Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

О. V. Mingalev at al. 12 24 36 48 The above pointed Out values yield the following quantities of some physically significant parameters. The equilibrium period of Langmuir oscillations of electrons, в°ре, is equal to 3.52 10"7 s. The Debye length of the plasma, \°De, is 7.6-l(T3m . The period of cyclotron oscillations of electrons, все, is equal to 8.12 •10_7s, that is, approximately a factor of 2.3 larger than the equilibrium period o f Langmuir oscillations of electrons ( 9ce « 2.3 -&p e ). The collisional mean free path of charged particles is about 50 m. The mean free time o f electron between successive collisions with other particles is larger than the equilibrium period of Langmuir oscillations of electrons by a factor of about 1047. A two-dimensional simulation region lays in the plane perpendicular to the magnetic field line. The simulation region is a square and its side length is equal to 96 Debye lengths of the plasma. The grid width is equal to one eighth of the Debye length of the plasma. The quantity of the grid cells is 768x768. The time step for the electric field is equal to one hundredth of an equilibrium period of Langmuir oscillations of electrons. Taking the input parameters of the mathematical model typical for the nocturnal ionosphere at the level of 300 km, we have calculated the time evolution of the distribution functions o f charged particles as well as self-consisting electric field for two distinct on principle situations. In these situations, the initial distributions of electric charge density have been different. The first situation corresponds to homogeneous spatial distributions o f the electron and positive ion concentrations at the initial moment inside the simulation region, with the plasma being electrically neutral and the electric charge density being equal to zero. The second situation corresponds to homogeneous spatial distribution o f the positive ion concentration only. The spatial distribution of the electron concentration, at the initial moment, contains an irregularity like a strait straight strip intersecting the simulation region across its center. Inside the irregularity, the electric neutrality of the plasma is broken whereas, beyond it, the plasma is electrically neutral at the initial moment. Fig. 1. The calculated spatial distributions of the relative decrease of the electron concentration, {n0 - n e)/n0 , in the plane perpendicular to the magnetic field. The distances (in the Debye length, X°De) from the central point o f the simulation region are shown on the horizontal (. X) and vertical ( Y) axes. The results are given for the following moments: (a) t = 0 , (b) f = O.74-0°e , (c) t = 2.2-6%, (d) t = 14-0®e . 134