-9380. - ISSN 2169-9402РУБ Astronomy & Astrophysics

Аннотация: We apply a semianalytic magnetohydrodynamic approach to describe effects in the nightside magnetosheath related to accelerated magnetosheath flows caused by the draping of interplanetary magnetic field (IMF). Assuming a northward IMF direction, we show the development of slow mode fronts in the far tail (tailward of approximately -60 RmE). We find that accelerated flows north and south of the equator start to converge toward lower latitudes. The ensuing plasma compression gives rise to slow mode waves in the equatorial region which, further down the tail, evolve into slow mode shocks. These fronts propagating along the magnetic field lines are characterized by sharp increases of plasma density, pressure, and temperature and a decrease in the magnetic field strength. The magnetic pressure exhibits an anticorrelation with the plasma pressure, but the total pressure is fairly constant across the fronts. The field-aligned plasma velocity component anticorrelates with the plasma density, while the perpendicular velocity component does not have sharp variations at the fronts. For northward IMF, these fronts appear near the equatorial region and then propagate to higher latitudes. This effect is not very sensitive to the particular shape of the magnetopause. Lowering the upstream Alfven Mach number increases the strength of the slow mode waves, which also develop closer to Earth. We predict that this effect can be observed by space probes skimming the far tail. Key Points Magnetic field lines drape around the magnetosphere The field line bend makes the flows converge in the far tail We show that these give rise to slow mode waves

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ИВМ СО РАН

Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Farrugia, C.J.; Mezentsev, A.V.; Torbert, R.B.; Biernat, H.K.; RFBR [N 12-05-00152-a]; Austrian "Fonds zur Forderung der wissenschaftlichen Forschung" [I 193-N16]; "Verwaltungsstelle fur Auslandsbeziehungen" of the Austrian Academy of Sciences; NASA [NNX10AQ29G, NNX13AP39G]; International Space Science Institute (ISSI, Switzerland)

/ S. A. Kiehas [et al.] // J. Geophys. Res-Space Phys. - 2017. - Vol. 122, Is. 3. - P3212-3231, DOI 10.1002/2016JA023169. - Cited References:48. - This work is supported by the Austrian Science Fund (FWF) J3041-N16 and P27012-N27 and by grants 16-05-00470, and 15-05-00879-a from the Russian Foundation of Basic Research. No data were used. . - ISSN 2169-9380. - ISSN 2169-9402РУБ Astronomy & Astrophysics

Аннотация: We evaluate the large-scale energy budget of magnetic reconnection utilizing an analytical time-dependent impulsive reconnection model and a numerical 2-D MHD simulation. With the generalization to compressible plasma, we can investigate changes in the thermal, kinetic, and magnetic energies. We study these changes in three different regions: (a) the region defined by the outflowing plasma (outflow region, OR), (b) the region of compressed magnetic fields above/below the OR (traveling compression region, TCR), and (c) the region trailing the OR and TCR (wake). For incompressible plasma, we find that the decrease inside the OR is compensated by the increase in kinetic energy. However, for the general compressible case, the decrease in magnetic energy inside the OR is not sufficient to explain the increase in thermal and kinetic energy. Hence, energy from other regions needs to be considered. We find that the decrease in thermal and magnetic energy in the wake, together with the decrease in magnetic energy inside the OR, is sufficient to feed the increase in kinetic and thermal energies in the OR and the increase in magnetic and thermal energies inside the TCR. That way, the energy budget is balanced, but consequently, not all magnetic energy is converted into kinetic and thermal energies of the OR. Instead, a certain fraction gets transfered into the TCR. As an upper limit of the efficiency of reconnection (magnetic energy kinetic energy) we find eta(eff)=1/2. A numerical simulation is used to include a finite thickness of the current sheet, which shows the importance of the pressure gradient inside the OR for the conversion of kinetic energy into thermal energy.

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Держатели документа:
Austrian Acad Sci, Space Res Inst, Graz, Austria.
St Petersburg State Univ, Inst Phys, St Petersburg, Russia.
Russian Acad Sci, Inst Computat Modelling, Siberian Branch, Krasnoyarsk, Russia.
Siberian Fed Univ, Dept Computat Phys, Krasnoyarsk, Russia.

Доп.точки доступа:
Kiehas, S. A.; Volkonskaya, N. N.; Semenov, V. S.; Erkaev, N.V.; Бекежанова, Виктория Бахытовна; Kubyshkin, I. V.; Zaitsev, I. V.; Austrian Science Fund (FWF) [J3041-N16, P27012-N27]; Russian Foundation of Basic Research [16-05-00470, 15-05-00879-a]