Труды сотрудников ИВМ СО РАН

w10=
Найдено документов в текущей БД: 83

    Deep Solar Activity Minimum 2007-2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere
/ 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 0038-0938
РУБ 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.

Полный текст


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.

    Magnetosheath for almost-aligned solar wind magnetic field and flow vectors: Wind observations across the dawnside magnetosheath at X =-12 Re
[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 0148-0227
РУБ 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.

    The role of magnetic handedness in magnetic cloud propagation
[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 0992-7689
РУБ 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.

    Observational aspects of IMF draping-related magnetosheath accelerations for northward IMF
[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 0992-7689
РУБ 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]

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

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


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

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

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


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

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

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


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

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

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


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

    MHD model of magnetosheath flow: comparison with AMPTE/IRM observations on 24 October, 1985
[Text] / C. J. Farrugia [et al.] // Ann. Geophys.-Atmos. Hydrospheres Space Sci. - 1998. - Vol. 16, Is. 5. - P518-527, DOI 10.1007/s00585-998-0518-7. - Cited References: 24 . - ISSN 0992-7689
РУБ Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: We compare numerical results obtained from a steady-state MHD model of solar wind flow past the terrestrial magnetosphere with documented observations made by the AMPTE!IRM spacecraft on 24 October, 1985, during an inbound crossing of the magnetosheath. Observations indicate that steady conditions prevailed during this about 4 hour-long crossing. The magnetic shear at spacecraft entry into the magnetosphere was 15 degrees. A steady density decrease and a concomitant magnetic field pile-up were observed during the 40 min interval just preceding the magnetopause crossing. In this plasma depletion layer (1) the plasma beta dropped to values below unity; (2) the flow speed tangential to the magnetopause was enhanced; and (3) the local magnetic field and velocity vectors became increasingly more orthogonal to each other as the magnetopause was approached (Phan er al., 1994). We model parameter variations along a spacecraft orbit approximating that of AMPTE/IRM, which was at slightly southern GSE latitudes and about 1.5 h post-noon Local Time. We model the magnetopause as a tangential discontinuity, as suggested by the observations, and take as input solar wind parameters those measured by AMPTE/IRM just prior to its bow shock crossing. We find that computed field and plasma profiles across the magnetosheath and plasma depletion layer match all observations closely. Theoretical predictions on stagnation line flow near this low-shear magnetopause are confirmed by the experimental findings. Our theory does not give, and the data on this pass do not show, any localized density enhancements in the inner magnetosheath region just outside the plasma depletion layer.


Доп.точки доступа:
Farrugia, C.J.; Biernat, H.K.; Erkaev, N.V.; Еркаев, Николай Васильевич; Kistler, L.M.; Le, G.; Russell, C.T.

    A comparison of predictions of an MHD model solar wind flow past the magnetopause with AMPTE/IRM observations on 24 October, 1985
[Text] / C. J. Farrugia [et al.] // SOLAR-TERRESTRIAL RELATIONS: PREDICTING THE EFFECTS ON THE NEAR- EARTH ENVIRONMENT. Ser. ADVANCES IN SPACE RESEARCH : PERGAMON PRESS LTD, 1998. - Vol. 22: DO 7 Symposium of COSPAR Scientific-Commission-D on Solar-Terrestrial Relations - Predicting the Effects on the Near-Earth Environment at the 31st COSPAR Sci Assembly (JUL 14-21, 1996, BIRMINGHAM, ENGLAND), Is. 1. - P67-72, DOI 10.1016/S0273-1177(97)01102-2. - Cited References: 19 . - ISBN 0273-1177. - ISBN 0-08-043465-7
РУБ Engineering, Aerospace + Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: We compare numerical results of a steady-state MHD model for solar wind flow past the terrestrial magnetosphere with documented observations made by the AMPTE/IRM spacecraft on 24 October, 1985, during an inbound crossing of the magnetosheath. Observations indicate that steady conditions prevail during this similar to 4 hour-long crossing. The magnetic shear at entry into the magnetosphere was 15 deg. A steady density decrease and a concomitant magnetic field pile-up were observed during the similar to 40 min interval just preceding the magnetopause crossing. In this so-called plasma depletion layer (i) the plasma beta fell generally below unity; (ii) the flow speed tangential to the magnetopause was enhanced; and (iii) the local magnetic field and velocity vectors became increasingly more orthogonal to each other as the magnetopause was approached (Phan et al., 1994). We model parameter variations along a orbit similar to the AMPTE/IRM trajectory, which was at slightly southerly latitudes and similar to 1.5 hours post-noon local time (GSE). In our model we consider the magnetopause to be a tangential discontinuity, as suggested by the observations, and take as input solar wind parameters those measured by AMPTE/IRM just prior to its bow shock crossing. We find that theoretical predictions match all observations closely. (C) 1998 COSPAR. Published by Elsevier Science Ltd. All rights reserved.


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

    MAGNETOSHEATH PARAMETERS AND RECONNECTION - A CASE-STUDY FOR THE NEAR-CUSP REGION AND THE EQUATORIAL FLANK
[Text] / H. K. BIERNAT [et al.] // Planet Space Sci. - 1995. - Vol. 43, Is. 9. - P1105-1120, DOI 10.1016/0032-0633(95)00054-9. - Cited References: 31 . - ISSN 0032-0633
РУБ Astronomy & Astrophysics
Рубрики:
SOLAR-WIND
   LAYERS

Аннотация: We use the magnetohydrodynamic approach to calculate all plasma and magnetic field quantities along a line normal to the magnetopause, beginning at the bow shock, through the magnetosheath and magnetopause, and into the magnetosphere. Our method is based on a perturbation calculation, where we expand in orders of 1/M(A infinity), with M(A infinity) the Alfven Mach number upstream of the bow shock. The calculations are carried out (1) in the noon-midnight meridian at latitudes just south of the northern cusp, and (2) in the equatorial flank region. Our calculations are for an interplanetary magnetic field (IMF) which is directed perpendicular to the upstream solar wind. We consider two orientations of the IMF. In one case, the interplanetary field points due south, i.e. antiparallel to the magnetospheric field in the subsolar point. In the second case, it lies in the equatorial plane and points from dusk to dawn. For each of these different orientations of the IMF, in situ observations of reconnection have been made. In the magnetosheath region adjacent to the magnetopause, i.e. in the so-called magnetic barrier, the magnetic forces react back on the plasma flow. This effect is included consistently in the calculation by the use of a special coordinate system. The magnetic field tension accelerates the plasma in a direction perpendicular to the field and thus the magnetic field produces an asymmetry in the flow field. At the magnetopause we describe shock-type reconnection, taking as input on the magnetosheath side the results of the above calculation and taking at the magnetospheric side typical values for the outer boundary of the magnetosphere. The format in which the results are presented is similar to that used in the presentation of bulk parameters and magnetic field measurements obtained from spacecraft.


Доп.точки доступа:
BIERNAT, H.K.; BACHMAIER, G.A.; KIENDL, M.T.; Erkaev, N.V.; Еркаев, Николай Васильевич; MEZENTSEV, A.V.; FARRUGIA, C.J.; SEMENOV, V.S.; RIJNBEEK, R.P.

    Effects on the distant geomagnetic tail of a fivefold density drop in the inner sheath region of a magnetic cloud: A joint Wind-ACE study
[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 0273-1177
РУБ 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]

    Cluster observations showing the indication of the formation of a modified-two-stream instability in the geomagnetic tail
[Text] / S. . Muhbachler [et al.] // Adv. Space Res. - 2009. - Vol. 43, Is. 10. - P1588-1593, DOI 10.1016/j.asr.2009.01.012. - Cited References: 11. - For the provision of prime parameter data the authors thank the instrument teams of Cluster-CIS, -FGM, -PEACE, and -STAFF, in particular I. Danduras, E. Lucek, A. Fazakerley, and N. Cornilleau-Wehrlin. This work is partly supported by ESTEC Contract 18.201/04/NL/NR, by DLR Grant 50 OC 0003, by RFBR Grant 04-05-64088, by Programs 2.17 and 16.3 of RAS, and by Project PI7100-N08 of the Austrian Science Fund. . - ISSN 0273-1177
РУБ Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences
Рубрики:
QUASI-PERPENDICULAR SHOCKS
Кл.слова (ненормированные):
Cluster -- Energetic particles -- Magnetotail -- Modified-two-stream instability

Аннотация: This study presents several observations of the Cluster spacecraft on September 24, 2003 around 15:10 UT, which show necessary prerequisites and consequences for the formation of the so-called modified-two-stream instability (MTSI). Theoretical studies suggest that the plasma is MTSI unstable if (1) a relative drift of electrons and ions is present, which exceeds the Alfven speed, and (2) this relative drift or current is in the cross-field direction. As consequences of the formation of a MTSI one expects to observe (1) a field-aligned electron beam, (2) heating of the plasma, and (3) an enhancement in the B-wave spectrum at frequencies in the range of the lower-hybrid-frequency (LHF). In this study we use prime parameter data of the CIS and PEACE instruments onboard the Cluster spacecraft to verify the drift velocities of ions and electrons, FGM data to calculate the expected LHF and Alfven velocity, and the direction of the current. The B-wave spectrum is recorded by the STAFF instrument of Cluster. Finally, a field aligned beam of electrons is observed by 3D measurements of the IES instrument of the RAPID unit. Observations are verified using a theoretical model showing the build-up of a MTSI under the given circumstances. (C) 2009 COSPAR. Published by Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Muhbachler, S.; Langmayr, D.; Lui, ATY; Erkaev, N.V.; Еркаев, Николай Васильевич; Alexeev, I.V.; Daly, P.W.; Biernat, H.K.; ESTEC [18.201/04/NL/NR]; DLR [50 OC 0003]; RFBR [04-05-64088]; Austrian Science Fund [PI7100-N08]

    The Kelvin-Helmholtz instability at Venus: What is the unstable boundary?
[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 0019-1035
РУБ 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.

    How to distinguish between kink and sausage modes in flapping oscillations?
[Text] / D. I. Kubyshkina [et al.] // J. Geophys. Res-Space Phys. - 2014. - Vol. 119, Is. 4. - P. 3002-3015, DOI 10.1002/2013JA019477. - Cited References: 32. - We thank C. W. Carlson and J. P. McFadden for use of THEMIS ESA data; K. H. Glassmeier, U. Auster, and W. Baumjohann for the use of FGM data provided under the lead of the Technical University of Braunschweig and with financial support through the German Ministry for Economy and Technology and the German Center for Aviation and Space (DLR) under contract 50 OC 0302. The work was partly supported by SPbU grant 11.38.84.12, by RFBR grants 12-05-00152-a and 12-05-00918-a, and by the grant for support of leading Scientific schools 2836.2014.5. The work of S. Dubyagin and N. Ganushkina was partly supported by the Academy of Finland. This work was supported by the Austrian Science Fund (FWF): I193-N16. N. V. E acknowledges 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. 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). . - ISSN 2169-9380. - ISSN 2169-9402
РУБ Astronomy & Astrophysics

Аннотация: Flapping waves are most noticeable large-scale perturbations of the magnetotail current sheet, whose nature is still under discussion. They represent rather slow (an order of magnitude less than typical Alfven speed) waves propagating from the center of the sheet to its flanks with a typical speed of 20-60 km/s, amplitude of 1-2 R-e and quasiperiod of 2-10 min. The double-gradient MHD model, which was elaborated in Erkaev et al. (2007) predicts two (kink and sausage) modes of the flapping waves with differences in their geometry and propagation velocity, but the mode structure is hard to resolve observationally. We investigate the possibility of mode identification by observing the rotation of magnetic field and plasma velocity vectors from a single spacecraft. We test theoretical results by analyzing the flapping oscillations observed by Time History of Events and Macroscale Interactions during Substorms spacecraft and confirm that character of observed rotation is consistent with kink mode determination made by using multispacecraft methods. Also, we checked how the existence of some obstructive conditions, such as noise, combined modes, and multiple sources of the flapping oscillations, can affect on the possibility of the modes separation with suggested method.

Полный текст (доступен только в локальной сети)

Держатели документа:
ИВМ СО РАН

Доп.точки доступа:
Kubyshkina, D.I.; Sormakov, D.A.; Sergeev, V.A.; Semenov, V.S.; Erkaev, N.V.; Еркаев, Николай Васильевич; Kubyshkin, I.V.; Ganushkina, N.Y.; Dubyagin, S.V.; German Ministry for Economy and Technology; German Center for Aviation and Space (DLR) [50 OC 0302]; SPbU [11.38.84.12]; RFBR [12-05-00152-a, 12-05-00918-a]; grant for support of leading Scientific schools [2836.2014.5]; Academy of Finland; Austrian Science Fund (FWF) [I193-N16]; International Space Science Institute (ISSI, Switzerland); European Union [269198, 218816]

    Computer Simulation of Spacecraft Onboard Equipment
[Text] / L. Nozhenkova, O. Isaeva, E. Gruzenko ; ed.: K. . Chan, J. . Yeh // PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON COMPUTER INFORMATION. - 2015. - Vol. 18: International Conference on Computer Information Systems and Industrial (JUN 28-29, 2015, Bangkok, THAILAND). - P943-945. - (ACSR-Advances in Comptuer Science Research). - Cited References:10 . - ISSN 2352-538X
РУБ Computer Science, Artificial Intelligence + Computer Science, Hardware & Architecture + Computer Science, Theory & Methods

Кл.слова (ненормированные):
c spacecraft -- onboard equipment -- command and measuring system -- program -- and mathematical model -- simulation modeling

Аннотация: This article presents the results of application of the computer simulation technology for intellectual support of spacecraft onboard equipment design. Methods and instruments allowing construction of informational and graphical models were developed describing architecture of onboard systems and configuration of switching connections. Knowledge base creation and application means allow to specify logics of the model functioning, carry out simulation experiments and analyze the results of modeling. The program complex "Program and mathematical model of a spacecraft command-measuring system's onboard equipment" was developed to unite instruments of simulation modeling and intellectual support of onboard equipment design.

WOS

Держатели документа:
Inst Computat Modelling SB RAS, Krasnoyarsk, Russia.

Доп.точки доступа:
Nozhenkova, L.F.; Ноженкова, Людмила Федоровна; Isaeva, O.S.; Исаева, Ольга Сергеевна; Gruzenko, E.A.; Грузенко, Евгений Андреевич
539.3
К 65

    Контроль точности решения при анализе напряженно-деформированного состояния высокоответственных технических объектов
[Текст] : статья / А. Н. Рогалев, С. В. Доронин, А. А. Рогалев // Системы. Методы. Технологии. - 2015. - № 3. - С. 32-38 . - ISSN 2077-5415
   Перевод заглавия: Solution accuracy control for analysis of stress-strain state of critical technical objects
УДК

Аннотация: В статье рассматриваются подходы к оценке вычислительной ошибки при решении системы линейных алгебраических уравнений, в качестве матрицы коэффициентов которой рассматривается матрица жесткости конечно-элементной модели технического объекта. Предлагаемый подход предполагает, что уровень вычислительной ошибки определяется структурой и значениями матрицы коэффициентов, и заключается в численном решении системы линейных уравнений с матрицей жесткости и такой специально подобранной правой частью, для которой известно точное решение. Сравнение численного и точного решений позволяет получить оценку вычислительной ошибки, позволяющую судить о приемлемости построенной конечно-элементной модели. Получение указанной оценки является дополнительной процедурой контроля точности численного решения при анализе его сходимости путем последовательного уменьшения шага конечных элементов. Развиваемый подход весьма актуален для конструкций ответственных технических объектов, где цена ошибки при проектных расчетах оказывается неприемлемо высокой. Для реализации предлагаемого подхода организован интерфейс между пакетом конечно-элементного моделирования ANSYS и вычислительным пакетом компьютерной алгебры Wolfram Mathematica. В качестве примера приводится получение оценки вычислительной ошибки численного решения системы линейных алгебраических уравнений с матрицей жесткости силовой конструкции бака высокого давления для перспективных электрореактивных двигателей космических аппаратов. Силовая конструкция представляет собой оболочку давления, подвешенную на системе вантов с регулируемым уровнем натяжения, закрепленных, в свою очередь, на пространственной стержневой системе - силовой структуре корпуса космического аппарата. Для рассматриваемой конструкции найден уровень конечно-элементной дискретизации, обеспечивающий сходимость численного решения.
The paper is devoted to approaches to a problem of numerical error evaluation when solving the system of linear equations. The stiffness matrix of a finite-element model of a technical object is a coefficient matrix of the system of linear equations. The approach proposed supposes that the level of numerical error is determined by a structure and magnitude of coefficient matrix. The approach consists of numerical solving system of linear equations with stiffness matrix and special right-hand member with exact solution known. Comparison of numerical and exact solutions allows evaluating numerical error and making decision on the quality of finite-element model. Evaluation numerical error is a supplementary procedure for checking accuracy of numerical solution within solution convergence analysis by means of cascade reduction mesh spacing. The approach is of great actuality for structures of critical technical objects with great worth of design calculations error. To implement the approach, data interface between the finite-element analysis package ANSYS and computer algebra package Wolfram Mathematica has been created. Evaluated numerical error has been given as an example for numerical solution system of linear equations with stiffness matrix for load-bearing unit of high pressure tank for perspective spacecraft electrojet engines. The load-bearing unit consists of pressure shell suspended by means of cable system with controlled tension. The cable system is attached to spatial bar system - load-bearing frame structure of spacecraft. For the structures considered the level of finite-element discretization has been determined to provide numerical solution convergence.

РИНЦ

Держатели документа:
Институт вычислительного моделирования СО РАН
Институт космических и информационных технологий Сибирского федерального университета
Специальное конструкторско-технологическое бюро «Наука» Красноярского научного центра СО РАН

Доп.точки доступа:
Доронин, С.В.; Doronin S.V.; Рогалев, А.А.; Rogalyov A.A.; Rogalyov A.N.

    Метод тепловакуумных испытаний бортовой радиоэлектронной аппаратуры негерметичных космических аппаратов на основе тепловизионной измерительной системы
[Текст] : статья / С. Г. Кочура [и др.] // Наукоемкие технологии. - 2015. - Т. 16, № 3. - С. 34-38 . - ISSN 1999-8465
   Перевод заглавия: The method of thermal vacuum tests onboard electronic equipment untightened spacecraft based on thermal measurement system
Аннотация: Описан метод тепловакуумных испытаний с применением специализированного стенда тепловакуумных испытаний и программы «АРМИТ». Показано, что предлагаемые решения позволяют выполнять обработку тепловизионных изображений, полученных с помощью системы контроля и измерения температур, расчет теплофизических характеристик и формирование исходной базы данных ЭРИ. Выяснено, что наличие более точных данных по тепловой обстановке функционального узла позволяет с большей вероятностью прогнозировать возможные сценарии поведения ЭРИ в условиях космического пространства при дальнейшей эксплуатации оборудования.
Describes a method for thermal vacuum tests using specialized equipment of thermal vacuum tests and programs «Armit». Proposed solutions allow you to perform the processing of thermal images obtained with the system of control and measurement of temperature, calculation of thermophysical properties and the formation of the source database of electronic components. The presence of more accurate data on the thermal environment of the functional unit allows more likely to predict possible scenarios behavior of electronic components in outer space at the further operation of the equipment. The proposed method also allows to make observations of thermal properties changes during working mode transitions.

РИНЦ

Держатели документа:
АО «Информационные спутниковые системы» им. академика М.Ф. Решетнева» (г. Железногорск)
Институт вычислительного моделирования СО РАН

Доп.точки доступа:
Кочура, С.Г.; Kochura S.G.; Косенко, В.Е.; Kosenko V.E.; Школьный, В.Н.; Shkolny W.N.; Сунцов, С.Б.; Suntsov S.B.; Морозов, Е.А.; Morozov E.A.; Деревянко, Валерий Александрович; Derevyanko V.A.; Макуха, Александр Васильевич

    Численные оценки предельных отклонений траекторий летательных аппаратов в атмосфере
[Текст] : статья / А. Н. Рогалев, А. А. Рогалев // Вестник Сибирского государственного аэрокосмического университета им. академика М.Ф. Решетнева. - 2015. - Т. 16, № 1. - С. 104-112 . - ISSN 1816-9724
   Перевод заглавия: NUMERICAL ESTIMATIONS OF MAXIMUM DEVIATIONS FOR AIRCRAFT TRAJECTORIES IN THE ATMOSPHERE
Аннотация: Основная задача статьи - описать гарантированные методы решения систем дифференциальных уравнений с учетом управляющих воздействий и их применение к задачам оценки предельных отклонений летательных аппаратов. Постановка задач оценки предельных отклонений обусловлена практическими потребностями оценки надежности сложных нелинейных управляемых систем, выполняющих свои функции в условиях возмущений. Примером такой системы является летательный аппарат: самолет, ракета, космический корабль. Среди задач оценки предельных отклонений следует отметить исследование движения самолета на этапе автоматического захода на посадку, где определяется, возможно ли нарушение ограничений, наложенных на кинематические параметры самолета, в момент касания взлетно-посадочной полосы. К таким задачам относится также оценка возможности потери устойчивости движения летательного аппарата на заданном интервале времени. Наибольшие сложности при решении такой задачи возникают в том случае, когда условия полета не являются стационарными, например, при рассмотрении участка спуска в атмосферу орбитальной ступени космического корабля. В этом случае отсутствуют сами критерии потери устойчивости, если не ограничиваться простейшим случаем линейной системы, для которой могут быть использованы условия Рауса-Гурвица. Упрощенным критерием потери устойчивости может служить некоторое пороговое или критическое значение одного из параметров движения самолета, например, угла атаки или угла скольжения. В подобных задачах важную роль играют множества достижимости - совокупности концов всех траекторий управляемой системы, начинающихся в начальный момент времени в точках начального множества. Эти множества применяются в задачах гарантированного или минимаксного оценивания решений динамических систем, если действующие на систему внешние возмущения и ошибки наблюдения заключены в определенных пределах (стеснены ограничениями). Анализ работ, выполняющих оценки множеств достижимости, свидетельствует о том, что получить надежную оценку множеств достижимости управляемых систем в условиях неопределенности, если в правые части этих систем управляющие воздействия входят произвольным образом, а не только как аддитивный член, удается не всегда. Поэтому возможности применения гарантированных методов, основанных на символьном представлении решений, для оценки множеств достижимости будут полезными специалистам в управлении. Представлены результаты применения численных методов, основанных на построении символьных формул решений и оценивании всех возможных ее значений
In this article we studyguaranteedmethods for solving differential equations systems with control actions and its application for problems of aircrafts trajectories maximum deviations estimating. The problem statement of maximum deviations estimating is caused by the necessity to evaluate reliability of complexnonlinear controlled systems that operate under the influenceof perturbations. The exampleof such system is an aircraft: an airplane, a rocket, a spacecraft. We should emphasize the research of an airplane movement during an autoland approach among problems of maximum deviations estimating. This research gives an answer whether a violation of restrictions imposed on the kinematic parameters of an airplane touching down a runway is possible or not. The problems of limit deviations evaluating also includeestimating ofthe possibilityof an aircraft motion stability’s loss for a given time interval. The greatest difficultyin solving suchproblems arises inthe case when flight conditionsare not fixed, for example, when consideringthe descentinto the atmosphere of a spacecraft orbiter. In this case the loss of stability criteriathemselves are not formulated, if we do not confine ourselves to the simplest case of a linear system, forwhich theRouth-Hurwitz conditions can be used. Some threshold orcritical valueof one of theparameters of an airplane can serve as a simplisticcriterion of stability loss. For example, the angle of attack orslip angle can be taken as such parameter. Reachable sets(collections of all the trajectories of controlled systems) make a figure in such problems. These setsare used in problems of guaranteed or minimax estimationof solutions of dynamical systems ifexternal perturbations that influence on a system andobservation errorsare enclosedwithin a certain range(constrained by limitations). The analysis of works that estimatereachable sets indicatesthat the reliable estimationof reachable setsof controlled systems under uncertainty, if theright-hand sidesof these systemsdepend nonlinearly on thecontrol actions,is not always possible. Therefore the possibility of the guaranteed methods based on symbolic representation of solutions for reachable sets evaluation will be useful for specialists in control. The article presents theresults of the applicationof the numericalmethods basedon the constructionof symbolicformulas of solutions andevaluating all of its possiblevalues.

РИНЦ

Держатели документа:
Институт вычислительного моделирования СО РАН
Сибирский федеральный университет, Институт космических и информационных технологий

Доп.точки доступа:
Рогалев, А.А.; Rogalyov A.A.; Rogalev A.N.

    Метод системного моделирования бортовой аппаратуры космического аппарата
[Текст] : статья / Л. Ф. Ноженкова, О. С. Исаева, Е. А. Грузенко // Вычислительные технологии. - 2015. - Т. 20, № 3. - С. 33-45 . - ISSN 1560-7534
   Перевод заглавия: The method for system modelling of the spacecraft on-board equipment
Аннотация: Рассмотрен метод системного моделирования бортовой аппаратуры командно-измерительной системы космического аппарата. Дано описание модели и эвристического метода направленного пошагового проектирования, в результате которого строится модель, имитирующая структуру, свойства и методы функционирования командно-измерительной системы. Описана программная реализация инструментальных средств, позволяющих выполнять построение модели: задавать конфигурацию, коммутационные соединения и логику информационного взаимодействия. Исследования проводятся в рамках создания программного обеспечения для поддержки конструирования бортовой аппаратуры командно-измерительной системы космического аппарата.
We address a method for modelling of onboard equipment for the command and the measuring system of the spacecraft. The result of the method is the information and graphical simulation model that represents the specified level of details for the configuration and functions of the on-board equipment. A heuristic approach is used to support the model construction that allows a sequence of model changes in order to simulate the required specifications and functions of the equipment. The model is designed to simulate the operation of a command-measuring system. The command-measuring system is designed for command-measuring control of onboard systems, transmission of telemetric information to Earth control complex, measurement of current navigation parameters of a spacecraft's orbit. We have formally described the model of a command-measuring system, and also designed the methods and instruments allowing to present its architecture and a configuration of connections. The model's function rules are explicitly set in the knowledge base of the product. The rules describe the logics for operation of the command-measuring system: transfer of command information to spacecraft's systems, acceptance and transmission of telemetric information, conditions of the onboard equipment control, choice of interfaces for the equipment. The research is carried out for creation of the “Program-mathematical model of the onboard equipment command and measurement system”. The program includes the tools for model building and simulation. During the simulation it renders the sequence of actions defined for a specific model configuration. The software includes advanced configuration features models, statistical modelling of storage, management simulations, and analyze the results of the model. These functions allow a user to enter a variety of heuristics to analyze design solutions. The program was put into trial operation in the JSC "Academician MF Reshetnev Information Satellite Systems".

РИНЦ

Держатели документа:
Институт вычислительного моделирования СО РАН

Доп.точки доступа:
Исаева, Ольга Сергеевна; Isaeva O.S.; Грузенко, Евгений Андреевич; Gruzenko E.A.; Nozhenkova L.F.