The dynamics of a group of narrow field-aligned plasma density irregularities is studied using the large-scale KROT plasma device. The chosen experimental conditions are similar to the conditions in the ionosphere of the Earth, where such irregularities develop under the impact of high-power, high-frequency radio waves. In our laboratory experiment, the irregularities are created by a set of rf antennas arranged in a row across the ambient magnetic field due to the heating of electrons and subsequent redistribution of the plasma. Near the heating sources, the irregularities have the form of a set of channels with reduced plasma density, which develop almost independently. At the same time, the relaxation time of a group of neighboring irregularities differs from that of each single irregularity. Evolution of density perturbations at the periphery of the heating region differs for a single irregularity and for a group of irregularities significantly. These effects are probably due to eddy currents excited by each of the irregularities in the background plasma, since narrow irregularities can develop in the “unipolar” thermal diffusion regime. The preliminary experimental results are consistent with the theoretical predictions of unipolar diffusion and excitation of eddy currents.
The transformation of a subnanosecond ultrawideband electromagnetic pulse (UWB EMP) in a large-volume transparent plasma has been demonstrated experimentally using a large-scale KROT plasma device. The column of the plasma generated in the device chamber has a length of more than 4 m and a diameter of more than 1 m. This allows one to implement the regime of quasiuniform ionization, which is necessary to simulate UWB EMP propagation through the ionosphere. It is shown that the length of the wave propagation path in the plasma is sufficient for dispersion transformation of the pulse retaining the envelope of its frequency spectrum.
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