Numerical Simulation of the Time Evolution of Small-Scale Irregularities in the F-Layer Ionospheric Plasma

Abstract

Dynamics of magnetic field-aligned small-scale irregularities in the electron concentration, existing in the F-layer ionospheric plasma, is investigated with the help of a mathematical model. The plasma is assumed to be a rarefied compound consisting of electrons and positive ions and being in a strong, external magnetic field. In the applied model, kinetic processes in the plasma are simulated by using the Vlasov-Poisson system of equations. The system of equations is numerically solved applying a macroparticle method. The time evolution of a plasma irregularity, having initial cross-section dimension commensurable with a Debye length, is simulated during the period sufficient for the irregularity to decay completely. The results of simulation indicate that the small-scale irregularity, created initially in the F-region ionosphere, decays accomplishing periodic damped vibrations, with the process being collisionless.

Numerical Modeling of the Time Evolution of Super-Small-Scale Irregularities in the Near-Earth Rarefied Plasma

“…Let us compare the results, obtained in the present paper for the first case, when the process starts from the completely electrically neutral state in all simulation region, with the results, obtained in the studies of Mingalev et al [31]- [33], when the electric neutrality of the plasma was broken inside the irregularity at the initial moment. These results of modeling illustrate both common characteristic features and distinctions caused by different initial conditions.…”

“…The time evolutions of the magnetic field aligned super-small-scale irregularities display the following distinctions caused by different initial conditions. It may be recalled that the time interval of about 35 periods of Langmuir oscillations of electrons was sufficient for the irregularity to decay completely, when the electric neutrality of the plasma was broken inside the irregularity at the initial moment [31]- [33]. Unlike, when the process starts from the completely electrically neutral state in all simulation region, the irregularity do not decay and exists during all period of calculations (100 periods of Langmuir oscillations of electrons).…”

“…The Vlasov Equation (1), describes the behavior of the distribution function of electrons (a = e) and ions (a =i), whereas Poisson Equation (2), describes the self consistent electric field in the plasma. More complete details of the utilized mathematical model, developed earlier in the Polar Geophysical Institute, may be found in the studies of Mingalev et al [31]- [33].…”

“…Moreover, in the present study, a new version of the mathematical model is applied in which positive ions can move. In the mathematical model, utilized in the studies of Mingalev et al [31]- [33], positive ions were supposed to be immovable. This supposition was based on the fact that the mass of the positive ion is much more than the mass of the electron.…”

“…The large-scale F-layer modification by powerful high frequency waves was investigated with the help of mathematical models in some studies (for example, see [16]- [29]). Also, the time evolution of the magnetic field aligned super-small-scale irregularities in the concentration of charged particles, existing in the near-Earth rarefied plasma, was studied with the help of the model simulation [30]- [33].…”