Труды сотрудников ИВМ СО РАН

[Text] : статья / I.L. Arshukova, N.V. Erkaev, H.K. Biernat // International journal of geomagnetism and aeronomy. - 2002. - Vol. 3, № 1. - p. 27–34
Аннотация: This article deals with the magnetohydrodynamic instability of the high magnetic shear magnetopause, which is considered to be a thin layer with a constant curvature radius and plasma velocity shear. In our model, the magnetic field and plasma density are assumed to be piecewise constant in three regions: in the magnetosphere adjacent to the magnetopause, in the magnetosheath, and inside a thin layer associated with the magnetopause. The plasma parameters and the magnetic field are assumed to obey the ideal incompressible magnetohydrodynamics. A Fourier analysis is used to calculate small perturbations of magnetic field and plasma parameters near the magnetopause in a linear approximation. The instability growth rate is obtained as a function of the angle between the velocity vector and the geomagnetic field direction for different plasma bulk speeds, wave numbers and curvature radii. The resulting instability is a mixture of interchange and Kelvin-Helmholtz instabilities on a surface with a nonzero curvature. The instability growth rate is an increasing function of the tangential velocity component perpendicular to the magnetic field. On the other hand, the growth rate is a decreasing function of the velocity component along the magnetic field.

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

Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.; Аршукова И.Л.

[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

29.27.45

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

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

[Text] : статья / V. B. Bekezhanova, O. Kabov // Book of abstracts Sixth Int. conf. «Two-Phase Systems for Ground and Space Applications». - 2011. - p. 46


Доп.точки доступа:
Kabov, O.; Бекежанова, Виктория Бахытовна

[Text] : статья / V.B. Bekezhanova // Journal of Applied Mechanics and Technical Physics. - 2011. - Vol. 52, Iss. 1. - p. 74-81DOI 10.1134/S0021894411010111 . -
Аннотация: An exact solution is obtained for the problem of steady flow in a system of two horizontal layers of immiscible fluids with a common interface. The stability of the flow is studied by a linearization method. It is shown that the occurrence of instabilities is due to the different governing parameters of the fluids (thickness, heating conditions, viscous and thermal conductivity of the fluids). It is found that under constant gravity conditions, the perturbations are monotonic, and in zero gravity, oscillatory thermocapillary instability occurs.

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Доп.точки доступа:
Бекежанова, Виктория Бахытовна

/ D.B. Korovinskiy [et al.] // J. Geophys. Res-Space Phys. - 2013. - Vol. 118, Is. 3. - P1146-1158, DOI 10.1002/jgra.50206. - Cited References: 39. - This work is supported by the Austrian Science Fund (FWF): I193-N16, by the Onderzoekfonds KU Leuven (Research Fund KU Leuven), by RFBR Grants 12-05-00918-a and 12-05-00152-a, and by SPSU Grants 11.38.47.2011 and 11.38.84.2012. The research has received funding also from the European Union Seventh Framework Programme [FP7/2007-2013] under grant agreement 269198-Geoplasmas (Marie Curie International Research Staff Exchange Scheme) and 218816 (SOTERIA project). The simulations were conducted on the resources of the Vlaams Supercomputer Centrum (VSC) at the Katholieke Universiteit Leuven. N.V.E., V.S.S. and D.B.K. thank also ISSI for hospitality and financial support. The authors thank reviewers for their comments, which gave us the substantial aid in preparing of this manuscript. . - 13. - ISSN 2169-9380РУБ Astronomy & Astrophysics

Аннотация: The paper presents the detailed numerical investigation of the "double-gradient mode," which is believed to be responsible for the magnetotail flapping oscillations-the fast vertical (normal to the layer) oscillations of the Earth's magnetotail plasma sheet with a quasiperiod similar to 100-200 s. The instability is studied using the magnetotail near-equilibrium configuration. For the first time, linear three-dimensional numerical analysis is complemented with full 3-D MHD simulations. It is known that the "double-gradient mode" has unstable solutions in the region of the tailward growth of the magnetic field component, normal to the current sheet. The unstable kink branch of the mode is the focus of our study. Linear MHD code results agree with the theory, and the growth rate is found to be close to the peak value, provided by the analytical estimates. Full 3-D simulations are initialized with the numerically relaxed magnetotail equilibrium, similar to the linear code initial condition. The calculations show that current layer with tailward gradient of the normal component of the magnetic field is unstable to wavelengths longer than the curvature radius of the field line. The segment of the current sheet with the earthward gradient of the normal component makes some stabilizing effect (the same effect is registered in the linearized MHD simulations) due to the minimum of the total pressure localized in the center of the sheet. The overall growth rate is close to the theoretical double-gradient estimate averaged over the computational domain.

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

[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]

/ C. J. Farrugia [et al.] // Sol. Phys. - 2012. - Vol. 281, Is. 1. - pp. 461-489, DOI 10.1007/s11207-012-0119-1. - Cited References: 53 . - 29. - ISSN 0038-0938РУБ Astronomy & Astrophysics

Аннотация: We discuss the temporal variations and frequency distributions of solar wind and interplanetary magnetic field parameters during the solar minimum of 2007-2009 from measurements returned by the IMPACT and PLASTIC instruments on STEREO-A. We find that the density and total field strength were significantly weaker than in the previous minimum. The Alfv,n Mach number was higher than typical. This reflects the weakness of magnetohydrodynamic (MHD) forces, and has a direct effect on the solar wind-magnetosphere interactions. We then discuss two major aspects that this weak solar activity had on the magnetosphere, using data from Wind and ground-based observations: i) the dayside contribution to the cross-polar cap potential (CPCP), and ii) the shapes of the magnetopause and bow shock. For i) we find a low interplanetary electric field of 1.3 +/- 0.9 mV m(-1) and a CPCP of 37.3 +/- 20.2 kV. The auroral activity is closely correlated to the prevalent stream-stream interactions. We suggest that the Alfven wave trains in the fast streams and Kelvin-Helmholtz instability were the predominant agents mediating the transfer of solar wind momentum and energy to the magnetosphere during this three-year period. For ii) we determine 328 magnetopause and 271 bow shock crossings made by Geotail, Cluster 1, and the THEMIS B and C spacecraft during a three-month interval when the daily averages of the magnetic and kinetic energy densities attained their lowest value during the three years under survey. We use the same numerical approach as in Fairfield's (J. Geophys. Res. 76, 7600, 1971) empirical model and compare our findings with three magnetopause models. The stand-off distance of the subsolar magnetopause and bow shock were 11.8 R-E and 14.35 R-E, respectively. When comparing with Fairfield's (1971) classic result, we find that the subsolar magnetosheath is thinner by similar to 1 R-E. This is mainly due to the low dynamic pressure which results in a sunward shift of the magnetopause. The magnetopause is more flared than in Fairfield's model. By contrast the bow shock is less flared, and the latter is the result of weaker MHD forces.

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Доп.точки доступа:
Farrugia, C.J.; Harris, B.; Leitner, M.; Mostl, C.; Galvin, A.B.; Simunac, K.D.C.; Torbert, R.B.; Temmer, M.B.; Veronig, A.M.; Erkaev, N.V.; Еркаев, Николай Васильевич; Szabo, A.; Ogilvie, K.W.; Luhmann, J.G.; Osherovich, V.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

[Text] / E.N. Vasil'ev, D.A. Nesterov // Comput. Math. Math. Phys. - 2010. - Vol. 50, Is. 11. - pp. 1851-1858, DOI 10.1134/S0965542510110096. - Cited References: 9 . - ISSN 0965-5425РУБ Mathematics, Applied + Physics, Mathematical

Аннотация: A nonstationary three-dimensional magnetohydrodynamic (MHD) model is used to numerically simulate the formation of a current layer interacting with a transverse magnetic field in a supersonic argon flow. The structural features of the current layer and the characteristics of the process are analyzed at various intensities of the MHD interaction. The problem is solved using the MacCormack method with splitting in spatial coordinates and flux-corrected transport.


Доп.точки доступа:
Vasil'ev, E.N.; Васильев, Евгений Николаевич; Nesterov, D.A.; Нестеров Д.А.

[Text] / N. Rubab [et al.] // Phys. Plasmas. - 2010. - Vol. 17, Is. 10. - Ст. 103704, DOI 10.1063/1.3491336. - Cited References: 54. - This work is funded by the Higher Education Commission of Pakistan under the HEC-Overseas scholarship program Grant No. Ref: 1-1/PM OS /Phase-II/Batch-I/Austria/2007/. Part of this work was done while N. V. Erkaev was at the Space Research Institute of the Austrian Academy of Sciences in Graz. This work is also supported due to the RFBR Grant No. 09-05-91000-ANF-a. Further support is due to the "Austrian Fonds zur Forderung der Wissenschaftlichen Forschung" under Grant No. P20145-N16. . - ISSN 1070-664XРУБ Physics, Fluids & Plasmas

Аннотация: This study presents a theoretical approach to analyze the influence of kappa distributed streaming ions and magnetized electrons on the plasma wave propagation in the presence of dust by employing two-potential theory. In particular, analytical expressions under certain conditions are derived for various modes of propagation comprising of kinetic Alfven wave streaming instability, two stream instability, and dust acoustic and whistler waves. A dispersion relation for kinetic Alfven-like streaming instability has been derived. The effects of dust particles and Lorentzian index on the growth rates and the threshold streaming velocity for the excitation of the instability are examined. The streaming velocity is observed to be destabilizing for slow motion and stabilizing for fast streaming motions. It is also observed that the presence of magnetic field and superthermal particles hinders the growth rate of instability. Possible applications to various space and astrophysical situations are discussed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3491336]


Доп.точки доступа:
Rubab, N.; Erkaev, N.V.; Еркаев, Николай Васильевич; Langmayr, D.; 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] : статья / V. K. Andreev, V. B. Bekezhanova // Fluid Dynamics. - 2008. - Vol. 43, № 2. - p. 176-184


Доп.точки доступа:
Bekezhanova, V.B.; Бекежанова, Виктория Бахытовна; Андреев, Виктор Константинович

[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] / N. V. Erkaev, V. S. Semenov, H. K. Biernat // Phys. Rev. Lett. - 2007. - Vol. 99, Is. 23. - Ст. 235003, DOI 10.1103/PhysRevLett.99.235003. - Cited References: 10 . - ISSN 0031-9007РУБ Physics, Multidisciplinary

Аннотация: A new kind of magnetohydrodynamic instability and waves are analyzed for a current sheet in the presence of a small normal magnetic field component varying along the sheet. These waves and instability are related to the existence of two gradients of the tangential (B(tau)) and normal (B(n)) magnetic field components along the normal (del(n)B(tau)) and tangential (del(tau)B(n)) directions with respect to the current sheet. The current sheet can be stable or unstable if the multiplication of two magnetic gradients is positive or negative. In the stable region, the kinklike wave mode is interpreted as so-called flapping waves observed in Earth's magnetotail current sheet. The kink wave group velocity estimated for the Earth's current sheet is of the order of a few tens of kilometers per second. This is in good agreement with the observations of the flapping motions of the magnetotail current sheet.


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

[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] / D.Langmayr, N. V. Erkaev, H. K. Biernat // Planet Space Sci. - 2007. - Vol. 55, Is. 12. - P1804-1810, DOI 10.1016/j.pss.2007.01.017. - Cited References: 19 . - ISSN 0032-0633РУБ Astronomy & Astrophysics

Аннотация: This paper is devoted to the application of the modified two stream or cross current instability (MTST) to the interaction of the solar wind and Venus. Two scenarios are presented providing favorable conditions for the excitation of the instability. For the first scenario, the free energy source of the MTSI is a significant gradient drift of the solar wind protons near the subsolar ionopause. The corresponding growth rates and frequencies of the MTSI are calculated within a full electromagnetic approach for a two-component plasma. The driving source of the second considered scenario consists in the relative drift velocity between solar wind and planetary particles. For modelling this situation, the dispersion equation for a four-component plasma is solved numerically. (C) 2007 Elsevier Ltd. All rights reserved.


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

[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] / D. Langmayr, H. K. Biernat, N. V. Erkaev // Phys. Plasmas. - 2005. - Vol. 12, Is. 10. - Ст. 102103, DOI 10.1063/1.2065370. - Cited References: 30 . - ISSN 1070-664XРУБ Physics, Fluids & Plasmas

Аннотация: This paper is the first approach for analyzing the influence of kappa-distributed particles on the modified two-stream instability (MTSI). It is assumed that the plasma consists of a magnetized Maxwellian electron contribution and unmagnetized kappa-distributed ions drifting across the electrons. Within an electrostatic approximation, the influence of the kappa parameter on the maximum growth rate of the MTSI is evaluated for the special case of parallel drift velocity and wave propagation.


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

[Text] / N. V. Erkaev [et al.] // Astrophys. J. Suppl. Ser. - 2005. - Vol. 157, Is. 2. - P396-401, DOI 10.1086/427904. - Cited References: 48 . - ISSN 0067-0049РУБ Astronomy & Astrophysics

Аннотация: During the past years, more than 130 giant planets were discovered in extrasolar planetary systems. Because of the fact that the orbital distances are very close to their host stars, these planets are embedded in a dense stellar wind, which can pick up planetary ions. We model the stellar wind interaction of the short-periodic exoplanets OGLE-TR-56b and HD 209458b at their orbital distances of approximate to 0.023 AU and approximate to 0.045 AU, by calculating the Alfven Mach number and the magnetosonic Mach number in the stellar wind plasma flow. We then analyze the different plasma interaction regimes around the planetary obstacles, which appear for different stellar wind parameters. Our study shows that the stellar wind plasma parameters like temperature, interplanetary magnetic field, particle density, and velocity near planetary obstacles at orbital distances closer than 0.1-0.2 AU have conditions such that no bow shocks evolve. Our study shows also that these close-in exoplanets are in a submagnetosonic regime comparable to the magnetospheric plasma interaction of the inner satellites of Jupiter and Saturn. Furthermore, we compare the results achieved for both exoplanets with the Jupiter-class exoplanet HD 28185b at its orbital distance of approximate to 1.03 AU. Finally, we also discuss the behavior of the stellar wind plasma flow close to the planetary obstacles of two highly eccentric gas giants, namely, HD 108147b and HD 162020b. Because of their eccentric orbits, these two exoplanets periodically experience both regimes with and without a bow shock. Finally, we simulate the neutral gas density of HD 209458b with a Monte Carlo model. By using the plasma parameters obtained in our study we calculate the ion production and loss rate of H+ with a test particle model. Our simulations yield H+ loss rates for HD 209458b or similar giant exoplanets in orders of about 10(8)-10(9) g s(-1). These ion loss rates are at least 1 order of magnitude lower than the observed loss rate of evaporating neutral H atoms. Our study indicates, that similar gas giants at larger orbital distances have lower ion loss rates. Thus, the dominating component of particle loss of short-periodic Jupiter-class exoplanets will be neutral hydrogen.


Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Penz, T.; Lammer, H.; Lichtenegger, H.I.M.; Biernat, H.K.; Wurz, P.; Griessmeier, J.M.; Weiss, W.W.