Труды сотрудников ИВМ СО РАН

[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 0148-0227РУБ 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.

[Text] / N. V. Erkaev [et al.] // COORDINATED MEASUREMENTS OF MAGNETOSPHERIC PROCESSES. Ser. ADVANCES IN SPACE RESEARCH : PERGAMON PRESS LTD, 2000. - Vol. 25: D0 1 Symposium of COSPAR Scientific Commission D Held at the 32nd COSPAR Scientific Assembly (JUL 12-19, 1998, NAGOYA, JAPAN), Is. 07.08.2013. - P1523-1528, DOI 10.1016/S0273-1177(99)00665-1. - Cited References: 18 . - ISBN 0273-1177РУБ Engineering, Aerospace + Astronomy & Astrophysics + Geosciences, Multidisciplinary + Meteorology & Atmospheric Sciences

Аннотация: We extend our "magnetic string" MHD model describing the flow of the shocked solar wind around the magnetosphere to include an anisotropic plasma pressure with p(perpendicular to) p(parallel to). Thermodynamic properties are determined by the law of conservation of energy of a magnetic string associated with a magnetic field line. The MHD equations are closed by a relation between p(perpendicular to) and p(parallel to) corresponding to the threshold of the electromagnetic proton cyclotron wave instability. Assuming no flow across the magnetopause, we compare profiles of the steady-state magnetic field and plasma parameters along the subsolar line for upstream sonic and Alfven Mach numbers = 10 with the isotropic case (p(perpendicular to) = p(parallel to)). In the anisotropic model, besides the density, both temperatures, plasma pressures and betas decrease toward the magnetopause. The temperature and plasma pressure parallel to the magnetic field decrease more strongly than those perpendicular to the field. Profiles for temperature and pressure in the case of isotropy lie between those of corresponding parallel and perpendicular values, but closer to the latter. The gradient of B near the magnetopause is larger than for isotropic pressure. (C) 2000 COSPAR. Published by Elsevier Science Ltd.


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

[Text] / N. V. Erkaev, C. J. Farrugia, H. K. Biernat // J. Geophys. Res-Space Phys. - 1999. - Vol. 104, Is. A4. - P6877-6887, DOI 10.1029/1998JA900134. - Cited References: 29 . - ISSN 0148-0227РУБ Astronomy & Astrophysics

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


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