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Three-dimensional (3-D) Monte Carlo simulation has been performed for predicting the percolation threshold in electrical conductivity of polymer composites filled with randomly oriented conductive particles of various morphologies. The conductive fillers like graphite nanoplatelets have been simulated as interpenetrating thin disks and oblate ellipsoids of revolution. For large aspect ratios we find close agreement between disks and oblate ellipsoids of revolution for the average number of bonds per object B C % 2.3, that is in agreement with previous calculations for other shapes of filler (e. g. oblate prisms). The vermicular particles of thermoexfoliated graphite (TEG) have been simulated as the chains of disks jointed in a special manner. The values of percolation threshold have been calculated for various configuration of graphite chains (fragments of vermicular TEG particles) using the Monte Carlo method. The percolation threshold was shown to be determined by the number of disks m and angle between connected disks. It was found that critical volume fraction strongly depends on disks' aspect ratio e, their orientation within a chain and length of this chain: b c decreases with increase of m and e. The comparison of numerical results with our previous experimental data showed a reasonably good agreement.

We have analyzed the role of auroral processes in the formation of the outer radiation belt, considering that the main part of the auroral oval maps to the outer part of the ring current, instead of the plasma sheet as is commonly postulated. In this approach, the outer ring current is the region where transverse magnetospheric currents close inside the magnetosphere. Specifically, we analyzed the role of magnetospheric substorms in the appearance of relativistic electrons in the outer radiation belt. We present experimental evidence that the presence of substorms during a geomagnetic storm recovery phase is, in fact, very important for the appearance of a new radiation belt during this phase. We discuss the possible role of adiabatic acceleration of relativistic electrons during storm recovery phase and show that this mechanism may accelerate the relativistic electrons by more than one order of magnitude.