PROBLEMS OF GEOCOSMOS

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Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008) z 2 1 0 -1 -2 10 y 0 -10 -6 -4 -2 x 0 2 4 6 y 10 8 6 4 2 0 -2 -4 -6 -8 -10 -6 -4 -2 0 x 2 4 6 (a) (b) Fig.4: Structure of shock waves and tangential discontinuities(a) and projection all disturbances on the current sheet(b) produced by a pulse of reconnection. 4. Conclusion The Green function for a delta-like reconnection rate is obtained for a 3D configuration in the frame of an incompressible plasma model. The developed method allows us to calculate the disturbances of the magnetic field and the plasma velocity in the surrounding media due to impulsive reconnection events. This analytical solution of three-dimensional time dependent reconnection in incompressible plasma with moving shocks is present. In this model it is assumed that all dissipative processes, which are responsible for reconnection, are localized in an idealized reconnection line of finite length and can be taken into account by specifying a time and space varying reconnection rate. We have shown that even for our simple model it is possible to reproduce the main features of reconnection such as BBF (accelerated plasma flows), FTE, TCR and others. Moreover the variations in By components of magnetic field and velocity can be used to estimate the effective length of the reconnection line. References: 1. Petschek H. E., Magnetic field annihilation, Physics of Solar Flares, edited by W. N. Hess, NASA Spec.Publ.,SP50,pp.425-440, 1964. 2. Semenov V. S., Heyn M. F., and Ivanov I. B., Magnetic reconnection with space and time varying reconnection rates in a compressible plasma, Phys. Plasma 11, pp 62-70 2004. 3. Priest E., Forbesr T., Magnetic Reconnection, Cambridge University Press 2000. 4. Heyn, M. F. and Semenov V. S., Rapid reconnection in compressible plasma, Phys. Plasma 3(7), 2725 1996. 5. Biernat, H. K., Heyn M. F., and Semenov V. S., Unsteady Petschek reconnection, J. Geophys. Res., 92, 3392, 1987. 6. Sasunov Y.L., Semenov V. S., Analytical investigation of 3D impulse magnetic reconnection in the frame of incompressible plasma using Green function, Proceedings of the XXXI Annual Seminar “Physics of Auroral Phenomena”, Apatity, pp.92-95, 2008. 259 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0
Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008) THE STRUCTURALLY ADEQUATE MODEL <strong>OF</strong> MAGNETOSPHERIC PROCESSES 85-08 Introduction P.A. Sedykh, E. A. Ponomarev , V.D. Urbanovich, O.V. Mager Institute of Solar-Terrestrial Physics, Siberian Branch of the Russian Academy of Sciences, Lermontov str., 126 a, p/o box 291, Irkutsk, 664033, Russia; e-mail: pvlsd@iszf.irk.ru Abstract. The structurally adequate model of magnetospheric disturbances consists of the following modules: A. Bow shock as a source of power for magnetospheric processes. B. Generation of magnetospheric convection. C. Plasma pressure distribution in the magnetosphere and electron-proton precipitations into the ionosphere. D. Magnetosphere-ionosphere coupling. Field-aligned currents. Essentially, each module presented in an analytical form is a model of a particular process described in physical terms. It has input and output for coupling with other modules. When combined, the modules comprise a single large physically adequate model describing a phenomenon in such a way that we understand its essence and contribution of each of the physical processes into the overall picture. According to their tasks, models are divided into two types. The first type models task is the maximally accurate description of the outcome parameters relation with the income ones. Such models are created as a combination of the regression equations, which coefficients present the model’s content. The coefficients are determined on the basis of the teaching samples, for which are known the income and outcome parameters. Such models correctly reflecting the system functions should be named as functionally adequate (FAM). The other type of models has in its basis the physics equations, which describe the real physical processes happening in the system. They more or less can form the physical structure of the object. That’s why they should be called as structurally adequate models (SAM). Models of the first and also of the second types can be formed from the blocks (modules). Each block (module) describes the structural element or the process. The blocks should be related with each other. The outcome of the previous block is the income for the next one. So, we have a difficult nature system – geomagnetosphere. The one review of the detailed «anatomy» of the magnetosphere is enough to understand that such complicated structure should have also the complicated functions. So it appeared to be. The most common appearance of it is the magnetosphere response to the disturbance of plasma density, velocity of solar wind and magnitude of the magnetic field in solar wind. At the present time there are created several functionally adequate models, which describe well the magnetosphere behavior, if the incoming parameters are located in the frames of provided teaching samples. With the structurally adequate models the case is facing another way. It is as follows. If the FAM cannot base on the knowledge of the certain physical processes and can be constructed only in formal, then for the SAM the giving of the real physical mechanisms is the work content. Here the case is not in the use of physics equations for the description or not. The case is in the use of the equations for the processes, which are in the system, but not of their «substitutes». Bow shock as a source of power for magnetospheric processes The solar wind undergoes the greatest change of its parameters during the passage through the bow shock front. Indeed, the magnetic field tangential component and magnetic energy density increase by factors of almost 4 and approximately 15, respectively, at the bow point when the front is crossed. The physical essence of this process consists in that the Earth in the solar wind stream disturbs this stream, which is supersonic for the Earth. This means that the bow shock front is formed, upstream of which the solar wind plasma is not disturbed and new scales of a change in the values appear downstream (a front thickness is the minimal of these scales). In describing the bow shock, we followed [Whang, 1987; Ponomarev et al., 2006 a, b]. A jump of the magnetic field tangential component at front crossing means that the front carries a current. The surface density of this current composed of two components is [Ponomarev et al., 2006, b]: Jl=-c(σ-1)B0τ/4π, Jτ=c(σ–1)B0l/4π, (1). 266
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2. Burlaga & Klein method. The main
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