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L. M. Zelenyi A. P. Kropotkin V. I. Domrin A. V. Artemyev H. V. Malova V. Y. Popov 《Cosmic Research》2009,47(5):352-360
The results of numerical modeling of thinning process in the Earth’s magnetotail current sheet are compared with the model
of an anisotropic current sheet in collisionless space plasma. Stability of the current sheet during its evolution is investigated.
In the evolution one can distinguish three basic stages: 1) transformation of the initial two-dimensional “isotropic” equilibrium
that is well described within the MHD-approximation into a relatively thin current structure; 2) further kinetic evolution,
as a result of which the virtually one-dimensional, extremely thin current sheet is formed; 3) relaxation of the system into
a new equilibrium that can be stable or unstable. A substorm scenario of transformation of the magnetospheric tail and its
transition into the unstable state is suggested. The spontaneously appearing tearing disturbance favors a current sheet disruption.
It is shown that the estimate of a tearing mode wavelength, obtained from the model, is in accordance with experimental observations
during the explosive phase of substorms. 相似文献
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A. S. Biryukov I. S. Veselovsky O. R. Grigoryan A. D. Koval'' S. N. Kuznetsov A. P. Kropotkin M. I. Panasyuk S. B. Ryabukha A. A. Us V. A. Shuvalov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(12):135-141
More than 20 years ago V.P. Shabansky suggested that the magnetic system installed aboard the satellite, could be used as a physical instrument for studying the processes which occur in the near Earth space. The corresponding space scales of an artificial “magnetosphere”—“magnisphere”—are 10 m in the experiment with relatively small magnets in the ionosphere and 100 m in the solar wind. The corresponding similarity criteria are estimated. The possible scheme of the experiment with a superconducting magnet (magnetic moment 105 A · m2) installed aboard the satellite is considered. The experimental complex includes a number of systems for measuring the fluxes of charged particles in a wide energy range, DC electric and magnetic fields, the electromagnetic fields in different frequency bands (from X-rays to radio). The scientific objectives are discussed in detail. 相似文献
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A.P. Kropotkin V.I. Domrin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Dynamics of the magnetotail involves elementary processes of magnetic field merging (reconnection layer formation) occurring on medium spatial scales. Every such process features two different stages, a fast one and a subsequent slower one. The corresponding short time scale T1 is associated with disturbances propagating in the tail lobes. The longer time scale T2 is associated with plasma motions in the plasma sheet. A disturbance appearing in the magnetotail on the time scale T1 results in a loss of equilibrium in the plasma sheet. By means of theoretical argument and numerical simulation, it is shown that the relaxation process which follows on the time scale T2, produces extremely thin embedded current sheets, along with generation of fast plasma flows. The process provides an effective mechanism for transformation of magnetic energy accumulated in the magnetotail, into energy of plasma flows. The fast flows may drive turbulent motions on shorter spatial scales. In their turn, those motions can locally produce very thin current sheets; after that, nonlinear tearing process leads to generation of neutral lines, and reconnection. The latter produces new fast disturbances on the time scale T1 closing the feedback loop. 相似文献
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We investigate the process of the self-consistent formation of a thin current sheet with a thickness close to the ion Larmor gyroradius in the presence of decreasing magnetic field’s normal component Bn. This behavior is typical of the current sheet of the Earth’s magnetospheric tail during geomagnetic substorms. It has been shown that, in a numerical model of the current sheet, based on the particle-in-cell method, the appearance of self-consistent electric field component Ey in the current sheet vicinity can lead to its significant thinning and, eventually, to the formation of a multiscale configuration with a thin current sheet (TCS) in the central region supported by transient particles. The structure of the resulting equilibrium is determined by the initial parameters of the model and by the particle dynamics during the sheet thinning. Under certain conditions, the particle drift in the crossed electric and magnetic fields leads to a significant portion of ions becoming trapped near the neutral sheet and, in this way, to the formation of a wider configuration with an embedded thin current sheet. The population of trapped particles produces diamagnetic negative currents that manifest in the form of negative wings at the periphery of the sheet. Correspondingly, in the direction perpendicular to the sheet, a nonmonotonic coordinate dependence of the magnetic field appears. The mechanisms of the evolution of the current sheet in the Earth’s magnetotail and the formation of a multiscale structure are discussed. 相似文献
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