ИСТИНА

A lot of spacecraft observations showed that closed magnetic configurations such as plasmoids and magnetic islands are often observed in the Earth magnetotail. The purpose of our study is to analyze the kinetic features of nonadiabatic ion dynamics in the current sheet (CS) inside the plasmoid and the efficiency of their acceleration in such configurations. Trajectories of test ions of different masses (H+ и O+) were studied in the prescribed magnetic configuration similar to the observed one by Cluster spacecraft (s/c). The magnetic configuration consists of a single stationary plasmoid in the tail side of the near-Earth magnetic X-line. The model of inverse magnetic field is used in the simulation. The spatial variation of the plasmoid-like δBz (x) is superimposed on the unperturbed magnetic field B=(Bx (z), 0, Bz0), where |Bz0|=1 nT. The constant and uniform dawn-dusk electric field (Ey = 0.1 mV / m) is present in the system everywhere. We launch into the system ions with initial energies and pitch-angles similar to the ones observed in the lobe region (200eV, θ=10-300). The simulations have shown that the character of the ion motion in the plasmoid-like configuration depends on the ion initial parameters (mass, energy, pitch angle, phase) and on the X-coordinates of the ion entries into the CS. Ions, which are trapped inside the plasmoid, experience the nonadiabatic interaction with the CS and are accelerated by the dawn-dusk electric field. Plasmoid localization in the dawn-dusk direction imposes a limit on the ion energy gain. However, our analysis shows that there is a group of ions going through the evening flank of plasmoid, which can be back again again. Inclusion of the shear component of magnetic field (By) in the model causes significant change in the ions dynamics in the symmetrical areas of the plasmoid, relative to the neutral plane. There is an asymmetry of the particle distribution, which depends on the amplitude of By, the spatial distributions of particle density for different amplitudes of By.